***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 1 of 790 Formatted: Left EO12866_PM NAAQS_2060 - AO47_ FRN Preamble_and_Reg_Text_ 20121120 6560 - 50 - P From: Lydia Wegman/RTP/USEPA/US To: "Frey, Nathan J." <Nathan_J._Frey@omb.eop.gov>, "Mancini, Dominic J."

<Dominic_J._Mancini@omb.eop.gov> Cc: Janet McCabe/DC/USEPA/US@EPA, Gina McCarthy/DC/USEPA/US@EPA, Joseph
- J

Dougherty/DC/USEPA/US@EPA, Karen Martin/RTP/USEPA/US@EPA, Beth Hassett
Sipple/R TP/USEPA/US@EPA, John Hannon/DC/USEPA/US@EPA, Erika Sasser/RTP/USEPA/US@EPA Date: 12/14/2012 11:43 AM Subject: Final compare version of PM NAAQS NFR Nathan and Dom, Here is the redline version of the PM NAAQS rule, compared to the version that was sen t to you originally. Please let me know if you have any questions. Also, please let me know if you want a clean version as well. Thanks.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 2 of 790 Formatted: Left ENVIRONMENTAL PROTECTION AGENCY 40 CFR Parts 50 , 51, 52, 53 and 58 [EPA - HQ - OAR - 200 7 - 0 492; FRL - XXXX - X ]

RIN 2060 - AO47 National Ambient Air Quality Standard s for Particulate Matter AGENCY: Environmental Protection Agency (EPA). ACTION: Final r ule. SUMMARY: Based on its review of the air quality criteria and the national ambient air quality standards (NAAQS) for particulate matter (PM), the EPA is making revisions to the suite of standards for PM to provide requisite protection of public health and welfare and to make corresponding revisions to the data handling conventions for PM and to the ambient air monitoring, reporting, and network design requirements
. The EPA also is making revisions to the prevention of significant deterioration (PSD) permitting program with respect to the NAAQS revisions
. With regard to primary (health

- based) standards for fine particles (generally referring to particles less than or equal to 2.5 micrometers (μm) in diameter, PM 2.5 ), the EPA is revis ing the annual PM 2.5 standard by lower ing the level to 12 .0 micrograms per cubic meter (μg/m 3 ) so as to provide increased protection against health effects associated with long

- and short

- term exposures (including premature mortality, increased hospital admissions and emergency department visits, and development of chronic respiratory disease) , and to retain the 24

- hour PM 2.5 standard at a level of 35 μg/m 3

. The EPA is revising the Air Quality Index (AQI) for PM 2.5 to be consistent with the revis ed primary PM 2.5 standards. With regard to the primary standard for particles generally less than or equal to 10 μ m in diameter (PM 10 ), the EPA is retain ing the current 24

- hour PM 10 standard to continue to provide protection against effects associated with short

- term exposure to thoracic coarse particles (i.e., PM 10

- 2.5 ). With regard to the secondary***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 3 of 790 Formatted: Left (welfare

- based) PM standard s, the EPA is generally retaining the current suite of secondary standards (i.e., 24

- hour and annual PM 2.5 standards and a 24

- hour PM 10 standard )
. Non

- visibility welfare effects are addressed by this suite of secondary standards, and PM

- related vis ibility impairment is addressed by the secondary 24

- hour PM 2.5 standard
. DATES: The final rule is effective on [ INSERT DATE 60 DAYS AFTER DATE OF PUBLICATION IN THE FEDERAL REGISTER ] . ADDRESSES ADDRESSES: Section X.B requests comments on an information collection request regarding changes to the monitoring requirements. Submit your comments, identified by Docket ID No. EPA

- HQ

- OAR

- 2007

- 0492 , to the EPA by one of the following methods: www.regulations.gov : Follow the on

- line instructions for submitting comments. Email: a - and

- r - Docket@epa.gov Fax: 202

- 566

- 9744 Mail: Docket No. EPA

- HQ

- OAR

- 2007

- 0492, Environmental Protection Agency, Mail code 6102T, 1200 Pennsylvania Ave., NW, Washington, DC 20460
. Please include a total of two copies
. Hand Delivery: Docket No. EPA

- HQ

- OAR

- 2007

- 0492, Environmental Protection Agency, EPA West, Room 3334, 1301 Constitution Ave., NW, Washington, DC. Such deliveries are only accepted during the Docket’s normal hours of operation, and special arrangements should be made for deliveries of boxed information. Instructions : Direct your comments to Docket ID No. EPA

- HQ

- OAR

- 2007

- 0492
. The EPA' s policy is that all comments received will be included in the public docket Formatted: No underline***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 4 of 790 Formatted: Left without change and may be made available online at www.regulations.gov , including any personal information provided, unless the comment in cludes information claimed to be Confidential Business Information (CBI) or other information whose disclosure is restricted by statute
. Do not submit information that you consider to be CBI or otherwise protected through www.regulations.gov or e - mail
. The www.regulations.gov website is an “anonymous access” system, which means the EPA will not know your identity or contact information unless you provide it in the body of your comment
. If you send an e

mail comment directly to the EPA without going through www.regulations.gov your e mail address will be automatically captured and included as part of the comment that is placed in the publ ic docket and made available on the Internet
. If you submit an electronic comment, the EPA recommends that you include your name and other contact information in the body of your comment and with any disk or CD

- ROM you submit
. If the EPA cannot read your c omment due to technical difficulties and cannot contact you for clarification, the EPA may not be able to consider your comment
. Electronic files should avoid the use of special characters, any form of encryption, and be free of any defects or viruses
. For additional information about EPA’s public docket visit the EPA Docket Center homepage at http://www.epa.gov/epahome/dockets.htm
. Comments on this information collection request should also be sent to the Office of Management and Budget (OMB). See section X.B below for additional information regarding submitting comments to OMB. Docket : The EPA has established a docket for this action under Docket No. EPA

HQ

- OAR

- 200 7

- 0 492
. All documents in the docket a re listed o n the www.regulations.gov website
. This includes documents in the rulemaking docket ( Docket ID No. EPA

- HQ

Formatted: Indent: First line: 0.5" Formatted: Font: Not Bold, Italic***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 5 of 790 Formatted: Left OAR

- 200 7

- 0 492) and a separate docket, established for 200 9 Integrated Science Assessment (Docket No. EPA

- HQ

- ORD

- 2007

- 0517), that has have been incorporated by reference into the rulemaking docket
. All documents in these dockets are listed on the www.regulations.gov website
. Although listed in the index , some information is not publicly available, e.g., CBI or other information whose disclosure is restricted by statute
. Certain other material, such as copyrighted material, is not placed on the Internet and may be viewed, with prior arrangement, at the EP A Docket Center
. Publicly available docket materials are available either electronically in www.regulations.gov or in hard copy at the Air and Radiation Docket and Information Center, EPA/DC, EPA West, Room 3334, 13 01 Constitution Ave., NW, Washington, DC
. The Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal holidays
. The telephone number for the Public Reading Room is (202) 566

- 1744 and the telephone number for the Air and Radiation Docket and Information Center is (202) 566

- 1742. For additional information about EPA’s public docket visit the EPA Docket Center homepage at : http://www.epa.gov/epahome/dockets.htm
. FOR FURTHER INFORMATION CONTACT: Ms. Beth M. Hassett

- Sipple , Health and Environmental Impacts Division, Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, Mail code C504

- 06, Research Triangle Park, NC 27711; telephone: ( 919 ) 54 1

- 4605 ; fax: ( 919 ) 541

- 0237; email: hassett

- sipple.beth@epa.gov

. SUPPLEMENTARY INFORMATION: General Information Availability of Related Information***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 6 of 790 Formatted: Left A number of the documents that are relevant to this rulemaking are available through the EPA’s Office of Air Quality Planning and Standards (OAQPS) Technology Transfer Network (TTN) website at http://www.epa.gov/ttn/naaqs/standards/pm/s _pm_index.html
. These documents include the Plan for Review of the National Ambient Air Quality Standards for Particulate Matter ( U.S. EPA, 2008 a ) , available at http://www.epa.gov/tt

n/naaqs/standards/pm/s_pm_2007_pd.html , the Integrated Science Assessment for Particulate Matter ( U.S. EPA, 20 09a ), available at http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_2007_isa.html , the Quantitative Health Risk Assessment for Particulate Matter ( U.S. EPA, 2010 a ), available at http://www.epa.gov/ttn/

naaqs/standards/pm/s_pm_2007_risk.html , the Particulate Matter Urban

- Focused Visibility Assessment ( U.S. EPA 2010b), available at http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_200 7_risk.html , and the Policy Assessment for the Review of the Particulate Matter National Ambient Air Quality Standards ( U.S. EPA, 201 1 a ), available at http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_2007_pa.html
. These and other related documents are also available for inspection and copying in the EPA docket identified above
. Table of Contents The following topics are discussed in this preamble: I. Executive Summary A. Purpose of this Regulatory Action B. Summary of Major Provisions C. Costs and Benefits II. Background A. Legislative Requirements B. Review of the Air Quality Criteria and Standards for PM***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 7 of 790 Formatted: Left 1. Previous PM NAAQS Reviews 2. Litigation Related to the 2006 PM Standards 3. Current PM NAAQS Review C. Related Control Programs to Implement PM Standards D. Summary of Proposed Revisions to the PM NAAQS E. Organization and Approach to Final PM NAAQS Decisions III. Rationale for Final Decisions on the Primary PM 2.5 Standards A. Background 1. General Approach Used in Previous Reviews 2. Remand of Primary Annual PM 2.5 Standard 3. General Approach Used in the Policy Assessment for the Current Review B. Overview of Health Effects Evidence C. Overview of Quantitative Characterization of Health Risks D. Conclusions on the Adequacy of the Current Primary PM 2.5 Standards 1. Introduction a. Evidence

- and Risk

- based Considerations in the Policy Assessment b. CASAC Advice c. Administrator’s Proposed Conclusions Concerning the Adequacy of the Current Primary PM 2.5 Standar ds 2. Comments on the Need for Revision 3. Administrator’s Final Conclusions Concerning the Adequacy of the Current Primary PM 2.5 Standards E. Conclusions on the Elements of the Primary Fine Particle Standards 1. Indicator 2. Averaging Time 3. Form a. Annual Standard b. 24

- Hour Standard 4. Level a. General Approach for Considering Standard Levels b. Proposed Decisions on Level i. Consideration of Alternative Standard Levels in the Policy Assessment ii. CASAC Advice iii. Administrator’s Proposed Decisions on the Primary PM 2.5 Standard Levels c. Comment s on Standard Levels i. Annual Standard Level ii. 24

- Hour Standard Level d. Administrator’s Final Conclusions on the Primary PM 2.5 Stan dard Levels F. Administrato r’s Final Decisions on the Primary PM 2.5 Standards IV. Rationale for Final Decision on Primary PM 10 Standard***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 8 of 790 Formatted: Left A. Background 1. Previous Reviews of the PM NAAQS a. Reviews Completed in 1987 and 1997 b. Review Completed in 2006 2. Litigation Related to the 2006 Primary PM 10 Standards 3. General Approach Used in the Current Review B. Health Effects Related to Exposure to Thoracic Coarse Particles C. Consideration of the Current and Potential Alternative Standards in the Policy Assessment 1. Consideration of the Current Standard in the Policy Assessment 2. Consideration of Potential Alternative Standards in the Policy Assessment D. CASAC Advice E. Admin istrator’s Proposed Conclusions Concerning the Adequacy of the Current Primary PM 10 Standard F. Public Comments on the Administrator’s Proposed Decision to Retain the Primary PM

10 Standard G. Administrator’s Final Decision on the Primary PM 10 Standard V. Communication of Public Health Information VI. Rationale for Final Decisions on the Secondary PM Standards A. Background 1. Approaches Used in Previous Reviews 2. Remand of 2006 Secondary PM 2.5 Standards 3. General Approach Used in the Policy Assessment for the Current Review B. Proposed Decisions on Secondary PM Standards 1. PM

- related Visibility Impairment a. Nature of PM

- related Visibility Impairment i. Relationship Between Ambient PM and Visibility ii. Temporal Variations of Light Extinction iii. Periods During the Day of Interest for Assessment

of Visibility iv. Exposure Durations of Interest v. Periods of Fog and Rain b. Public Perception of Visibility Impairment c. Summary of Proposed Conclusions i. Adequacy ii. Indicator iii. Averaging Time iv. Form v. Level vi. Administrator’s Proposed Conclusions vii. Related Technical Analysis 2. Other (Non

- Visibility) PM

- related Welfare Effects a. Evidence of Other Welfare Effects Related to PM***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 9 of 790 Formatted: Left b. CASAC Advice c. Summary of Proposed Decisions Regarding Other Welfare Effects C. Comments on Proposed Rule 1. Comments on Proposed Secondary PM Standard for Visibility Protection a. Overview of Comments b. Indicator i. Comments on Calculated vs. Directly Measured Light Extinction ii. Comments on Specific Aspects of Calculated Light Extinction Indicator c. Averaging Time d. Form e. Level i. Comments on Visibility Preference Studies ii. Specific C omments on Level f. Need for a Distinct Secondary Standard g. Legal Issues h. Relationship with Regional Haze Program 2. Comments on the Proposed Decision Regarding Non

- Visibility Welfare Effects D. Conclusions on Secondary PM Standards 1. Conclusions Regarding Secondary PM Standards to Address Non

Visibility Welfare Effects 2. Conclusions Regarding Secondary PM Standards for Visibility Protection E. Administrator’s Final Decisions on Secondary PM Standards VII. Interpretation of the NAAQS for PM A. Amendments to Appendix N: Interpretation of the NAAQS for PM 2.5 1. General 2. Monitoring Considerations 3. Requirements for Data Use and Reporting for Comparison with the NAAQS for PM 2.5 4. Comparisons with the PM 2.5 NAAQS B. Exceptional Events C. Updates for Data Handling Procedures for Reporting the Air Quality Index VIII. Amendments to Ambient Monitoring and Reporting Requirements A. Issues Related to 40 CFR Part 53 (Reference and Equivalent Methods) 1. PM 2.5 and PM 10

- 2.5 Federal Equivalent Methods 2. Use of Chemical Speciation Network (CSN) Methods to Support the Proposed New Secondary PM 2.5 Visibility Index NAAQS B. Changes to 40 CFR Part 58 (Ambient Air Quality Surveillance)***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 10 of 790 Formatted: Left 1. Terminology Changes 2. Special Considerations for Comparability of PM 2.5 Ambient Air Monitoring Data to the NAAQS a. Revoking Use of Population

- Oriented as a Condition for Comparability of PM 2.5 Monitoring Sites to the NAAQS b. Applicability of Micro

- and Middle

- s cale Monitoring Sites to the Annual PM 2.5 NAAQS 3. Changes to Monitoring for the National Ambient Air Monitoring System a. Background b. Primary PM 2.5 NAAQS i. Addition of a Near

- r oad Component to the PM 2.5 Monitoring Network ii. Use of PM 2.5 Continuous FEMs at SLAMS c. Revoking PM 10

- 2.5 Speciation Requirements at NCore Sites d. Measurements for the Proposed New PM 2.5 Visibility Index NAAQS 4. Revisions to the Quality Assurance Requirements for SLAMS, SPM s , and PSD a. Quality Assurance Weight of Evidence b. Quality Assurance Requirements for the Chemical Speciation Network c. Waivers for Maximum Allowable Separation of Collocated PM 2.5 Samplers and Monitors 5. Revisions to Probe and Monitoring Path Siting Criteria a. Near

- road Component to the PM 2.5 Monitoring Network b. CSN Network c. Reinsertion of Table E

- 1 to Appendix E 6. Additional Ambient Air Monitoring Topics a. Annual Monitoring Network Plans and Periodic Assessment b. O perating Schedules c. Data Reporting and Certification for CSN and IMPROVE Data d. Requirements for Archiving Filters IX. Clean Air Act Implementation Requirements for the PM NAAQS A. Designation of Areas 1. Overview of Clean Air Act Designations Requirements 2. Proposed Designations Schedules 3. Comments and Responses 4. Final Intended Designations Schedules B. Section 110(a)(2) Infrastructure SIP Requirements C. Implementing the Revised Primary Annual PM 2.5 NAAQS in Nonattainment Areas D. Prevention of Significant Deterioration and Nonattainment New Source Review Programs for the Revised Primary Annual PM 2.5 NAAQS***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 11 of 790 Formatted: Left 1. Prevention of Significant Deterioration a. Transition Provision ( Grandfathering ) i. Proposal ii. Comments and Responses iii. Final Action b. Modeling Tools and Guidance Applicable to the Rev ised Primary Annual PM 2.5 NAAQS c. PSD Screening Tools: Significant Emissions Rates, Significant Impact Levels, and Significant Modeling Mo nitor ing Concentration d. PSD Increments e. Other PSD Tra nsi tion Issues 2. Nonattainment New Source Review E. Transportation Conformity P rogram F. General Conformity Program X. Statutory and Executive Order Reviews A. Executive Order 12866: Regulatory Planning and Review and Executive Order 13563: Improving Regulation and Regulatory Review B. Paperwork Reduction Act C. Regulatory Flexibility Act D. Unfunded Mandates Reform Act E. Executive Order 13132: Federalism F. Executive Order 13175: Consultation and Coordination with Indian Tribal Governments G. Executive Order 13045: Protection of Children From Environmental Health and Safety Risks H. Executive Order 13211: Actions that Significantly Affect Energy Supply, Distribution, or Use I. National Technology Transfer and Advancement Act J. Executive Order 12898: Federal Actions to Address Environmental Justice in Minority Populations and Low

- Income Populations K. Congres sional Review Act References I. Executive Summary A. Purpose of this Regulatory Action Sections 108 and 109 of the Clean Air Act (CAA) govern the establishment, review, and revision, as appropriate, of the national ambient air quality standards (NAAQS) to protect public health and welfare. The CAA requires periodic review of the air quality criteria

– the science upon which the standards are based

– and the standards***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 12 of 790 Formatted: Left themselves. This rulemaking is being done pursuant to these statutory requirements. The schedule for completing this review is established by a court order. In 2006, the EPA comp leted its last review of the PM NAAQS. In that review, the EPA took three principal actions: (1) With regard to fine particles (generally referring to particles less than or equal to 2.5 micrometers (μm) in diameter, PM 2.5 ), at that time, the EPA revised t

he level of the primary 24

- hour PM 2.5 standard from 65 to 35 μg/m 3 and retained the level of the primary annual PM 2.5 standard
. ; (2) With regard to the primary standards for particles less than or equal to 10 μm in diameter (PM 10 ), the EPA retained the primary 24

- hour PM 10 standard to continue to provide protection against effects associated with short

- term exposure to thoracic coarse particles (i.e., PM 10

- 2.5 ) and revoked the primary annual PM 10 standard ; and (3) t he EPA also revised the secondary stand ards to be identical in all respects to the primary standards. In subsequent litigation, the U.S. Court of Appeals for the District of Columbia Circuit remanded the primary annual PM 2.5 standard to the EPA because the Agency had failed to explain adequatel y why the standard provided the requisite protection from both short

- and long

- term exposures to fine particles, including protection for at

- risk populations such as children. The c ourt remanded the secondary PM 2.5 standards to the EPA because the A gency f ailed to explain adequately why setting the secondary standards identical to the primary standards provided the required protection for public welfare, including protection from PM

- related visibility impairment. The EPA initiated this review in June 2007. Between 2007 and 2011, the EPA prepared draft and final Integrated Science Assessments, Risk and Exposure Assessments, and Policy Assessments. Multiple drafts of all of these documents were***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 13 of 790 Formatted: Left subject to review by the public and were peer review ed by the EPA’s Clean Air Scientific Advisory Committee (CASAC)
. The EPA proposed revisions to the primary and secondary PM NAAQS on June 29, 2012 (77 FR 38890 ). This final rulemaking is the final step in the review process
. In this rulemaking, t

he EPA is revisin g the suite of standards for PM to provide requisite protection of public health and welfare
. The EPA is revisin g the PSD permitting regulations to address the changes in the PM NAAQS. In addition, t he EPA is updat

ing the Air Quality Index ( AQI ) fo r PM 2.5 and mak ing changes in the data handling conventions for PM and ambient air monitoring, reporting , and network design requirements to correspond with the changes to the PM NAAQS
. B. Summary of Major Provisions With regard to the primary standards for fine particles, the EPA is revis ing the annual PM 2.5 standard by lowering the level from 15.0 to 12 .0 μg/m 3 so as to provide increased protection against health effects associated with long

- and short

- term exposures
. The EPA is retain ing the level (35 μg/m 3 ) and the form (98 th percentile) of the 24

- hour PM 2.5 standard to continue to provide supplemental protection against health effects associated with short

- term exposures. This action provide s increased protection fo r children, older adults, persons with pre

- existing heart and lung disease, and other at

- risk populations against an array of PM 2.5 - related adverse health effects that include premature mortality, increased hospital admissions and emergency department visi ts, and development of chronic respiratory disease. The EPA also is eliminat ing spatial averaging provisions as part of the form of the annual standard to avoid potential disproportionate impacts on at

- risk populations
.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 14 of 790 Formatted: Left The final decisions for the primary annual and 24

- hour PM 2.5 standard s are within the range s that CASAC advised the Agency to consider. These decisions are based on an integrative assessment of an extensive body of new scientific evidence, which substantially strengthens what was known about PM 2.5 - related health effects in the last review , including extended analyses of key epidemiological studies, and evidence of health effects observed at lower ambient PM 2.5 concentrations , including effects in areas that likely met the current standards. T he revised suite of PM 2.5 standards also reflect s consideration of a quantitative risk assessment that estimates public health risks likely to remain upon just meeting the current and various alternative standards
. Based on this information, the Administra tor conclude s that the current primary PM 2.5 standards are not requisite to protect public health with an adequate margin of safety, as required by the CAA, and that these revisions are warranted to provide the appropriate degree of increased public health protection. With regard to the primary standard for thoracic coarse particles ( PM 10

- 2.5 , ) , ) , the EPA is retain ing the current 24

- hour PM 10 standard, with a level of 150 μg/m 3 and a one

expected exceedance form, to continue to provide protection against effects associated with short

- term exposure to PM 10

- 2.5 including premature mortality and increased hospital admissions and emergency department visits. In reaching this decisio n, the Administrator conclude s that the available health evidence and air quality information for PM 10

- 2.5 , taken together with the considerable uncertainties and limitations associated with that information, suggests that a standard is needed to protect a gainst short

- term exposure to all types of PM 10

- 2.5 and that the degree of public health protection provided against short

-***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 15 of 790 Formatted: Left term exposures to PM 10

- 2.5 does not need to be increased beyond that provided by the current PM 10 standard. With regard to the secon dary PM standards, the Administrator is retaining the current suite of secondary PM standards , except for a change to the form of the annual PM 2.5 standard. Specifically, the EPA is retaining the current secondary 24

- hour PM 2.5 and PM 10 standard s to addres s PM

- related non

- visibility welfare effects including ecological effects, effects on materials, and climate impacts , and is revising only the form of the secondary annual PM 2.5 standard to remove the option for spatial averaging consistent with this change to the primary annual PM 2.5 standard. This suite of secondary standards address es PM

- related non

- visibility welfare effects including ecological effects, effects on materials, and climate impacts
. With respect to PM

- related visibility impairment, the Administrator has identified a target degree of protection, defined in terms of a PM 2.5 visibility index (based on speciated PM 2.5 mass concentrations and relative humidity data to calculate PM 2.5 ligh t extinction), a 24

- hour averaging time, and a 90 th percentile form, averaged over 3 years, and a level of 30 deciviews (dv), which she judges to be requisite to protect public welfare with regard to visual air quality
. (VAQ)
. The EPA’s analysis of monitor ing data provides the basis for concluding that the current secondary 24

- hour PM 2.5 standard would provide sufficient protection, and in some areas greater protection, relative to this target protection level. Adding a distinct secondary standard to addres s visibility would not affect this protection. Since sufficient protection from visibility impairment will be provided for all areas of the country without adoption of a distinct secondary standard, and adoption of a distinct secondary standard will not ch ange the degree of over

- protection of visual air quality VAQ provided for some areas of***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 16 of 790 Formatted: Left the country by the secondary 24

- hour PM 2.5 standard, the Administrator judges that adoption of a distinct secondary standard , in addition to the current suite of seconda ry standards, is not needed to provide requisite protection for both visibility and non

visibility related welfare effects. The revisions to the PM NAAQS trigger s trigger a process under which states (and tribes, if they choose) will make recommendations to the Administrator regarding designations, identifying areas of the country that either meet or do not meet the revised NAAQS. States will also review, modify and supplement their existing state implementation plans , (SIPs) , as needed
. With regard to these implementation

- related activities, t

he EPA intends to promulgate a separate implementation rule on a schedule that provides timely clarity to the states, tribes, and other parties responsible for NAAQS implementation. The NAAQS revisions also affect the a pplicable air permitting requirement , but cause no significant change to the transportation conformity and general conformity processes. T he EPA is revis ing its PSD regulations to provide limited grandfathering from the requirements that result from the re vised PM NAAQS for permit applications for which the reviewing authority has first published public notice that a draft permit or preliminary determination for the permit has been issued prior to the effective date of the revised PM NAAQS. On other topics , the EPA is chang ing the Air Quality Index ( AQI ) for PM 2.5 to be consistent with the revise d primary PM 2.5 NAAQS . The EPA also is revisin g the data handling procedures for PM 2.5 consistent with the revise d PM 2.5 NAAQS including the computations necessary for determining when the standards are met and the measurement data that are appropriate for comparison to the standards. With regard to monitoring

-***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 17 of 790 Formatted: Left related activities, the EPA is updat ing several aspects of the monitori ng regulations and specifically requir ing that a small number of PM 2.5 monitors be relocated to be collocated with measurements of other pollutants (e.g., nitrogen dioxide, carbon monoxide) in the

near - road environment. C. Costs and Benefits In setting the NA AQS, the EPA may not consider the costs of implementing the standards. This was confirmed by the United States Supreme Court in Whitman v. American Trucking Associations , 531 U.S. 457, 465

- 472, 475

- 76 (2001), as discussed not ed in section II.A of this notice. As has traditionally been done in NAAQS rulemaking, the EPA has conducted a Regulatory Impact Analysis (RIA) to provide the public with information on the potential costs and benefits of attaining several alternative PM 2.5 standards. In NAAQS rulemaking, the RIA is done for informational purposes only, and the final decisions on the NAAQS in this rulemaking are not in any way based on consideration of the information or analyses in the RIA. The RIA fulfills the requirements of Executive Order s 13563 and 12866

. The summary of the RIA, which is discussed in more detail below in section X.A , estimates benefits ranging from $ 4,000 million to $9.1 00 million at a 3 percent discount rate and $ 3,600 million to $ 8,200 million at a 7 percent discount rate in 2020 and costs ranging from $ 53 million to $ 350 million per year at a 7 percent discount rate
. II. Background A. Legislative Requirements Two sections of the CAA govern the establishment , review and revision of the NAAQS
. Section 108 (42 U.S.C. 7408) directs the Administrator to identify and list***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 18 of 790 Formatted: Left certain air pollutants and then to issue air quality criteria for those pollutants
. The Administrator is to list those air pollutants that in her “judgment, cause or contribute to air pollution wh ich may reasonably be anticipated to endanger public health or welfare;” “the presence of which in the ambient air results from numerous or diverse mobile or stationary sources;” and “for which . . . [the Administrator] plans to issue air quality criteria... ” Air quality criteria are intended to “accurately reflect the latest scientific knowledge useful in indicating the kind and extent of all identifiable effects on public health or welfare which may be expected from the presence of [a] pollutant in the ambi ent air . . .” 42 U.S.C. 7408(b)

. Section 109 (42 U.S.C. 7409) directs the Administrator to propose and promulgate “primary” and “secondary” NAAQS for pollutants for which air quality criteria are issued
. Section 109(b)(1) defines a primary standard as one “the attainment and maintenance of which in the judgment of the Administrator, based on such criteria and allowing an adequate margin of safety, are requisite to protect the public health.” 1 A secondary standard, as defined in section 109(b)(2), must “spe cify a level of air quality the attainment and maintenance of which, in the judgment of the Administrator, based on such criteria, is requisite to protect the public welfare from any known or anticipated adverse effects associated with the presence of [the ] pollutant in the ambient air.” 2

1 The legislative history of section 109 indicates that a primary standard is to be set at “the maximum permissible ambient air level . . . which will protect the health of any [sensitive] group of the population,” and that for thi s purpose “reference should be made to a representative sample of persons comprising the sensitive group rather than to a single person in such a group ” .” S. Rep. No. 91

- 1196, 91st Cong., 2d Sess. 10 (1970). 2 Welfare effects as defined in section 302(h) ( 42 U.S.C. 7602(h)) include, but are not limited to, “effects on soils, water, crops, vegetation, man

- made materials, animals, wildlife, weather, visibility and climate, damage to and deterioration of property, and hazards to transportation, as well as effe cts on economic values and on personal comfort and well

- being.”***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 19 of 790 Formatted: Left The requirement that primary standards provide an adequate margin of safety was intended to address uncertainties associated with inconclusive scientific and technical information available at the time of standard setting
. It was also intended to provide a reasonable degree of protection against hazards that research has not yet identified
. See Lead Industries Association v. EPA , 647 F.2d 1130, 1154 (D.C. Cir 1980) ; American Petroleum Institute v. Costle , 665 F.2d 1176, 11 86 (D.C. Cir. 1981 ; ) ; American Farm Bureau Federation v. EPA , 559 F. 3d 512, 533 (D.C. Cir. 2009); Association of Battery Recyclers v. EPA , 604 F. 3d 613, 617

- 18 (D.C. Cir. 2010)
. Both kinds of uncertainties are components of the risk associated with pollu tion at levels below those at which human health effects can be said to occur with reasonable scientific certainty
. Thus, in selecting primary standards that provide an adequate margin of safety, the Administrator is seeking not only to prevent pollution l evels that have been demonstrated to be harmful but also to prevent lower pollutant levels that may pose an unacceptable risk of harm, even if the risk is not precisely identified as to nature or degree
. The CAA does not require the Administrator to establish a primary NAAQS at a zero

- risk level or at background concentration levels, see Lead Industries v. EPA , 647 F.2d at 1156 n.51, but rather at a level that reduces risk sufficiently so as to protect public heal th with an adequate margin of safety. In addressing the requirement for an adequate margin of safety, the EPA considers such factors as the nature and severity of the health effects involved, the size of at
- risk population(s), and the kind and degree of th e uncertainties that must be addressed
. The selection of any particular approach to providing an adequate margin of safety is a policy choice left specifically to the Administrator’s judgment

. See Lead Industries***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 20 of 790 Formatted: Left Association v. EPA , 647 F.2d at 1161

- 62; Wh itman v. American Trucking Associations , 531 U.S. 457, 495 (2001). In setting standards that are “requisite” to protect public health and welfare, as provided in section 109(b), the EPA’s task is to establish standards that are neither more nor less string ent than necessary for these purposes
. In so doing, the EPA may not consider the costs of implementing the standards
. See generally, Whitman v. American Trucking Associations , 531 U.S. 457, 465

- 472, 475

- 76 (2001)
. Likewise, “[a]ttainability and technologic al feasibility are not relevant considerations in the promulgation of national ambient air quality standards.” American Petroleum Institute v. Costle , 665 F. 2d at 1185. Section 109(d)(1) requires that “not later than December 31, 1980, and at 5

- year inter vals thereafter, the Administrator shall complete a thorough review of the criteria published under section 108 and the national ambient air quality standards . . . and shall make such revisions in such criteria and standards and promulgate such new standa rds as may be appropriate . . . ” Section 109(d)(2) requires that an independent scientific review committee “shall complete a review of the criteria . . . and the national primary and secondary ambient air quality standards. . . and shall recommend to the Administrator any new . . . standards and revisions of existing criteria and standards as may be appropriate . . . .” Since the early 1980's, this independent review function has been performed by the CASAC. 3

3 The CASAC PM Review Panel is comprised of the seven members of the chartered CASAC, supplemented by fifteen subject

- matter experts appointed by the Administrator to provide additional scient ific expertise relevant to this review of the PM NAAQS. Lists of current CASAC members and of members of the CASAC PM Review Panel review panels are available at: http://yosemite.epa.gov/sab/sabproduct.nsf/WebCASAC/CommitteesandMembership?Op***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 21 of 790 Formatted: Left
B. Review of the Air Quality Criteria and Standa rds for PM 1. Previous PM NAAQS Reviews The EPA initially established NAAQS for PM under section 109 of the CAA in 1971
. Since then, the Agency has made a number of changes to these standards to reflect continually expanding scientific information, particularly with respect to the selection of indicator

4 and level
. Table 1 provides a summary of the PM NAAQS that have been promulgated to date
. These decisions are briefly discussed below
. In 1971, the EPA established NAAQS for PM based on the original air quality criteria document (DHEW, 1969; 36 FR 8186, April 30, 1971)
. The reference method specified for determining attainment of the original standards was the high

- volume sampler, which collects PM up to a nominal size of 25 to 45 μm (referred to as total suspended particles or TSP)
. The primary standards (measured by the indicator TSP) were 260 μg/m 3 , 24

- hour average, not to be exceeded more than once per year, and 75 μg/m 3 , annual geometric mean
. The secondary standard was 150 μg/m 3 , 24

- hour average , not to be exceeded more than once per year. In October 1979, the EPA announced the first periodic review of the criteria and NAAQS for PM, and significant revisions to the original standards were promulgated in 1987 (52 FR 24634, July 1, 1987)
. In that d ecision, the EPA changed the indicator for PM from TSP to PM 10 , the latter including particles with an aerodynamic diameter less than or equal to a nominal 10 μm, which delineates thoracic particles (i.e., that subset of

enDocument
. Members of the CASAC PM Review Panel are listed in the CASAC letters providing advice on draft assessment documents (Samet, 2009a

- f , 2012a

- d). 4 Particulate matter is the generic term for a broad class of chemically and physically diverse substances that exist as discrete particles (liquid droplets or solids) over a wide range of sizes, such that the indicator for a PM NAAQS has historically been defined in terms of particle size ranges.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 22 of 790 Formatted: Left inhalable particles small enough to penetrate beyond the larynx to the thoracic region of the respiratory tract)
. The EPA also revised the primary standards by (1) replacing the 24

- hour TSP standard with a 24

- hour PM 10 standard of 150 μg/m 3 with no more than one expected exceedance per year and (2) replacing the annual TSP standard with a PM 10 standard of 50 μg/m 3 , annual arithmetic mean
. The secondary standard was revised by replacing it with 24

- hour and annual PM 10 standards identical in all respects to the primary standards
. The revisions also included a new reference method for the measurement of PM 10 in the ambient air and rules for determining attainment of the new standards
. On judicial review, the revised standards were upheld in all respects
. Natural Resources Defense Council v. EPA , 902 F. 2d 962 (D.C. Cir. 1990). In April 1994, the EPA announced its plans for the second periodic review of the criteria and NAAQS for PM, and promulgated significant revisions to the NAAQS in 1997 (62 FR 38652, July 18, 1997)
. Most significantly, the EP A determined that although the PM NAAQS should continue to focus on thoracic particles (PM 10 ), the fine and coarse fractions of PM 10 should be considered separately
. New standards were added, using PM 2.5 as the indicator for fine particles
. The PM 10 standards were retained for the purpose of regulating the coarse fraction of PM 10 (referred to as thoracic coarse particles or PM 10

- 2.5 ). 5 The EPA established two new PM 2.5 standards: an annual standard of 15 .0 μg/m 3 , based on the 3

- year average of annual arithmetic mean PM 2.5 concentrations from single or multiple monitors sited to represent community

- wide air quality 6 and a 24

- hour

5 See 40 CFR parts 50, 53, and 58 for more information on reference and equivalent methods for measuring PM in ambient air. 6 Monitoring stations sited to represent community

- wide air quality would typically be at the neighborhood or urban

- scale; however, where a population

- oriented micro or middle

scale PM 2.5 monitoring station represents many such locations throughout a metropolitan Formatted: No widow/orphan control, Don't adjust space between Latin and Asian text, Don't adjust space between Asian text and numbers***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 23 of 790 Formatted: Left standard of 65 μg/m 3 , based on the 3

- year average of the 98 th percentile of 24

- hour PM 2.5

area, these smaller scales might also be considered to represent community

- wide ai r quality [40 CFR part 58, appendix D, 4.7.1(b)].***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 24 of 790 Formatted: Left Table 1 . Summary of National Ambi ent Air Quality Standards Promulgated for PM 1971 - 2006 a Final Rule Indicator Averaging Time Level Form
1971 36 FR 8186 April 30, 1971 TSP 24

- hour 260 μg/m 3 (primary) 150 μg/m 3 (secondary) Not to be exceeded more than

once per year
Annual 75 μg/m 3

(primary) Annual average
1987 52 FR 24634 July 1, 1987 PM 10 24

- hour 150 μg/m 3 Not to be exceeded more than once per year on average over a 3

- year period Annual 50 μg/m 3 Annual arithmetic mean, averaged over 3 years

1997 62 FR 38652 July 18, 1997 PM 2.5 24

- hour 65 μg/m 3 98 th percentile, averaged over 3 years b Annual 15 .0 μg/m 3 Annual arithmetic mean, averaged over 3 years c,d

PM 10 24

- hour 150 μg/m 3 Initially promulgated 99 th percentile, averaged over 3 years; when 1997 standards for PM 10 were vacated, the form of 1987 standards remained in place (not to be exceeded more than once per year on average over a 3

- year

period) Annual 50 μg/m 3 Annual arithmetic mean, averaged over 3 years

2006 71 FR 61144 October 17, 2006 PM 2.5 24

- hour 35 μg/m 3 98 th percentile, averaged over 3 years b Annual 15 .0 μg/m 3 Annual arithmetic mean, averaged over 3 years c,e
PM 10 24

- hour 150 μg/m 3 Not to be exceeded more than once per year on average over a 3

- year period
a When not specified, primary and secondary standards are identical. b The level of the 24

- hour standard is defined as an integer (zero decimal places) as determined by rounding
. For example, a 3

- year average 98 th percentile concentration of 35.49 μg/m 3 would round to 35 μg/m 3 and thus meet the 24

- hour standard and a 3

- year***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 25 of 790 Formatted: Left average of 35.50 μg/m 3 would round to 36 and, hence, violate the 24

- hour standard (40 CFR part 50, appendix N). c The level of the annual standard is defined to one decimal place (i.e., 15.0 μg/m 3 ) as determ ined by rounding
. For example, a 3

- year average annual mean of 15.04 μg/m 3 would round to 15.0 μg/m 3 and, thus, meet the annual standard and a 3

- year average of 15.05 μg/m 3 would round to 15.1 μg/m 3 and, hence, violate the annual standard (40 CFR part 50, appendix N). d The level of the standard was to be compared to measurements made at sites that represent “community

- wide air quality” recording the highest level, or, if specific requirements were satisfied, to average measurements from multiple community

- wide air quality monitoring sites (“spatial averaging”). e The EPA tightened the constraints on the spatial averaging criteria by further limiting the conditions under which some areas may average measurements from multiple community

- oriented monitors to determine compliance ( See 71 FR 61165 to 61167, October 17, 2006).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 26 of 790 Formatted: Left suspended particles or TSP)
. The primary standards (measured by the indicator TSP) were 260 μg/m 3 , 24

- hour average, not to be exceeded more than once per year, and 75 μg/m 3 , annual geometric mean
. The secondary standard was 150 μg/m 3 , 24

- hour average, not to be exceeded more than once per year. In October 1979, the EPA announced the first periodic review of the criteria and NAAQS for PM, and significant revisions to the original stan dards were promulgated in 1987 (52 FR 24634, July 1, 1987)
. In that decision, the EPA changed the indicator for PM from TSP to PM 10 , the latter including particles with an aerodynamic diameter less than or equal to a nominal 10 μm, which delineates thoraci c particles (i.e., that subset of inhalable particles small enough to penetrate beyond the larynx to the thoracic region of the respiratory tract)
. The EPA also revised the primary standards by (1) replacing the 24

- hour TSP standard with a 24

- hour PM 10 sta ndard of 150 μg/m 3 with no more than one expected exceedance per year and (2) replacing the annual TSP standard with a PM 10 standard of 50 μg/m 3 , annual arithmetic mean
. The secondary standard was revised by replacing it with 24

- hour and annual PM 10 standa rds identical in all respects to the primary standards
. The revisions also included a new reference method for the measurement of PM 10 in the ambient air and rules for determining attainment of the new standards
. On judicial review, the revised standards w ere upheld in all respects
. Natural Resources Defense Council v. EPA , 902 F. 2d 962 (D.C. Cir. 1990). In April 1994, the EPA announced its plans for the second periodic review of the criteria and NAAQS for PM, and promulgated significant revisions to the NAAQS in 1997 (62 FR 38652, July 18, 1997)
. Most significantly, the EPA determined that although the PM NAAQS should continue to focus on thoracic particles (PM 10 ), the fine and coarse Formatted: Indent: First line: 0"***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 27 of 790 Formatted: Left fractions of PM 10 should be considered separately
. New standards were a dded, using PM 2.5 as the indicator for fine particles
. The PM 10 standards were retained for the purpose of regulating the coarse fraction of PM 10 (referred to as thoracic coarse particles or PM 10

-
2.5 ). 7 The EPA established two new PM 2.5 standards: an annua l standard of 15 .0 μg/m 3 , based on the 3

- year average of annual arithmetic mean PM 2.5 concentrations from single or multiple monitors sited to represent community

- wide air quality 8 and a 24

- hour standard of 65 μg/m 3 , based on the 3

- year average of the 98 th percentile of 24

- hour PM 2.5 concentrations at each population

- oriented monitor 9 within an area
. Also, the EPA established a new reference method for the measurement of PM 2.5 in the ambient air and rules for determining attainment of the new standards
. To continue to address thoracic coarse particles, the annual PM 10 standard was retained, while the form, but not the level, of the 24

- hour PM 10 standard was revised to be based on the 99 th percentile of 24

- hour PM 10 concentrations at each monitor in an area
. The EPA revised the secondary standards by making them identical in all respects to the primary standards. Following promulgation of the revised PM NAAQS in 1997, petitions for review were filed by a large number of parties, addressing a broad range of iss ues . In May 1998, a three

- judge panel of the U.S. Court of Appeals for the District of Columbia Circuit issued an initial decision that upheld the EPA’s decision to establish fine particle
7 See 40 CFR parts 50, 53, and 58 for more information on reference and equivalent methods for measuring PM in ambient air. 8 Monitoring stations sited to represent community

- wide air quality would typically be at the neighborhood or urban

- scale; however, where a population

- oriented micro or middle

scale PM 2.5 monitoring station represents many such locations throughout a metropolitan area, these smaller scales might also be consid ered to represent community

- wide air quality [40 CFR part 58, appendix D, 4.7.1(b)]. 9 Population

- oriented monitoring (or sites) means residential areas, commercial areas, recreational areas, industrial areas where workers from more than one company are lo cated, and other areas where a substantial number of people may spend a significant fraction of their day (40 CFR 58.1).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 28 of 790 Formatted: Left standards, holding that "the growing empirical evidence demonstrati ng a relationship between fine particle pollution and adverse health effects amply justifies establishment of new fine particle standards." American Trucking Associations v. EPA , 175 F. 3d 1027, 1055

- 56 (D.C. Cir. 1999), rehearing granted in part and denie d in part, 195 F. 3d 4 (D.C. Cir. 1999), affirmed in part and reversed in part, Whitman v. American Trucking Associations , 531 U.S. 457 (2001)
. The panel also found "ample support" for the EPA's decision to regulate coarse particle pollution, but vacated t he 1997 PM 10 standards, concluding, in part, that PM 10 is a "poorly matched indicator for coarse particulate pollution" because it includes fine particles
. Id . at 1053

- 55
. Pursuant to the court’s decision, the EPA removed the vacated 1997 PM 10 standards fr om the CFR (69 FR 45592, July 30, 2004) and deleted the regulatory provision [at 40 CFR section 50.6(d)] that controlled the transition from the pre

- existing 1987 PM 10 standards to the 1997 PM 10 standards
. The pre

- existing 1987 PM 10 standards remained in p lace (65 FR 80776, December 22, 2000)
. The court also upheld the EPA’s determination not to establish more stringent secondary standards for fine particles to address effects on visibility (175 F. 3d at 1027). More generally, the panel held (over a strong dissent) that the EPA’s approach to establishing the level of the standards in 1997, both for the PM and for the ozone NAAQS promulgated on the same day, effected “an unconstitutional delegation of legislative authority.” Id . at 1034

- 40
. Although the panel stated that “the factors EPA uses in determining the degree of public health concern associated with different levels of ozone and PM are reasonable,” it remanded the rule to the EPA, stating that when the EPA considers these factors for potential non

- thr eshold pollutants “what EPA lacks is Formatted: Font: Italic***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 29 of 790 Formatted: Left any determinate criterion for drawing lines” to determine where the standards should be set
. Consistent with the EPA’s long

- standing interpretation and D.C. Circuit precedent, the panel also reaffirmed its prior holding s that in setting NAAQS , the EPA is “not permitted to consider the cost of implementing those standards
. ” Id . at 1040

- 41. On EPA’s petition for rehearing, the panel adhered to its position on these points

. American Trucking Associations v. EPA , 195 F. 3d 4 (D.C. Cir. 1999)
. The full Court of Appeals denied the EPA’s request for rehearing en banc , with five judges dissenting
. Id
. at 13
. Both sides filed cross appeals on these issues to the United States Supreme Court, which granted certiorari
. In February 20 01, the Supreme Court issued a unanimous decision upholding the EPA’s position on both the constitutional and cost issues

. Whitman v. American Trucking Associations , 531 U.S. 457, 464, 475

- 76
. On the constitutional issue, the Court held that the statutory requirement that NAAQS be “requisite” to protect public health with an adequate margin of safety sufficiently cabined the EPA’s discretion, affirming the EPA’s approach of setting standards tha t are neither more nor less stringent than necessary
. The Supreme Court remanded the case to the Court of Appeals for resolution of any remaining issues that had not been addressed in that court’s earlier rulings

. I d . at 475

- 76
. In March 2002, the Court of Appeals rejected all remaining challenges to the standards, holding under the statutory standard of review that the EPA’s PM 2.5 standards were reasonably supported by the administrative record and were not “arbitrary and capricious

. ” American Trucking Ass ociations Association v. EPA , 283 F. 3d 355, 369

- 72 (D.C. Cir. 2002). In October 1997, the EPA published its plans for the next periodic review of the air quality criteria and NAAQS for PM (62 FR 55201, October 23, 1997)
. After CASAC Formatted: Font: Italic

Formatted: Font: Italic***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 30 of 790 Formatted: Left and public review of several drafts, the EPA’s National Center for Environmental Assessment (NCEA) finalized the Air Quality Criteria Document for Particulate Matter (henceforth, AQCD or the "Criteria Document") in October 2004 ( U.S. EPA, 2004) and OAQPS finalized an assessmen t document, Particulate Matter Health Risk Assessment for Selected Urban Areas (Abt Associates, 2005), and the Review of the National Ambient Air Quality Standards for Particulate Matter: Policy Assessment of Scientific and Technical Information , in Decemb er 2005 ( henceforth, “Staff Paper,” U.S. EPA, 2005)
. In conjunction with their its review of the Staff Paper, CASAC provided advice to the Admin i strator on revisions to the PM NAAQS (Henderson, 2005a)
. In particular, most CASAC PM Panel members favored revi sing the level of the primary 24

- hour PM 2.5 standard in with in the range of 35 to 30 μg/m 3 with a 98 th percentile form, in concert with revising the level of the primary annual PM 2.5 standard in with in the range of 14 to 13 μg/m 3 (Henderson, 2005a, p.7)
. For thoracic coarse particles, the Panel had reservations in recommending a primary 24

- hour PM 10

- 2.5 standard, and agreed that there was a need for more research on the health effects of thoracic coarse particles (Henderson, 2005b)
. With regard to secondary s tandards, most Panel members strongly supported establishing a new, distinct secondary PM 2.5 standard to protect urban visibility (Henderson, 2005a, p. 9)
. On January 17, 2006, the EPA proposed to revise the primary and secondary NAAQS for PM (71 FR 2620) and solicited comment on a broad range of options
. Proposed revisions included: (1) revising the level of the primary 24

- hour PM 2.5 standard to 35 μg/m 3 ; (2) revising the form, but not the level, of the primary annual PM 2.5 standard by tightening the cons traints on the use of spatial averaging; (3) replacing the primary 24

-***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 31 of 790 Formatted: Left

- hour PM 10 standard with a 24

- hour standard defined in terms of a new indicator, PM 10

-
2.5 , which was qualified so as to include any ambient mix of PM 10

- 2.5 dominated by particles generat ed by high

- density traffic on paved roads, industrial sources, and construction sources, and to exclude any ambient mix of particles dominated by rural windblown dust and soils and agricultural and mining sources (71 FR 2667 to 2668), set at a level of 70 μg/m 3 based on the 3

- year average of the 98 th percentile of 24

- hour PM 10

-

- 2.5 concentrations; (4) revoking the primary annual PM 10 standard; and (5) revising the secondary standards by making them identical in all respects to the proposed suite of primary standards for fine and coarse particles. 10 Subsequent to the proposal, CASAC provided additional advice to the EPA in a letter to the Administrator requesting reconsideration of CASAC’s recommendations for both the primary and secondary PM 2.5 standards as w ell as the standards for thoracic coarse particles (Henderson, 2006a). On October 17, 2006, the EPA published revisions to the PM NAAQS to provide increased protection of public health and welfare (71 FR 61144)
. With regard to the primary and secondary sta ndards for fine particles, the EPA revised the level of the primary 24

- hour PM 2.5 standard to 35 μg/m 3 , retained the level of the primary annual PM 2.5 standard at 15 .0 μg/m 3 , and revised the form of the primary annual PM 2.5 standard by adding further const

raints on the optional use of spatial averaging
. The EPA revised the secondary standards for fine particles by making them identical in all respects to the primary standards
. With regard to the primary and secondary standards for thoracic coarse particles, the EPA retained the level and form of the 24

- hour PM 10 standard (such
10 In recognition of an alternative view expressed by most members of the CASAC PM Panel, the Agency also solicited comments on a subdai ly (4

- to 8

- hour averaging time) secondary PM 2.5 standard to address visibility impairment, considering alternative standard levels within a range of 20 to 30 μg/m 3 in conjunction with a form within a range of the 92 nd to 98 th percentile (71 FR 2685, Janua ry 17, 2006).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 32 of 790 Formatted: Left that the standard remained at a level of 150 μg/m 3 with a one

- expected exceedance form and retained the PM 10 indicator ) and revoked the annual PM 10 standard
. The EPA also established a new Federal Reference Method (FRM) for the measurement of PM 10

- 2.5 in the ambient air (71 FR 61212 to 13)
. Although the standards for thoracic coarse particles were not defined in terms of a PM 10

- 2.5 indicator, the EPA adopted a new FRM for PM 10

-

- 2.5 to f acilitate consistent research on PM 10

- 2.5 air quality and health effects and to promote commercial development of Federal Equivalent Methods (FEMs) to support future reviews of the PM NAAQS ( 71 FR 61212 /2 ). Following issuance of the final rule, CASAC artic ulated its concern that the “EPA’s final rule on the NAAQS for PM does not reflect several important aspects of the CASAC’s advice” (Henderson et al., 2006b , p. 1 )
. With regard to the primary PM 2.5 annual standard, CASAC expressed serious concerns regarding the decision to retain the level of the standard at 15 μg/m 3

. Specifically, CASAC stated, “It is the CASAC’s consensus scientific opinion that the decision to retain without change the annual PM 2 .5 standard does not provide an ‘adequate margin of safety... requisite to protect the public health’ (as required by the Clean Air Act), leaving parts of the population of this country at significant risk of adverse health effects from exposure to fine PM” (Henderson et al., 2006b, p. 2)
. Furthermore, CASAC pointed out that its recommendations “were consistent with the mainstream scientific advice that EPA received from virtually every major medical association and public health organization that provided th eir input to the***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 33 of 790 Formatted: Left Agency ” (Henderson et al., 2006b, p. 2). 11 With regard to EPA’s final decision to retain the 24

- hour PM 10 standard for thoracic coarse particles, CASAC had mixed views with regard to the decision to retain the 24

- hour standard and the conti nued use of PM 10 as the indicator of coarse particles, while also recognizing the need to have a standard in place to protect against effects associated with short

- term exposures to thoracic coarse particles (Henderson et al., 2006b, p. 2)
. With regard to the EPA’s final decision to revise the secondary PM 2.5 standards to be identical in all respects to the revised primary PM 2.5 standards, CASAC expressed concerns that its advice to establish a distinct secondary standard for fine particles to address visib ility impairment was not followed and emphasized “that continuing to rely on the primary standard to protect against all PM

-

- related adverse environmental and welfare effects assures neglect, and will allow substantial continued degradation, of visual air quality over large areas of the country ” (Henderson et al, 2006b, p. 2)
. 2. Litigation Related to the 2006 PM Standards Several parties filed petitions for review following promulgation of the revised PM NAAQS in 2006
. These petitions addressed the following issues: (1) selecting the level of the primary annual PM 2.5 standard; (2) retaining PM 10 as the indicator of a standard for thoracic coarse particles, retaining the level and form of the 24

- hour PM 10 standard, and revoking the PM 10 annual standard; and (3) setting the secondary PM 2.5 standards identical to the primary standards
. On February 24, 2009, the U.S. Court of Appeals for the District of Columbia Circuit issued its opinion in the case American
11 CASAC specifically identified input provided by the American Medical Association, the American Thoracic Society, the American Lung Association, the American Academy of Pediatrics, the American College of Cardiology, the American Heart Assoc iation, the American Cancer Society, the American Public Health Association, and the National Association of Local Boards of Health (Henderson et al., 2006b, p. 2).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 34 of 790 Formatted: Left Farm Bureau Federation v. EPA , 559 F. 3d 512 (D.C. Cir. 2009)
. The court remanded the primary annual PM 2.5 NAAQS to the EPA because the EPA failed to adequately explain why the standard provided the requisite protection from both short

- and long

- term exposures to fine particles, including protection for at

- risk populations such as children
. American Farm Bureau Federation v. EPA , 559 F. 3d 512, 520

- 27 (D.C. Cir. 2009)
. With regard to the standards for PM 10 , the court upheld the EPA’s decisions to retain the 24

-

- hour PM 10 standard to provide protection from thoracic coarse particle exposures and to revoke the annual PM 10 standard
. American Farm Bureau Federation v. EPA , 559 F. 2d at 533

- 38
. With regard to the secondary PM 2.5 standards, the court remanded the standards to t

he EPA because the Agency ’s decision was “unreasonable and contrary to the requirements of section 109(b)(2)” of the CAA

. The court further concluded that the EPA failed to adequately explain why setting the secondary PM standards identical to the primary standards provided the required protection for public welfare, including protection from visibility impairment
. American Farm Bureau Federation v. EPA , 559 F. 2d at 528

- 32. The decisions of the court with regard to these three issues are discussed further in sections I II .A.2 , I V .A.2 , and V I .A.2 below
. The EPA is responding to the court’s remands as part of the current review of the PM NAAQS. 3. Current PM NAAQS Review The EPA initiated the current review of the air quality criteria for PM in June 2007 with a g eneral call for information (72 FR 35462, June 28, 2007)
. In July 2007, the EPA held two “kick

- off” workshops on the primary and secondary PM NAAQS,***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 35 of 790 Formatted: Left respectively (72 FR 34003 to 34004, June 20, 2007). 12 These workshops provided an opportunity for a public discussion of the key policy

- relevant issues around which the EPA would structure this PM NAAQS review and the most meaningful new science that would be available to inform our understanding of these iss ues. Based in part on the workshop discussions, the EPA developed a draft I ntegrated R eview P lan outlining the schedule, process, and key policy

- relevant questions that would guide the evaluation of the air quality criteria for PM and the review of the pr imary and secondary PM NAAQS ( U.S. EPA, 2007 a )
. On November 30, 2007, the EPA held a consultation with CASAC on the draft I ntegrated R eview P lan (72 FR 63177, November 8, 2007), which included the opportunity for public comment
. The final I ntegrated R eview P lan ( U.S. EPA, 2008a) incorporated comments from CASAC (Henderson, 2008) and the public on the draft plan as well as input from senior Agency managers. 13 , 14 A major element in the process for reviewing the NAAQS is the development of

12 See workshop materials available at: http://www.regulations.gov/search/Regs/home.html#home Docket ID numbers EPA

- HQ

OAR

- 2007

- 0492

- 008; EPA

- HQ

- OAR

- 2007

- 0492

- 009; EPA

- HQ

- OAR

- 2007

- 0492

- 010; and EPA

- HQ

- OAR

- 2007

- 0492

- 012. 13 The process followed in this review varies from the NAAQS review process described in section 1.1 of the Integrated Review Plan (U.S. EPA, 2008a). On May 21, 2009, Administrator Jackson called for key changes to the NAAQS review process including reinstat ing a policy assessment document that contains staff analyses of the scientific bases for alternative policy options for consideration by senior Agency management prior to rulemaking. In conjunction with this change, the EPA will no longer issue a policy a ssessment in the form of an advance notice of proposed rulemaking (ANPR) as discussed in the Integrated Review Plan (U.S. EPA, 2008a, p. 3). For more information on the overall process followed in this review including a description of the major elements o f the process for reviewing NAAQS see Jackson (2009). 14 All written comments submitted to the Agency are available in the docket for this PM NAAQS review (EPA

- HQ

- OAR

- 2007

- 0429). Transcripts of public meetings and teleconferences held in conjunction with C ASAC’s reviews are also included in the docket.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 36 of 790 Formatted: Left an Integrated Science Assessment
. This document provides a concise evaluation and integration of the policy

- relevant science, including key science judgments upon w hich the risk and exposure assessments build
. As part of the process of preparing the PM I ntegrated S cience A ssessment , NCEA hosted a peer review workshop in June 2008 on preliminary drafts of key I ntegrated S cience A ssessment chapters (73 FR 30391, May 27, 2008)
. CASAC and the public reviewed t he first external review draft I ntegrated S cience A ssessment ( U.S. EP A, 2008b; 73 FR 77686, December 19, 2008) at a meeting held o n April 1 to 2, 2009 (74 FR 2688, February 19, 2009)
. Based on CASAC (Samet, 2009e) and public comments, NCEA prepared a second draft I ntegrated S cience A ssessment ( U.S. EPA, 2009b; 74 FR 38185, July 31, 2009), which was reviewed by CASAC and the public at a meeting held on October 5 and 6, 2009 (74 FR 46586, September 10, 2009)
. Based on CASAC (Samet, 2009f) and public comments, NCEA prepared the final I ntegrated S cience A ssessment titled Integra ted Science Assessment for Particulate Matter , December 2009 ( U.S. EPA, 2009a; 74 FR 66353, December 15, 2009). Building upon the information presented in the PM Integrated Science Assessment, the EPA prepar ed Risk and Exposure Assessment s that provide a concise presentation of the methods, key results, observations, and related uncertainties
. In developing the Risk and Exposure Assessments for this PM NAAQ S review , OAQPS released two planning documents: Particulate Matter National Ambient Air Quality Standards: Scope and Methods Plan for Health Risk and Exposure Assessment and Particulate Matter National Ambient Air Quality Standards: Scope and Methods Plan for Urban Visibility Impact Assessmen t (henceforth, Scope and Methods Plans, U.S. EP A, 2009c,d; 74 FR 11580, March 18, 2009)
. These planning documents outlined the scope Formatted: Underline***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 37 of 790 Formatted: Left and approaches that staff planned to use in conducting quantitative assessments as well as key issues that would be addressed as part of the assessments
. In designing and conducting the initial health risk and visibility impact assessments, th e Agency considered CASAC comments (Samet 2009a,b) on the Scope and Methods Plans made during an April 2009 consultation (74 FR 7688, February 19, 2009) as well as public comments
. CA SAC and the public reviewed t wo draft assessment documents, Risk Assessment to Support the Review of the PM 2.5 Primary National Ambient Air Quality Standards: External Review Draft , September 2009 ( U.S. EPA , 2009e) and Particulate Matter Urban

- Focused Visibility Assessment

- External Review Draft, September 2009 ( U.S. EPA, 2009f) at a meeting held on October 5 and 6, 2009 (74 FR 46586, September 10, 2009)
. Based on CASAC (Samet 2009c,d) and public comments, OAQPS staff revised these draft documents and released second draft assessment documents ( U.S. EPA, 2010d,e) in January and February 2010 (75 FR 4067, January 26, 2010) for CASAC and public review at a meeting held on March 10 and 11, 2010 (75 FR 8062, February 23, 2010)
. Based on CASAC (Samet, 2010a, b) and public comments on the second draft assessment documents, the EPA revised these documents and released final assessment documents titled Quantitative Health Risk Assessment for Particulate Matter, June 2010 ( henceforth , “ Risk Assessment, ” U.S. EPA, 2010a) and Particulate Matter Urban

- Focused Visibility Assessment

– Final Document , July 2010 ( henceforth,

“ Visibility Assessment, ” U.S. EPA, 2010b ) ( 75 FR 39252, July 8, 2010). Based on the scientific and technical information available in this review as assessed in the I ntegrated S cience A ssessment and R isk and E xposure A ssessment s, the EPA staff prepared a Policy Assessment
. The P olicy A ssessment is intended to help Formatted: No underline***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 38 of 790 Formatted: Left “bridge the gap” between the relevant scientific information and assessments and the judgments required of the Administrator in reaching decisions on the NAAQS (Jackson, 2009, attachment, p. 2)
. American Farm Bureau Federation v. EPA  ̧559 F. 3d at 521
. The P olicy A ssessment is not a decision document ; rather it pres ents the EPA staff conclusions related to the broadest range of policy options that could be supported by the currently available information
. A preliminary draft P olicy A ssessment ( U.S. EPA, 2009g) was released in September 2009 for informational purposes and to facilitate discussion with CASAC at the October 5 and 6, 2009 meeting on the overall structure, areas of focus, and level of detail to be included in the P olicy A ssessment
. The E PA considered CASAC’s comments on this preliminary draft in developing a first draft P olicy A ssessment ( U.S. EPA, 2010c; 75 FR 4067, January 26, 2010) that built upon the information presented and assessed in the final I ntegrated S cience A ssessment and

sec ond draft R isk and E xposure A ssessment s . The EPA presented an overview of the first draft P olicy A ssessment at a CASAC meeting on March 10, 2010 (75 FR 8062, February 23, 2010) and it was discussed during public CASAC teleconferences on April 8 and 9, 2010 (75 FR 8062, February 23, 2010) and May 7, 2010 (75 FR 19971, April 16, 2010)
. The EPA develop ed a second draft P olicy A ssessment ( U.S. EPA, 2010f; 75 FR 39253, July 8, 2010) based on CASAC (Samet, 2010c) and public comments on the first draft Policy Ass essment
. CASAC reviewed the second draft document at a meeting on July 26 and 27, 2010 (75 FR 32763, June 9, 2010)
. The EPA staff considered CASAC (Samet, 2010d) and public comments on the second draft P olicy A ssessment in preparing

a final P olicy A ssessme nt titled Policy Assessment for the Review of the Particulate Matter National Ambient Air Quality Standards , April , 2011 ( U.S. EPA, 2011 a ; 76, FR***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 39 of 790 Formatted: Left 22665, April 22, 2011 )
. Thi s document includes final staff conclusions on the adequacy of the current PM standards and alternative standards for consideration
. The schedule for the rulemaking in this review is subject to a court order in a lawsuit filed in February 2012 by a group of plaintiffs who alleged that the EPA had fai led to perform its mandatory duty, under section 109(d)(1), to complete a review of the PM NAAQS within the period provided by statute. American Lung Association and National Parks Conservation Association v. EPA , D.D.C. No. 12

- cv - 00243 (consol. w ith No. 1 2

- cv - 00531) C ourt order s in that case provide that the EPA sign a notice of proposed rulemaking concerning its review of the PM NAAQS no later than June 14, 2012 and a notice of final rulemaking no later than December 14, 2012
. On June 14, 2012, the EPA issued its proposed decision to revise the NAAQS for PM (77 FR 38890 , June 29, 2012) (henceforth “proposal”). In the proposal, the EPA identified revisions to the standards, based on the air quality criteria for PM, and to related data handling conventions and ambient air monitoring, reporting, and network design requirements . The EPA proposed revisions to the prevention of significant deterioration ( PSD ) permitting program with respect to the proposed NAAQS revisions
. The Agency a lso proposed changes to the AQI for PM 2.5 , consistent with the proposed primary PM 2.5 standards. The proposal solicited public comments on alternative primary and secondary standards and related matters. The proposal is summarized in section II.D below. The EPA held two public hearings to receive public comment on the proposed revisions to the PM NAAQS (77 FR 39205 , July 2, 2012) . One hearing took place in Philadelphia, PA on July 17, 2012 and a second hearing took place in Sacramento, CA on***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 40 of 790 Formatted: Left July 19, 2012 . At these public hearings, the EPA heard testimony from 16 8 individuals representing themselves or specific interested organizations. The EPA received m ore than 230,000 comments from members of the public and various interest groups on the proposed revisions to the PM NAAQS by the close of the public comment period on August 31, 2012. Major issues raised in the public comments are discussed throughout the preamble of this final action. A more detailed summary of all significant comments, along with the EPA’s responses (henceforth “Response to Comments”) can be found in the docket for this rulemaking (Docket N o. EPA

- HQ

- OAR

2007

- 0492) ( U.S. EPA, 2012a). In the proposal, t

he EPA recognized that there were a number of new scientific studies on the health effects of PM that ha d been published since the mid

- 200 9 cutoff date for inclusion in the Integrated Science Assessment
. 15 As in the last PM NAAQS review, the EPA committed to conduct a provisional review and assessment of any significant “ new ” studies published since the close of the Integrated Science Assessment , including studies submitted to the EPA during the public comment period
. The purpose of the provisional science assessment was to ensure that the Administrator wa s fully aware of the “ new ” science that has developed since 200 9 before making final decisions on whether to retain or revise the current PM NAAQS
. T he EPA screened and surveyed the recent health literatur e, including studies submitted during the public comment
15 For ease of reference, these studies will be referred to as “new” studies or “new” science, using quotation marks around the word new . Referring to studies that were published too recently to have been incl uded in the 2009 Integrated Science Assessment as “new” studies is intended to clearly differentiate such studies from those that have been published since the last review and which are included in the 2009 Integrated Science Assessment (these studies are sometimes referred to as new (without quotation marks) or more recent studies, to indicate that they were not included in the 2004 Air Quality Criteria Document Integrated Science Assessment and thus are newly available in this review).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 41 of 790 Formatted: Left period, and conducted a provisional assessment ( U.S. EPA, 2012b) that places the results of th o se studies of potentially greatest policy relevance in the context of the findings of the Integrated Sci ence Assessment ( U.S. EPA, 2009a)
. This provisional assessment , including a summary of the key conclusions , can be found in the rulemaking docket (EPA

- HQ

- OAR

- 2007

- 0492)
. The provisional assessment found that the “new” studies expand the scientific information considered in the Integrated Science Assessment and provide important insights on the relationship between PM exposure and health effects
. The provisional assessment also found that the “ new ” studies generally strengthen the evidence that long

- and short

- term exposure s to fine particles are associated with a wide range of health effects
. S ome of the “ new ” epidemiologic al studies report effects in areas with lower PM 2.5 concentrations than those in earlier studies considered in the Integrated Science Assessment. “N ew ” toxicolog ical and epidemiologic al studies continue to link various health effects with a range of fine particle sources and components. With regard to thoracic coarse particles, the provisional assessment recognized th at a limited number of “new” studies provide eviden ce of an association with short

- term PM 10

- 2.5 exposures and increased asthma

- related emergency department visits in children , but continue to provide no evidence of an association between long

- term PM 10

- 2. 5 exposure and mortality
. Further, the provisional assessment found that the results reported in “new” studies do not materially change any of the broad scientific conclusions regarding the health effects of PM exposure made in the Integrated Science Asses sment. The EPA believes it was important to conduct a prov isional assessment in this proceeding , so that the Administrator would be aware of the science that developed too Formatted: Strikethrough***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 42 of 790 Formatted: Left recently for inclusion in the Integ rated Science Assessment
. However , it is also important to note that the EPA’s review of that science to date has been limited to screening, surveying, and preparing a provisional assessment of these studies. Having performed this limited provisional assessment, the EPA must decide whether to consider the “ new ” studies in this review and to take such steps as may be necessary to include them in the basis for the final decision, or to reserve such action for the next review of the PM NAAQS. As in prior NAAQS reviews, the EPA is basi ng its decision in this review on studies and related information included in the Integrated Science Assessment , Risk and Exposure Assessment , and Policy Assessment , which have undergone CASAC and public review. The studies assessed in the Integrated Scien ce Assessment Document , and the integration of the scientific evidence presented in that document, have undergone extensive critical review by the EPA, CASAC, and the public during the development of the Integrated Science Assessment . The rigor of that rev iew makes these studies, and their integrative assessment, the most reliable source of scientific information on which to base decisions on the NAAQS. NAAQS decisions can have profound impacts on public health and welfare, and NAAQS decisions should be bas ed on studies that have been rigorously assessed in an integrative manner not only by the EPA but also by the statutorily

- mandated independent advisory committee, CASAC, and have been subject as well to the public review that accompanies this process. As described above, the provisional assessment did not and could not provide that kind of in

- depth critical review. This decision is consistent with the EPA’s practice in prior NAAQS reviews. Since the 1970 amendments, the EPA has taken the view that NAAQS decisions are to be***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 43 of 790 Formatted: Left based on scientific studies and related information that have been assessed as a part of the pertinent air quality criteria
. See e.g., 36 FR 8186 ( April 30, 1971 ) ( the EPA based origin al NAAQS for six pollutants on scientific studies discussed in air quality criteria documents and limited consideration of comments to those concerni ng validity of scientific basis) ; 38 FR 25678, 25679

- 25680 ( September 14, 1973 ) ( the EPA revised air qual ity criteria for sulfur oxides to provide basis for reevaluation of secondary NAAQS). This longstanding interpretation was strengthened by new legislative requirements enacted in 1977, which added section 109(d)(2) of the CAA concerning CASAC review of air quality criteria. The EPA has consistently followed this approach
. 52 FR 24634, 24637 ( July 1, 1987 ) ( after review by CASAC, the EPA issued a post

- proposal addendum to the PM Air Quality Criteria Document, to address certain new scientific studies not inc lude d in the 1982 Air Quality Criteria Document) ; 61 FR 25566, 25568 ( May 22, 1996 ) ( after review by CASAC, the EPA issued a post

- proposal supplement to the 1982 Air Quality Criteria Document to address certain new health studies not included in the 1982 Air 1982 Air Quality Criter ia Document or 1986 Addendum). The EPA reaffirmed this approach in its decision not to revise the ozone NAAQS in 1993, as well as in its final decision on the PM NAAQS in the 1997 and 2006 review s . 58 FR 13008, 13013

- to 13014 ( Ma rch 9, 1993 ) (ozone review); 62 FR 38652, 38662 ( July 18, 1997 ) and 71 FR 61141 , 61148

- to 61149 ( October 17, 2006 ) (PM review s ) (The EPA conducted a provisional assessment but based the final PM decision s on studies and related information included in the air quality criteria that had been reviewed by CASAC). As discussed in the EPA's 1993 decision not to revise the NAAQS for ozone,

‘ new ’ studies may sometimes be of such significance that it is appropriate to delay a Formatted: Font: Italic***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 44 of 790 Formatted: Left decision on revision of NAAQS and to supplement the pertinent air quality criteria so the

“ new ” studies can be taken into account (58 FR at , 13013

- to 13014, March 9, 1993). In th is proceeding , the provisional assessment of recent studies concl udes that, taken in context, the “ new ” information and findings do not materially change any of the broad scientific conclusions regarding the health effects of PM exposure made in the Integrated Science Assessment (U.S. EPA, 2012b) . For this reason, reope ning the air quality criteria review would not be warranted even if there were time to do so under the court order governing the schedule for this rulemaking. Accordingly, the EPA is basing the final decisions in this review on the studies and related info rmation included in the PM air quality criteria that have undergone CASAC and public review. The EPA will consider the “ new ” published studies for purposes of decision making in the next periodic review of the PM NAAQS, which will provide the opportunity t o fully assess them through a more rigorous review process involving the EPA, CASAC, and the public. C. Related Control Programs to Implement PM Standards States are primarily responsible for ensuring attainment and maintenance of ambient air quality standards NAAQS once the EPA has established them
. Under section 110 of the CA A and related provisions, s tates are to submit, for the EPA ’s approval, s tate implementation plans ( SIPs ) that provide for the attainment and maintenance of such standards through control programs directed to sources of the pollutants involved
. The

s tates, in conjunction with the EPA, also administer the PSD permitting program ( CAA sections 160 to 169 )
. In addition, Federal f ederal programs provide for nationwide reductions in emissions of PM and other air pollutants through the Federal f ederal motor vehicle and motor vehicle fuel control program under title II of the Act ( CAA sections***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 45 of 790 Formatted: Left 202 to 250) which involves controls for emission s from mobile sources and controls for the fuels used by these sou rces , and new source performance standards (NSPS) for stationary sources und er section 111 of the CAA
. Currently, there are 3 5 areas in the U.S. that are designated as nonattainment for the current annual PM 2.5 standard and 32 are a s in the U.S. that are designated as nonattainment for the current 24

- hour PM 2.5 standards
. With the revision s t o the PM NAAQS that are being finalized in this rule, the EPA w ill work with the states to conduct a new area designation process
. Those states with new nonattainment areas w ill be required to develop SIPs to attain the standards
. In developing their attainment plans, states w ill have to take into account projected emiss ion reductions from federal and state rules that have already been adopted at the time of plan submittal
. A number of significant emission reduction programs that will lead to reductions of PM and its precursors are in place today or are expected to be in place by the time any new SIPs will be due
. Examples of such rules include regulations for onroad and nonroad engines and fuels, the u tility and industrial boilers toxics rules, and various other programs already adopted by states to reduce emissions from key emissions sources
. States will then evaluate the level of additional emission reductions needed for each nonattainment area to attain the standards "as expeditiously as practicable" and adopt new state regulations , as appropriate
. Section I X includes a dditional discussion of designation and implementation issues associated with the revised PM NAAQS
. D. Summary of Proposed Revisions to the PM NAAQS For reasons discussed in the proposal, the Administrator proposed to revise the current primary and secondary PM standards. With regard to the primary PM 2.5 standards,***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 46 of 7 90 Formatted: Left the Administrator proposed to revise the level of the annual PM 2.5 standard from 15.0 μg/m 3 to a level within a range of 12.0 to 13.0 μg/m 3 and to retain the level of the 24

-

- hour PM 2.5 standard at 35 μg/m 3 . The Administrator also proposed to eliminate spatial averaging provisions as part of the form of the annual standard to avoid potential disproportionate impacts on at

- risk populations . The EPA proposed to revise the AQI for PM 2.5 , consistent with the proposed primary PM 2.5 standards, With regard to the primary coarse particle standard , the EPA proposed to retain the current 24

- hour PM 10 standard to continue to provide protection against effects associated with short

- term exposure to thoracic coars e particles (i.e., PM 10

- 2.5 ). With regard to the secondary PM standard s, the EPA proposed to revis e the suite of secondary PM standards by adding a distinct standard for PM 2.5 to address PM

- related visibility impairment. The separate secondary standard was proposed to be defined in terms of a PM 2.5 visibility index , which would use speciated PM 2.5 mass concentrations and relative humidity data to calculate PM 2.5 light extinction, translated to the deciview (dv) scale, similar to the Regional Haze Program; a 24

- hour averaging time; a 90 th percentile form averaged over 3 years ; and a level set at one of two options

– either 30 or 28 dv. The EPA also proposed to retain the current secondary standards generally to address non - visibility welfare effects. The EPA also proposed to revise the data handling procedures consistent with the revised primary and secondary standards for PM 2.5 including the computations necessary for determining when these standards are met and the me asurement data that are appropriate for comparison to the standards. With regard to monitoring

- related activities, the EPA proposed to update several aspects of the monitoring regulations and specifically***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 47 of 790 Formatted: Left to require that a small number of PM 2.5 monitors be relocated to be collocated with measurements of other pollutants (e.g., nitrogen dioxide, carbon monoxide) in the near

road environment. E. Organization and Approach to Final PM NAAQS Decisions This action presents the Administrator’s final decisions on the review of the current primary and secondary PM 2.5 and PM 10 standards. Consistent with the decisions made by the EPA in the last review and with the conclusions in the Integrated Science Assessment and Policy Assessment , fine and thoracic coarse particles continue to be considered as separate subclasses of PM pollution. Primary standards for fine particles and for thoracic coarse particles are addressed in sections I II and I V , respectively. Changes to the AQI for PM 2.5 , consistent with the revised primary P M 2.5 standards , are addressed in section V. Secondary standards for fine and coarse particles are addressed in section V I . Related data handling conventions and exceptional events are addressed in section VII. Updates to the monitoring regulations are addr essed in section VIII. Implementation activities, including PSD

- related actions , are address ed in section IX. Section X addresses applicable statutory and executive order reviews. Today's final decisions addressing standards for fine and coarse particles a re based on a thorough review in the Integrated Science Assessment of scientific information on known and potential human health and welfare effects associated with exposure to these subclasses of PM at levels typically found in the ambient air. These fina l decisions also take into account: (1) staff assessments in the Policy Assessment of the most policy

- relevant information in the Integrated Science Assessment as well as a quantitative health risk assessment and urban

- focused visibility assessment based o n that***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 48 of 790 Formatted: Left information ; (2) CASAC advice and recommendations, as reflected in its letters to the Administrator, its discussions of drafts of the Integrated Science Assessment, Risk and Exposure Assessments, and Policy Assessment at public meetings, and separat e written comments prepared by individual members of the CASAC PM Review Panel ; (3) public comments received during the development of these documents, either both in connection with CASAC meetings or and separately; and (4) extensive public comments received on the proposed rulemaking. III. Rationale for Final Decisions on the Primary PM 2.5 Standards This section presents the Administrator’s final decision regarding the need to revise the current primary PM 2.5 standards and, more specifically, regarding revisions to the level and form of the existing primary annual PM 2.5 standard in conjunction with retaining the existing primary 24

- hour PM 2.5 standard. As discussed more fully below, the rationale for the final decision is based on a thorough review, in the Integrated Science Assessment, of the latest scientific information, published through mid

- 2009, on human health effects associated with long

- and short

- term exposures to fine particles in the ambient air. Th e final decisions also take into account: (1) staff assessments of the most policy

- relevant information presented and assessed in the Integrated Science Assessment and staff analyses of air quality and human risks presented in the Risk Assessment and the P olicy Assessment, upon which staff conclusions regarding appropriate considerations in this review are based; (2) CASAC advice and recommendations, as reflected in discussions of drafts of the Integrated Science Assessment, Risk Assessment, and Policy Asse ssment at public meetings, in separate written comments, and in CASAC’s letters to the Administrator; (3) the multiple rounds of public comments***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 49 of 790 Formatted: Left received during the development of these documents, both in connection with CASAC meetings and separately; and (4) extensive public comments received on the proposal. In developing this final rule, the Administrator recognizes that the CAA requires her to reach a public health policy judgment as to what standards would be requisite

-- neither more nor less string ent than necessary

-- to protect public health with an adequate margin of safety, based on scientific evidence and technical assessments that have inherent uncertainties and limitations. This judgment requires making reasoned decisions as to what weight to place on various types of evidence and assessments, and on the related uncertainties and limitations. Thus, in selecting the final standards, the Administrator is seeking not only to prevent fine particle concentrations that have been demonstrated to be h armful but also to prevent lower fine particle concentrations that may pose an unacceptable risk of harm, even if the risk is not precisely identified as to nature or degree. As discussed below, as well as in more detail in the proposal, a substantial amo unt of new research has been conducted since the close of the science assessment in the last review of the PM 2.5 NAAQS ( U.S. EPA, 2004), with important new information coming from epidemiological studies, in particular. This body of evidence includes hundr eds of new epidemiological studies conducted in many countries around the world. In its assessment of the evidence judged to be most relevant to making decisions on elements of the primary PM 2.5 standards, the EPA has placed greater weight on U.S. and Cana dian***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 50 of 790 Formatted: Left studies using PM 2.5 measurements, since studies conducted in other countries may reflect different demographic and air pollution characteristics. 16 The newly available research studies as well as the earlier body of scientific evidence presented and assessed in the Integrated Science Assessment have undergone intensive scrutiny through multiple layers of peer review and opportunities for public review and comment. In developing this final rule, the EPA has drawn upon an integrative synthesis of the en tire body of evidence concerning exposure to ambient fine particles and a broad range of health endpoints ( U.S. EPA, 2009a, Chapters 2, 4, 5, 6, 7, and 8) focusing on those health endpoints for which the Integrated Science Assessment concludes that there i s a causal or likely causal relationship with long

- or short

- term PM 2.5 exposures. The EPA has also considered health endpoints for which the Integrated Science Assessment concludes there is evidence suggestive of a causal relationship with long

- term PM 2.5 exposures. The EPA has also drawn upon a quantitative risk assessment based upon the scientific evidence described and assessed in the Integrated Science Assessment. These analyses, discussed in the Risk Assessment ( U.S. EPA, 2010a) and Policy Assessment ( U.S. EPA, 2011a, chapter 2), have also undergone intensive scrutiny through multiple layers of peer review and multiple opportunities for public review and comment. Although important uncertainties remain in the qualitative and quantitative characteriza tions of health effects attributable to ambient fine particles, progress has been made in addressing these uncertainties in this review . The EPA ’s review of this information has been extensive and deliberate. This intensive evaluation of the scientific
16 Nonetheless, the A dministrator recognizes the importance of all studies, including international studies, in the Integrated Science Assessment’s considerations of the weight of the evidence that informs causality determinations.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 51 of 790 Formatted: Left evi dence and quantitative assessments has provided a comprehensive and adequate basis for regulatory decision making at this time. This section describes the integrative synthesis of the evidence and technical information contained in the Integrated Science Assessment , the Risk Assessment , and the Policy Assessment with regard to the current and alternative standards. The EPA notes that the final decision for retaining or revising the current primary PM 2.5 standards is a public health policy judgment made by the Administrator. The Administrator’s final decision draws upon scientific information and analyses related to health effects and risks; judgments about uncertainties that are inherent in the scientific evidence and analyses; CASAC advice; and comments re ceived in response to the proposal. In presenting the rationale for the final decisions on the primary PM 2.5 standards, this section begins with a summary of the approaches used in setting the initial primary PM 2.5 NAAQS in 1997 and in reviewing and revisi ng those standards in 2006 (section III.A.1). The D.C. Circuit Court of Appeals remand of the primary annual PM 2.5 standard in 2009 is discussed in section III.A.2. Taking into consideration this history, section II I II .A.3 describes the EPA’s general approach used in the current review for considering the need to retain or revise the current suite of fine particle standards, taking into account public comment on the proposed approach. The scientific evidence and quantitative risk assessment were presented in sections III.B and III.C of the proposal, respectively (77 FR 38906 to 38917, June 29, 2012) and are outlined in sections III.B and III.C below. Subsequent sections of this preamble provide a more complete discussion of the Adm inistrator’s rationale, in light of key issues raised in public comments, for concluding that it is appropriate to revise the***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 52 of 790 Formatted: Left suite of current primary PM 2.5 standards (section III.D), as well as a more complete discussion of the Administrator’s rationale f or retaining or revising the specific elements of the primary PM 2.5 standards, namely the indicator (section III.E.1); averaging time (section III.E.2); form (section III.E.3); and level (section III.E.4). A summary of the final decisions to revise the sui te of primary PM 2.5 standards is presented in section III.F. A. Background There are currently two primary PM 2.5 standards providing public health protection from effects associated with fine particle exposures. The annual standard is set at a level of 15.0 μg/m 3 , based on the 3

- year average of annual arithmetic mean PM 2.5 concentrations from single or multiple monitors sited to represent community

- wide air quality. The 24

- hour standard is set at a level of 35 μg/m 3 , based on the 3

- year average of the 98 th pe rcentile of 24

- hour PM 2.5 concentrations at each population

- oriented monitor within an area. The past and current approaches for reviewing the primary PM 2.5 standards described below are all based most fundamentally on using information from epidemiologic al studies to inform the selection of PM 2.5 standards that, in the Administrator’s judgment, protect public health with an adequate margin of safety. Such information can be in the form of air quality distributions over which health effect associations hav e been observed in scientific studies or in the form of concentration

response functions that support quantitative risk assessment. However, evidence

- and risk

- based approaches using information from epidemiological studies to inform decisions on PM 2.5 sta ndards are complicated by the recognition that no population threshold, below which it can be concluded with confidence that PM 2.5 - related effects do***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 53 of 790 Formatted: Left not occur, can be discerned from the available evidence. 17 As a result, any general approach to reaching de cisions on what standards are appropriate necessarily requires judgments about how to translate the information available from the epidemiological studies into a basis for appropriate standards. This includes consideration of how to weigh the uncertainties in the reported associations across the distributions of PM 2.5 concentrations in the studies and the uncertainties in quantitative estimates of risk, in the context of the entire body of evidence before the Agency. Such approaches are consistent with sett ing standards that are neither more nor less stringent than necessary, recognizing that a zero

- risk standard is not required by the CAA. 1. General Approach Used in Previous Reviews The general approach used to translate scientific information into standards in the previous PM NAAQS reviews focused on consideration of alternative standard levels that were somewhat below the long

- term mean PM 2.5 concentrations reported in key epidemiological studies ( U.S. EPA, 2011a, section 2.1.1). This approach recognized that the strongest evidence of PM 2.5 - related associations occurs where the bulk of the data exists, which is over a range of concentrations around the long

- term (i.e., annual) mean. In setting primary PM 2.5 annual and 24

- hour standards for the first time in 1997, the Agency relied primarily on an evidence

- based approach that focused on epidemiological evidence, especially from short

- term exposure studies of fine particles judged to be the strongest evid ence at that time ( U.S. EPA, 2011a, section 2.1.1.1). The EPA selected a level for the annual standard that was at or below the long

- term mean

17 The term "evidence

- based" approach or consi deration generally refers to using the information in the scientific evidence to inform judgments on the need to retain or revise the NAAQS. The term "risk

- based" generally refers to using the quantitative information in the Risk Assessment to inform such judgments.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 54 of 790 Formatted: Left
PM 2.5 concentrations in studies providing evidence of associations with short

- term PM 2.5 exposures, placing great est weight on those short

- term exposure studies that reported clearly statistically significant associations with mortality and morbidity effects. Further consideration of long

- term mean PM 2.5 concentrations associated with mortality and respiratory effect s in children did not provide a basis for establishing a lower annual standard level. The EPA did not place much weight on quantitative risk estimates from the very limited risk assessment conducted, but did conclude that the risk assessment results confir med the general conclusions drawn from the epidemiological evidence that a serious public health problem was associated with ambient PM levels allowed under the then current PM 10 standards (62 FR 38665/1, July 18, 1997). The EPA considered the epidemiologi cal evidence and data on air quality relationships to set an annual PM 2.5 standard that was intended to be the “generally controlling” standard; i.e., the primary means of lowering both long

- and short

- term ambient concentrations of PM 2.5 . 18 In conjunction with the annual standard, the EPA also established a 24

- hour PM 2.5 standard to provide supplemental protection against days with high peak concentrations, localized “hotspots,” and risks arising from seasonal emissions that might not be well controlled by an annual standard (62 FR 38669/3).

18 In so doing, the EPA noted that because an annual standard would focus control programs on annual average PM 2.5 concentrations, it would not only control long

- term exposure levels, but would also generally control the overall distribution of 2 4

- hour exposure levels, resulting in fewer and lower 24

- hour peak concentrations. Alternatively, a 24

- hour standard that focused controls on peak concentrations could also result in lower annual average concentrations. Thus, the EPA recognized that either standard could provide some degree of protection from both short

- and long

- term exposures, with the other standard serving to address situations where the daily peaks and annual averages are not consistently correlated (62 FR 38669, July 18, 1997). In the circumstances presented in that review, the EPA determined that it was appropriate to focus on the annual standard as the standard based best suited to control both annual and daily air quality distributions (62 FR 38670).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 55 of 790 Formatted: Left In 2006, the EPA used a different evidence

- based approach to assess the appropriateness of the levels of the 24

- hour and annual PM 2.5 standards ( U.S. EPA, 2011a, section 2.1.1.2). Based on an expanded body of epidemiolo gical evidence that was stronger and more robust than that available in the 1997 review, including additional studies of both short

- and long

- term exposures, the EPA decided that using evidence of effects associated with periods of exposure that were most closely matched to the averaging time of each standard was the most appropriate public health policy approach for evaluating the scientific evidence to inform selecting the level of each standard. Thus, the EPA relied upon evidence from the short

- term expo sure studies as the principal basis for revising the level of the 24

- hour PM 2.5 standard from 65 to 35 μg/m 3 to protect against effects associated with short

- term exposures. The EPA relied upon evidence from long

- term exposure studies as the principal basi s for retaining the level of the annual PM 2.5 standard at 15 μg/m 3 to protect against effects associated with long

- term exposures. This approach essentially took the view that short

- term studies were not appropriate to inform decisions relating to the leve l of the annual standard, and long

- term studies were not appropriate to inform decisions relating to the level of the 24

- hour standard. With respect to quantitative risk

- based considerations, the EPA determined that the estimates of risks likely to remain upon attainment of the 1997 suite of PM 2.5 standards were indicative of risks that could be reasonably judged important from a public health perspective and, thus, supported revision of the standards. However, the EPA judged that the quantitative risk asse ssment had important limitations and did not provide an appropriate basis for selecting the levels of the revised standards in 2006 (71 FR 61174/1

- 2, October 17, 2006).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 56 of 790 Formatted: Left 2. Remand of Primary Annual PM 2.5 Standard As noted above in section II.B.2, several part ies filed petitions for review in the U.S. Court of Appeals for the District of Columbia Circuit following promulgation of the revised PM NAAQS in 2006. These petitions challenged several aspects of the final rule including the level of the primary PM 2.5 a nnual standard. The primary 24

- hour PM 2.5 standard was not challenged by any of the litigants and, thus, was not considered in the court’s review and decision. On judicial review, the D.C. Circuit remanded the primary annual PM 2.5 NAAQS to the EPA on grou nds that the Agency failed to adequately explain why the annual standard provided the requisite protection from both short

- and long

- term exposures to fine particles including protection for at

- risk populations. American Farm Bureau Federation v. EPA , 559 F. 3d 512 (D.C. Cir. 2009). With respect to human health protection from short

- term PM 2.5 exposures, the court considered the different approaches used by the EPA in the 1997 and 2006 PM NAAQS decisions, as summarized in section III.A.1 above. The court fo und that the EPA failed to adequately explain why a primary 24

- hour PM 2.5 standard by itself would provide the protection needed from short

- term exposures and remanded the primary annual PM 2.5 standard to the EPA “for further consideration of whether it is set at a level requisite to protect the public health while providing an adequate margin of safety from the risk of short

- term exposures to PM 2.5 .” American Farm Bureau Federation v. EPA , 559 F. 3d at 520

- 24. With respect to protection from long

- term exp osure to fine particles, the court found that the EPA failed to adequately explain how the primary annual PM 2.5 standard provided an adequate margin of safety for children and other at

- risk populations. The***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 57 of 790 Formatted: Left court found that the EPA did not provide a reason able explanation of why certain morbidity studies, including a study of children in Southern California showing lung damage associated with long

- term PM 2.5 exposure (Gauderman et.al, 2000) and a multi

city study (24

- Cities Study) evaluating decreased lung function in children associated with long

- term PM 2.5 exposures (Raizenne et al., 1996), did not warrant a more stringent annual PM 2.5 standard. Id. at 522

- 23. Specifically, the court found that: EPA was unreasonably confident that, even though it relied solely upon long

- term mortality studies, the revised standard would provide an adequate margin of safety with respect to morbidity among children. Notably ab sent from the final rule, moreover, is any indication of how the standard will adequately reduce risk to the elderly or to those with certain heart or lung diseases despite (a) the EPA’s determination in its proposed rule that those subpopulations are at g reater risk from exposure to fine particles and (b) the evidence in the record supporting that determination. Id. at 525. In addition, the court held that the EPA had not adequately explained its decision to base the level of the annual standard essentiall y exclusively on the results of long

- term studies and the 24

- hour standard level essentially exclusively on the results of short

- term studies. See 559 F. 3d at 522 (“[e]ven if the long

- term studies available today are useful for setting an annual standard, ..., it is not clear why the EPA no longer believes it useful to look as well to short

- term studies in order to design the suite of standards that will most effectively reduce the risks associated with short

- term exposure”); see also id Id
. at 523

- 24 (holding that the EPA had not adequately explained why a standard based on levels in short

- term exposure studies alone provided appropriate protection from health effects associated with short

- term PM 2.5 exposures given the stated need to lower the entire air qual ity distribution, and not just peak concentrations, in order to control against short

- term effects). Formatted: Font: Italic

Formatted: Font: Italic

Formatted: Font: Italic

Formatted: Font: Italic Formatted: Font: Italic***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 58 of 790 Formatted: Left In remanding the primary annual PM 2.5 standard for reconsideration, the court did not vacate the standard, Id
. at 530, so the standard remains in effect a nd is therefore the standard considered by the EPA in this review. 3. General Approach Used in the Policy Assessment for the Current Review This review is based on an assessment of a much expanded body of scientific evidence, more extensive air quality data a nd analyses, and a more comprehensive quantitative risk assessment relative to the information available in past reviews, as presented and assessed in the Integrated Science Assessment and Risk Assessment and discussed in the Policy Assessment . As a result , the EPA’s general approach to reaching conclusions about the adequacy of the current suite of PM 2.5 standards and potential alternative standards that are appropriate to consider was broader and more integrative than in past reviews. Our general approach also reflected consideration of the issues raised by the court in its remand of the primary annual PM 2.5 standard as discussed in section III.A.2 above , since decisions made in this review, and the rationales for those decisions, will comprise the Agency’ s response to the remand. The EPA’s general approach took into account both evidence

- based and risk

based considerations and the uncertainties related to both types of information, as well as advice from CASAC (Samet, 2010c,d) and public comments on the fi rst and second draft Policy Assessments ( U.S. EPA, 2010c,f). In so doing, the EPA staff developed a final Policy Assessment ( U.S. EPA, 2011a) which provided as broad an array of policy options as was supported by the available information, recognizing that the selection of a specific approach to reaching final decisions on the primary PM 2.5 standards will reflect the judgments of th e Administrator as to what weight to place on the various approaches and***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 59 of 790 Formatted: Left types of information available in the current review. The Policy Assessment concluded it was most appropriate to consider the protection against PM 2.5 - related mortality and morbidity effects, associated with both long

- and short

- term exposures, afforded by the annual and 24

- hour standards taken together, as was done in the 1997 review, rather than to consider each standard separately, as was done in the 2006 review ( U.S. EPA, 2011a, se ction 2.1.3). 19 As the EPA recognized in 1997, there are various ways to combine two standards to achieve an appropriate degree of public health protection. The extent to which these two standards are interrelated in any given area depends in large part on the relative levels of the standards, the peak

- to
- mean ratios that characterize air quality patterns in an area, and whether changes in air quality designed to meet a given suite of standards are likely to be of a more regional or more localized nature. In considering the combined effect of annual and 24

- hour standards, the Policy Assessment recognized that changes in PM 2.5 air quality designed to meet an annual standard would likely result not only in lower annual average PM 2.5 concentrations but also in fewer and lower peak 24

- hour PM 2.5 concentrations. The Policy Assessment also recognized that changes designed to meet a 24

- hour standard would result not only in fewer and lower peak 24

- hour PM 2.5 concentrations but also in lower annual average PM 2.5 con centrations. Thus, either standard could be viewed as providing protection from

19 By utilizing this approach, the Agency also is responsive to the remand of the 2006 standard. As noted in section III.A.2, the D.C. Circuit, in remanding the 2006 primary annual PM 2.5 standard, concluded that the Administrator had failed to adequately explain why an annual standard was s ufficiently protective in the absence of consideration of the long

- term mean PM 2.5 concentrations in short

- term exposure studies as well, and likewise had failed to explain why a 24

- hour standard was sufficiently protective in the absence of consideration of the effect of an annual standard on reducing the overall distribution of 24

- hour average PM 2.5 concentrations. 559 F. 3d at 520

- 24.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 60 of 790 Formatted: Left effects associated with both short

- and long

- term exposures, with the other standard serving to address situations where the daily peak and annual average concentrations are

no t consistently correlated. In considering the currently available evidence, the Policy Assessment recognized that the short

- term exposure studies were primarily drawn from epidemiological studies that associated variations in area

- wide health effects with monitor(s) that measured the variation in daily PM 2.5 concentrations over the course of several years. The strength of the associations in these data was demonstrably in the numerous “typical” days within the air quality distribution, not in the peak days
. See also 71 FR 61168, October 17, 2006 and American Farm Bureau Federation v EPA , 559 F. 3d at 523, 524 (making the same point). The quantitative risk assessments conducted for this and previous reviews demonstrated the same point ; that is, much, if not most of the aggregate risk associated with short

- term exposures results from the large number of days during which the 24

- hour average concentrations are in the low

- to mid

- range, below the peak 24

- hour concentrations ( U.S. EPA, 2011a, section 2.2.2; U.S. E PA, 2010a, section 3.1.2.2). In addition, there was no evidence suggesting that risks associated with long

- term exposures were likely to be disproportionately driven by peak 24

- hour concentrations. 20 For these reasons, the Policy Assessment concluded that strategies that focused primarily on reducing peak days were less likely to achieve reductions in the PM 2.5 concentrations that were most strongly associated with the observed health effects. Furthermore, the Policy Assessment concluded that a policy appro ach that focused on

20 In confirmation, a number of studies have presented analyses excluding higher PM concentration days and reported a limited effect on the magnitude of the effect estimates or statistical significance of the association (e.g., Dominici, 2006b; Schwartz et a l, 1996; Pope and Dockery, 1992).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 61 of 790 Formatted: Left reducing peak exposures would most likely result in more uneven public health protection across the U.S. by either providing inadequate protection in some areas or overprotecting in other areas ( U.S. EPA, 2011a, p. 2

- 9; U.S. EPA, 2010a, section 5.2.3). This is because, as discussed above, reductions based on control of peak days are less likely to control the bulk of the air quality distribution. The Policy Assessment concluded that a policy goal of setting a “generally controlling” ann ual standard that will lower a wide range of ambient 24

- hour PM 2.5 concentrations, as opposed to focusing on control of peak 24

- hour PM 2.5 concentrations, was the most effective and efficient way to reduce total population risk and so provide appropriate p rotection. This approach, in contrast to one focusing on a generally controlling 24

- hour standard, would likely reduce aggregate risks associated with both long

- and short

- term exposures with more consistency and would likely avoid setting national standar ds that could result in relatively uneven protection across the country, due to setting standards that are either more or less stringent than necessary in different geographical areas (U.S. EPA, 2011a, p. 2

- 9)
. The Policy Assessment also concluded that an annual standard intended to serve as the primary means for providing protection from effects associated with both long

- and short

- term PM 2.5 exposures cannot be expected to offer sufficient protection against the effects of all short

- term PM 2.5 exposures. As a result, in conjunction with a generally controlling annual standard, the Policy Assessment concluded it was appropriate to consider setting a 24

- hour standard to provide supplemental protection, particularly for areas with high peak

- to
- mean ratios pos sibly associated with strong local or seasonal sources, or PM 2.5 - related effects that may be associated with shorter

- than

- daily exposure***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 62 of 790 Formatted: Left periods ( U.S. EPA, 2011a, p. 2

- 10). The Policy Assessment ’s consideration of the protection afforded by the current and alternative suites of standards focused on PM 2.5 - related health effects associated with long

- term exposures for which the magnitude of quantitative estimates of risks to public health generated in the risk assessment was appreciably larger in terms of ove rall incidence and percent of total mortality or morbidity effects than for short

- term PM 2.5 - related effects. Nonetheless, the EPA also considered health effects and estimated risks associated with short

- term exposures. In both cases, the Policy Assessment placed greatest weight on health effects that had been judged in the Integrated Science Assessment to have a causal or likely causal relationship with PM 2.5 exposures, while also considering health effects judged to be suggestive of a causal relationship or evidence that focused on specific at

- risk populations. The Policy Assessment placed relatively greater weight on statistically significant associations that yielded relatively more precise effect estimates and that were judged to be robust to confoundin g by other air pollutants. In the case of short

- term exposure studies, the Policy Assessment placed greatest weight on evidence from large multi

- city studies, while also considering associations in single

- city studies. In translating information from epid emiological studies into the basis for reaching staff conclusions on the adequacy of the current suite of standards, the Policy Assessment considered a number of factors. As an initial matter, the Policy Assessment considered the extent to which the curren tly available evidence and related uncertainties strengthens or calls into question conclusions from the last review regarding associations between fine particle exposures and health effects. The Policy Assessment also considered***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 63 of 790 Formatted: Left evidence of health effects in at

- risk populations and the potential impacts on such populations. Further, the Policy Assessment explored the extent to which PM 2.5 - related health effects had been observed in areas where air quality distributions extend to lower concentrations than p reviously reported or in areas that would likely have met the current suite of standards. In translating information from epidemiological studies into the basis for reaching staff conclusions on standard levels for consideration ( U.S. EPA, 2011a, sections 2.1.3 and 2.3.4), the Policy Assessment first recognized the absence of discernible thresholds in the concentration

- response functions from long

- and short

- term PM 2.5 exposure studies ( U.S. EPA, 2011a, section 2.4.3). 21 In the absence of any discernible th resholds, the Agency’s general approach for identifying appropriate standard levels for consideration involved characterizing the range of PM 2.5 concentrations over which we have the most confidence in the associations reported in epidemiological studies. In so doing, the Policy Assessment recognized that there is no single factor or criterion that comprises the “correct” approach, but rather there are various approaches that are reasonable to consider for characterizing the confidence in the associations a nd the limitations and uncertainties in the evidence. Identifying the implications of various approaches for reaching conclusions on the range of alternative standard levels that is appropriate to

21 The epidemiological studies evaluated in the Integrated Science Assessment that examined the shape of concentration

- response relationships and the potential presence of a threshold focused on cardiovascular

- related hospi tal admissions and emergency department visits associated with short

- term PM 10 exposures and premature mortality associated with long

- term PM 2.5 exposure (U.S. EPA, 2009a, sections 6.5, 6.2.10.10 and 7.6). Overall, the Integrated Science Assessment conclud ed that the studies evaluated support the use of a no

- threshold, log

- linear model but recognized that “additional issues such as the influence of heterogeneity in estimates between cities, and the effect of seasonal and regional differences in PM on the co ncentration

- response relationship still require further investigation” (U.S. EPA, 2009a, section 2.4.3).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 64 of 790 Formatted: Left consider can help inform the final decisions to either reta in or revise the standards. Today’s final decisions also take into account public health policy judgments as to the degree of health protection that is to be achieved. In reaching staff conclusions on the range of annual standard levels that was appropria te to consider, the Policy Assessment focused on identifying an annual standard that provided requisite protection from effects associated with both long

- and short

- term exposures. In so doing, the Policy Assessment explored different approaches for charac terizing the range of PM 2.5 concentrations over which our confidence in the nature of the associations for both long

- and short

- term exposures is greatest, as well as the extent to which our confidence is reduced at lower PM 2.5 concentrations. First, the Policy Assessment recognized that the approach that most directly addressed this issue considered studies that analyzed confidence intervals around concentration

- response relationships and in particular, analyses that averaged across multiple concentration

- response models rather than considering a single concentration

response model. 22 The Policy Assessment explored the extent to which such analyses had been published for studies of health effects associated with long

- or short

- term PM 2.5 exposures. Such ana lyses could potentially be used to characterize a concentration below which uncertainty in a concentration

- response relationship substantially increases or is judged to be indicative of an unacceptable degree of uncertainty about the existence of a continu ing concentration

- response relationship. The Policy Assessment concluded that

22 This is distinct from confidence intervals around concentration

- response relationships that are related to the magnitude of effect estimates generate d at specific PM 2.5 concentrations (i.e., point

- wise confidence intervals) and that are relevant to the precision of the effect estimate across the air quality distribution, rather than to our confidence in the existence of a continuing concentration

- respo nse relationship across the entire air quality distribution on which a reported association was based.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 65 of 790 Formatted: Left identifying this area of uncertainty in the concentration

- response relationship could be used to inform identification of alternative standard levels that are appropriate to

cons ider. Further, the Policy Assessment explored other approaches that considered different statistical metrics from epidemiological studies. The Policy Assessment first took into account the general approach used in previous PM reviews which focused on

cons ideration of alternative standard levels that were somewhat below the long

- term mean PM 2.5 concentrations reported in epidemiological studies using air quality distributions based on composite monitor concentrations. 23 This approach recognized that the stro ngest evidence of PM 2.5 - related associations occurs at concentrations around the long

- term (i.e., annual) mean. In using this approach, the Policy Assessment placed greatest weight on those long

- and short

- term exposure studies that reported statistically significant associations with mortality and morbidity effects. In extending this approach, the Policy Assessment also considered information beyond a single statistical metric of PM 2.5 concentrations (i.e., the mean) to the extent such information was ava ilable. Pursuant to an express comment from CASAC (Samet 2010d, p. 2), the Policy Assessment utilized distributional statistics (i.e., statistical characterization of an entire distribution of data) to identify the broader range of PM 2.5 concentrations tha

t had the most influence on the calculation of relative risk estimates in
23 Using the term “composite monitor” does not imply that the EPA can identify one monitor that represents the air quality evaluated in a specific study area. Rather, the composite monitor concentration represents the average concentration across monitors within each area with more than one monitor included in a given study as typically reported in epidemiological studies. For multi

- city studies, this metr ic reflects concentrations averaged across multiple monitors or from single monitors within each area and then averaged across study areas for an overall study mean PM 2.5 concentration. This is consistent with the epidemiological evidence considered in oth er NAAQS reviews.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 66 of 790 Formatted: Left both long

- and short

- term exposure epidemiological studies. Thus, the Policy Assessment considered the part of the distribution of PM 2.5 concentrations in which the data analyzed in the study (i.e., air quality and population

- level data, as discussed below) w ere most concentrated, specifically, the range of PM 2.5 concentrations around the long

- term mean over which our confidence in the magnitude and significance of associations observ ed in the epidemiological studies was greatest. The Policy Assessment then focused on the lower part of th e distribution to characterize where the data became appreciably more sparse and, thus, where our understanding of the magnitude and significance of t he associations correspondingly became more uncertain. The Policy Assessment recognized there was no single percentile value within a given distribution that was most appropriate or “correct” to use to characterize where our confidence in the associations becomes appreciably lower. The Policy Assessment concluded that the range from the 25 th to 10 th percentiles is a reasonable range to consider as a region where we had appreciably less confidence in the associations observed in epidemiological studies. 24 In considering distributional statistics from epidemiological studies, the final Policy Assessment focused on two types of population

- level metrics that CASAC advised were most useful to consider in identifying the PM 2.5 concentrations most influential in

24 In the PM NAAQS review completed in 2006, the Staff Paper similarly recognized that the evidence of an association in any epidemiological study is “strongest at and around the long

- term average where the data in the study are most conce ntrated. For example, the interquartile range of long

- term average concentrations within a study [with a lower bound of the 25 th percentile] or a range within one standard deviation around the study mean, may reasonably be used to characterize the range ov er which the evidence of association is strongest” (U.S. EPA, 2005, p. 5

- 22). A range of one standard deviation around the mean represents approximately 68 percent of normally distributed data, and below the mean falls between the 25 th and 10 th percentiles
.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 67 of 790 Formatted: Left
ge nerating the health effect estimates reported in the epidemiological studies. 25 Consistent with CASAC advice, the most relevant information was the distribution of health events (e.g., deaths, hospitalizations) occurring within a study population in relatio n to the distribution of PM 2.5 concentrations. However, in recognizing that access to health event data can be restricted, the Policy Assessment also considered the number of study participants within each study area as an appropriate surrogate for health event data. The Policy Assessment recognize d that an approach considering analyses of confidence intervals around concentration

- response functions wa s intrinsically related to an approach that consider ed different distributional statistics. Both of these approaches could be employed to understand the broader distribution of PM 2.5 concentrations which correspond to the health events reported in epidemiological studies. In applying these approaches, the Policy Assessment, consistent with CASAC advice (Samet, 2010d, p.3), considered PM 2.5 concentrations from long

- and short

- term PM 2.5 exposure studies using composite monitor distributions. In reaching staff conclusions on alternative standard levels that were appropriate to consider, the Policy Assessm ent also included a broader consideration of the

25 The second draft Policy Assessment focused on the distributions of ambient PM 2.5 concentrations and associated population data across areas included in several multi

- city studies for which such data were available in seeking to identify the most influe ntial range of concentrations (U.S. EPA, 2010f, section 2.3.4.1). In its review of the second draft Policy Assessment, CASAC advised that it “would be preferable to have information on the concentrations that were most influential in generating the health effect estimates in individual studies” (Samet, 2010d, p.2). Therefore, in the final Policy Assessment, the EPA considered population

- level data (i.e., area

- specific health event data and study area population data) along with corresponding PM 2.5 concentra tions to generate a cumulative distribution of the population

- level data relative to long

- term mean PM 2.5 concentrations to determine the most influential part of the air quality distribution (U.S. EPA, 2011a, Figure 2

- 7 and associated text). Formatted: Not Superscript/ Subscript***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 68 of 790 Formatted: Left uncertainties and limitations of the current scientific evidence. Most notably, these uncertainties are related to the heterogeneity observed in the epidemiological studies in the eastern versus western part s of the U.S., the relative toxicity of PM 2.5 components, and the potential role of co

- pollutants ( U.S. EPA, 2011a, pp. 2

- 25 to 2

- 26). The limitations and uncertainties associated with the currently available scientific evidence, including the availability of fewer studies toward the lower range of alternative annual standard levels being considered in this proposal, are summarized in section III.B below and further discussed in section III.B.2 of the preamble to the proposed rule propos al
. The Policy Assess ment recognized that the level of protection afforded by the NAAQS relies both on the level and the form of the standard. The Policy Assessment concluded that a policy approach that used data based on composite monitor distributions to identify alternative standard levels, and then compared those levels to concentrations at maximum monitors to determine whether an area meets a given standard, inherently has the potential to build in some margin of safety ( U.S. EPA, 2011a, p. 2

- 14). 26 This conclusion was cons istent with CASAC’s comments on the second draft Policy Assessment , in which CASAC expressed its preference for focusing on an approach using composite monitor distributions “because of its stability, and for the additional

26 Statistical metrics (e.g., means) based on composite monitor distributions may be identical to or below the same statistical metrics based on maximum monitor distributions. For example, some areas may have only one monitor, in which case the composite and maximum mon itor distributions will be identical in those areas. Other areas may have multiple monitors that may be very close to the monitor measuring the highest concentrations, in which case the composite and maximum monitor distributions could be similar in those areas. As noted in Hassett

- Sipple et al. (2010), for studies involving a large number of areas, the composite and maximum concentrations are generally within 5 percent of each other (77 FR 38905, fn. 30). Still other areas may have multiple monitors that m ay be separately impacted by local sources in which case the composite and maximum monitor distributions could be quite different (U.S. EPA, 2011a, p. 2

- 14). See further discussion of this issue in section III.E.4.c.i below.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 69 of 790 Formatted: Left margin of safety it provides” wh en “compared to the maximum monitor perspective” (Samet, et al., 2010d, pp. 2 to 3). In reaching staff conclusions on alternative 24

- hour standard levels that are appropriate to consider for setting a 24

- hour standard intended to supplement the protection afforded by a generally controlling annual standard, the Policy Assessment considered currently available short

- term PM 2.5 exposure studies. The evidence from these studies informed our understanding of the protection afforded by the suite of standards ag ainst effects associated with short

- term exposures. In considering the short

term exposure studies, the Policy Assessment evaluated both the distributions of 24

- hour PM 2.5 concentrations, with a focus on the 98 th percentile concentrations (to the extent

su ch data were available) to match the form of the current 24

- hour PM 2.5 standard, as well as the long

- term mean PM 2.5 concentrations reported in these studies. In addition to considering the epidemiological evidence, the Policy Assessment also considered air quality information based on county

- level 24

- hour and annual design values 27 to understand the policy implications of the alternative standard levels supported by the underlying science. In particular, the Policy Assessment considered t he extent to which different combinations of alternative annual and 24

- hour standards would support the policy goal of focusing on a generally controlling annual standard in conjunction with a 24

- hour standard that would provide supplemental protection. In so doing, the Policy Assessment discussed the roles that each standard might be expected to play in the protection afforded by alternative suites of standards. Beyond these evidence

- based considerations, the Policy Assessment also

27 Design values are the metrics (i.e., statistics) that are compared to the NAAQS levels to determine compliance.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 70 of 790 Formatted: Left considered the quantitat ive risk estimates and the key observations presented in the Risk Assessment. This assessment included an evaluation of 15 urban case study areas and estimated risk associated with a number of health endpoints associated with long

- and short

- term PM 2.5 exp osures ( U.S. EPA, 2010a). As part of the risk

- based considerations, the Policy Assessment considered estimates of the magnitude of PM 2.5 - related risks associated with recent air quality levels and air quality simulated to just meet the current and alternat ive suites of standards using alternative simulation approaches. The Policy Assessment also characterized the risk reductions, relative to the risks remaining upon just meeting the current standards, associated with just meeting alternative suites of stand ards. In so doing, the Policy Assessment recognized the uncertainties inherent in such risk estimates, and took such uncertainties into account by considering the sensitivity of the “core” risk estimates to alternative assumptions and methods likely to hav e substantial impact on the estimates. In addition, the Policy Assessment considered additional analyses characterizing the representativeness of the urban study areas within a broader national context to understand the roles that the annual and 24

- hour st andards may play in affording protection against effects related to both long

- and short

- term PM 2.5 exposures. Based on the approach discussed above, the Policy Assessment reached conclusions related to the primary PM 2.5 standards that reflected an underst anding of both evidence

- based and risk

- based considerations to inform two overarching questions related to: (1) the adequacy of the current suite of PM 2.5 standards and (2) revisions to the standards that were appropriate to consider in this review to prot ect against health effects associated with both long

- and short

- term exposures to fine particles. When evaluating***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 71 of 790 Formatted: Left the health protection afforded by the current or any alternative suites of standards considered, the Policy Assessment took into account the f our basic elements of the NAAQS: the indicator, averaging time, form, and level. The general approach for reviewing the primary PM 2.5 standards described above provided a comprehensive basis that helped to inform the Administrator’s judgments in reaching h er proposed and final decisions to revise the current suite of primary fine particle NAAQS and in responding to the remand of the 2006 primary annual PM 2.5 standard. B. Overview of Health Effects Evidence This section outlines the key information presented in section III.B of the proposal (77 FR 38906 to 38911, June 29, 2012) and discussed more fully in the Integrated Science Assessment (Chapters 2, 4, 5, 6, 7, and 8) and the Policy Assessment (Chapter 2) related to health effects associated with fine particle exposures. Section III.B. of the proposal discusses available information on the health effects associated with exposures to PM 2.5 , including the nature of such health effects (section III.B.1) and associated limitations and uncertainties (section III.B.2 ), at

- risk populations (section III.B.3), and potential PM 2.5 - related impacts on public health (section III.B.4). As was true in the last two reviews, evidence from epidemiologic epidemiologic al , controlled human exposure and animal toxicological studies played a key role in the Integrated Science Assessment ’s evaluation of the scientific evidence. The 2006 PM NAAQS review concluded that there was “strong epidemiological evidence” for linking lo ng - term PM 2.5 exposures with cardiovascular

- related and lung cancer mortality and respiratory

- related morbidity and for linking short

- term PM 2.5***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 72 of 790 Formatted: Left exposures with cardiovascular

- related and respiratory

- related mortality and morbidity ( U.S. EPA, 2004, p. 9

- 46; U.S. EPA, 2005, p. 5

- 4). Overall, the evidence from epidemiological, toxicological, and controlled human exposure studies supported “likely causal associations” between PM 2.5 and both mortality and morbidity from cardiovascular and respiratory diseases, b ased on “an assessment of strength, robustness, and consistency in results” ( U.S. EPA, 2004, p. 9

- 48). 28 In this review, based on the expanded body of evidence, the EPA finds that: (1) In looking across the extensive new scientific evidence available in this review, our overall understanding of health effects associated with fine particle exposures has been greatly expanded. The currently available evidence is largely consistent with evi dence available in the last review and substantially strengthens what is known about the effects associated with fine particle exposures. (2) A number of large multi

- city epidemiological studies have been conducted throughout the U.S., including extended anal yses of long

- term exposure studies that were important to inform decision

- making in the last review. The body of currently available scientific evidence has also been expanded greatly by the publication of a number of new multi

- city, time

- series studies th at have used uniform methodologies to investigate the effects of short

- term PM 2.5 exposures on public health. This body of evidence provides a more expansive data base and considers multiple locations representing varying regions and seasons that provide e vidence of the influence of different air pollution mixes on PM 2.5 - associated health effects. These studies provide more precise estimates of the magnitude of effects associated with short

- term PM 2.5 exposure than most smaller

- scale single

city studies tha t were more commonly available in the last review. These studies have reported consistent increases in morbidity and/or premature mortality related to ambient PM 2.5 concentrations, with the strongest evidence reported for cardiovascular

- related effects. (3) I n addition, the findings of new toxicological and controlled human exposure studies greatly expand and provide stronger support for a number of potential biologic biologic al mechanisms or pathways for cardiovascular and respiratory effects associated with l ong - and short

- term PM exposures. These studies provide
28 The term “likely causal association” was used in the 2004 Criteria Document to summarize the strength of the available evidence available in the last review for PM 2.5 . How ever, this terminology was not based on a formal framework for evaluating evidence for inferring causation. Since the last review, the EPA has developed a more formal framework for reaching causal determinations with standardized language to express evalua tion of the evidence (U.S. EPA, 2009a, section 1.5). Formatted: Font: 12 pt Formatted: Font: 12 pt, Not Superscript/ Subscript***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 73 of 790 Formatted: Left coherence and biological plausibility for the effects observed in epidemiological studies. (4) Using a more formal framework for reaching causal determinations than used in prior reviews 29 , , 30 the EPA concludes that a causal relationship exists between both long

- and short

- term exposures to PM 2.5 and premature mortality and cardiovascular effects and a likely causal relationship exists between long

- and short

- term PM 2.5 exposures and respirator y effects. Further, there is evidence suggestive of a causal relationship between long

- term PM 2.5 exposures and other health effects, including developmental and reproductive effects (e.g., low birth weight, infant mortality) and carcinogenic, mutagenic, a nd genotoxic effects (e.g., lung cancer mortality). 31 (5) The newly available evidence significantly strengthens the link between long

- and short

- term exposure to PM 2.5 and premature mortality, while providing indications that the magnitude of the PM 2.5 - mortal ity association with long

- term exposures may be larger than previously estimated. The strongest evidence comes from
29 The causal framework draws upon the assessment and integration of evidence from across epidemiological, controlled human exposure, and toxicological studies, and the related uncertainties that ultimately influence our understanding of the evidence. This framework employs a fiv e - level hierarchy that classifies the overall weight of evidence and causality using the following categorizations: causal relationship, likely to be causal relationship, suggestive of a causal relationship, inadequate to infer a causal relationship, and n ot likely to be a causal relationship ( U.S. EPA, 2009a, Table 1

- 3). Th e development of the causal framework reflects considerable input from CASAC and the public, with CASAC concluding that , “ T he five

- level classification of strength of evidence for causal inference has been systemically applied [for PM] ; this approach has provided transparency and a clear statement of the level of confidence with regard to causation, and we recommend its continued use in future ISAs” (Samet, 2009f, p. 1). 30 The causal fram ework draws upon the assessment and integration of evidence from across epidemiological, controlled human exposure, and toxicological studies, and the related uncertainties that ultimately influence our understanding of the evidence. This framework employs a five

- level hierarchy that classifies the overall weight of evidence and causality using the following categorizations: causal relationship, likely to be causal relationship, suggestive of a causal relationship, inadequate to infer a causal relationship, and not likely to be a causal relationship (U.S. EPA, 2009a, Table 1

- 3). The development of the causal framework reflects considerable input from CASAC and the public, with CASAC concluding that, “The five

- level classification of strength of evidence for causal inference has been systemically applied [for PM]; this approach has provided transparency and a clear statement of the level of confidence with regard to causation, and we recommend its continued use in future ISAs” (Samet, 2009f, p. 1). 31 These cau sal inferences are based not only on the more expansive epidemiological evidence available in this review but also reflect consideration of important progress that has been made to advance our understanding of a number of potential biologic modes of action or pathways for PM

- related cardiovascular and respiratory effects (U.S. EPA, 2009a, chapter 5).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 74 of 790 Formatted: Left recent studies investigating long

- term exposure to PM 2.5 and cardiovascular

related mortality. The evidence supporting a causal relationship between long

term PM 2.5 exposure and mortality also includes consideration of new studies that demonstrated an improvement in community health following reductions in ambient fine particles. (6) Several new studies have examined the association between cardio vascular effects and long

- term PM 2.5 exposures in multi

- city studies conducted in the U.S. and Europe. While studies were not available in the last review with regard to long

term exposure and cardiovascular

- related morbidity, recent studies have provided new evidence linking long

- term exposure to PM 2.5 with an array of cardiovascular effects such as heart attacks, congestive heart failure, stroke, and mortality. This evidence is coherent with studies of short

- term exposure to PM 2.5 that have observed assoc iations with a continuum of effects ranging from subtle changes in indicators of cardiovascular health to serious clinical events, such as increased hospitalizations and emergency department visits due to cardiovascular disease and cardiovascular mortality
. (7) Extended analyses of studies available in the last review as well as new epidemiological studies conducted in the U.S. and abroad provide stronger evidence of respiratory

- related morbidity effects associated with long

- term PM 2.5 exposure. The strongest e vidence for respiratory

- related effects is from studies that evaluated decrements in lung function growth, increased respiratory symptoms, and asthma development. The strongest evidence from short

- term PM 2.5 exposure studies has been observed for increased respiratory

- related emergency department visits and hospital admissions for chronic obstructive pulmonary disease (COPD) and respiratory infections. (8) The body of scientific evidence is somewhat expanded from the 2006 review but is still limited with respe ct to associations between long

- term PM 2.5 exposures and developmental and reproductive effects as well as cancer, mutagenic, and genotoxic effects. The strongest evidence for an association between PM 2.5 and developmental and reproductive effects comes fr om epidemiological studies of low birth weight and infant mortality, especially due to respiratory causes during the post

- neonatal period (i.e., 1 month

- 12 months of age). With regard to cancer effects, “[m]ultiple epidemiologic studies have shown a consi stent positive association between PM 2.5 and lung cancer mortality, but studies have generally not reported associations between PM 2.5 and lung cancer incidence” (U.S. EPA 2009a p. 2

- 13 )
. (9) Efforts to evaluate the relationships between PM composition and he alth effects continue to evolve. While many constituents of PM 2.5 can be linked with differing health effects, the evidence is not yet sufficient to allow differentiation of those constituents or sources that may be more closely related to specific health outcomes nor to exclude any individual component or group of components associated with any source categories from the fine particle mixture of concern.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 75 of 790 Formatted: Left (10) Specific groups within the general population are at increased risk for experiencing adverse health eff ects related to PM exposures . The currently available evidence expands our understanding of previously identified at

- risk populations (i.e., children, older adults, and individuals with pre

- existing heart and lung disease) and supports the identification o f additional at

- risk populations (e.g., persons with lower socioeconomic status, genetic differences). Evidence for PM

- related effects in these at

- risk populations has expanded and is stronger than previously observed. There is emerging, though still limit ed, evidence for additional potentially at

- risk populations, such as those with diabetes, people who are obese, pregnant women, and the developing fetus. (11) The population potentially affected by PM 2.5 is large. In addition, large subgroups of the U.S. popula tion have been identified as at

- risk populations. While individual effect estimates from epidemiological studies may be small in size, the public health impact of the mortality and morbidity associations can be quite large given the extent of exposure. Tak en together, this suggests that exposure to ambient PM 2.5 concentrations can have substantial public health impacts. (12) While the currently available scientific evidence is stronger and more consistent than in previous reviews, providing a strong basis for decision making in this review, the EPA recognizes that important uncertainties and limitations in the health effects evidence remain. Epidemiological studies evaluating health effects associated with long

- and short

- term PM 2.5 exposures have reported hete rogeneity in responses between cities and geographic regions within the U.S. This heterogeneity may be attributed, in part, to differences in the fine particle composition or related to exposure measurement error, which can introduce bias and increased unc ertainty in associated health effect estimates. Variability in the associations observed across PM 2.5 epidemiological studies may be due in part to exposure error related to measurement

- related issues, the use of central fixed

- site monitors to represent po pulation exposure to PM 2.5 , models used in lieu of or to supplement ambient measurements, and our limited understanding of factors that may influence exposures (e.g., topography, the built environment, weather, source characteristics, ventilation usage, pe rsonal activity patterns, photochemistry). In addition, where PM 2.5 and other pollutants (e.g., ozone, nitrogen dioxide, and carbon monoxide) are correlated, it can be difficult to distinguish the effects of the various pollutants in the ambient mixture (i .e., co - pollutant confounding). 32 While uncertainties and limitations still remain in the available health effects evidence, the Administrator judges the currently available scientific data base to be stronger and more consistent than in previous reviews p roviding a strong basis for

32 A copollutant meets the criteria for potential confounding in PM

- health associations if: (1) it is a potential risk factor for the health effect under study; (2) it is correlated with PM; and (3) it does not act as an intermediate step in the pathway between PM exposure and the health effect under study (U.S. EPA, 2004, p. 8

- 10).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 76 of 790 Formatted: Left decision making in this review. C. Overview of Quantitative Characterization of Health Risks In addition to a comprehensive evaluation of the health effects evidence available in this review, the EPA conducted an expanded quantita tive risk assessment for selected health endpoints to provide additional information and insights to inform decisions on the primary PM 2.5 NAAQS. 33 As discussed in section III.C of the proposal, the approach used to develop quantitative risk estimates assoc iated with PM 2.5 exposures was built on the approach used and lessons learned in the last review and focused on improving the characterization of the overall confidence in the risk estimates, including related uncertainties, by incorporating a number of en hancements, in terms of both the methods and data used in the analyses. The goals of this quantitative risk assessment were largely the same as those articulated in the risk assessment conducted for the last review. These goals included: (1) to provide es timates of the potential magnitude of premature mortality and/or selected morbidity effects in the population associated with recent ambient levels of PM 2.5 and with simulating just meeting the current and alternative suites of PM 2.5 standards in 15

33 The quantitative risk assessment conducted for this review is more fully descr ibed and presented in the Risk Assessment (U.S. EPA, 2010a) and summarized in detail in the Policy Assessment (U.S. EPA, 2011a, sections 2.2.2. and 2.3.4.2). The scope and methodology for this risk assessment were developed over the last few years with con siderable input from CASAC and the public as described in section I. C.2 of the proposal
. II.B.3 above
. Formatted: Not Superscript/ Subscript

Formatted: Font: 12 pt Formatted: Font: 12 pt, Not Superscript/ Subscript***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 77 of 790 Formatted: Left select ed urban study areas 34 , , 35 including, where data were available, consideration of impacts on at

- risk populations; (2) to develop a better understanding of the influence of various inputs and assumptions on the risk estimates to more clearly differentiate amo ng alternative suites of standards; and (3) to gain insights into the distribution of risks and patterns of risk reductions and the variability and uncertainties in those risk estimates. In addition, the quantitative risk assessment included nationwide est imates of the potential magnitude of premature mortality associated with long

- term exposure to recent ambient PM 2.5 concentrations to more broadly characterize this risk on a national scale and to support the interpretation of the more detailed risk estimates generated for selected urban study areas. The expanded and updated risk assessment conducted in this review in cluded estimates of risk for: (1) all

- cause, ischemic heart disease

- related, cardiopulmonary

-

34 T he Risk Assessment conclude d that these 15 urban study areas we re generally representative of urban areas in the U.S. likely to experience relatively elevated levels of risk related to ambient PM 2.5 exposure with the potential for better characterization at the higher end of that distribution ( U.S. EPA, 2011a, p. 2

- 42; U.S. EPA, 2010a, section 4.4, Figure 4

- 17). The representativeness analysis also sho wed that the 15 urban study areas do not capture areas with the highest baseline morality risks or the oldest populations (both of which can result in higher PM 2.5 - related mortality estimates)
. However, some of the areas with the highest values for these a ttributes ha d relatively low PM 2.5 concentrations (e.g., urban areas in Florida) and, consequently, the Risk Assessment conclude d failure to include these areas i n the set of urban study areas wa s unlikely to exclude high PM 2.5 - risk locations ( U.S. EPA, 20 10a, section 4.4.1). 35 The Risk Assessment concluded that these 15 urban study areas were generally representative of urban areas in the U.S. likely to experience relatively elevated levels of risk related to ambient PM 2.5 exposure with the potential for better characterization at the higher end of that distribution (U.S. EPA, 2011a, p. 2

- 42; U.S. EPA, 2010a, section 4.4, Figure 4

- 17). The representativeness analysis also showed that the 15 urban study areas do not capture areas with the highest baseline morality risks or the oldest populations (both of which can result in higher PM 2.5 - related mortality estimates). However, some of the areas with the highest values for these attributes had relatively low PM 2.5 concentrations (e.g., urban areas in Florida) and, consequently, the Risk Assessment concluded failure to include these areas in the set of urban study areas was unlikely to exclude high PM 2.5 - risk locations (U.S. EPA, 2010a, section 4.4.1).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 78 of 790 Formatted: Left related, and lung cancer

- related mortality associated with long

- term PM 2.5 exposure; (2)

non - accidental, cardiovascular

- related, and respiratory

- related mortality associated with short

- term PM 2.5 exposure; and (3) cardiovascular

- related and respiratory

- related hospital admissions and asthma

- related emergency department visits associated with short

- term PM 2.5 exposure. 36 The Risk Assessment included a core set of ris k estimates supplemented by an alternative set of risk results generated using single

- factor and multi

- factor sensitivity analyses. The core set of risk estimates was developed using the combination of modeling elements and input data sets identified in th e Risk Assessment as having higher confidence relative to inputs used in the sensitivity analyses. The results of the sensitivity analyses provided information to evaluate and rank the potential impacts of key sources of uncertainty on the core risk estima tes. In addition, the sensitivity analyses represented a set of reasonable alternatives to the core set of risk estimates that fell within an overall set of plausible risk estimates surrounding the core estimates. The EPA recognized that there were many s ources of variability and uncertainty inherent in the inputs to its quantitative risk assessment. 37 The design of the risk assessment included a number of elements to address these issues in order to increase the overall confidence in the risk estimates gen erated for the 15 urban study areas, including using guidance from the World Health Organization (WHO, 2008) as a framework for

36 The evidence available for these selected health effect endpoints generally focused on the entire population, although some information was available to support analyses that considered differences in estimated risk for at

- risk populations including older adults and persons with pr e - existing cardiovascular and respiratory diseases. 37 Variability refers to the heterogeneity of a variable of interest within a population or across different populations. Uncertainty refers to the lack of knowledge regarding the actual values of inputs t o an analysis (U.S. EPA, 2010a, p. 3

- 63).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 79 of 790 Formatted: Left characterizing uncertainty in the analyses. 38 With respect to the sources of variability, the Risk Assessment considered those t hat contributed to differences in risk across urban study areas, but did not directly affect the degree of risk reduction associated with the simulation of just meeting current or alternative standard levels (e.g., differences in baseline incidence rates, demographics and population behavior). The Risk Assessment also focused on factors that not only introduced variability into risk estimates across study areas, but also played an important role in determining the magnitude of risk reductions upon simulatio n of just meeting current or alternative standard levels (e.g., peak

- to
- mean ratios of ambient PM 2.5 concentrations within individual urban study areas and the nature of the rollback approach used to simulate just meeting the current or alternative standar ds). Key sources of potential variability that were likely to affect population risks included the following : (1) intra

- urban variability in ambient PM 2.5 concentrations, including PM 2.5 composition; (2) variability in the patterns of reductions in PM 2.5 c oncentrations associated with different rollback approaches when simulating just meeting the current or alternative standards; co

- pollutant exposures; (3) factors related to demographic and socioeconomic status; (4) behavioral differences across urban stud y areas (e.g., time spent outdoors); (5) baseline incidence rates; and (6) longer

- term temporal variability in ambient PM 2.5 concentrations reflecting meteorological trends as well as future changes in the mix of PM 2.5 sources, including changes in air qua lity related to future regulatory actions. With regard to uncertainties, single and multi

- factor sensitivity analyses were combined with a qualitative analysis to assess the impact of potential sources of
38 The extent to which key sources of potential variability were (or were not) fully captured in the design of the risk assessment are discussed in section 3.5.2 of the Risk Assessment (U.S. EPA, 2010a, pp. 3

- 67 to 3

- 69). Formatted: Font: 12 pt Formatted: Font: 12 pt, Not Superscript/ Subscript***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 80 of 790 Formatted: Left uncertainty on the core risk estimates. Key source s of uncertainty included: (1) characterizing intra

- urban population exposure in the context of epidemiology epidemiolog ical studies linking PM 2.5 to specific health effects; (2) statistical fit of the concentration

- response functions for short

- term exposure
- related health endpoints; (3) shape of the concentration

- response functions; (4) specifying the appropriate lag structure for short

- term exposu re studies; (5) transferability of concentration

- response functions from study locations to urban study area locations for long

- term exposure
- related health endpoints; (6) use of single

- city versus multi

- city studies in the derivation of concentration

- resp onse functions; (7) impact of historical air quality on estimates of health risk associate with long

- term PM 2.5 exposures; and (8) potential variation in effect estimates reflecting compositional differences in PM 2.5 . Beyond characterizing uncertainty and variability, a number of design elements were included in the risk assessment to increase the overall confidence in the risk estimates generated for the 15 urban study areas ( U.S. EPA, 2011a, pp. 2

- 38 to 2

- 41). These elements included: (1) use of a deliber ative process for specifying components of the risk model that reflects consideration of the latest research on PM 2.5 exposure and risk ( U.S. EPA, 2010a, section 5.1.1); (2) integration of key sources of variability into the design as well as the interpret ation of risk estimates (U.S.EPA, 2010a, section 5.1.2); (3) assessment of the degree to which the urban study areas are representative of areas in the U.S. experiencing higher PM 2.5 - related risk (U.S.EPA, 2010a, section 5.1.3); and (4) identification and assessment of important sources of uncertainty and the impact of these uncertainties on the core risk estimates (U.S.EPA, 2010a, section 5.1.4). Further, additional analyses examined potential bias and overall confidence in the risk estimates.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 81 of 790 Formatted: Left Greater conf

idence is associated with risk estimates based on simulated annual mean PM 2.5 concentrations that are within the region of the air quality distribution used in deriving the concentration

- response functions where the bulk of the data reside (e.g., within on e standard deviation around the long

- term mean PM 2.5 concentration) ( U.S. EPA, 2011a, p. 2

- 38). Key observations and insights from the PM 2.5 risk assessment, together with important caveats and limitations , were discussed in section III.C.3 of the proposal . In general, in considering the set of quantitative risk estimates and related uncertainties and limitations related to long

- and short

- term PM 2.5 exposure together with consideration of the health endpoints which could not be quantified, the Policy Asses sment concluded this information provided strong evidence that risks estimated to remain upon simulating just meeting the current suite of PM 2.5 standards are important from a public health perspective, both in terms of severity and magnitude of effects. P atterns of increasing estimated risk reductions were generally observed as either the annual or 24

- hour standard level, or both, were reduced over the ranges considered in the Risk Assessment. The magnitude of both long

- and short

- term exposure
- related ris k estimated to remain upon just meeting the current suite of standards as well as alternative standard levels w as strongly associated with the simulated change in annual mean PM 2.5 concentrations. Although long

- and short

- term exposure
- related mortality ra tes have similar patterns in terms of the subset of urban study areas experiencing risk reductions for the current suite of standard levels, the magnitude of risk remaining is higher for long

term exposure
- related mortality and substantially lower for shor t
- term exposure
- related mortality. Short

- term exposure
- related morbidity risk estimates w ere greater for***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 82 of 790 Formatted: Left cardiovascular

- related than respiratory

- related events and emergency department visits for asthma

- related events were significant: Furthermore, most of the aggregate risk associated with short

- term exposures was not primarily driven by the small number of days with PM 2.5 concentrations in the upper tail of the air quality distribution, but rather by the large number of days with PM 2.5 concentrations at a nd around the mean of the distribution, that is, the 24

- hour average concentrations that are in the low

- to mid

- range, well below the peak 24

- hour concentrations (U.S. EPA, 2011a, p. 2

- 3)
. With regard to characterizing estimates of PM 2.5 - related risk associ ated with simulation of alternative standards, the Policy Assessment recognized that greater overall confidence was associated with estimates of risk reduction than for estimates of absolute risk remaining ( U.S. EPA, 2011a, p. 2

- 94). Furthermore, the Policy Assessment recognized that estimates of absolute risk remaining for each of the alternative standard levels considered, particularly in the context of long

- term exposure
- related mortality, may be underestimate d 39 . In addition, the Policy Assessment observed that in considering the overall confidence associated with the quantitative analyses, the Risk Assessment recognized that: (1) substantial variability existed in the magnitude of risk remaining across urban s tudy areas and (2) in general, higher confidence was associated with risk

39 Based on the consideration of both the qualitative and quantitative assessments of uncertainty, the Risk Assessment concluded that it is unlikely that the estimated risks are over - stated, particularly for premature mortality related to long

- term PM 2.5 exposures. In fact, the Policy Assessment and the Risk Assessment concluded that the core risk estimates for this category of health effects may well be biased low based on consideration of alternative model specifications evaluated in the sensitivit y analyses (U.S. EPA, 2011a, p. 2

- 41; U.S. EPA, 2010a, p. 5

- 16; Figures 4

- 7 and 4

- 8). In addition, the Policy Assessment recognized that the currently available scientific information included evidence for a broader range of health endpoints and at

- risk po pulations beyond those included in the quantitative risk assessment, including decrements in lung function growth and respiratory symptoms in children as well as reproductive and developmental effects (U.S. EPA, 2011a, section 2.2.1).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 83 of 790 Formatted: Left estimates based on PM 2.5 concentrations near the mean PM 2.5 concentrations in the underlying epidemiological studies providing the concentration

- response functions ( i. e . g . , within on e standard deviation of the mean PM 2.5 concentration reported). Furthermore, although the Risk Assessment estimated that the alternative 24

- hour standard levels considered (when controlling) would result in additional estimated risk reductions beyond those estimated for alternative annual standard levels alone, these additional estimated reductions were highly variable. Conversely, the Risk Assessment recognized that alternative annual standard levels, when controlling, resulted in more consistent risk redu ctions across urban study areas, thereby potentially providing a more consistent degree of public health protection ( U.S. EPA, 2010a, p. 5

- 17). D. Conclusions on the Adequacy of the Current Primary PM 2.5 Standards 1. Introduction The initial issue to be addresse d in the current review of the primary PM 2.5 standards is whether, in view of the advances in scientific knowledge and other information reflected in the Integrated Science Assessment, the Risk Assessment, and the Policy Assessment, the existing standards should be retained or revised. In considering the adequacy of the current suite of PM 2.5 standards, the Administrator has considered the large body of evidence presented and assessed in the Integrated Science Assessment ( U.S. EPA, 2009a), the quantitative assessment of risks, staff conclusions and associated rationales presented in the Policy Assessment , views expressed by CASAC, and public comments. The Administrator has taken into account both evidence

- and risk

- based consid erations 40 in developing final conclusions on the adequacy of the current primary

40 Evidence

- based cons iderations include the assessment of epidemiological, toxicological, and controlled human exposure studies evaluating long

- or short

- term***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 84 of 790 Formatted: Left
PM 2.5 standards.

a. Evidence

- and Risk

- based Considerations in the Policy Assessment In considering the available epidemiologic epidemiologic al evidence in this review, the Po licy Assessment took a broader approach than was used in the last review. This approach reflected the more extensive and stronger body of evidence available since the last review on health effects related to both long

- and short

- term exposure to PM 2.5 . As discussed in section III.A.3 above, this broader approach focused on setting the annual standard as the “generally controlling” standard for lowering both short

- and long

- term PM 2.5 concentrations and so providing requisite protection to public health . In conjunction with such an annual standard, this approach focused on setting the 24

- hour standard to provide supplemental protection against days with high peak PM 2.5 concentrations. In addressing the question whether the evidence now available in this revie w supports consideration of standards that are more protective than the current PM 2.5 standards, the Policy Assessment considered whether : (1) statistically significant health effects associations with long

- or short

- term exposures to fine particles occur in areas that would likely have met the current PM 2.5 standards ( [ see American Trucking Ass’ns Ass ociatio n s , 283 F. 3d at 369, 376 (revision of level of PM NAAQS justified when health effects are observed in areas meeting the existing standard )), ) ] , and (2) exposures to PM 2.5 , with supporting evidence related to dosimetry and potential pathways/modes of action, as well as t he integration of evidence across each of these disciplines, as assessed in the Integrated Science Assessment (U.S. EPA, 2009a) and focus on the policy

- relevant considerations as discussed in section III.B above and in the Policy Assessment (U.S. EPA, 2011 a, section 2.2.1). Risk

- based considerations draw from the results of the quantitative analyses presented in the Risk Assessment (U.S. EPA, 2010a) and focus on the policy

- relevant considerations as discussed in section III.C above and in the Policy Assessm ent (U.S. EPA, 2011a, section 2.2.2).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 85 of 790 Formatted: Left associations with long

- term exposures to fine particles extend down to lower air quality concentrations than had previously been observed. With regard to associations observed in long

- term PM 2.5 exposure studies, the Policy Assessment recognized t hat extended follow

- up analyses of the ACS and Harvard Six Cities studies provided consistent and stronger evidence of an association with mortality at lower air quality distributions than had previously been observed ( U.S. EPA, 2011a, pp. 2

- 31 to 2

- 32). T he original and reanalysis of the ACS study reported positive and statistically significant effects associated with a long

- term mean PM 2.5 concentration of 18.2 μg/m 3 across 50 metropolitan areas for 1979 to 1983 (Pope et al., 1995; Krewski et al., 2000). 41 In extended analyses, positive and statistically significant effects of approximately similar magnitude were associated with declining PM 2.5 concentrations, from an aggregate long

term mean in 58 metropolitan areas of 21.2 μg/m 3 in the original monitoring period (1979 to 1983) to 14.0 μg/m 3 for 116 metropolitan areas in the most recent years evaluated (1999

- 2000), with an overall average across the two study periods in 51 metropolitan areas of 17.7 μg/m 3 (Pope et al., 2002; Krewski et al., 2009). With rega rd to the Harvard Six Cities Study, the original and reanalysis reported positive and statistically significant effects associated with a long

- term mean PM 2.5 concentration of 18.0 μg/m 3 for 1980 to 1985 (Dockery et al., 1993; Krewski et al., 2000). In an extended follow

- up of this study, the aggregate long

- term mean concentration across all years evaluated was 16.4 μg/m 3 for 1980 to 1988 42 (Laden et al., 2006). In an additional analysis of the extended follow

-

41 The study periods referred to in the Policy Assessment (U.S. EPA, 2011a) and in this final rule reflect the years of air quality data that were included in the analyses, whereas the study periods identified in the In tegrated Science Assessment (U.S. EPA, 2009a) reflect the years of health status event data that were included. 42 Aggregate mean concentration provided by study author (personal communication from Dr. Francine Laden, 2009).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 86 of 790 Formatted: Left up of the Harvard Six Cities study, investigator s reported that the concentration

- response relationship was linear and “clearly continuing below the level” of the current annual standard ( U.S. EPA, 2009a, p. 7

- 92; Schwartz et al., 2008). Cohort studies conducted since the last review provided additiona l evidence of mortality associated with air quality distributions that are generally lower than those reported in the ACS and Harvard Six Cities studies, with effect estimates that were similar or, in some studies, significantly greater in magnitude than i n the ACS and Harvard Six Cities studies (see also, section III.D.1.a of the proposal, 77 FR 38918 to 28919; U.S. EPA, 2011a, pp. 2

- 32 to 2

- 33). The Women’s Health Initiative (WHI) study reported positive and most often statistically significant associatio ns between long

- term PM 2.5 exposure and cardiovascular

- related mortality as well as morbidity effects, with much larger relative risk estimates for mortality than in the ACS and Harvard Six Cities studies, at an aggregate long

- term mean PM 2.5 concentration of 12.9 μg/m 3 for 2000 (Miller et al., 2007). 43 Using the Medicare cohort, Eftim et al. (2008) reported somewhat higher effect estimates than in the ACS and Harvard Six Cities studies with aggregate long

- term mean concentrations of 13.6 μg/m 3 and 14.1 μg/m 3 , respectively, for 2000

- to 2002. Zeger et al. (2008) reported associations between long

- term PM 2.5 exposure and mortality for the eastern region of the U.S. at an aggregated long

- term PM 2.5 median concentration of 14.0 μg/m 3 , although no a ssociation was reported for the western region with an aggregate

43 The Policy Assessment noted that in comparison to other long

- term exposure studies, the Miller et al. (2007) study was more limited in that it was based on only one year of air quality data (U.S. EPA, 2011a, p. 2

- 82). The proposal further noted that the air quality data considered we re extrapolated from that one single year of air quality data (2000) to the whole study, and that the air quality data post

- dated the years of health events considered (i.e., 1994 to 1998) (77 FR 38918, fn 62). Formatted: Font: 12 pt Formatted: Font: 12 pt, Not Superscript/ Subscript***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 87 of 790 Formatted: Left long

- term PM 2.5 median concentration of 13.1 μg/m 3 ( U.S. EPA, 2009a, p. 7

- 88). 44 Premature mortality in children reported in a national infant mortality study as well as mortality in a cystic fibrosis cohort including both children and adults reported positive but statistically nonsignificant effects associated with long

- term aggregate mean concentrations of 14.8 μg/m 3 and 13.7 μg/m 3 , respectively (Woodruff et al., 2008; Goss et al., 2004). Wi th respect to respiratory morbidity effects associated with long

- term PM 2.5 exposure, the across

- city mean of 2

- week average PM 2.5 concentrations reported in the initial Southern California Children’s Health Study was approximately 15.1 μg/m 3 (Peters et al ., 1999). These results were found to be consistent with results of cross

sectional analyses of the 24

- Cities Study (Dockery et al., 1996; Raizenne et al., 1996), which reported a long

- term cross
- city mean PM 2.5 concentration of 14.5 μg/m 3

. 45 In this review , extended analyses o f the Southern California Children’s Health Study provide stronger evidence of PM 2.5 - related respiratory effects, at lower air quality concentrations than had previously been reported, with a four

- year aggregate mean concentration of 1 3.8 μg/m 3 across the 12 study communities (McConnell et al., 2003; Gauderman et al., 2004, U.S. EPA, 2009a, Figure 7

- 4). In also considering health effects for which the Integrated Science Assessment

44 Zeger et al. (2008) also reported positive and statistically significant effects for the central region, with an aggregate long

- term mean PM 2.5 concentration of 10.7 μg/m 3

. However, in contrast to the eastern and western risk estimates, the central risk estimate increased with adjustment for COPD ( used as a proxy for smoking status). Due to the potential for confounding bias influencing the risk estimate for the central region, the Policy Assessment did not focus on the results reported in the central region to inform the adequacy of the current sui te of standards or alternative annual standard levels (U.S. EPA, 2011a, p. 2

- 32). 45 See American Farm Bureau Federation v. EPA , 559 F. 3d at 525 (noting the importance of these studies, as well as EPA’s failure to properly take them into account).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 88 of 790 Formatted: Left concluded evidence was suggestive of a causal relations hip, the Policy Assessment noted a limited number of birth outcome studies that reported positive and statistically significant effects related to aggregate long

- term mean PM 2.5 concentrations down to approximately 12 μg/m 3 ( U.S. EPA, 2011a, p. 2

- 33). Coll ectively, the Policy Assessment concluded that currently available evidence provided support for associations between long

- term PM 2.5 exposure and mortality and morbidity effects that extend to distributions of PM 2.5 concentrations that are lower than those that had previously been associated with such effects, with aggregate long

- term mean PM 2.5 concentrations extending to well below the level of the current annual standard. The Policy Assessment also considered the long

- term mean PM 2.5 concentrations in short

- term exposure studies in assessing the appropriateness of the level of the current annual standard. See American Farm Bureau Federation v. EPA , 559 F. 3d at 522, 523

- 24 (remanding 2006 standard because the EPA had not adequately explained its choice not to consider long

- term means of short

- term exposure studies in assessing adequacy of primary annual PM 2.5 standard). In light of the mixed findings reported in single

- city, short

- term exposure studies, the Policy Assessment placed comparatively greater weight on the results from multi

- city studies in considering the adequacy of the current suite of standards ( U.S. EPA, 2011a, pp. 2

- 34 to 2

- 35). With regard to associations reported in short

- term PM 2.5 exposure stu dies, the Policy Assessment recognized that long

- term mean concentrations reported in new multi

city U.S. and Canadian studies provided evidence of associations between short

- term PM 2.5 exposure and mortality at similar air quality distributions t o those t hat had***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 89 of 790 Formatted: Left previously been observed in an 8

- cities Canadian study (Burnett and Goldberg, 2003; aggregate long

- term mean PM 2.5 concentration of 13.3 μg/m 3 ). In a multi

- city time

- series analysis of 112 U.S. cities, Zanobetti and Schwartz (2009) reported a posit ive and statistically significant association with all

- cause, cardiovascular

- related (e.g., heart attacks, stroke), and respiratory

- related mortality and short

- term PM 2.5 exposure, in which the aggregate long

- term mean PM 2.5 concentration was 13.2 μg/m 3 ( U .S. EPA, 2009a, Figure 6

- 24). Furthermore, city

- specific effect estimates indicated the association between short

- term exposure to PM 2.5 and total mortality and cardiovascular

- and respiratory

- related mortality was consistently positive for an overwhelming majority (99 percent) of the 112 cities across a wide range of air quality concentrations (long

- term mean concentrations ranging from 6.6 μg/m 3 to 24.7 μg/m 3 ; U.S. EPA, 2009a, Figure 6

- 24, p. 6

- 178 to 179). The EPA staff noted that for all

- cause mortality, city

- specific effect estimates were statistically significant for 55 percent of the 112 cities, with long

- term city

- mean PM 2.5 concentrations ranging from 7.8 μg/ m 3 to 18.7 μg/m 3 and 24

- hour PM 2.5 city

- mean 98 th percentile concentrations ranging from 18.4 to 64.9 μg/m 3 (personal communication with Dr. Antonella Zanobetti, 2009). 46 With regard to cardiovascular and respiratory morbidity effects, in the first analysi s of the Medicare cohort conducted by Dominici et al. (2006a) across 204 U.S. counties, investigators reported a statistically significant association with hospitalizations for cardiovascular and respiratory diseases and short

- term PM 2.5 exposure, in which the aggregate long

- term mean PM 2.5 concentration was 13.4 μg/m 3 . Furthermore, a sub

analysis restricted to days with 24

- hour average concentrations of PM 2.5 at or below 35
46 Single

- city Bayes

- adjusted effect estimates for the 112 cities analyzed in Zanobetti and Schwartz (2009) were provided by the study authors (personal communication with Dr. Antonella Zanobetti, 2009; see also U.S. EPA, 2009a, Figure 6

- 24).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 90 of 790 Formatted: Left μg/m 3 indicated that, in spite of a reduced statistical power from a smaller number of study days, statistically significant associations were still observed between short

- term exposure to PM 2.5 and hospital admissions for cardiovascular and respiratory diseases (Dominici, 2006b). 47 In an extended analysis of this cohort, Bell et al (2008 ) reported a positive and statistically significant increase in cardiovascular hospitalizations associated with short

- term PM 2.5 exposure, in which the aggregate long

- term mean PM 2.5 concentration was 12.9 μg/m 3 . These results, along with the observation t hat approximately 50 percent of the 204 county

- specific mean 98 th percentile PM 2.5 concentrations in the study aggregated across all years were below the 24

- hour standard of 35 μg/m 3 , not only indicated that effects are occurring in areas that would meet t he current standards but also suggested that the overall health effects observed across the U.S. are not primarily driven by the higher end of the PM 2.5 air quality distribution (Bell, 2009a, personal communication from Dr. Michelle Bell regarding air qual ity data for Bell et al., 2008 and Dominici et al., 2006a). Collectively, the Policy Assessment concluded that the findings from short

- term PM 2.5 exposure studies provided evidence of PM 2.5 - associated health effects occurring in areas that would likely ha ve met the current suite of PM 2.5 standards ( U.S. EPA, 2011a, p. 2

- 35). These findings were further bolstered by evidence of statistically significant PM 2.5 - related health effects occurring in analyses restricted to days in which 24

- hour average PM 2.5 conc entrations were below 35 μg/m 3 (Dominici, 2006b).
47 This sub

- analysis w as not included in the original publication (Dominici et al., 2006a). The study authors provided sub

- analysis results for the Administrator’s consideration as a letter to the docket following publication of the proposed rule in January 2006 (personal commu nication with Dr. Francesca Dominici, 2006b). As noted in section III.A.3, this study is part of the basis for the conclusion that there is no evidence suggesting that risks associated with long

- term exposures are likely to be disproportionately driven by peak 24

- hour concentrations.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 91 of 790 Formatted: Left In evaluating the currently available scientific evidence, as summarized in section III.B of the proposal, the Policy Assessment first concluded that there was stronger and more consistent and coherent sup port for associations between long

- and short

- term PM 2.5 exposures and a broad range of health outcomes than was available in the last review, providing the basis for fine particle standards at least as protective as the current PM 2.5 standards ( U.S. EPA, 2011a, p. 2

- 26). Having reached this initial conclusion, the Policy Assessment addressed the question of whether the available evidence supported consideration of standards that were more protective than the current standards. In so doing, the Policy Assessment considered whether there was now evidence that health effect associations have been observed in areas that likely met the current suite of PM 2.5 standards. As discussed above, long

- and short

- term PM 2.5 exposure studies provided evidence of ass ociations with mortality and cardiovascular and respiratory effects both at lower ambient PM 2.5 concentrations than had been observed in the previous review and at concentrations allowed by the current standards ( U.S. EPA, 2011a, p. 2

- 35). In reviewing this information, the Policy Assessment recognized that important limitations and uncertainties associated with this expanded body of scientific evidence, as discussed in section III.B.2 of the proposal, needed to be carefully considered in determining the weight to be placed on the body of studies available in this review. Taking these limitations and uncertainties into consideration, the Policy Assessment concluded that the currently available evidence clearly calls into question whether the current suite of primary PM 2.5 standards protects public health with an adequate margin of safety from effects associated with long

- and short

- term exposures. Furthermore, the Policy Assessment concluded this evidence provides strong support for considering fine***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 92 of 790 Formatted: Left partic le standards that would afford increased protection beyond that afforded by the current standards ( U.S. EPA, 2011a, p. 2

- 35). In addition to evidence

- based consideration, the Policy Assessment also considered the extent to which health risks estimated to o ccur upon simulating just meeting the current PM 2.5 standards may be judged to be important from a public health perspective, taking into account key uncertainties associated with the quantitative health risk estimates. In so doing, the Policy Assessment f irst noted that the quantitative risk assessment addresses: (1) the core PM 2.5 - related risk estimates; (2) the related uncertainty and sensitivity analyses, including additional sets of reasonable risk estimates generated to supplement the core analysis; ( 3) an assessment of the representativeness of the urban study areas within a national context; 48 and (4) consideration of patterns in design values and air quality monitoring data to inform interpretation of the risk estimates, as discussed in section III.C above. In considering the health risks estimated to remain upon simulation of just meeting the current suite of standards and considering both the qualitative and quantitative assessment of uncertainty completed as part of the assessment, the Policy Asse ssment concluded these risks are important from a public health standpoint and provided strong support for consideration of alternative standards that would provide increased protection beyond that afforded by the current PM 2.5 ( U.S. EPA, 2011a, pp. 2

- 47 t o 2

- 48). This conclusion reflected consideration of both the severity and the magnitude of the effects. For example, the Risk Assessment indicated the possibility that

48 Based on analyses of the representativeness of the 15 urban study areas in the broader national context, the Policy Assessment concludes that these study areas are generally representative of urban areas in the U.S. likely to experience relatively elevated levels of risk related to ambient PM 2.5 exposures (U.S. EPA, 2011a, p. 2

- 42).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 93 of 790 Formatted: Left premature deaths related to ischemic heart disease associated with long

- term PM 2.5 expos ure alone would likely be on the order of thousands of deaths per year in the 15 urban study areas upon simulating just meeting the current standards 49 ( U.S. EPA, 2011a, pp. 2

- 46 to 2

- 47). Moreover, additional risks were anticipated for premature mortality related to cardiopulmonary effects and lung cancer associated with long

- term PM 2.5 exposure as well as mortality and cardiovascular

- and respiratory

- related morbidity effects (e.g., hospital admissions, emergency department visits) associated with short

te rm PM 2.5 exposures. Based on the consideration of both qualitative and quantitative assessments of uncertainty completed as part of the quantitative risk assessment, the Risk Assessment concluded that it was unlikely that the estimated risks are over

- state d, particularly for mortality related to long

- term PM 2.5 exposure, and may well be biased low based on consideration of alternative model specifications evaluated in the sensitivity analyses ( U.S. EPA, 2010a, p. 5

- 16; U.S. EPA, 2011a, p. 2

- 41). Furthermore , the currently available scientific information summarized in section III.B of the proposal provided evidence for a broader range of health endpoints and at

- risk populations beyond those included in the quantitative risk assessment ( U.S. EPA, 2011a, p. 2

- 47). b. CASAC Advice The CASAC, based on their its review of drafts of the Integrated Science Assessment, the Risk Assessment, and the Policy Assessment, provided an array of advice both with regard to interpreting the scientific evidence and quantitative r isk assessment, as well as with regard to consideration of the adequacy of the current PM 2.5 standards (Samet, 2009a b,c,d,e,f; Samet 2010a,b,c,d). With regard to the adequacy of the
49 Premature mortality for all causes attributed to PM 2.5 exposure was estimated to be on the order of tens of thousands of deaths per year on a n ational scale based on 2005 air quality data (U.S. EPA, 2010a, Appendix G, Table G

- 1).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 94 of 790 Formatted: Left current standards, CASAC concluded that the “currently available informat ion clearly calls into question the adequacy of the current standards” (Samet, 2010d, p. i) and that the current standards are “not protective” (Samet, 2010d, p. 1). Further, in commenting on the first draft Policy Assessment, CASAC noted: With regard to t

he integration of evidence

- based and risk

- based considerations, CASAC concurs with EPA’s conclusion that the new data strengthens the evidence available on associations previously considered in the last round of the assessment of the PM 2.5 standard. CASAC also agrees that there are significant public health consequences at the current levels of the standard that justify consideration of lowering the PM 2.5 NAAQS further (Samet, 2010c, p.12).
c. Administrator's Proposed Conclusions Concerning the Adequacy of the Current Primary PM 2.5 Standards At the time of the proposal, in considering the body of scientific evidence, the Administrator concluded there was stronger and more consistent and coherent support for associations between long

- and short

- term PM 2.5 e xposure and a broader range of health outcomes than was available in the last review, providing the basis for fine particle standards at least as protective as th e current PM 2.5 standards. In particular, the Administrator recognized in section III.D.4 of t he proposal that the Integrated Science Assessment concluded that the results of epidemiological and experimental studies form a plausible and coherent data set that supports a causal relationship between long

- and short

- term PM 2.5 exposures and mortality and cardiovascular effects and a likely causal relationship between long

- and short

- term PM 2.5 exposures and respiratory effects. Furthermore, the Administrator reflected that effects had been observed at lower ambient PM 2.5 concentrations than what had be en observed in the last review, including at ambient PM 2.5 concentrations in areas that likely met the current PM 2.5 NAAQS. With regard to the results of the quantitative risk assessment, the Administrator note d that the Risk Assessment concludes conclude d that the risks estimated to remain upon simulation***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 95 of 790 Formatted: Left of just meeting the current standards are we re important from a public health standpoint in terms of both the severity and magnitude of the effects. At the time of the proposal, in considering whether the current suite of PM 2.5 standards should be revised to provide requisite public health protection, the Administrator carefully considered the staff conclusions and rationales presented in the Policy Assessment, the advice and recommendations from CASAC, and public comments to date on this issue. In so doing, the Administrator placed primary consideration on the evidence obtained from the epidemiological studies and provisionally found the evidence of serious health effects reported in long

- and short

- term ex posure studies conducted in areas that would have met the current standards to be compelling, especially in light of the extent to which such studies are part of an overall pattern of positive and frequently statistically significant associations across a broad range of studies that collectively represent a strong and robust body of evidence. As discussed in the Integrated Science Assessment and Policy Assessment, the Administrator recognized that much progress has been made since the last review in addres sing some of the key uncertainties that were important considerations in establishing the current suite of PM 2.5 standards. For example, progress made since the last review provides increased confidence in the long

- and short

- term exposure studies as a bas is for considering whether any revision of the annual standard is appropriate and increased confidence in the short

- term exposure studies as a basis for considering whether any revision of the 24

- hour standard is appropriate. 50

50 The EPA notes that this increased confidence in the long

- and short

- term associations generally reflects less uncertainty as to the likely causal nature of such associ ations, but does not address directly the question of the extent to which such associations remain toward the lower end of the range of ambient PM 2.5 concentrations. This question is***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 96 of 790 Formatted: Left Based on her consideration o f these conclusions, as well as consideration of CASAC’s conclusion that the evidence and risk assessment clearly call call ed into question the adequacy of the public health protection provided by the current PM 2.5 NAAQS and public comments on the proposal, the Administrator provisionally concluded that the current primary PM 2.5 standards, taken together, are we re not requisite to protect public health with an adequate margin of safety and that revision is wa s needed to provide increased public health protecti on. The Administrator provisionally concluded that the scientific evidence and information on risk provide provide d strong support for consideration of alternative standards that would provide increased public health protection beyond that afforded by the current PM 2.5 standards. 2. Comments on the Need for Revision This section addresses general comments based on relevan t facts that either support or oppose any change to the current suite of primary PM 2.5 standards. Comments on specific long

- and short

- term exposure studies that relate to consideration of the appropriate levels of the annual and 24

- hour standards are addr essed in section III.E.4 below. Many public comments asserted that the current PM 2.5 standards are insufficient to protect public health with an adequate margin of safety and that revisions to the standards are therefore appropriate, indeed necessitated. Among those calling for revisions to the current standards were the Children’s Health Protection Advisory Committee (CHPAC); major medical and public health groups including the American Heart Association (AHA), American Lung Association (ALA), American Pu blic Health Association (APHA), American Thoracic Society central to the Agency’s evaluation of the relevant evidence to determine appropriate standards levels, as discussed below in section III.E.4.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 97 of 79 0 Formatted: Left (ATS); the Physicians for Social Responsibility (PSR); major environmental groups such as the Clean Air Council, Clean Air Task Force, Earthjustice, Environmental Defense Fund (EDF), National Resour ces Defense Council (NRDC), and Sierra Club; many environmental justice organizations as well as medical doctors, academic researchers, health professionals, and many private citizens. For example, the American Heart Association and other major national pu blic health and medical organizations stated that, “[o]ur organizations are keenly aware of the public health and medical threats from particulate matter” and called on the EPA to “significantly strengthen” both the annual and 24

- hour PM 2.5 standards “to h elp us protect the health of our patients and our nation” (AHA et al., 2012, pp 1 and 13). AHA et al. and ALA et al., as well as a group of more than 350 physicians, environmental health researchers, and public health and medical professionals articulated similar comments on the available evidence: Ample scientific evidence supports adopting tighter standards to protect the health of people who are most susceptible to the serious health effects of these pollutants. More than 10,000 peer

- reviewed scientific studies have been published since 1997 when EPA adopted the current annual standard. These studies validate and extend earlier epidemiologic research linking both acute and chronic fine particle pollution with serious morbidity and mortality. The newer res earch has also expanded our understanding of the range of health outcomes associated with PM and has identified adverse respiratory and cardiovascular health effects at lower exposure levels than previously reported. As discussed and interpreted in the EPA ’s 2009 Integrated Science Assessment for Particulate Matter, the new evidence reinforces already strong existing studies and supports the conclusion that PM 2.5 is causally associated with numerous adverse health effects in humans at exposure levels far be low the current standard. Such a conclusion demands prompt action to protect human health. (AHA et al., 2012, pp. 1 to 2; ALA et al., pp. 4 to 5; similar comment submitted by Rom et al., 2012, p. 1). All of these medical and public health commenters stated that the current PM 2.5 standards need to be revised, and that even more protective standards than those proposed by the EPA are needed to adequately protect public health, particularly for at

- risk populations. Many environmental justice organizations and individual commenters also***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 98 of 790 Formatted: Left expressed such views. The National Association of Clean Air Agencies (NACAA), the Northeast States for Coordinated Air Use Management (NESCAUM), and many State and local air agencies and health departments who commented on the PM 2.5 standards supported revision of the suite of current PM 2.5 standards, as did five State Attorneys General s tate
a ttorneys g eneral (Schneiderman et al., 2012) and the National Tribal Air Association (NTAA). These commenters based their views chiefly on the body of evidence and technical analyses presented and discussed in the Integrated Science Assessment, the Risk Assessment, and the Policy Assessment finding the available scientific information to be strong er and more compelling than in the last review. These commenters generally placed much weight on CASAC’s recommendation to revise the PM 2.5 standards to provide increased public health protection and on the EPA staff conclusions presented in the final Poli cy Assessment. Some of these commenters specifically mentioned extended analyses of seminal long

- term exposure studies

- the ACS (Krewski et al., 2009), Harvard Six Cities (Laden et al., 2006), and Southern California Children’s Health (Gauderman et al., 2 004) studies. These commenters also highlighted the availability of additional long

- term exposure studies in this review, specifically a study of premature mortality in older adults (Eftim et al., 2008) and the WHI study of cardiovascular morbidity and mor tality effects in women (Miller et al., 2007) providing stronger evidence of mortality and morbidity effects associated with long

- term PM 2.5 exposures at lower concentrations than had previously been observed, including studies of effects in at

- risk popula tions. For example, some***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 99 of 790 Formatted: Left commenters asserted: Evidence during the last review showed clearly that the annual average standard needed to be much lower than the standard of 15 μg/m 3 that was first set in 1997. The evidence has only grown since then. Multiple, multi

- city studies over long periods of time have shown clear evidence of premature death, cardiovascular and respiratory harm as well as reproductive and developmental harm at contemporary concentrations far below the level of the current (annual) standard (ALA et al., 2012, p. 39; AHA et al., 2012, p. 10). These commenters also highlighted the availability of a number of short

- term PM 2.5 exposure studies as providing evidence of mortality and morbidity effects at levels concentration s below the level of the current 24

- hour PM 2.5 standard. Specifically, these commenters made note of multi

- city studies of premature mortality (Zanobetti and Schwartz, 2009) and increased hospitaliza tions for cardiovascular and respiratory

- related effects in older adults (Bell et al., 2008). These commenters also asserted the importance of many of the single

- city studies, arguing that these studies “provide valuable information regarding impacts on su sceptible populations and on health risk in areas with high peak to mean concentration ratios” (ALA, et al., 2012, p. 65). Collectively, considering the multi

- and single

- city short

- term exposure studies, these commenters asserted “the record clearly suppo rts a more stringent 24

- hour standard of 25 μg/m 3 to provide uniform protection in all regions of the country particularly from short

- term spikes in pollution and from the sub

- daily exposures that trigger heart attacks and strokes” (ALA et al., 2012, p. 62 ). A group of more than 350 physicians, environmental health researchers, and public health and medical professionals argued, “[s]tudies of short

- term exposure demonstrate that PM 2.5 air pollution increases the risk of hospital admissions for heart and lun g problems even when you exclude days with pollution concentrations at or above the current daily standard of 35 μg/m 3 . Daily concentrations must be capped at lower levels to protect against peak exposure days that occur due to***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 100 of 790 Formatted: Left local and seasonal sources o f emissions” (Rom et al., 2012, p. 2). In addition, many of these commenters generally concluded that progress had been made in reducing many of the uncertainties identified in the last review, in better understanding mechanisms by which PM 2.5 may be causi ng the observed health effects, and in improving our understanding of at

- risk populations. 51 Further, these Further, a number of commenters argued that by making the standards more protective, the PM 2.5 NAAQS would be more consistent with other existing standards (e.g., California's annual average standard of 12 μg/m 3 ) (CARB, 2012; CA OEHHA, 2012). Other commenters argued that revising the primary PM 2.5 standards would be more consistent with the

recomme ndations of the World Health Organization (WHO) and/or Canada (e.g., ALA et al., 2012, p. 62; ISEE, 2012, p. 2 ; MOE

- Ontario, 2012, p. 1 ; ISEE, 2012, p. 2 ). With regard to the scope of the literature reviewed for PM 2.5 - related health effects, some commente rs asserted that the EPA inappropriately narrowed the scope of the review by excluding a number of categories of relevant studies, specifically related to studies of diesel pollution and traffic

- related pollution (ALA, et al., 2012, p. 17). These commenter s argued that, based upon the exclusion of these types of studies, the Integrated Science Assessment “came to the erroneous conclusion that the causal relationship between PM and cancer is merely suggestive. This conclusion does not square with the Interna

tional Agency Research on Cancer (IARC) finding that diesel emissions are a known human carcinogen nor with the conclusions of the extended analyses of the [Harvard] Six Cities and ACS cohort studies that report positive and

51 In addition, the EPA notes that CASAC found that the Integrated Science Assessment clearly presented and discussed the current scientific information related to potential modes of action (Chapter 5) and at

- risk populations (Chapter 8) (Samet, 2009e, pp. 7 to 8; Samet, 2009f, pp. 2 and 11 to 12).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 101 of 790 Formatted: Left statistically significant assoc iations between PM 2.5 and lung cancer.” Id. Some of these commenters also noted the results of the EPA’s quantitative risk assessment, concluding that it showed that the risks estimated to remain when the current standards are met are large and important from a public health perspective and warrant increased protection. For example, ALA et al., noted that the Risk Assessment indicated the quantitative risk analyses likely underestimated PM 2.5 - related mortality ( U.S. EPA, 2010a, p. 5

- 16) and argued that “th e measurements of risk should be treated conservatively” (ALA, et al., 2012, p. 73). These commenters also summarized an expanded analysis of alternative PM 2.5 standard levels that they argued documented the need for more protective standards (McCubbin, 2 011). In general, all of these commenters agreed on the importance of results from the large body of scientific studies reviewed in the Integrated Science Assessment and on the need to revise the suite of PM 2.5 standards as articulated in the EPA’s propos al, while generally differing with the EPA’s proposed judgments about the extent to which the standards should be revised based on this evidence, specifically for providing protection for at

- risk populations. The EPA generally agrees with these commenters ’ conclusion regarding the need to revise the current suite of PM 2.5 standards. The scientific evidence noted by these commenters was generally the same as that assessed in the Integrated Science Assessment and the Policy Assessment, and the EPA agrees tha t this evidence provides a strong basis for concluding that the current PM 2.5 standards, taken together, are not requisite to protect public health with an adequate margin of safety, and they need to be revised to provide increased protection. For reasons discussed in section III.E.4.c below,***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 102 of 790 Formatted: Left however, the EPA disagrees with aspects of these commenters’ views on the level of protection that is appropriate
. T he EPA disagrees with these commenters’ views that diesel exhaust studies were excluded from the Integ rated Science Assessment and were not considered when making the causality determination for cancer, mutagenicity, and genotoxicity. As discussed in Section s ection 7.5 of the Integrated Science Assessment, diesel exhaust studies were integrated within the broader body of scientific evidence that was considered in reaching the causality determination for these health endpoints. Additionally, as discussed in section 1.5.3 of the Integrated Science Assessment, the evidence from diesel exhaust studies was also considered as part of the collective evidence evaluated when making determinations for other, noncancer health outcomes (e.g., cardiovascular and respiratory effects). 52 Specifically, when evaluating this evidence , the focus was on understanding the effects of diesel exhaust particles. It is important to recognize that the Integrated Science Assessment focused on experimental studies of diesel exhaust that evaluated exposures that were relevant to ambient concentrations, i.e., “within one or two orders of m agnitude of ambient PM concentrations” ( U.S. EPA, 2009a, section 1.3). The causal determination for cancer, mutagenicity, and genotoxicity presented in the Integrated Science Assessment represents an integration of experimental and observational evidence o f exposures to ambient PM
52 In developing the second draft Integrated Science Assessment, the EPA reexamined the controlled human exposure and toxicological studies of fresh diesel and gasoline exhaust and considered this
. This information , in addition to other considerations , supported a change in the causal determinations for ultrafine particles. Specifically, in reevaluating the causal determinations for short

- term ultrafine particle exposures and cardiovascular and respiratory effects, the EPA changed the classification from “inadequate” to “suggestive ” for both categories of health outcomes (Vandenberg, 2009, p. 3). CASAC agreed with the EPA’s rationale for revising these causal determinations (Samet, 2009f, p. 10).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 103 of 790 Formatted: Left concentrations. T he EPA fully considered the findings of studies that assessed the se and other health effects associated with exposure to diesel particles in reaching causality determinations regarding health outcomes associated w ith PM 2.5 exposures. Furthermore, CASAC supported the EPA’s change to the causal determination for cancer and long

term PM 2.5 concentrations from “inadequate” to “suggestive” (Samet, 2009f, p. 2). With regard to traffic studies, the EPA disagrees with the commenters’ views that traffic studies that focused on exposure indicators such as distance to roadways should have been included in the Integrated Science Assessment. These studies were excluded from consideration because they did not measure ambient conc entrations of specific air pollutants, including PM 2.5 , but instead we re studies evaluating exposure to the undifferentiated “traffic related air pollution” mixture (ALA et al., 2012, p.17) ( U.S. EPA, 2009a, section 1.3). As a result, these studies do not add to the collective body of evidence on the relationship between long

- or short

- term exposure to ambient concentrations of PM 2.5 and health effects. Some of these commenters also identified “new” studies that were not included in the Integrated Science A ssessment as providing further support for the need to revise the primary PM 2.5 standards. As discussed above in section II.B.3 above , the EPA notes that, as in past NAAQS reviews, the Agency is basing the final decisions in this review on the studies and related information included in the PM air quality criteria that have undergone CASAC and public review and will consider the “new” studies for purposes of decision making in the next PM NAAQS review. Nonetheless, in provisionally evaluating commenters’ ar guments (see Response to Comments document), the EPA notes that its provisional assessment of “new” science found that such studies did not***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 104 of 790 Formatted: Left materially change the conclusions in the Integrated Science Assessment (U.S. EPA, 2012b)
. Another group of commenter s opposed revising the current PM 2.5 standards. These views were most extensively presented in comments from the Utility Air Regulatory Group (UARG), representing a group of electric generating companies and organizations and several national trade associa tions; the American Petroleum Institute (API) representing more than 500 oil and natural gas companies; the National Association of Manufacturers (NAM), the American Chemistry Council (ACC), the American Fuel & Petroleum Manufacturers (AFPM), the Alliance of Automobile Manufacturers , (AAM) , and other manufacturing associations; the Electric Power Research Institute (EPRI); and the Texas Commission on Environmental Quality (T exas CEQ). These commenters generally mentioned many of the same studies that were c ited by the commenters who supported revising the standards, as well as other studies, but highlighted different aspects of these studies in reaching substantially different conclusions about their strength and the extent to which progress has been made in reducing uncertainties in the evidence since the last review. Furthermore, they asserted that the evidence that has become available since the last review does not establish a more certain risk or a risk of effects that are significantly different in char acter to those that provided a basis for the current standards, nor does the evidence demonstrate that the risk to public health upon attainment of the current standards would be greater than was understood when the EPA established the current standards in 2006. These commenters generally expressed the view that the current standards provide the requisite degree of public health protection. In supporting their view, these***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 105 of 790 Formatted: Left commenters generally argued that the EPA’s conclusions are inconsistent with the curr ent state of the science and questioned the underlying scientific evidence including the causal determinations reached in the Integrated Science Assessment. More specifically, this group of commenters argued that: (1) the EPA did not apply its framework fo r causal determination consistently across studies or health outcomes and, in the process, the EPA relied on a selective group of long

- and short

- term exposure studies to reach conclusions regarding causality; (2) toxicological and controlled human exposur e studies do not provide supportive evidence that the health effects observed in epidemiological studies are biologically plausible; (3) uncertainties in the underlying health science are as great or greater than in 2006; ( 4 ) there is no evidence of greate r risk since the last review to justify tightening the current annual PM 2.5 standard; and ( 5 ) “new” studies not included in the Integrated Science Assessment continue to increase uncertainty about possible health risks associated with exposure to PM 2.5 . Th ese comments are discussed in turn below. (l) Some of these commenters asserted that the EPA did not apply its framework for causal determinations consistently across studies or health outcomes ( e.g., ACC, 2012, Attachment A, pp. 1 to 2; API, 2012, Attachm ent 1, p. 30; NAM et al., 2012, pp. 22 to 25; Texas CEQ, 2012, pp 2 to 3 ). 53 These commenters argued that the EPA downplayed epidemiological studies with null or inconsistent results, inappropriately used the Hill criteria when evaluating the epidemiologic e pidemiological evidence, and used the same study and the same underlying database to conclude that there was a causal association between mortality and multiple criteria pollutants
. 53 The EPA notes that the same concerns about the causal determinations presented in the Integrated Science Assessment were raised in comments to CASAC on the draft Integrated Science Assessments (e.g., UARG, 2009; API, 2009; ACC, 2012, Appendix B). CASAC, therefore, had the o pportunity to consider these comments in reaching consensus conclusions on this issue. Formatted: Font: 12 pt

Formatted: Font: 12 pt***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 106 of 790 Formatted: Left The EPA disagrees with these commenters’ views. First, the EPA recognizes that the evaluation of the scientific evidence and its application of the causal framework used in the current PM NAAQS review was the subject of exhaustive and detailed review by CASAC and the public. Prior As summarized in section II.B.3 above, p rior to finalizing the Integrated Science Assessment, two drafts were released for CASAC and public review to evaluate the scientific integrity of the documents. Evidence related to the substantive issues raised by CASAC and public commenters with regard to th e content of the first and second draft Integrated Science Assessments were discussed at length during these public CASAC meetings and considered in developing the final Integrated Science Assessment. CASAC supported the development of the EPA’s causality framework and its use in the current PM NAAQS review and concluded: The five

- level classification of strength of evidence for causal inference has been systematically applied; this approach has provided transparency and a clear statement of the level of co nfidence with regard to causation, and we recommend its continued use in future Integrated Science Assessments (Samet 2009f, p. 1). These commenters asserted that during the application of the causal framework the EPA inappropriately relied on a selective group of long

- and short

- term exposure studies in reaching causal inferences (API, 2012, pp 12 to 17; ACC, 2012, Attachment A, pp 1 to 2; NAM et al., 2012, pp. 22 to 25; Texas CEQ, 2012, pp 2 to 3). Additionally, these commenters expressed the view that t he EPA focused on a subset of epidemiological studies that reported positive and statistically significan t results while ignoring other studies, especially those that reported no statistically significan t associations, those that reported potential thresho lds, or those that highlighted uncertainties and limitations in study design or results. Furthermore, some of these commenters argued that epidemiological studies are observational in nature and cannot***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 107 of 790 Formatted: Left provide evidence of a causal association. The EPA disa grees with these commenters’ views on assessing the health effects evidence and on the conclusions regarding the causal ity determinations reached in the Integrated Science Assessment
. In conducting a comprehensive evaluation of the evidence in the Integrat ed Science Assessment, the EPA recognized the distinction between the evaluation of the relative scientific quality of individual study results and the evaluation of the pattern of results within the broader body of scientific evidence and considered both in reaching causality determinations. The more detailed characterizations of individual studies included an assessment of the quality of the study based on specific criteria as described in the Integrated Science Assessment ( U.S. EPA, 2009a, section 1.5.3)
. In developing an integrated assessment of the health effects evidence for PM, the EPA emphasized the importance of examining the pattern of results across various studies and did not focus solely on statistical significance 54 as a criterion of study strength. This approach is consistent with views clearly articulated throughout the epidemiological and causal inference literature, specifically, that it is important not to focus on results of statistical tests to the exclusion o f other information. 55 The concepts

54 Statistical significance is an indicator of the precision of a study’s results, which is influenced by a variety of factors including, but not limited to, the size of the study, exposure and measurement error, and statistical model specifications. Studies typically calculate “p

- values” to determine whether the study results are statistically significant or whether the study results are likely to occur simply by chance. In general practice, effects are considered statistically significant if p values are less than 0.05. 55 For example, Rothman (1998) stated, “Many data analysts appear to remain oblivious to the qualitative nature of significance testing [and that]... statis tical significance is itself only a dichotomous indicator. As it has only two values, significant or not significant ....Nevertheless, p

- values still confound effect size with study size, the two components of estimation that we believe need to be reported s eparately.” As a result, Rothman Formatted: Font: 12 pt Formatted: Font: 12 pt, Not Superscript/ Subscript

Formatted: Font: 12 pt Formatted: Font: 12 pt, Not Superscript/ Subscript***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 108 of 790 Formatted: Left underlying the EPA’s approach to evaluating statistical associations have been discussed in numerous publications, including a report by the U.S. Surgeon General on the health consequences of smoking (Centers for Disease Control and Prevention, 2004). This report cautions against over

- reliance on statistical significance in evaluating the overall evidence for an exposure

- response relationship. Criteria characterized by Hill (1965) also addressed the value, or lack thereof, of statistical tests in the determination of cause: No formal tests of significance can answer those [causal] questions. Such tests can, and should, remind us of the effects the play of chance can create, and they will instruct us in the likely magnitude of those effects. Beyond that, they contribute nothing to the ‘proof’ of our hypothesis (Hill, 1965, p. 299). The statistical significance of individual study findings has played an important role in the EPA’s evaluation of the study’s results and the EP A has placed greater emphasis on studies reporting statistically significant results. However, in the broader evaluation of the evidence from many epidemiological studies, and subsequently during the process of forming causality determinations in integrati ng evidence across epidemiological, controlled human exposure, and toxicological studies, the EPA has emphasized the pattern of results across epidemiological studies, and whether the effects observed were coherent across the scientific disciplines for dra wing conclusions on the relationship between PM 2.5 and different health outcomes. Thus, the EPA did not limit its focus or consideration to just studies that reported positive associations or where the results were statistically significant. In addition, some commenters asserted that the EPA inappropriately used the Hill criteria by failing to consider the limitations of studies with weak associations, thereby overstating the consistency of the observed associations (API, 2012, Attachment 1, pp
. 30 recommended that p

- values be omitted as long as point and interval estimates are available.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 109 of 790 Formatted: Left to 35). These commenters argued that risk estimates greater than 3 to 4 reflect strong associations supportive of a causal link, while smaller risk estimates (i.e., 1.5 to 3) are considered to be weak and require other lines of evidence to demonstrate causality. As discussed in section 1.5.3 of the Integrated Science Assessment, the EPA thoroughly considered the limitations of all studies during its evaluation of the scientific literature (U.S. EPA,, 2009a, p. 1

- 14). This collective body of evidence, i ncluding known uncertainties and limitations of the studies evaluated, were considered during the process of forming causality determinations as discussed in chapters 6 and 7 of the Integrated Science Assessment. For example, the EPA concluded that “a caus al relationship exists between short

- term PM 2.5 exposure and cardiovascular effects , ” however, in reaching this conclusion, the Agency recognized and considered limitations of the current evidence that still requires further examination (U.S. EPA, 2009a
. , in s ection 6.2.12.1 ). Therefore, t he EPA disagrees with these commenters’ views that the Hill criteria were inappropriately used in that the limitations of studies were not considered. The EPA also disagrees with the commenters commenters’ assertion that t he magnitude of the association must be large to support a determination of causality. As discussed in the Integrated Science Assessment, the strength of the observed association is an important aspect to aid in judging causality and “while large effects s upport causality, modest effects therefore do not preclude it” ( U.S. EPA, 2009a, Table 1

- 2, section 1.5.4). The weight of evidence approach used by the EPA encompasses a multitude of factors of which the magnitude of the association is only one component ( U.S. EPA, 2009a, Table 1

- 3). An evaluation of the association across multiple investigators and locations supports the “reproducibility of findings [which] constitutes***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 110 of 790 Formatted: Left one of the strongest arguments for causality” ( U.S. EPA, 2009a, Table 1

- 2). Even though the risk estimates for air pollution studies may be modest, the associations are consistent across hundreds of studies as demonstrated in the Integrated Science Assessment. Furthermore, the causality determinations rely on different lines of evidence, by i ntegrating evidence across disciplines, including animal toxicological studies and controlled human exposure studies. Furthermore, as summarized in section III.B above and discussed more fully in section III.B.3 of the proposal , the EPA recognizes that the population potentially affected by PM 2.5 is considerable, including large subgroups of the U.S. population that have been identified as at

- risk populations (e.g., children, older adults, persons with underlying cardiovascular or respiratory disease). Whil e individual effect estimates from epidemiological studies may be modest in size, the public health impact of the mortality and morbidity associations can be quite large given that air pollution is ubiquitous. Indeed, with the large population exposed, exp osure to a pollutant causally associated at a population level with mortality and serious illness has significant public health consequences, virtually regardless of the relative risk. Taken together, th is information indicates that exposure to ambient PM 2 .5 concentrations has substantial public health impacts. In addition, these commenters believed that the EPA downplayed null or inconsistent findings in numerous long

- term mortality studies with reported PM 2.5 concentrations above and below the level of th e current annual standard. The EPA disagrees that studies with null or inconsistent findings were not accurately presented and considered in the Integrated Science Assessment. For example, as discussed throughout***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 111 of 790 Formatted: Left section 7.6 and depicted in Figures 7

- 6 and 7

- 7 of the Integrated Science Assessment, the EPA presented the collective evidence from all studies that examined the association between long

- term PM 2.5 exposure and mortality. Overall, across these studies there was evidence of consistent positive asso ciations in different cohorts. That evidence, in combination with the biological plausibility provided by experimental and toxicological studies evaluated in sections 7.1 and 7.2 of the Integrated Science Assessment, supported a causal relationship exists between long

- term PM 2.5 exposure and mortality
. Lastly, some of these commenters argued that in some cases, the EPA used the same study and the same underlying database to conclude that there is a causal association between mortality and multiple criteria pollutants. These commenter s argued, “[i]n doing so, EPA attributes the cause of the mortality effects observed to whichever criteria pollutant it is reviewing at the time” (API, 2012, pp. 14 to 16). The EPA strongly disagrees that the Agency “attributes the cause of mortality effects observed to whichever criteria pollutant it is reviewing at the time.” The EPA consistently recognizes that other pollutants are also associated with health outcomes, as is reflected in the fact that the EPA has established regulations to limit emissions of the particulate criteria pollutants as well as other gaseous criteria pollutants. Epidemiologic al studies often examine the association between short

- and long

- term exposures to multiple air pollutants and mortality within a common dataset in an attempt to identify the air pollutant(s) of the complex mixture most strongly associated with mortality. In evaluating these studies , the EPA employs specific study selection criteria to identify those studies most relevant to the review of the NAAQS. In its assessment of the health evidence regarding PM 2.5 , the EPA has carefully evaluated the potential for con founding, effect***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 112 of 790 Formatted: Left measure modification , and the role of PM PM 2.5 as a component of a complex mixture of air pollutants ( U.S. EPA, 2009 2009 a , p. 1

- 9). The EPA use d a rigorous weight of evidence approach to inform causality that evaluate d consistency across st udies within a discipline, evidence for coherence across disciplines, and biological plausibility. Additionally, during this process, the EPA assesse d the limitations of each study in the context of the collective body of evidence. It wa s the collective ev idence, not one individual study that ultimately determine d whether a causal relationship exists between a pollutant and health outcome. In the Integrated Science Assessment , the combination of epidemiologic al and experimental evidence formed the basis for the Agency concluding for the first time that a causal relationship exists between short

- or long

- term exposure to a criteria pollutant and mortality ( U.S. EPA, 2009, Section s ection s 2.3.1.1 and 2.3.1.2). Additionally, while the EPA has evaluated some of the studies used to inform the causality determination for PM in the Integrated Science Assessments for the other criteria air pollutants, the Agency has done so in the context of examining the collective body of evidence for each of the respective criter ia air pollutants. As such, the body of evidence to inform causality has varied from pollutant to pollutant resulting in the association between each criteria air pollutant and mortality being classified at a different level of the five

- level hierarchy use d to inform causation ( See e.g., U.S. EPA, 2008 e , U.S. EPA, 2008 f , U.S. EPA, 2010 k ). The EPA notes that the final causality determinations presented in the Integrated Science Assessment reflected CASAC’s recommendations on the second draft Integrated Science Assessment (Samet, 2009f, pp. 2 to 3). Specifically, CASAC supported the EPA’s changes (in the second versus first draft Integrated Science Assessment) from***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 113 of 790 Formatted: Left “likely causal” to “causal” for long

- term exposure to PM 2.5 and cardiovascular effects and for cancer and PM 2.5 (from “inadequate” to “suggestive”)

. Id . Furthermore, CASAC recommended “upgrading” the causal classification for PM 2.5 and total mortality to “causal” for both the short

- and long

- term timeframes. Id. W i th regard to mortality, the “EP A carefully reevaluated the body of evidence, including the collective evidence for biological plausibility for mortality effects, and determined that a causal relationship exists for short

- and long

- term exposure to PM 2.5 and mortality, consistent with th e CASAC comments” (Jackson, 2012 2010 ). (2) With regard to toxicological and controlled human exposure studies, these commenters argued that the available evidence does not provide coherence or biological plausibility for health effects observed in epidemi ological studies (API, 2012, pp. 21 to 22, Attachment 1, pp. 25 to 29; AAM, 2012, pp. 15 to 16; T exas CEQ, 2012, p. 3). With regard to the issue of mechanisms, these commenters noted that although the EPA recognizes that new evidence is now available on po tential mechanisms and plausible biological pathways, the evidence provided by toxicological and controlled human exposure studies still does not resolve all questions about how PM 2.5 at ambient concentrations could produce the mortality and morbidity effe cts observed in epidemiological studies. More specifically, for example, some of these commenters argued that: A review of the Integrated Science Assessment, however, suggests that the experimental evidence is inconsistent and not coherent with findings in epidemiology studies. Specifically, the findings of mild and reversible effects in most experimental studies conducted at elevated exposures are not consistent with the more serious associations described in epidemiology studies (e.g., hospital admissions and mortality). Also, both animal studies and controlled human exposure studies have identified no effect levels for acute and chronic exposure to PM and PM constituents at concentrations considerably above ambient levels.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 114 of 790 Formatted: Left EPA should consider the experime ntal findings in light of these higher exposure levels and what the relevance may be for ambient exposures (API, 2012, Attachment 1, p. 25). The EPA notes that in the review completed in 1997 , the Agency considered the lack of demonstrated biologic biologic al mechanisms for the varying effects observed in epidemiological studies to be an important caution in its integrated assessment of the health evidence upon which the standards were based ( 71 FR 61157, October 17, 2006 ). In the review completed in 2006, the EPA recognized the findings from additional research that indicated that different health responses were linked with different particle characteristics and that both individual components and complex particle mixtures

a ppeared to be responsible for many biologic responses relevant to fine particle exposures. Id. Since that review, there has been a great deal of research directed toward advancing our understanding of biologic mechanisms. While this research has not resolv ed all questions, and further research is warranted ( U.S. EPA, 2011a, section 2.5), it has provided important insights as discussed in section III.B.1 of the proposal (77 FR at 38906 to 38909) and discussed more fully in the Integrated Science Assessment ( U.S. EPA, 2009a, chapter C hapter 5). As noted in the proposal, toxicological studies provide evidence to support the biologic biologic al plausibility of cardiovascular and respiratory effects associated with long

- and short

- term PM exposures observed in epi demiological studies (77 FR 38906) and provide supportive mechanistic evidence that the cardiovascular morbidity effects observed in long

- term exposure epidemiological studies are coherent with studies of cardiovascular

- related mortality (77 FR 38907). The Integrated Science Assessment concluded that t

he new evidence available in this review “greatly expands” upon the evidence available in the last review “particularly in providing greater understanding of***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 115 of 790 Formatted: Left the underlying mechanisms for PM 2.5 induced cardiov ascular and respiratory effects for both short

- and long

- term exposures ” ( U.S. EPA, 2009a, p. 2

- 17). The mechanistic evidence now available, taken together with newly available epidemiological evidence, increases the Agency’s confidence that a causal relat ionship exists between long

- and short

- term exposure to PM 2.5 and cardiovascular effects and mortality. 56 In addition, CASAC supported the Integrated Science Assessment approach and characterization of potential mechanisms or modes of action (Samet, 2009e, pp. 7 to 8; Samet, 2009f, p. 11), as well as the findings of a causal relationship at the population level between exposure to PM 2.5 and mortality and cardiovascular effects (Samet, 2009f, pp. 2 to 3). 57 Additionally, the EPA disagrees with commenters that the mild and reversible effects observed in controlled human exposure studies are inconsistent with the more serious effects observed in epidemiologic epidemiologic al studies. Ethical considerations regarding the types of studies that can be performed with human subjects generally limit the effects that can be evaluated to those that are transient, reversible, and of limited short

- term consequence. The relatively small number of subjects recruited for controlled exposure studies should also be expected to h ave less variability in health status and risk

56 See American Trucking Assn’s Ass ociations v. EPA, 175 F. 3d 1027, 1055

- 56 (D.C. Cir. 1999) rev’d rev erse d in part and affirmed in part sub nom , Whitman v. American Trucking Assn’s, Ass ociations , 531 U.S. 457 (2001) holding that the EPA could establish NAAQS without identifying a biological mechanism (“ To begin with, the statute itself requires no such proof. The Administrator may regulate air pollutants "emissions of which, in his judgment, cause or contribute to air pollution which may reasonably be anticipated to endanger public health or welfare ." ( emphasis added by the court). Moreover, this court has neve r required the type of explanation petitioners seek from EPA. In fact, we have expressly held that EPA's decision to adopt and set air quality standards need only be based on ‘reasonable extrapolations from some reliable evidence’.... Indeed, were we to acce pt petitioners' view, EPA (or any agency for that matter) would be powerless to act whenever it first recognizes clear trends of mortality or morbidity in areas dominated by a particular pathogen.”). Formatted: Font: 12 pt***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 116 of 790 Formatted: Left factors than occurring in the general population. 58 Consequently, the severity of health effects observed in controlled human exposure studies evaluating the effects of PM should be expected to be less than observed in epidemiologic studies. Nonetheless, that effects are observed in relatively healthy indi viduals participating in controlled exposure studies serves as an indicator that PM is initiating health responses and that more severe responses may reasonably be expected in a more diverse population. It should also be noted that there is a small body o f toxicological evidence demonstrating mortality in rodents exposed to PM (e.g., Killingsworth et al. 1997 ; Godleski et al. 1996 ). Overall it is not surprising that lethality is not induced in more toxicological research, as these types of studies do not r eadily lend themselves to this endpoint. Epidemiologic Epidemiologic al studies have observed associations between PM and mortality in communities with populations in the range of many thousands to millions of people. Clearly, it is not feasible to expose h undreds (if not thousands) of animals to ambient PM (potentially over many years) in a laboratory setting to induce enough lethalities to distinguish between natural deaths and those attributable to PM.

58 For example, the EPA excludes from its controlled human exposure studies involving exposure to PM 2.5 any individual with a significant risk factor for experiencing adverse effects from such exposure. Thus, the EPA excludes a priori the following categorie s of persons: those with a history of angina, cardiac arrhythmias, and ischemic myocardial infarction or coronary bypass surgery; those with a cardiac pacemaker; those with uncontrolled hypertension (greater than 150 systolic and 90 diastolic); those with neurogenetive diseases; those with a history of bleeding diathesis; those taking beta

blockers; those using oral anticoagulants; those who are pregnant, attempting to become pregnant, or breastfeeding; those who have experienced a respiratory infection wit hin four weeks of exposure; those experiencing eye or abdominal surgery within six weeks of exposure; those with active allergies; those with a history of chronic illnesses such as diabetes, cancer, rheumatologic diseases, immunodeficiency state, known car diovascular disease, or chronic respiratory diseases; smokers. The EPA “Application for Independent Review Board Approval of Human Subjects Research: Cardiopulmonary Effects of healthy Older GSTM1 Null and Sufficient individuals to Concentrated Ambient Air Particles (CAPTAIN)”, Nov. 9, 2011, p. 9.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 117 of 790 Formatted: Left Furthermore, the heterogeneous human populations sam pled in epidemiological studies are comprised of individuals with different physical, genetic, health, and socioeconomic backgrounds which may impact the outcome. However, in toxicological studies, the rodent groups are typically inbred, such that inter

- i ndividual variability is minimized. Thus, if the rodent strain used is quite robust, PM

- induced effects may not be observed at low exposure concentrations. (3) In asserting that the uncertainties in the underlying health science are as great or greater tha n in the last review and therefore do not support revision to the standards at this time, commenters in this group variously discussed a number of issues related to: (a) confounding, (b) heterogeneity in risk estimates, (c) exposure measurement error, (d) model specification , (e) the shape of the concentration

- response relationship, and ( f ) understanding the relative toxicity of components within the mixture of fine particles. Each of these issues is addressed below and some are discussed in more detail in the Response to Comments document
. In summary, these commenters concluded that the substantial uncertainties present in the last review have not been resolved and/or that the uncertainty about the possible health risks associated with PM 2.5 exposure has n ot diminished. As discussed below, the EPA believes that the overall uncertainty about possible health risks associated with both long

- and short

- term PM 2.5 exposure has diminished to an important degree since the last review. While the EPA agrees that imp ortant uncertainties remain, and that future research directed toward addressing these uncertainties is warranted, the EPA disagrees with commenters’ views that the remaining uncertainties in the scientific evidence are too great to warrant revising the cu rrent PM 2.5 NAAQS.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 118 of 790 Formatted: Left ( a ) Confounding Some commenters have criticized the EPA for not adequately addressing the issue of confounding in both long

- and short

- term exposure studies of mortality and morbidity. This includes confounding due to copollutants, as well as unmeasured confounding. 59 With regard to copollutant confounding, these commenters asserted that the EPA has not adequately interpreted the results from studies that examined the effect of copollutants on the relationship between long

- and short

- term PM 2.5 exposures and mortality and morbidity outcomes. These commenters contend that the EPA has inappropriately concluded that PM 2.5 - related mortality and morbidity associations are generally robust to confounding. The commenters stated that sta tistically significant PM 2.5 associations in single

- pollutant models in epidemiologic epidemiologic al studies do not remain statistically significant in copollutant models. The loss of statistical significance or the reduction in the magnitude of the effec t estimate when a co

- pollutant model is used may be the result of factors other than confounding. These changes do not prove either the existence or absence of confounding. These impacts must be evaluated in a broader context that considers the entire body of evidence. The broader examination of this issue in the Integrated Science Assessment included a focus on evaluating the stability of the size of the effect estimates in

59 The Integrated Science Assessment defines confounding as “a confusion of effects. Specifically, the apparent effect of the exposure of interest is distorted because the effect of an extraneous factor is mistaken for or mixed with the actual exposure effec t (which may be null) (Rothman and Greenland, 1998)” (U.S. EPA, 2009a, p. 1

- 16). Epidemiological analyses attempt to adjust or control for these characteristics (i.e., potential confounders) that differ between exposed and non

- exposed individuals (U.S. EPA , 2009a, section 1.5.3). Not all risk factors can be controlled for within a study design/model and are termed “unmeasured confounders.” An unmeasured confounder is a confounder that has not previously been measured and therefore is not included in the stu dy design/model. Formatted: Font: 12 pt***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 119 of 790 Formatted: Left epidemiological studies conducted by a number of research groups using single

- and copollutant models ( U.S. EPA, 2009a, sections 6.2.10.9, 6.3.8.5, and 6.5, Figures 6

- 5, 6

- 9, and 6

- 15). This examination found that, for most epidemiological studies, there was little change in effect estimates based on single

- and copollutant models, altho ugh the Integrated Science Assessment recognized that in some cases, the PM 2.5 effect estimates were markedly reduced in size and lost statistical significance. Additionally, the EPA notes that these comments do not adequately reflect the complexities inhe rent in assessing the issue of copollutant confounding. As discussed in the proposal (77 FR 38907, 38909, and 38910) and more fully in the Integrated Science Assessment ( U.S. EPA, 2009a, sections 6.2, 6.3, and 6.5), although copollutant models may be useful tools for assessing whether gaseous copollutants may be potential confounders, such models alone cannot determine whether copollutants are in fact confounders. Interpretation of the results of copollutant models is complicated by correlations that often e xist among air pollutants, by the fact that some pollutants play a role in the atmospheric reactions that form other pollutants such as secondary fine particles, and by the statistical power of the studies in question inherent in the study methodology. For example, the every

- third or sixth

- day sampling schedule often employed for PM 2.5 measurements compared to daily measurements of gaseous copollutants drastically reduces the overall sample size to assess the effect of copollutants on the PM 2.5 - morbidity

or mortality relationship, such that the reduced sample size can lead to less precise effect estimates (e.g., wider confidence intervals). The EPA recognizes that when PM 2.5 is correlated with gaseous pollutants it can be difficult to identify the effect of individual pollutants in the ambient mixture (77 FR***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 120 of 790 Formatted: Left 38910). However, based on the available evidence, the EPA concludes epidemiological studies continue to support the conclusion that PM 2.5 associations with mortality and morbidity outcomes are robust to t he inclusion of gaseous copollutants in statistical models. The EPA evaluated the potential confounding effects of gaseous copollutants and, although it is recognized that uncertainties and limitations still remain, the Agency concluded the collective body of scientific evidence is “stronger and more consistent than in previous reviews providing a strong basis for decision making in this review" (77 FR 38910/1). Several commenters offered detailed comments on the long

- term PM 2.5 exposure studies arguing th at associations from mortality studies are subjected to unmeasured confounding and as a result are not appropriately characterized as being cau s al ( providing evidence of a causal relationship between long

- term PM 2.5 exposure and mortality (e.g., UARG, 2012, pp. 10 to 11, Attachment A, pp. 17 to 23; API, 2012, pp. 13 to 14, Attachment 1, pp. 11 to 14 , Attachment 7, pp. 2

- 10 ; ACC, 2012, p. 18 to 21; AFPM, 2012, p. 8; TCEQ Texas CEQ , 2012, p. 4). Specifically, these commenters cited two studies (i.e., Janes et al. , 2007 and Greven et al. , 2011) that used a new type of statistical analysis , in which the study authors to examine associations between annual (long

- term) and monthly (sub

- chronic) PM 2.5 exposure and mortality. The commenters interpreted the result s of the analysis these analyses as evidence of unmeasured confounding in the long

term PM 2.5 exposure - mortality relationship. These commenters interpreted these studies as raising fundamental questions regarding the EPA’s determination that a causal relati onship exists between long

- term PM 2.5 exposure and mortality. The first study, Janes et al., 2007, In addition to the commenters mentioned above, all of the authors of***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 121 of 790 Formatted: Left the publications by Janes et al. (2007) and Greven et al. (2011) (i.e., Francesca Domini ci, Scott Zeger, Holly Janes, and Sonja Greven) submitted a joint comment to the public docket in order to clarify specific points regarding these two studies (Dominici et al., 2012). The first study, Janes et al. ( 2007 ) , was evaluated in the Integrated Sc ience Assessment (U.S. EPA, 2009a, p. 7

- 88). The second study, Greven et al ., . ( 2011 , ), an extension of the Janes et al. (2007) study adding three more years of data, is a “new” study discussed in the Provisional Science Assessment (U.S. EPA, 2012 ) and th e Response to Comments document. ). Both studies used nationwide Medicare mortality data to examine the association between monthly average PM 2.5 concentrations over the preceding 12 months and monthly mortality rates in 113 U.S. counties
. and examined whet her community

- specific trends in monthly PM 2.5 concentrations and mortality declined at the same rate as the national rate. The investigators decomposed examined this by decomposing the association between PM 2.5 and mortality into two components: (1) “national trends” national trends , defined as the association between the national average trend in monthly PM 2.5 concentrations averaged over the previous 12 months and the national average trend in monthly mortality rates , and (2) “ local trends ,” , defined as county
- specific deviations in monthly PM 2.5 concentrations and monthly mortality rates from national trends. The EPA does not question the results of the national trends analyses conducted by Janes et al. (2007) and Greven et al. (2011). These analyse s demonstrated associations similar in magnitude and precision to other studies of long

- term PM 2.5 exposure and mortality. However, the authors hypothesized that the results from the “local” and Formatted: Don't adjust space between Latin and Asian text, Don't adjust space between Asian text and numbers***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 122 of 790 Formatted: Left “national” analyses should be similar in magnitude, and that any difference between the two results would be due to unmeasured confounding. 60 The authors provide d no references to support their assumptions that associations between PM 2.5 and mortality should be similar across temporal and spatial scales nor why any d ifferences in effect estimate size would be due to unmeasured confounding. 61 Both Janes et al. (2007) and Greven et al. (2011) observed positive and statistically significant associations between long

- term exposure to PM 2.5 and mortality in their national a nalyses. However, Janes et al. (2007) and Greven et al. (2011) eliminated all of the spatial variation in air pollution and mortality in their data set when estimating the national effect, focusing instead on both chronic (yearly) and sub

- chronic (monthly) temporal differences in the data (Dominici et al. 2012). Janes et al. (2007) (Table 1) highlight ed that over 90 percent of the variance in the data set used for the analyses conducted by both Janes et al. (2007) and Greven et al. (2011) was attributable t o spatial variability, which the authors chose to discard. As noted above, the focus of the analyses by Janes et al. (2007) and Greven et al. (2011) was on two components: (1) a temporal or time component, i.e., the “national” trends analysis, which examin ed the association between the national average trend in monthly PM 2.5 concentrations averaged over the previous 12 months and the national average trend in monthly mortality rates and (2) a space

- by

- time component, i.e., the “local” trends analysis, which examined county
- specific deviations in monthly PM 2.5
60 Unmeasured confound ers need to be factors that are associated with both the exposure and outcome of interest, but in the case of the Janes and Greven stud ies this would also need to hold true over multiple dimensions of time and space a s stated by Pope and Burnett , 2007
. 61 In its evaluation of Janes et al. (2007) in the I ntegrated S cience A ssessment , the EPA did not identify limitations in the statistical methods used per se (U.S. EPA, 2009a, p. 7

- 88) and included the results of the national

- scale analyses in that study in the body of evidence that supported the determination that there is a causal relationship between long

- term PM 2.5 exposure and mortality
.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 123 of 790 Formatted: Left concentrations and monthly mortality rates from national trends. These two components combined comprised less than 10 percent of the variance in the data set. The authors i ncluded a focus on the space

- by

- time component, which represented approximately 5 percent of the variance in the data set, in an attempt to identify, absent confounding, if PM 2.5 was associated with mortality at this unique exposure window. Thus, these stu dies are not directly comparable to other cohort studies investigating the relationship between long

- term exposure to PM 2.5 and mortality, which make use of spatial variability in air pollution and mortality data. 62 This point was highlighted by the study a uthors who stated that “when one considers that this wealth of information is not accounted for in [Janes 2007], it is not as surprising that... vastly different estimates of the PM 2.5 /mortality relationship [were observed] than in other studies that do expl oit that variability” (Dominici et al., 2012, p. 2 ). Consistent The EPA notes that the results of the local trends analyses conducted by Janes et al. (2007) and Greven et al. (2011) are limited by the monthly timescale used in these analyses. This view is consistent with comments on the Janes et al. (2007) study articulated in Pope and Burnett (2007), the EPA notes 63 which noted that an important limitation of the local scale analysis conducted by Janes et al. (2007) and subsequently by

62 Though not directly comparable, the national effect estimates for mortality reported by Janes et al. (2007) and Greven et al. (2011) are coincidentally similar in magnitude to those previously reported. It is important to note that previous cohort studies have focused on identifying spatial differences in PM 2.5 concentrations bet ween cities, while Janes et al. (2007) and Greven et al. (2011) focus primarily on temporal differences in PM 2.5 concentrations. In fact, Greven et al. (2011) state “We do not focus here on a third type [of statistical approach] used in cohort studies, mea suring the association between average PM 2.5 levels and average age

- adjusted mortality rates across cities (purely spatial or cross - sectional association).” 63 S ome commenters argued that there were flaws in the criticisms offered by Pope and Burnett (2007) on the paper by Janes et al. (2007) (UARG, 2012, Attachment A, pp. 19 to 23). The EPA responds to each of these specific comments in the Response to Comments document.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 124 of 790 Formatted: Left Greven et al. (2011) is was the subchronic exposure window considered in these analyses. Both studies used annual average PM 2.5 concentrations to characterize long

- term national trends which is was consistent with exposure windows considered in other studies of long

term exposur e to PM 2.5 and mortality studies.
. 64 However, the local scale analyses used monthly average PM 2.5 concentrations to characterize county

- specific deviations from national trends (the “ local ” scale). The use of monthly average data likely does not provide eno ugh exposure contrast to observe temporal changes in mortality at the local scale. It also represents a different exposure window than considered in the large body of evidence of health effects related to short

- term (from less than one day to up to several days) and chronic (one or more years) measures of PM 2.5 . As discussed by Pope and Burnett (2007) and highlighted in the I ntegrated S cience A ssessment , the conclusions of Janes et al
. Furthermore, the EPA disagrees with commenters that studies by Janes et al. (2007) and Greven et al. (2011) provide evidence that other studies of long

- term exposure to PM 2.5 and mortality are affected by unmeasured confounding. As noted above, the design of the studies conducted by Janes et al (2007) and Greven et al (2011) a re fundamentally different than those used in other studies of long

- term exposure to PM 2.5 and mortality, including the ACS cohort and the Harvard Six Cities study. Studies, such as the ACS and Harvard Six Cities studies, used the spatial variation between cities to measure the effect of long

- term (annual) exposures to PM 2.5 on mortality risk, and did not conduct any analyses relying on the temporal variation in PM 2.5 . The opposite is true of the Janes et al. (2007) and Greven et al. (2011) studies which fi rst removed the spatial variability in PM 2.5 and then examined the

64 As noted above, however, Janes et al. (2007) and Greven et al. (2011) focus ed on temp oral variability and other studies of long

- term exposure to PM 2.5 and mortality focus on spatial variability
.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 125 of 790 Formatted: Left temporal variation at both the national and local scale to measure the effects of temporal differences in PM 2.5 on mortality risk. Janes et al. (2007) and Greven et al. (2011) focus

on changes in PM 2.5 concentrations over time and , therefore , control for confounders would be based on including variables that vary over time rather than over space. As a result, any evidence of potential confounding of the PM 2.5 - mortality risk relationship derived from Janes et al. (2007) and Greven et al. (2011) cannot be extrapolated to draw conclusions related to potential spatial confounding in studies based on the spatial variation in PM 2.5 concentrations. As detailed in the Integrated Science Assessme nt (U.S. EPA, 2009a, section 7.6) , and recognized by the authors of Janes et al. (2007) and Greven et al. (2011), the cohort studies that informed the causality determination for long

- term PM 2.5 exposure and mortality “have developed approaches to adjust f or measured and unmeasured confounders” (Dominici et al., 2012, p. 2). These approaches were specifically designed to adjust for spatial confounding. The hypothesis that the authors of Janes et al. (2007) and Greven et al. (2011) chose to examine was that differences in the local and national effects indicated unmeasured temporal confounding in either the local or national effect estimate. This hypothesis was specific to these two studies that examined temporal variability in exposure to air pollution and d id not include known potential confounders at either the national or local scale as time

- varying covariates in the statistical model. The authors acknowledge d that the interpretation of either the national or local estimates needs to occur with an apprecia tion of the potential confounding effects of national and local scale covariates that were omitted from the model ( Dominici et al., 2012 ). It is important to recognize that because Janes et al. (2007) and Greven et al. Formatted: Don't adjust space between Latin and Asian text, Don't adjust space between Asian text and numbers***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 126 of 790 Formatted: Left (2011) focus ed on variations in PM 2.5 over time and not space, the results from these two studies do not provide any indication that other studies of long

- term exposure to PM 2.5 and mortality exhibit spatial confounding, or that PM 2.5 does not cause mortality. 65 The authors of Janes et al. (2007) and Greven et al. (2011) recognized that “it is entirely possible that these papers are looking for an association at a timescale for which no association truly exists” (Dominici et al.,. 2012, p. 3). Furthermore, as hig hlighted in the Integrated Science Assessment and discussed by Pope and Burnett (2007), the conclusions of Janes et al. (2007) “are overstated. . . [T]heir analysis tells us little or nothing about unmeasured confounding in those and related studies becaus e the methodology of Janes et al
. largely excludes the sources of variability that are exploited in those other studies. By using monthly mortality counts and lagged 12

- month average pollution concentrations, the authors eliminate the opportunity to exploi t short

- term or day

- to
- day variability.” Some commenters argued that there were flaws in the criticisms offered by Pope and Burnett (2007) on the paper by Janes et al. (2007) (UARG, 2012, Attachment A, pp. 19 to 23). The EPA responds to each of these speci fic comments in the Response to Comments document. In its evaluation of Janes et al. (2007), the EPA did not identify limitations in the statistical methods used per se ( U.S. EPA, 2009a, p. 7

- 88) and the results of the national

- scale analyses were included in the body of evidence that supported the determination that there is a causal relationship between long

- term PM 2.5 exposure and mortality In conclusion, the EPA believes interprets the results of the analyses conducted by Janes et al. (2007) and Greven e t al. (2011) are as being consistent with prior knowledge

65 Further, the EPA notes that Janes et al. (2007) and Greve n et al. (2011) provide no information relevant to examining confounding in studies of short

- term exposure to PM 2.5 .***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 127 of 790 Formatted: Left of examining associations with long

- term exposure to PM 2.5 at the national scale using long

- term average PM 2.5 concentrations. However, for For the reasons presented above and discussed in more detail in the Response to Comments document, the Agency disagrees with the commenters’ assumption that their “national” and “local” scale analyses should produce similar the results and their conclusion th at differing results is evidence of Janes et al. (2007) and Greven et al. (2011) indicate unmeasured confounding . in the results of other cohort studies of long

- term exposure to PM 2.5 and mortality
. Therefore, the EPA concludes that these studies do not b ring into question invalidate the large body of epidemiological evidence indicating that supports the EPA’s determination that a causal association relationship exists between long

- term PM 2.5 exposure and mortality. 66 ( b ) Heterogeneity in Risk Estimates Industry Some commenters argued that the heterogeneity in risk estimates observed in multicity multi

- city epidemiological studies and the lack of statistical significance in many regional or seasonal estimates highlights a potential bias associated with comb ined multi

- city epidemiological study results (e.g., API, 2012, Attachment 1, pp. 15 to 19). These commenters further argued that more refined intra

- urban exposure estimates conducted for two of the largest cities included in the ACS study, Los Angeles and New York City, based on land

- use regression models and/or kriging methods (Krewski et al., 2009) “underscore the importance of considering city

- specific health estimates, which may account for heterogeneity in PM 2.5 concentrations or other

66 The EPA notes that the EPA’s conclusion with regard to interpretation of the results from Janes et al. (2007) and Greven et al. (2012) is supported by the study authors ’ conclusion that “[ o]ur results do not invalidate previous epidemiologic al studies ” (Dominici, 2012, p. 1 (emphasis original)). Formatted: Default Paragraph Font, Font: 10 pt, Font color: Auto

Formatted: None***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 128 of 790 Formatted: Left differences amo ng cities, rather than relying on pooled nationwide results from multi

- city studies” (API, 2012, Attachment 1, p. 17). With respect to understanding the nature and magnitude of PM 2.5 - related risks, the EPA agrees that epidemiological studies evaluating hea lth effects associated with long

and short

- term PM 2.5 exposures have reported heterogeneity in responses between cities and effect estimates across geographic regions of the U.S. ( U.S. EPA, 2009a, sections 6.2.12.1, 6.3.8.1, 6.5.2, and 7.6.1; U.S. EPA, 20 11a, p. 2

- 25). For example, when focusing on short

- term PM 2.5 exposure, the Integrated Science Assessment found that multi

- city studies that examined associations with mortality and cardiovascular and respiratory hospital admissions and emergency departmen t visits demonstrated greater cardiovascular effects in the eastern versus the western U.S. (Dominici, et al., 2006 2006 a ; Bell et al., 2008; Franklin et al. (2007, 2008)). In addition, the Integrated Science Assessment evaluated studies that provided

some evidence for seasonal differences in PM 2.5 risk estimates, specifically in the northeast. The PM ISA I ntegrated S cience A ssessment found evidence indicating that individuals may be at greater risk of dying from higher exposures to PM 2.5 in the warmer months, and at greater risk of PM 2.5 associated hospitalization for cardiovascular and respiratory diseases during colder months of the year. The limited influence of seasonality on PM risk estimates in other regions of the U.S. may be due t o a number of factors including varying PM composition by season, exposure misclassification due to regional tendencies to spend more or less time outdoors and air conditioning usage, and the prevalence of infectious diseases during the winter months ( U.S. EPA, 2009a, p. 3

- 182). Formatted: Not Superscript/ Subscript***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 129 of 790 Formatted: Left Overall, the EPA took note in the proposal that uncertainties still remain regarding various factors that contribute to heterogeneity observed in epidemiological studies (77 FR 38909/3). Nonetheless, the EPA recognizes that this he terogeneity could be attributed, at least in part, to differences in PM 2.5 composition across the U.S., as well as to exposure differences that vary regionally such as personal activity patterns, microenvironmental characteristics, and the spatial variabil ity of PM 2.5 concentrations in urban areas ( U.S. EPA, 2009a, section 2.3.2; 77 FR 38910). As recognized in the Policy Assessment, the current epidemiological evidence and the limited amount of city

- specific speciated PM 2.5 data do not allow conclusions to be drawn that specifically differentiate effects of PM 2.5 in different locations ( U.S. EPA, 2011a, p. 2

- 25). Furthermore, the Integrated Science Assessment concluded “that many constituents of PM 2.5 can be linked with multiple health effects, and the evid ence is not yet sufficient to allow differentiation of those constituents or sources that are more closely related to specific health outcomes ” ( U.S. EPA, 2009a, p. 2

- 17). CASAC thoroughly reviewed the EPA’s presentation of the scientific evidence indicati ng heterogeneity in PM 2.5 effect estimates in epidemiological studies and concurred with the overall conclusions presented in the Integrated Science Assessment. (c) Exposure Measurement Error Industry Some commenters argued that the EPA did not adequately consider exposure measurement error, which they asserted is an important source of bias in epidemiological studies that can bias effect estimates in either direction (e.g., API, 2012, Attachment 1, pp. 19 to 20). The EPA agrees that exposure measurement e rror is an important source of Formatted: Indent: First line: 0.5"***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 130 of 790 Formatted: Left uncertainty and that the variability in risk estimates observed in multi

- city studies could be attributed, in part, to exposure error due to measurement

- related issues (77 FR 38910). However, the Agency disagrees with the com menters’ assertion that exposure measurement error was not adequately considered in this review. The Integrated Science Assessment included an extensive discussion that addresses issues of exposure measurement error ( U.S. EPA, 2009a, sections 2.3.2
. and 3. 8.6). Exposure measurement error may lead to bias in effect estimates in epidemiological studies. A number of studies evaluated in the last review ( U.S. EPA, 2004, section 8.4.5) and in the current review ( U.S. EPA, 2009a, section 3.8.6) have discussed the direction and magnitude of bias resulting from specified patterns of exposure measurement error (Armstrong 1998; Thomas et al. 1993; Carroll et al. 1995) and have generally concluded “classical” (i.e., random, within

- person) exposure measurement error can bias effect estimates towards the null. Therefore, consistent with conclusions reached in the last review, the Integrated Science Assessment concluded “in most circumstances, exposure error tends to bias a health effect estimate downward ” ( U.S. EPA, 2009a , sections 2.3.2 and 3.8.6) (emphasis added). Thus, the EPA has both considered and accounted for the possibility of exposure measurement error, and the possible bias would make it more difficult to detect true associations, not less difficult. ( d ) Model Specification Commenters contend contend ed that the EPA did not account for the fact that “selecting an appropriate statistical model for epidemiologic studies of air pollution involves several choices that involve much ambiguity, scant biological ev idence, and a profound impact on analytic results, given that many estimated associations are weak” (ACC, 2012, p. 5) For short

- term exposure studies , the EPA recognizes, as summarized Formatted: Don't keep lines together***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 131 of 790 Formatted: Left in the HEI review panel commentary that selecting a level of control to adjust for time

varying factors, such as temperature, in time

- series epidemiologic epidemiologic al studies involves a trade

- off (HEI, 2003). For example, if the model does not sufficiently adjust for the relationship between the health outcome and temperat ure, some effects of temperature could be falsely ascribed to the pollution variable. Conversely, if an overly aggressive approach is used to control for temperature, the result would possibly underestimate the pollution

- related effect and compromise the a bility to detect a small but true pollution effect ( U.S. EPA, 2004, p. 8

- 236; HEI, 2003, p. 266). The selection of approaches to address such variables depends in part on prior knowledge and judgments made by the investigators, for example, about weather p atterns in the study area and expected relationships between weather and other time

- varying factors and health outcomes considered in the study. As demonstrated in S ection s ection 6.5 of the Integrated Science Assessment, the EPA thoroughly considered each of these issues and the overall effect of different model specifications on the association between short

- term PM 2.5 exposure and mortality. Regardless of the model employed, consistent positive associations were observed across studies that controlled for the potential confounding effects of time and weather using different approaches (U
. S
. EPA 2009 2009 a , Figure 6

- 27). The EPA also considered the influence of model specification in the examination of long

- term PM 2.5 exposure studies. For example, in Sectio n 7.6 s ection 7.6 of the Integrated Science Assessment , Figures 7

- 6 and 7

- 7 summarize the collective evidence that evaluated the association between long

- term PM 2.5 exposure and mortality. Regardless of the model used, these studies collectively found evide nce of consistent positive associations between long

- term PM 2.5 exposure and mortality.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 132 of 790 Formatted: Left The EPA, therefore, disagrees with commenters that model specification was not considered when evaluating the epidemiologic epidemiologic al evidence used to form causality determinations. The EPA specifically points out that the process of assessing the scientific quality and relevance of epidemiologic epidemiologic al studies includes examining “important methodological issues (e.g., lag or ti me period between exposure and effects, model specifications, thresholds, mortality displacement) related to interpretation of the health evidence (U
. S
. EPA, 2009, p. 1

- 9).” Consistent with the conclusions of the 2004 PM AQCD A ir Q uality C riteria D ocument , the EPA recognizes that there is still no clear consensus at this time as to what constitutes appropriate control of weather and temporal trends in short

- term exposure studies, and that no single statistical modeling approach is likely to be most appropria te in all cases ( U.S. EPA, 2004, p. 8

- 238). However, the EPA believes that the available evidence interpreted in light of these remaining uncertainties does provide increased confidence relative to the last review in the reported associations between short

- and long

- term PM 2.5 exposures and mortality and morbidity effects, alone and in combination with other pollutants. ( e ) Concentration

- response Relationship Additionally, commenters questioned the interpretation of the shape of the concentration

- response r elationship, specifically stat ing that multiple studies have demonstrated that there is a threshold in the PM

- health effect relationship and that the log

- linear model is not biologically plausible (API, 2012, Attachment 9; ACC, 2012, Appendix A, pp. 7 to 8 ). The EPA disagrees with this assertion due to the number of studies evaluated in the Integrated Science Assessment that continue to support the use of

a no - threshold, log

- linear model to most appropriately represent the PM concentration

-***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 133 of 790 Formatted: Left response relation ship ( U.S. EPA, 2009a, section 2.4.3). W hile recognizing that uncertainties remain, the EPA believes that our understanding of this issue for both long

and short

- term exposure studies has advanced since the last review. As discussed in the Integrated Scien ce Assessment, both long

- and short

- term exposure studies have employed a variety of statistical approaches to examine the shape of the concentration

response function and whether a threshold exists. While the EPA recognizes that there likely are individua l biologic biologic al thresholds for specific health responses, the Integrated Science Assessment concluded the overall evidence from existing epidemiological studies do es not support the existence of thresholds at the population level, for effects associated with either long

- term or short

- term PM exposures within the ranges of air quality observed in these studies (U.S. EPA, 2009a, section 2.4.3)
. 67 The Integrated Science A ssessment concluded that this evidence collectively supported the conclusion that a no

- threshold, log

- linear model is most appropriate ( U.S. EPA, 2009a, sections 6.2.10.10, 6.5.2.7, and 7.6.4). CASAC likewise advised that “[a]lthough there is increasing un certainty at lower levels, there is no evidence of a threshold (Samet, 2010d, p. ii). The EPA recognizes that some short

- term exposure studies have examined the PM PM 2.5 concentration

- response relationship in individual cities or on a city

- to
- city basis and observed heterogeneity in the shape of the concentration

- response curve across cities. As discussed in (b) above, these findings are a source of uncertainty that the EPA agrees requires further investigation. Nonetheless, the Integrated Science Assessment concluded

67 While epidemiological analyses have not identified a population threshold in the range of air quality concentrations evaluated in these studies, the EPA recognizes that it is p ossible that such thresholds exist towards the lower end of these ranges (or below these ranges).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 134 of 790 Formatted: Left that “the studies evaluated further support the use of a no

- threshold, log

- linear model, but additional issues such as the influence of heterogeneity in estimates between cities and the effects of seasonal and regional differences in PM on the c oncentration

- response relationship still require further investigation” ( U.S. EPA, 2009a, p. 2

- 25). (f) Relative Toxicity of PM 2.5 Components Some commenters highlighted uncertainties in understanding the role of individual constituents with with in the m ix of fine particles. These commenters asserted that a mass

- based standard may not be appropriate due to the growing body of evidence indicating that certain PM 2.5 components may be more closely related to specific health outcomes (e.g., EC and OC) (EPRI, 2012, p. 2). With regard to questions about the role of individual constituents within the mix of fine particle s , as a general matter, the EPA recognizes that although new research directed toward this question has been conducted since the last review, im portant questions remain and the issue remains an important element in the Agency’s ongoing research program. At the time of the last review, the Agency determined that it was appropriate to continue to control fine particles as a group, as opposed to sing ling out any particular component or class of fine particles (71 FR 61162 to 61164, October 17, 2006). This distinction was based largely on epidemiological evidence of health effects using various indicators of fine particles in a large number of areas th at had significant contributions of differing components or sources of fine particles, together with some limited experimental studies that provided some evidence suggestive of health effects associated with high concentrations of numerous fine particle co mponents. In this review, as discussed in the proposal (77 FR 38922 to 38923) and in section***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 135 of 790 Formatted: Left III.E.1 below, while most epidemiological studies continue to be indexed by PM 2.5 mass, several recent epidemiological studies included in the Integrated Science Assessment have used PM 2.5 speciation data to evaluate health effects associated with fine particle exposures. In the Integrated Science Assessment, the EPA thoroughly evaluated the scientific evidence that examined the effect of different PM 2.5 components and sources on a variety of health outcomes ( U.S. EPA, 2009a, section 6.6) and observed that the available information continues to suggest that many different chemical components of fine particles and a variety of different types of source categories are all associated with, and probably contribute to, effects associated with PM 2.5 . The Integrated Science Assessment concluded that the current body of scientific evidence indicated that “many constituents of PM can be linked with differing health effects an d the evidence is not yet sufficient to allow differentiation of those constituents or sources that are more closely related to specific health outcomes” ( U.S. EPA, 2009a, p. 2

- 26 and 6

- 212). Furthermore, the Policy Assessment concluded that the evidence i s not sufficient to support eliminating any component or group of components associated with any specific source categories from the mix of fine particles included in the PM 2.5 indicator ( U.S. EPA, 2009a, p. 2

- 56). CASAC agreed that it was reasonable to re tain PM 2.5 as an indicator for fine particles in this review as “[t]here was insufficient peer

- reviewed literature to support any other indicator at this time” (Samet, 2010c, p. 12). This information is relevant to the Agency’s decision to retain PM 2.5 as the indicator for fine particles as discussed in section III.E.1 below. The EPA also believes that it is relevant to the Agency’s conclusion as to whether revision of the suite of primary PM 2.5 standards is appropriate. While there remain uncertainties about the role***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 136 of 790 Formatted: Left and relative toxicity of various components of fine PM, the current evidence continues to support the view that fine particles should be addressed as a group for purposes of public health protection. In summary, in considering the above issues related to uncertainties in the underlying health science, on balance, the EPA believes that the available evidence interpreted in light of these remaining uncertainties does provide increased confidence relative to the last review in the reported associations between long

- and short

- term PM 2.5 exposures and mortality and morbidity effects, alone and in combination with other pollutants, and supports stronger inferences as to the causal nature of the associations. The EPA also believes that this increased confidence, when taken in context of the entire body of available health effects evidence and in light of the evidence from epidemiological studies of associations observed in areas meeting th e current primary PM 2.5 standards, specifically in areas meeting the current primary annual PM 2.5 standard, adds support to its conclusion that the current suite of PM 2.5 standards needs to be revised to provide increased public health protection. (4) In asserting that there is no evidence of greater risk since the 2006 review to justify lowering the current annual PM 2.5 standard, some commenters argued that, “if the current primary PM 2.5 annual standard of 15 μg/m 3 was considered to be adequately protecti ve of public health in 2006, given relative risk estimates that EPA was using at that time, then that standard would surely still be adequately protective of the public health if relative risk estimates remain at the same level (or lower)” (UARG, 2012, Att achment 1, p. 24). These commenters compared risk coefficients used for mortality in the EPA’s risk assessment done in the last review with those from the Agency’s core risk***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 137 of 790 Formatted: Left assessment done as part of this review, and they concluded that “the entire range of the core relative risk for long

- term mortality is lower now than it was in the prior review” (UARG, 2012, Attachment 1, p. 24). These commenters used this conclusion as the basis for a claim that there is no reason to revise the current annual PM 2.5 sta ndard. The EPA believes that this claim is fundamentally flawed as it fails to take into account that exposure to a pollutant causally associated at a population

- level with premature mortality and serious illness has significant public health consequences, virtually regardless of the relative risk.
. In comparing the scientific understanding of the risk presented by exposure to PM 2.5 between the last and current reviews, one must examine not only the quantitative estimate of risk from those exposures (e.g., the numbers of premature deaths or increased hospital admissions at various concentrations), but also the degree of confidence that the Agency has that the observed health effects are causally linked to PM 2.5 exposure at those concentrations. As documented in the Integrated Science Assessment and in the recommendations and conclusions of CASAC, the EPA recognizes significant advances in our understanding of the health effects of PM 2.5 , based on evidence that is stronger than in the last review because of it s breadth and the substantiation of previously observed health effects.
. As a result of these advances, the EPA is now more certain that fine particles, alone or in combination with other pollutants, present a significant risk to public health at concentra tions allowed by the current primary PM 2.5 standards. From this more comprehensive perspective, since the risks presented by PM 2.5 are more certain, similar or even somewhat lower relative risk estimates would not be a basis to conclude that no revision to the suite of PM 2.5 standards is “requisite” to protect public health with an adequate margin of safety. This***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 138 of 790 Formatted: Left also ignores that the relative risk estimate is only one factor considered by the Administrator, e.g. it ignores that epidemiological studies sin ce the last review indicate associations between PM 2.5 and mor t ality and morbidity in areas meeting the current annual standard. In any case, the commenters’ reliance on the flawed 2006 review is misplaced. As discussed in section III.A.2 above, the D.C. Circuit remanded Administrator Johnson’s 2006 decision to retain the primary annual PM 2.5 standard because the Agency failed to adequately explain why the annual standard provided the requisite protection from both short

- and long

- term exposure to fine par ticles including protection for at

- risk populations. The 2006 standard was also at sharp odds with CASAC advice and recommendations as to the requisite level of protection (Henderson, 2006a,b). In other words , the judgment of the then

- Administrator that th e 2006 primary annual PM 2.5 standard was requisite to protect public health with an adequate margin of safety is not an appropriate benchmark for comparison. (5) Some of these commenters also identified “new” as well as older studies that had been include d in prior reviews as providing additional evidence that the causality determinations presented in the Integrated Science Assessment did not consider the totality of the scientific literature , further supporting the ir view that a revision of the PM 2.5 is u nwarranted. As discussed in section II.B.3 above, the EPA notes that, as in past NAAQS reviews, the Agency is basing the final decisions in this review on the studies and related information included in the PM ISA I ntegrated S cience A ssessment that have und ergone CASAC and public review, and will consider newly published studies for purposes of decision making in the next PM NAAQS review. In provisionally evaluating***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 139 of 790 Formatted: Left commenters’ arguments (see Response to Comments document), the EPA notes that its provisional assessment of “new” science found that such studies did not materially change the conclusions reached in the Integrated S cience Assessment (U.S. EPA, 2012b)
. 3. Administrator’s Final Conclusions Concerning the Adequacy of the Current Primary PM 2.5 Standards Having carefully considered the public comments, as discussed above, the Administrator believes the fundamental scientific conclusions on the effects of PM 2.5 reached in the Integrated Science Assessment, and discussed in the Policy Assessment, are valid. In considering whether the suite of primary PM 2.5 standards should be revised, the Administrator places primary consideration on the evidence obtained from the epidemiological studies. The Administrator believes that this literature, combined with the oth er scientific evidence discussed in the ISA I ntegrated S cience A ssessment , collectively represents a strong and generally robust body of evidence of serious health effects associated with both long

- and short

- term exposures to PM 2.5 . As discussed in the Integrated Science Assessment and Policy Assessment, the EPA believes that much progress has been made since the last review in reducing some of the major uncertainties that were important considerations in establishing the current suite of PM 2.5 standards . In that context, the Administrator finds the evidence of serious health effects reported in exposure studies conducted in areas with long

- term means mean concentration s ranging from approximately at or above the level of the annual standard to long

- term m eans mean concentration s significantly below the level of the annual standard to be compelling, especially in light of the extent to which such studies are part of an overall pattern of positive and frequently statistically significant associations across a broad range of studies. The information in the quantitative risk assessment lends support to this***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 140 of 79 0 Formatted: Left conclusion. There has been extensive critical review of this body of evidence, the quantitative risk assessment, and related uncertainties, including review by CASAC and the public. The public comments on the basis for the EPA’s proposed decision to revise the suite of primary PM 2.5 standards have identified a number of issues about which different parties disagree including issues for which additional researc h is warranted. Having weighed all comments and the advice of CASAC, the Administrator believes that since the last review the overall uncertainty about the public health risks associated with both long

- and short

- term exposure to PM 2.5 has been diminished to an important degree. The remaining uncertainties in the available evidence do not diminish confidence in the associations between exposure to fine particles and mortality and serious morbidity effects. Based on her increased confidence in the associati on between exposure to PM 2.5 and serious public health effects, combined with evidence of such an association in areas that would meet the current standards , the Administrator agrees with CASAC that revision of the current suite of PM 2.5 standards to pr ovide increased public health protection is necessary. Based on these considerations, the Administrator concludes that the current suite of primary PM 2.5 standards is not sufficient, and thus not requisite, to protect public health with an adequate margin of safety, and that revision is needed to increase public health protection. It is important to note that this conclusion, and the reasoning on which it is based, do not resolve the question of what specific revisions are appropriate. That requires lookin g specifically at the current 24

- hour and annual PM 2.5 standards, including their indicator, averaging times, forms, and levels, and evaluating the scientific evidence and***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 141 of 790 Formatted: Left other information relevant to determining the appropriate revision of the suite of

s tandards. E. Conclusions on the Elements of the Primary Fine Particle Standards 1. Indicator In initially setting standards for fine particles in 1997, the EPA concluded it was appropriate to control fine particles as a group, rather than singling out any partic ular component or class of fine particles. The EPA noted that community health studies had found significant associations between various indicators of fine particles, and that health effects in a large number of areas had significant mass contributions of differing components or sources of fine particles. In addition, a number of toxicological and controlled human exposure studies had reported health effects associations with high concentrations of numerous fine particle components. It was also not possibl e to rule out any component within the mix of fine particles as not contributing to the fine particle effects found in the epidemiologic studies (62 FR 38667, July 18, 1977). In establishing a size

- based indicator in 1977 to distinguish fine particles from particles in the coarse mode, the EPA noted that the available epidemiological studies of fine particles were based largely on PM 2.5 and also considered monitoring technology that was generally available. The selection of a 2.5 μm size cut reflected the regulatory importance of defining an indicator that would more completely capture fine particles under all conditions likely to be enc ountered across the U.S., especially when fine particle concentrations and humidity are likely to be high, while recognizing that some small coarse particles would also be captured by current methods to monitor PM 2.5 (62 FR 38666 to 38668, July 18, 1997). In the last review, based on the same considerations, the***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 142 of 790 Formatted: Left EPA again recognized that the available information supported retaining the PM 2.5 indicator and remained too limited to support a distinct standard for any specific PM 2.5 component or group of compo nents associated with any source categories of fine particles (71 FR 61162 to 61164, October 17, 2006). In this current review, the same considerations continue to apply for selection of an appropriate indicator for fine particles. As an initial matter, th e Policy Assessment recognizes that the available epidemiological studies linking mortality and morbidity effects with long

- and short

- term exposures to fine particles continue to be largely indexed by PM 2.5 . For the same reasons discussed in the last two reviews, the Policy Assessment concluded that it was appropriate to consider retaining a PM 2.5 indicator to provide protection from effects associated with long

- and short

- term fine particle exposures ( U.S. EPA, 2011 2011 a , p. 2

- 50). The Policy Assessment a lso considered the expanded body of evidence available in this review to consider whether there was sufficient evidence to support a separate standard for ultrafine particles 68 or whether there was sufficient evidence to establish distinct standards focused on regulating specific PM 2.5 components or a group of components associated with any source categories of fine particles ( U.S. EPA, 2011a, section 2.3.1). A number of studies available in this review have evaluated potential health effects associated with short

- term exposures to ultrafine particles. As noted in the Integrated Science Assessment, the enormous number and larger, collective surface area of ultrafine particles are important considerations for focusing on this particle size
68 Ultrafine particles, generally including particles with a mobility diameter less than or equal to 0.1 μm, are emitted directly to the atmosphere or are form ed by nucleation of gaseous constituents in the atmosphere (U.S. EPA, 2009a, p. 3

- 3).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 143 of 790 Formatted: Left fraction in assessin g potential public health impacts ( U.S. EPA, 2009a, p. 6

- 83). Per unit mass, ultrafine particles may have more opportunity to interact with cell surfaces due to their greater surface area and their greater particle number compared with larger particles ( U. S. EPA, 2009a, p. 5

- 3). Greater surface area also increases the potential for soluble components (e.g., transition metals, organics) to adsorb to ultrafine particles and potentially cross cell membranes and epithelial barriers ( U.S. EPA, 2009a, p. 6

- 83). I n addition, evidence available in this review suggests that the ability of particles to enhance allergic sensitization is associated more strongly with particle number and surface area than with particle mass ( U.S. EPA, 2009a, p. 6

- 127). New evidence, pri marily from controlled human exposure and toxicological studies, expands our understanding of cardiovascular and respiratory effects related to short

- term ultrafine particle exposures. However, the Policy Assessment concluded that this evidence was still v ery limited and largely focused on exposure to diesel exhaust, for which the Integrated Science Assessment concluded it was unclear whether the effects observed are due to ultrafine particles, larger particles within the PM 2.5 mixture, or the gaseous compo nents of diesel exhaust ( U.S. EPA, 2009a, p. 2

- 22). In addition, the Integrated Science Assessment noted uncertainties associated with the controlled human exposure studies using concentrated ambient particle systems which have been shown to modify the com

position of ultrafine particles ( U.S. EPA, 2009a, p. 2

- 22, see also section 1.5.3). The Policy Assessment recognized that there are relatively few epidemiological studies that have examined potential cardiovascular and respiratory effects associated with short

- term exposures to ultrafine particles ( U.S. EPA, 2011a, p. 2

- 51). These studies***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 144 of 790 Formatted: Left have reported inconsistent and mixed results ( U.S. EPA, 2009a, section 2.3.5). Collectively, in considering the body of scientific evidence available in this review, the Integrated Science Assessment concluded that the currently available evidence was suggestive of a causal relationship between short

- term exposures to ultrafine particles and cardiovascular and respiratory effects. Furthermore, the Integrated Science Assess ment concluded that evidence was inadequate to infer a causal relationship between short

- term exposure to ultrafine particles and mortality as well as long

- term exposure to ultrafine particles and all outcomes evaluated ( U.S. EPA, 2009a, sections 2.3.5, 6. 2.12.3, 6.3.10.3, 6.5.3.3, 7.2.11.3, 7.3.9, 7.4.3.3, 7.5.4.3, and 7.6.5.3; Table 2

- 6). With respect to our understanding of ambient ultrafine particle concentrations, at present, there is no national network of ultrafine particle samplers; thus, only epis odic and/or site

- specific data sets exist ( U.S. EPA, 2009a, p. 2

- 2). Therefore, the Policy Assessment recognized a national characterization of concentrations, temporal and spatial patterns, and trends was not possible at this time, and the availability of ambient ultrafine measurements to support health studies was extremely limited ( U.S. EPA, 2011a, p. 2

- 51). In general, measurements of ultrafine particles are highly dependent on monitor location and, therefore, more subject to exposure error than accumul ation mode particles ( U.S. EPA, 2009a, p. 2

- 22). Furthermore, the number of ultrafine particles generally decreases sharply downwind from sources, as ultrafine particles may grow into the accumulation mode by coagulation or condensation ( U.S. EPA, 2009a, p . 3

- 89). Limited studies of ambient ultrafine particle measurements have suggested that these particles exhibit a high degree of spatial and temporal heterogeneity driven primarily by differences in nearby source characteristics ( U.S. EPA, 2009a, p. 3

- 84). Internal***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 145 of 790 Formatted: Left combustion engines and, therefore, roadways are a notable source of ultrafine particles, so concentrations of these particles near roadways are generally expected to be elevated ( U.S. EPA, 2009a, p. 2

- 3). Concentrations of u ltrafine particles have been reported to drop off much more quickly with distance from roadways than fine particles ( U.S. EPA, 2009a, p. 3

- 84). In considering both the currently available health effects evidence and the air quality data, the Policy Assessm ent concluded that this information was still too limited to provide support for consideration of a distinct PM standard for ultrafine particles ( U.S. EPA, 2011a, p. 2

- 52). In addressing the issue of particle composition, the Integrated Science Assessment concluded that, “[f]rom a mechanistic perspective, it is highly plausible that the chemical composition of PM would be a better predictor of health effects than particle size” ( U.S. EPA, 2009a, p. 6

- 202). Heterogeneity of ambient concentrations of PM 2.5 co nstituents (e.g., elemental carbon, organic carbon, sulfates, nitrates) observed in different geographical regions as well as regional heterogeneity in PM 2.5 - related health effects reported in a number of epidemiological studies are consistent with this hy pothesis ( U.S. EPA, 2009a, section 6.6). With respect to the availability of ambient measurement data for fine particle components in this review, the Policy Assessment noted that there were now more extensive ambient PM 2.5 speciation measurement data ava ilable through the Chemical Speciation Network (CSN) than in previous reviews ( U.S. EPA, 2011a, section 1.3.2 and Appendix B, section B.1.3). The Integrated Science Assessment observed that data from the CSN provided further evidence of spatial and seasona l variation in both PM 2.5 mass***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 146 of 790 Formatted: Left and composition among cities and geographic regions ( U.S. EPA, 2009a, pp. 3

- 50 to 3

- 60; Figures 3

- 12 to 3

- 18; Figure 3

- 47). Some of this variation may be related to regional differences in meteorology, sources, and topography ( U.S. EPA, 2009a, p. 2

- 3). The currently available epidemiological, toxicological, and controlled human exposure studies evaluated in the Integrated Science Assessment on the health effects associated with ambient PM 2.5 constituents and categories of fin e particle sources used a variety of quantitative methods applied to a broad set of PM 2.5 constituents, rather than selecting a few constituents a priori ( U.S. EPA, 2009a, p. 2

- 26). Epidemiological studies have used measured ambient PM 2.5 speciation data, including monitoring data from the CSN, while all of the controlled human exposure and most of the toxicological studies have used concentrated ambient particles and analyzed the constituents therein ( U.S. EPA, 2009a, p. 6

- 203). 69 The CSN provides PM 2.5 spe ciation measurements generally on

a one - in

- three or one

- in

- six day sampling schedule and, thus, do es not capture data every day at most sites. 70 The Policy Assessment recognized that several new multi

- city studies evaluating short

- term exposures to fine particle constituents are now available. These studies continued to show an association between mortality and cardiovascular and/or respiratory
69 Most studies considered between 7 to 20 ambient PM 2.5 constituents, with elemental carbon, organic carbon, sulfates, nitrates, and metals most commonly measured. Many o f the studies grouped the constituents with various factorization or source apportionment techniques to examine the relationship between the grouped constituents and various health effects. However, not all studies labeled the constituent groupings accordi ng to their presumed source and a small number of controlled human exposure and toxicological studies did not use any constituent grouping. These differences across studies substantially limit any integrative interpretation of these studies (U.S. EPA, 2009 a, p. 6

- 203). 70 To expand our understanding of the role of specific PM 2.5 components and sources with respect to the observed health effects, researchers have expressed a strong interest in having access to PM 2.5 speciation measurements collected more fre quently (U.S. EPA, 2011a, p. 2

- 53, including footnote 47).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 147 of 790 Formatted: Left morbidity effects and short

- term exposures to various PM 2.5 components including nickel, vanadium, elemental car bon, organic carbon, nitrates, and sulfates ( U.S. EPA, 2011a, section 2.3.1; U.S. EPA, 2009a, sections 6.5.2.5 and 6.6). Limited evidence is available to evaluate the health effects associated with long

term exposures to PM 2.5 components ( U.S. EPA, 2009a, section 7.6.2). The Policy Assessment noted the most significant new evidence was provided by a study that evaluated multiple PM 2.5 components and an indicator of traffic density in an assessment of health effects related to long

- term exposure to PM 2.5 (L ipfert et al., 2006 2006 a ). Using health data from a cohort of U.S. military veterans and PM 2.5 measurement data from the CSN, Lipfert et al. ( 2006 2006 a ) reported positive associations between mortality and long

- term exposures to nitrates, elemental carbon, nickel, and vanadium as well as traffic density and peak ozone concentrations ( U.S. EPA, 2011a, p. 2

- 54; U.S. EPA, 2009a, pp. 7

- 89 to 7

- 90). With respect to source categories of fine particles potentially associated with a range of health endpoints, the Integrated Science Assessment reported that the currently available evidence suggests associations between cardiovascular effects and a number of specific PM 2.5 –

related source categories, specifically including oil combustion, wood or biomass burning, motor vehicle emissions, and crustal or road dust sources ( U.S. EPA, 2009a, section 6.6; Table 6

- 18). In addition, a few studies have evaluated associations between PM 2.5 - related source categories and mortality. One For example, one stud y reported an association between mortality and a PM 2.5 coal combustion factor (Laden et al., 2000), while other studies linked mortality to a secondary sulfate long

- range transport PM 2.5 source (Ito et al., 2006; Mar et al., 2006) ( U.S. EPA, 2009a, section 6.6.2.1). Other***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 148 of 790 Formatted: Left studies have looked at different components of particulate matter. There was less consistency in associations observed between selected sources of fine particles and respiratory health effects endpoints , which may be partially due to the fact that fewer studies ha ve evaluated respiratory

- related outcomes and measures. However, there was some evidence for PM 2.5 - related associations with secondary sulfate and decrements in lung function in asthmatic and healthy adults ( U.S. EPA, 2009a, p. 6

- 211; Gong et al., 2005; La nki et al., 2006). Respiratory effects relating to A couple of studies have observed an association between r espiratory e ndpoints in children and adults with asthma and surrogates for the crustal/soil/road dust and traffic sources of PM have been observed i n asthmatic children and adults ( U.S. EPA, 2009a, p. 6

- 205; Gent et al., 2009; Penttinen et al., 2006). Recent studies have shown that source apportionment methods have the potential to add useful insights into which sources and/or PM constituents may con tribute to different health effects. Of particular interest are several epidemiological studies that compared source apportionment methods and reported consistent results across research groups ( U.S. EPA, 2009a, p. 6

- 211; Hopke et al., 2006; Ito et al., 20 06; Mar et al., 2006; Thurston et al., 2005). These studies reported associations between total mortality and secondary sulfate in two cities for two different lag times. The sulfate effect was stronger for total mortality in Washington D.C. and for cardio vascular

- related mor t ality in Phoenix ( U.S. EPA, 2009a, p. 6

- 204). These studies also found some evidence for associations with mortality and a number of source categories (e.g., biomass/wood combustion, traffic, copper smelter, coal combustion, sea salt) at various lag times ( U.S. EPA, 2009a, p. 6

- 204). Sarnat et al. (2008) compared three different source***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 149 of 790 Formatted: Left apportionment methods and reported consistent associations between emergency department visits for cardiovascular diseases with mobile sources and biomas s combustion as well as increased respiratory

- related emergency department visits associated with secondary sulfate ( U.S. EPA, 2009a, pp. 6

- 204 and 6

- 211). Collectively, in considering the currently available evidence for health effects associated with spe cific PM 2.5 components or groups of components associated with any source categories of fine particles as presented in the Integrated Science Assessment, the Policy Assessment concluded that additional information available in this review continues to prov ide evidence that many different constituents of the fine particle mixture as well as groups of components associated with specific source categories of fine particles are linked to adverse health effects ( U.S. EPA, 2011a, p. 2

- 55). However, as noted in the Integrated Science Assessment, while “[t]here is some evidence for trends and patterns that link particular ambient PM constituents or sources with specific health outcomes...there is insufficient evidence to d etermine whether these patterns are consistent or robust” ( U.S. EPA, 2009a, p. 6

- 210). Assessing this information, the Integrated Science Assessment concluded that “the evidence is not yet sufficient to allow differentiation of those constituents or source s that are more closely related to specific health outcomes” ( U.S. EPA, 2009a, pp. 2

- 26 and 6

- 212). Therefore, the Policy Assessment concluded that the currently available evidence is not sufficient to support consideration of a separate indicator for a sp ecific PM 2.5 component or group of components associated with any source category of fine particles. Furthermore, the Policy Assessment concluded that the evidence is not sufficient to support eliminating any component or group of components associated wit h any source categories of fine***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 150 of 790 Formatted: Left particles from the mix of fine particles included in the PM 2.5 indicator ( U.S. EPA, 2011a, p. 2

- 56). The CASAC agreed with the EPA staff conclusions presented in the Policy Assessmen t and concluded that it is appropriate to consider retaining PM 2.5 as the indicator for fine particles and further asserted, “There [is] insufficient peer

- reviewed literature to support any other indicator at this time” (Samet, 2010c, p. 12). CASAC expressed a strong desire for the EPA to “look a head to future review cycles and reinvigorate support for the development of evidence that might lead to newer indicators that may correlate better with the health effects associated with ambient air concentrations of PM ...” (Samet, 2010c, p 2). Consistent with the staff conclusions presented in the Policy Assessment and CASAC advice, the Administrator proposed to retain PM 2.5 as the indicator for fine particles. Further, the Administrator provisionally concluded that currently available scientific informat ion does not provide a sufficient basis for supplementing mass

- based, primary fine particle standards with standards using a separate indicator for ultrafine particles or a separate indicator for a specific PM 2.5 component or group of components associated with any source categories of fine particles. In addition, the Administrator also provisionally concluded that the currently available scientific information did not provide a sufficient basis for eliminating any individual component or group of component s associated with any source categories from the mix of fine particles included in the PM 2.5
mass - based indicator. The EPA received comparatively few public comments on issues related to the***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 151 of 790 Formatted: Left indicator for fine particles. 71 Some commenters emphasized the ne ed to conduct additional research to more fully understand the effect of specific PM 2.5 components and/or sources on public health. These commenters expressed views about the importance of evaluating health effect associations with various fine particle co mponents and types of source categories as a basis for focusing ongoing and future research to reduce uncertainties in this area and for considering whether alternative indicator(s) may be appropriate to consider in future PM NAAQS reviews for standards in tended to protect against the array of health effects that have been associated with fine particles as indexed by PM 2.5 . For example, the PSR encouraged more research and monitoring related to PM 2.5 components and noted the importance of components associa ted with coal combustion (PSR, 2012, pp. 5 to 6). EPRI asserted that “new” studies support focusing on EC and OC and encouraged the EPA to seriously consider the mass

- based approach (EPRI, 2012, p. 2). Likewise, Georgia Mining Association supported additio nal monitoring and research efforts related to PM 2.5 composition and specifically encouraged the evaluation of using particle number (e.g., particle count) (GMA, 2012, pp. 2 to 3). The Administrator agrees with CASAC as well as these commenters that the

r esults of additional research and monitoring efforts will be helpful for informing future PM NAAQS reviews. Information from such studies could also help inform the development of strategies that emphasize control of specific types of emission sources so

a s to address particles of greatest concern to public health. However, based upon the scientific information considered in the Integrated Science Assessment as well as the public comments summarized above, the Administrator continues to take note there is

71 No public comments were submitted regarding the use of a different size cut for fine particles.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 152 of 790 Formatted: Left

e vidence that many different constituents of the fine particle mixture as well as groups of components associated with specific sources of fine particles are linked to adverse health effects. Furthermore, she recognizes that the evidence is not yet sufficie nt to differentiate those constituents or sources that are most closely related to specific health outcomes nor to exclude any PM 2.5 components or sources of fine particles from the mix of particles included in the PM 2.5 indicator. Having considered the p ublic comments on this issue, the Administrator concurs with the Policy Assessment conclusions and CASAC recommendations and concludes that it is appropriate to retain PM 2.5 as the indicator for fine particles. 2. Averaging Time In 1997, the EPA initially se t both an annual standard, to provide protection from health effects associated with both long

- and short

- term exposures to PM 2.5 , and a 24

- hour standard to supplement the protection afforded by the annual standard (62 FR 38667 to 38668, July, 18, 1997). I n the last review, the EPA retained both annual and 24

- hour averaging times (71 FR 61164, October 17, 2006). These decisions were based, in part, on evidence of health effects related to both long

- term (from a year to several years) and short

- term (from le ss than one day to up to several days) measures of PM 2.5 . The overwhelming majority of studies conducted since the last review continue to utilize annual (or multi

- year) and 24

- hour averaging times, reflecting the averaging times of the current PM 2.5 stand ards. These studies continue to provide evidence that health effects are associated with annual and 24

- hour averaging times. Therefore, the Policy Assessment concluded it is appropriate to retain the current annual and 24

- hour averaging times to provide pr otection from effects associated with both long

- and short

- term PM 2.5***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 153 of 790 Formatted: Left exposures ( U.S. EPA, 2011a, p. 2

- 57). In considering whether the information available in this review supports consideration of different averaging times for PM 2.5 standards specifically with regard to considering a standard with an averaging time less than 24 hours to address health effects associated with sub

- daily PM 2.5 exposures, the Policy Assessment noted there continues to be a growing body of studies that provide additional eviden ce of effects associated with exposure periods less than 24

- hours ( U.S. EPA, 2011a, p. 2

- 57). Relative to information available in the last review, recent studies provide additional evidence for cardiovascular effects associated with sub

- daily (e.g., one t o several hours) exposure to PM, especially effects related to cardiac ischemia, vasomotor function, and more subtle changes in markers of systemic inflammation, hemostasis, thrombosis and coagulation ( U.S. EPA, 2009a, section 6.2). Because these studies h ave used different indicators (e.g., PM 2.5 , PM 10 , PM 10

- 2.5 , ultrafine particles), averaging times (e.g., 1, 2, and 4 hours), and health outcomes, it is difficult to draw conclusions about cardiovascular effects associated specifically with sub

- daily exposu res to PM 2.5 . With regard to respiratory effects associated with sub

- daily PM 2.5 exposures, the currently available evidence was much sparser than for cardiovascular effects and continues to be very limited. The Integrated Science Assessment concluded tha t for several studies of hospital admissions or medical visits for respiratory diseases, the strongest associations were observed with 24

- hour average or longer exposures, not with less than 24

- hour exposures ( U.S. EPA, 2009a, section 6.3). Collectively, the Policy Assessment concluded that this information, when viewed as a whole, is too unclear, with respect to the indicator, averaging time and health***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 154 of 790 Formatted: Left outcome, to serve as a basis for consideration of establishing a primary PM 2.5 standard with an averagin g time shorter than 24

- hours at this time ( U.S. EPA, 2011a, p. 2

- 57). With regard to health effects associated with PM 2.5 exposure across varying seasons in this review, Bell et al. (2008) reported higher PM 2.5 risk estimates for hospitalization for cardi ovascular and respiratory diseases in the winter compared to other seasons. In comparison to the winter season, smaller statistically significant associations were also reported between PM 2.5 and cardiovascular morbidity for spring and autumn, and a positi ve, but statistically non

- significant association was observed for the summer months. In the case of mortality, Zanobetti and Schwartz (2009) reported a 4

- fold higher effect estimate for PM 2.5 - associated mortality for the spring as compared to the winter. Taken together, these results provided emerging but limited evidence that individuals may be at greater risk of dying from higher exposures to PM 2.5 in the warmer months and may be at greater risk of PM 2.5 - associated hospitalization for cardiovascular and respiratory diseases during colder months of the year ( U.S. EPA, 2011a, p. 2

- 58). Overall, the Policy Assessment observed that there are few studies presently available to deduce a general pattern in PM 2.5 - related risk across seasons. In addition, these s tudies utilized 24

- hour exposure periods within each season to assess the PM 2.5 - associated health effects and do not provide information on health effects associated with a season

- long exposure to PM 2.5 . Due to these limitations in the currently available evidence, the Policy Assessment concluded that there was no basis to consider a seasonal averaging time separate from a 24

- hour averaging time. Based on the above considerations, the Policy Assessment concluded that the currently available information prov ided strong support for consideration of retaining the***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 155 of 790 Formatted: Left current annual and 24

- hour averaging times but does not provide support for considering alternative averaging times ( U.S. EPA, 2011a, p. 2

- 58). In addition, CASAC considered it appropriate to retain th e current annual and 24

- hour averaging times for the primary PM 2.5 standards (Samet, 2010c, pp. 2 to 3). At the time of the proposal, the Administrator concurred with the staff conclusions and CASAC advice and proposed that the averaging times for the prim ary PM 2.5 standards should continue to include annual and 24

- hour averages to protect against health effects associated with long

- and short

- term exposures. Furthermore, the Administrator provisionally concluded, consistent with conclusions reached in the Policy Assessment and by CASAC, that the currently available information was too limited to support consideration of alternative averaging times to establish a national standard with a shorter

- than 24

- hour averaging time or with a seasonal averaging time. The EPA received no significant public comments on the issue of averaging time for the PM 2.5 primary standards. The Administrator concurs with recommendations made by CASAC and the staff conclusions presented in the Policy Assessment and concludes, as pro posed, that it is appropriate to retain the current annual and 24

- hour averaging times for the primary PM 2.5 standards to protect against health effects associated with long

- and short

- term exposure periods. 3. Form The “form” of a standard defines the air qu ality statistic that is to be compared to the level of the standard in determining whether an area attains the standard. In this review, the EPA considers whether currently available information supports retaining or revising the forms for the annual or 24

- hour PM 2.5 standards.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 156 of 790 Formatted: Left

a. Annual Standard In 1997, the EPA established the form of the annual PM 2.5 standard as an annual arithmetic mean, averaged over 3 years, from single or multiple community

- oriented monitors. This form was intended to represent a relatively stable measure of air quality and to characterize longer

- term area
- wide PM 2.5 concentration s, in conjunction with a 24

- hour standard designed to provide adequate protection against localized peak or seasonal PM 2.5 concentrations. The level of the standard was to be compared to measurements made at each community

- oriented monitoring site, or, if specific criteria were met, measurements from multiple community

- oriented monitoring sites could be averaged (i.e., spatial averaging) 72 (62 FR 38671 to 38672, July 18, 1997). The constraints were intended to ensure that spatial averaging would not result i n inequities in the level of protection provided by the standard (62 FR 38672, July 18, 1997). This approach was consistent with the epidemiological studies on which the PM 2.5 standard was primarily based, in which air quality data were generally averaged across multiple monitors in an area or were taken from a single monitor that was selected to represent community

- wide exposures. In the last review, the EPA tightened the criteria for use of spatial averaging to pr ovide increased protection for vulnerable populations exposed to PM 2.5 . This change was based in part on an analysis of the potential for disproportionate impacts on potentially at

- risk populations, which found that the highest concentrations in an area tend to be measured at monitors located in areas where the surrounding population is more likely to have lower education and income levels and higher percentages of

72 Spatial averaging as part of the form of the annual PM 2.5 standard is unique to this standard an d is not used with other PM standards nor with other NAAQS.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 157 of 790 Formatted: Left minority populations (71 FR 61166/2, October 17, 2006; U.S. EPA, 2005, section 5.3.6.1). In this review, as outlined in section III.B above and discussed more fully in section III.B.3 of the proposal, there now exist more health data such that the Integrated Science Assessment has identified persons from lower socioeconomic strata as an at

- risk population ( U.S. EPA, 2009a, section 8.1.7; U.S. EPA, 2011a, section 2.2.1). Moreover, there now exist more years of PM 2.5 air quality data than were available in the last review. Consideration in the Policy Assessment of the spatial variability across urban areas that was revealed by this expanded data base has raised questions as to whether an annual standard that allows for spatial averaging, even within specified constraints as narrowed in 2006 (71 FR 61165 to 61167, October 17, 2006) , would provide appropriate public health protection. In considering the potential for disproportionate impacts on at

- risk populations, the Policy Assessment considered an update of an air quality analysis conducted for the last review ( U.S. EPA, 2011a, pp. 2

- 59 to 60; Schmidt, 2011a 2011 , Analysis A). This

an alysis focused on determining whether the spatial averaging provisions, as modified in 2006, could introduce inequities in protection for at

- risk populations exposed to PM 2.5 . Specifically, the Policy Assessment considered whether persons of lower socioeco nomic status , minority groups, or different age groups (i.e., children or older adults) are more likely than the general population to live in areas in which the monitors recording the highest air quality values in an area are located. Data used in this an alysis included demographic parameters measured at the Census Block or Census Block Group level, including percent minority population, percent minority subgroup population, percent of***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 158 of 790 Formatted: Left persons living below the poverty level, percent of persons 18 years of age or older, and percent of persons 65 years of age and older. In each candidate geographic area, data from the Census Block(s) or Census Block Group(s) surrounding the location of the monitoring site (as delineated by radii buffers of 0.5, 1.0, 2.0, and 3.0 miles) in which the highest air quality value was monitored were compared to the average of monitored values in the area. This analysis looked beyond areas that would meet the current spatial averaging criteria and considered all urban areas (i.e., Cor e Based Statistical Areas or CBSAs) with at least two valid annual desig n value monitors (Schmidt, 2011 , Analysis A). Recognizing the limitations of such cross

- sectional analyses, the Policy Assessment observed that the highest concentrations in an area te nd to be measured at monitors located in areas where the surrounding populations are more likely to live below the poverty line and to have higher percentage of minorities ( U.S. EPA, 2011a, p. 2

- 60). Based upon the analysis described above, the Policy Ass essment concluded that the existing constraints on spatial averaging, as modified in 2006, may be inadequate to avoid substantially greater exposures in some areas, potentially resulting in disproportionate impacts on at

- risk populations of persons with lo wer SES levels as well as minorities. Therefore, the Policy Assessment concluded that it was appropriate to consider revising the form of the annual PM 2.5 standard such that it did not allow for the use of spatial averaging across monitors. In doing so, th e level of the annual PM 2.5 standard would be compared to measurements made at the monitoring site that represents

area - wide air quality recording the highest PM 2.5 concentrations 73 ( U.S. EPA, 2011a, p. 2

- 60).
73 As discussed in section VIII.B.1 below, the EPA is revising several terms associated with PM 2.5 monitor placement. Specifically, the EPA is revoking the term “community

oriented” and replacing i t with the term “area

- wide” monitoring.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 159 of 790 Formatted: Left The CASAC agreed with staff conclusions that i t was “reasonable” for the EPA to eliminate the spatial averaging provisions (Samet, 2010d, p. 2). Further, in CASAC’s comments on the first draft Policy Assessment, it noted, “Given mounting evidence showing that persons with lower SES levels are a suscep tible group for PM

- related health risks, CASAC recommends that the provisions that allow for spatial averaging across monitors be eliminated for the reasons cited in the (first draft) Policy Assessment” (Samet, 2010c, p. 13). In its review of the second dr aft Policy Assessment, CASAC recognized “although much of the epidemiological research has been conducted using community

- wide averages, several key studies reference the nearest measurement site, so that some risk estimates are not necessarily biased by t he averaging process. Further, the number of such studies is likely to expand in the future” (Samet, 2010d, pp. 1 to 2). Only two areas in the country used the initial spatial averaging provisions for demonstrating attainment with the primary annual PM 2.5 standard set in 1997 ( 70 FR 19847, April 14, 2005; U.S. EPA, 2006c ). Since these provisions were tightened in 2006 , no area has used spatial averaging to demonstrate attainment. No areas in the country are currently using the spatial averaging provisions t o demonstrate attainment with the current primary annual PM 2.5 standard. In considering the Policy Assessment’s conclusions based on the results of the analysis discussed above and concern over the evidence of potential disproportionate impacts on at

- risk populations as well as CASAC advice, the Administrator proposed to revise the form of the annual PM 2.5 standard to eliminate the use of spatial averaging. Thus, the Administrator proposed revising the form of the annual PM 2.5 standard to compare the level of the standard with measurements from each “appropriate” monitor in***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 160 of 790 Formatted: Left

an area 74 with no allowance for spatial averaging. Thus, for an area with multiple monitors, the appropriate reporting monitor with the highest design value would determine the attainment status for that area. Of the commenters noted in section III.D.2 above who supported a more stringent annual PM 2.5 standard, those who commented on the form of the annual PM 2.5 standard supported the EPA’s proposal to eliminat e the spatial averaging provisions. These commenters contended that the EPA ’s analyses of the potential impacts of spatial averaging, discussed above and in the proposal , (77 FR 38924) , demonstrate d that the current form results in uneven public health prot ection leading to disproportionate impacts on at

- risk populations. Specifically, the ALA and other environmental and public health commenters contended that “ spatial averaging allows exposure of people to unhealthy levels of pollution at specific locales e ven within an area meeting the standard” (ALA et al., 2012, p. 23 ). These commenters particularly focused on the importance for low

- income and minority populations of eliminating the spatial averaging provisions. They concluded that spatial averaging “is a n environmental justice concern because poor people are more likely to live near roads, depots, factories, ports, and other pollution sources.” Id. p. 24. Other commenters (e.g., AAM , 2012 ; Dow , 2012 ) also supported the elimination of spatial averaging in order to “avoid potential disproportionate impacts on at

- risk populations” and to maximize “the benefits to public health of reducing the annual PM 2.5 standard.” However, these groups expressed conc ern that the elimination of spatial
74 As discussed in section VIII.B.2.b below, the EPA concludes that PM 2.5 monitoring sites at micro

- and middle

- scale locations should be are comparable to the annual standard unless if the monitoring site has been approved by the Regional Administrator as a “relatively unique micro

- scale , or localized hot

- spot, or unique middle

- scale site.” representing an area

- wide location.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 161 of 790 Formatted: Left averaging, in combinat ion with the requirement for near road monitors (as discussed in section VIII.B.3.b.i of the proposal) , would effectively and inappropriately increase the stringency of the annual PM 2.5 standard. This concern was also shared by other commenters who disagr eed with the elimination of spatial averaging. For example, the Class of ’85 RRG emphasized concerns about increasing the stringency of the standard while providing few health benefits if spatial averaging is eliminated, particularly in combination with th e requirement for near

- road monitors. These commenters contended that “[b]ecause EPA proposes to use the readings from the highest single worst case monitor (rather than the average of all community area monitors), and since roadway monitoring locations wi ll likely be worst case monitors, the proposed NAAQS will become more stringent without targeting the PM 2.5 species most harmful to human health” (Class of ’85 RRG, 2012, p. 6). Several commenters also ma intained that because spatial averaging is consistent with how air quality data are considered in the underlying epidemiological studies, such averaging should not be eliminated. Specifically, commenters including NAM et al. , AFPM, and ACC pointed out that PM 2.5 e pidemiological studies use spatially averaged multi

- monitor concentrations, rather than the single highest monitor, when evaluating health effects. Therefore, these commenters contended that allowing spatial averaging would make the PM 2.5 standard more con sistent with the approaches used in the epidemiological studies upon which the standard is based. In addition, some commenters also contended that the EPA failed to consider whether modifying, rather than eliminating, the constraints on spatial averaging would have been sufficient to protect the***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 162 of 790 Formatted: Left public health. If so, th ese commenter s argued that “elimination of spatial averaging would go beyond what is requisite to protect the public health” (NAM et al., 2012, p. 20 ) ). In considering the public comments on the form of the annual standard, the EPA recognizes a number of commenters agreed with the basis for the EPA’s proposal to eliminate spatial averaging. While other commenters expressed disagreement or concern with the proposed decision to eliminate the sp atial averaging provisions, the A gency notes that these comment er s did not challenge the analyses or considerations that provided the fundamental basis for the Administrator’s propos ed decision
. Rather, these commenters generally raised concerns that elimi nating the option for spatial averaging would increase the stringency of the standard, especially in light of additional monitoring sites in near

- road environments (as discussed in section VIII.B.3.b.1 below). In The EPA does not agree with the comment that siting some monitors in near roadway environments makes the standard more stringent or impermissibly more stringent. As discussed in section VIII.B.3.b.i below, a significant fraction of the population lives in proximity to major roads, and these exposures occur in locations that represent ambient air. Monitoring in such areas does not make the standard more stringent than warranted, but rather affords the intended protection to the exposed populations, among the m at
- risk populations, exposed to fine particles in these areas. Thus, in cases where monitors in near roadway environments are deemed to be representative of area

- wide air quality they would be compared to the annual standard (as discussed more fully in s ection VIII below). The 24

- hour and annual NAAQS are designed to protect the public with an adequate margin of safety, and this siting provision***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 163 of 790 Formatted: Left is fully consistent with providing the protection the standard is designed to provide and does not make the sta ndard more stringent or more stringent than necessary. Monitors that are representative of area

- wide air quality may be compared to the annual standard. This is consistent with the use of monitoring data in the epidemiological studies that provide the pr imary basis for determining the level of the annual standard. In addition, the EPA notes that the annual standard is designed to protect against both long

and short

- term exposures through controlling the broad distribution of air quality across

an area ov er time. 75 It is fully consistent with the protection the standard is designed to provide for near road monitors to be compared to the annual standard if the monitor is representative of area

- wide air quality. This does not make the standard either more str ingent or impermissibly more stringent. In further considering these comments, the EPA notes that the stringency or level of protection provided by each NAAQS is not based solely on the form of the standard; rather, the four elements of the standard that together serve to define each standard (i.e., indica tor, averaging time, form, and level) must be considered collectively in evaluating the protection afforded by each standard. Therefore, the EPA considers these comments

are more also appropriate to discuss collectively with other issues related to the appr opriate level for annual standard, and are discussed below in section sections III.E.4.c

- d. In reaching a final decision on the form of the annual standard, the Administrator considers the available analyses, CASAC advice, and public comments on form as

75 This is in contrast to the 24

- hour standard which is designed to provide supplemental prot ection, addressing peak exposures that might not otherwise be addressed by the annual standard. Consistent with this, monitors are not required to be representative of area

- wide air quality to be compared to the 24

- hour standard. Formatted: Default, Tab stops: Not at 0" + 0.5" + 1" + 1.5" + 2" + 2.5" + 3" + 3.5" + 4" + 4.5" + 5" + 5.5"***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 164 of 790 Formatted: Left di scussed above . She also considers related issues in the public comments on the level of the annual standard as discussed in section III.E.4.c below . She notes that even when the annual PM 2.5 standard was first set in 1997, the spatial averaging provisions included constraints intended to ensure that inequities in the level of protection would not result. These constraints on spatial averaging were tightened in the last review, based on an analysis showing the potential for spatial averaging to allow higher PM 2.5 concentrations in locations where subgroups within the general population we re potentially disproportionately exposed and hence, at disproportionate risk (e.g., low income and minority communities). The Administrator notes that in proposing to elimin ate spatial averaging altogether in this review, she has relied on further analyses in the current review (Schmidt, 2011a 2011 , Analysis A ). As discussed above and in the proposal (77 FR 38924) , these analyses showed that the current constraints on spatial averaging may be inadequate in some areas to avoid substantially greater exposures for people living near monitors recording the highest PM 2.5 concentrations. Such exposures could result in disproportionate impacts to at
- risk populations, including low

- inc ome populations as well

as minority groups. On this basis, t

he Administrator concludes that public health would not be protected with an adequate margin of safety in all locations , as required by law, if disproportionately higher exposure concentrations i n at
- risk populations such as low income communities as well as minority communities were averaged together with lower concentrations measured at other sites in a large urban area. See ALA v. EPA , 134 F. 3d 388, 389 (D.C. Cir., 1998) (“this court has held that ‘NAAQS must protect not only average healthy individuals, but also sensitive citizens such as children,’ and ‘if a***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 165 of 790 Formatted: Left pollutant adversely affects the health of these sensitive individuals, EPA must strengthen the entire national standard’”) and Coalition of Battery Recyclers Association v. EPA, 604 F 3d. 613, 617 (D.C. Cir., 2010) (“Petitioners’ assertion that the revised lead NAAQS is overprotective because it is more stringent than necessary to protect the entire population of young U.S. children ignore s that the Clean Air Act allows protection of sensitive subpopulations.”) In reaching this conclusion, the Administrator further notes that her concern over possible disproportionate PM 2.5 - related health impacts in at

- risk populations extends to population s living near important sources of PM 2.5 , including the large populations that live near major roadways. 76 In light of all of the above considerations, including consideration of available analyses, CASAC advice, and public comments, the Administrator conc ludes that the current form of the annual PM 2.5 standard should be revised to eliminate spatial averaging provisions. Thus, the level of the revised annual PM 2.5 standard established with this notice will be compared with measurements from each appropriate monitor in an area, with no allowance for spatial averaging. The Administrator’s conclusions with regard to the appropriate level of the annual PM 2.5 standard to set in conjunction with this form are discussed below in section III.E.4.d. b. 24

- Hour Standard In 1997, the EPA established the form of the 24

- hour PM 2.5 standard as the 98 th percentile of 24

- hour concentrations at each population

- oriented monitor within an area, averaged over three years (62 FR at 38671 to 38674, July 18, 1997). The Agency selected the 98 th percentile as an appropriate balance between adequately limiting the occurrence

76 Section VIII.B.3.b.i belo w discusses public comments specifically related to the proposed requirement for near

- road monitors.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 166 of 790 Formatted: Left of peak concentrations and providing increased stability which, when averaged over 3 years, facilitated effective health protection through the development of more stable impl ementation programs. By basing the form of the standard on concentrations measured at population

- oriented monitoring sites, the EPA intended to provide protection for people residing in or near localized areas of elevated concentrations. In the last review , in conjunction with lowering the level of the 24

- hour standard, the EPA retained this form based in part on a comparison with the 99 th percentile form. 77 In revisiting the stability of a 98 th versus 99 th percentile form for a 24

- hour standard intended to provide supplemental protection for a generally controlling annual standard, an analysis presented in the Policy Assessment considered air quality data reported in 2000 to 2008 to update our understanding of the ratio between peak

- to
- mean PM 2.5 concentrat ions. This analysis provided evidence that the 98 th percentile value was a more stable metric than the 99 th percentile ( U.S. EPA, 2011a, Figure 2

- 2, p. 2

- 62). At the time of the proposal, the Agency recognized that the selection of the appropriate form of the 24

- hour standard includes maintaining adequate protection against peak 24

- hour concentrations while also providing a stable target for risk management programs, which serves to provide for the most effective public health protection in the long run. 78 As in previous reviews, the EPA recognized that a

77 In reaching this final decision, the EPA recognized a technical problem associated with a potential bias in the method used to calculate the 98 th percen tile concentration for this form. The EPA adjusted the sampling frequency requirement in order to reduce this bias. Accordingly, the Agency modified the final monitoring requirements such that areas that are within 5 percent of the standards are required t o increase the sampling frequency to every day (71 FR 61164 to 61165, October 17, 2006). 78 See ATA III , 283 F.3d at 374

- 376 which concludes that it is legitimate for the EPA to consider overall stability of the standard and its resulting promotion of overa ll effectiveness of NAAQS control programs in setting a standard that is requisite to protect the public health.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 167 of 790 Formatted: Left concentration

- based form, compared to an exceedance

- based form, was more reflective of the health risks posed by elevated pollutant concentrations because such a form gives proportionally greater weight to days when concentrations are well above the level of the standard than to days when the concentrations are just above the level of the standard. Further, the Agency provisionally concluded that a concentration

- based form, when averaged over three years, pr ovided an appropriate balance between limiting peak pollutant concentrations and providing a stable regulatory target, thus facilitating the development of more stable implementation programs. In considering the information provided in the Policy Assessme nt and recognizing that the degree of public health protection likely to be afforded by a standard is a result of the combination of the form and the level of the standard, the Administrator proposed to retain the 98 th percentile form of the 24

- hour standa rd. The Administrator provisionally concluded that the 98 th percentile form represents an appropriate balance between adequately limiting the occurrence of peak concentrations and providing increased stability relative to an alternative 99 th percentile for m. Few public commenters commented specifically on the form of the 24

- hour standard. None of the public commenters raised objections to continuing the use of a concentration

- based form for the 24

- hour standard. Many of the individuals and groups who suppo rted a more stringent 24

- hour PM 2.5 standard noted in section III.D.2 above, however, recommended a more restrictive concentration

- based percentile form, specifically a 99 th percentile form. The limited number of these commenters who provided a specific ra

tionale for this recommendation generally expressed their concern that the 98 th percentile form could allow too many days where concentrations exceeded***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 168 of 790 Formatted: Left the level of the standard, and thus fail to adequately protect public health. Other public commenters re presenting s tate and local air agencies and industry groups generally supported retaining the current 98 th percentile form. In most cases, these groups expressed the overall view that the current 24

- hour PM 2.5 standard, including the form of the current st andard, should be retained. The EPA notes that the viewpoints represented in this review are similar to comments submitted in the last review and through various NAAQS reviews. The EPA recognizes that the selection of the appropriate form includes maintai ning adequate protection against peak 24

- hour values while also providing a stable target for risk management programs, which serves to provide for the most effective public health protection in the long run. 79 Nothing in the commenters’ views has provided a reason to change the Administrator’s previous conclusion regarding the appropriate balance represented in the proposed form of the 24

- hour PM 2.5 standard. Therefore, the Administrator concurs with staff conclusions presented in the Policy Assessment and CASAC recommendations and concludes that it is appropriate to retain the 98 th percentile form for the 24

- hour PM 2.5 standard. 4. Level In the last review, the EPA selected levels for the annual and the 24

- hour PM 2.5 standards using evidence of effects associated with periods of exposure that were most closely matched to the averaging time of each standard. Thus, as discussed in section

79 As just noted above, it is legitimate for the EPA to consider promotion of overall effectiveness of risk management programs designed to att ain the NAAQS, including their overall stability, in setting a standard that is requisite to protect the public health. The context for the court’s discussion in ATA III is identical to that here; whether to adopt a 98 th percentile form for a 24

- hour stand ard intended to provide supplemental protection for a generally controlling annual standard.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 169 of 790 Formatted: Left III.A.1, the EPA relied upon evidence from long

- term exposure studies as the princ ipal basis for selecting the level of the annual PM 2.5 standard that would protect against effects associated with long

- term exposures. The EPA relied upon evidence from the short

- term exposure studies as the principal basis for selecting the level of the 24

- hour PM 2.5 standard that would protect against effects associated with short

- term exposures. As summarized in section III.A.2 above, the 2006 decision to retain the level of the annual PM 2.5 standard at 15 μg/m 3 80 was challenged and on judicial review, the D.C. Circuit remanded the primary annual PM 2.5 standard to the EPA, finding that EPA’s explanation for its approach to setting the level of the annual standard was inadequate.

a. General Approach for Considering Standard Levels Building upon the lessons learned in the previous PM NAAQS reviews, in considering alternative standard levels supported by the currently available scientific information, the Policy Assessment used an approach that integrated evidence

- based and risk

- based considerations, took into account CASAC advice, and considered the issues raised by the court in remanding the primary annual PM 2.5 standard. Following the general approach outlined in section III.A.3 above, for the reasons discussed below, the Policy Assessment concluded it was a ppropriate to consider the protection afforded by the annual and 24

- hour standards taken together against mortality and morbidity effects associated with both long

- and short

- term PM 2.5 exposures. This was consistent with the approach taken in the review c ompleted in 1997 rather than considering each standard separately, as was done in the review completed in 2006.
80 Throughout this section, the annual standard levels are denoted as integer values for simplicity, although, as noted above in section II.B.1, Table 1, the annual standard level is defined to one decimal place, such that the current annual standard level i s 15.0 μg/m 3

. Alternative annual standard levels discussed in this section are similarly defined to one decimal place.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 170 of 790 Formatted: Left Beyond looking directly at the relevant epidemiologic evidence, the Policy Assessment considered the extent to which specific alternative PM 2.5 standard levels were likely to reduce the nature and magnitude of both long

- term exposure
- related mortality risk and short

- term exposure
- related mortality and morbidity risk ( U.S. EPA, 2011a, section 2.3.4.2; U.S.EPA, 2010a, section 4.2.2). As noted in se ction III.C.3 above, patterns of increasing estimated risk reductions were generally observed as either the annual or 24

- hour standard, or both, were reduced below the level of the current standards ( U.S. 2011a, Figures 2

- 11 and 2

- 12; U.S. EPA, 2010a, sections 4.2.2, 5.2.2, and 5.2.3). Based on the quantitative risk assessment, the Policy Assessment observed, as discussed in section III.A.3, that analyses conducted for this and previous reviews demonstrated that much, if not most, of the a ggregate risk associated with short

- term exposures results from the large number of days during which the 24

- hour average concentrations are in the low

- to mid

- range, below the peak 24

- hour concentrations ( U.S. EPA, 2011a, p. 2

- 9). Furthermore, as discussed in section III.C above and in section III.C.3 of the proposal, the Risk Assessment observed that alternative annual standard levels, when controlling, resulted in more consistent risk reductions across urban study areas, thereby potentially providing a mo re consistent degree of public health protection ( U.S. EPA, 2010a, pp. 5

- 15 to 5

- 16). In contrast, the Risk Assessment noted that the results of simulating alternative suites of PM 2.5 standards including different combinations of alternative annual and 24

- hour standard levels suggested that an alternative 24

- hour standard level can produce additional estimated risk reductions beyond that provided by an alternative annual standard alone. However, the degree of***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 171 of 790 Formatted: Left estimated risk reduction provided by alternative 24

- hour standard levels was highly variable, in part due to the choice of rollback approached used ( U.S. EPA, 2010a, p. 5

- 17). Based on its review of the second draft Policy Assessment, CASAC agreed with the EPA staff’s general approach for translating t he available epidemiological evidence, risk information, and air quality information into the basis for reaching conclusions on alternative standards for consideration. Furthermore, CASAC agreed “that it is appropriate to return to the strategy used in 199 7 that considers the annual and the short

term standards together, with the annual standard as the controlling standard, and the short

- term standard supplementing the protection afforded by the annual standard” and “considers it appropriate to place the gr eatest emphasis” on health effects judged to have evidence supportive of a causal or likely causal relationship as presented in the Integrated Science Assessment (Samet, 2010d, p. 1). Therefore, the Policy Assessment concluded, consistent with specific CA SAC advice, that it was appropriate to set a “generally controlling” annual standard that will lower a wide range of ambient 24

- hour concentrations. The Policy Assessment concluded this approach would likely reduce aggregate risks associated with both long

- and short

term exposures with more consistency than a generally controlling 24

- hour standard and would be the most effective and efficient way to reduce total PM 2.5 - related population risk and so provide appropriate protection. The staff believed this ap proach, in contrast to one focusing on a generally controlling 24

- hour standard, would likely reduce aggregate risks associated with both long

- and short

- term exposures with more consistency and would likely avoid setting national standards that could resu lt in relatively uneven***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 172 of 790 Formatted: Left protection across the country due to setting standards that were either more or less stringent than necessary in different geographical areas. The Policy Assessment recognized that an annual standard intended to serve as the primar y means for providing protection against effects associated with both long

- and short

- term PM 2.5 exposures cannot be expected to offer an adequate margin of safety against the effects of all short

- term PM 2.5 exposures. As a result, in conjunction with a ge nerally controlling annual standard, the Policy Assessment concluded it was appropriate to consider setting a 24

- hour standard to provide supplemental protection, particularly for areas with high peak

- to
- mean ratios possibly associated with strong local

or seasonal sources, or PM 2.5 - related effects that may be associated with shorter

- than

daily exposure periods. At the time of the proposal, the Administrator agreed with the approach discussed in the Policy Assessment as summarized in section III.A.3 above, and supported by CASAC, of considering the protection afforded by the annual and 24

- hour standards taken together for mortality and morbidity effects associated with both long

- and short

term exposures to PM 2.5 . Furthermore, based on the evidence and quant itative risk assessment, the Administrator provisionally concluded it was appropriate to set a “generally controlling” annual standard that will lower a wide range of ambient 24

- hour concentrations, with a 24

- hour standard focused on providing supplemental protection, particularly for areas with high peak

- to
- mean ratios possibly associated with strong local or seasonal sources, or PM 2.5 - related effects that may be associated with shorter

- than daily exposure periods. The Administrator provisionally concluded this approach would likely reduce aggregate risks associated with both long

- and short

- term exposures more***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 173 of 790 Formatted: Left consistently than a generally controlling 24

- hour standard and would be the most effective and efficient way to reduce total PM 2

- 5 - related populatio n risk. The Administrator is mindful that considering what standards are requisite to protect public health with an adequate margin of safety requires pub lic health policy judgments that neither overstate nor understate the strength and limitations of the evidence or the appropriate inferences to be drawn from the evidence. At the time of the proposal, in considering how to translate the available information into appropriate standard levels, the Administrator weighed the available scientific information an d associated uncertainties and limitations. For the purpose of determining what standard levels were appropriate to propose, the Administrator recognized, as did the EPA staff in the Policy Assessment, that there was no single factor or criterion that comp rised the “correct” approach to weighing the various types of available evidence and information, but rather there were various approaches that were appropriate to consider. The Administrator further recognized that different evaluations of the evidence an d other information before the Administrator could reflect placing different weight on the relative strengths and limitations of the scientific information, and different judgments could be made as to how such information should appropriately be used in ma king public health policy decisions on standard levels. This recognition led the Administrator to consider various approaches to weighing the evidence so as to identify appropriate standard levels to propose. In so doing, the Administrator encouraged exten sive public comment on alternative approaches to weighing the evidence and other information so as to inform her public health policy judgments before reaching final decisions on appropriate standard levels.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 174 of 790 Formatted: Left b. Proposed Decisions on Standard Levels i. Considerat ion of the Alternative Standard Levels in the Policy Assessment In recognizing the absence of a discernible population threshold below which effects would not occur, the Policy Assessment’s general approach for identifying alternative annual standard level s that were appropriate to consider focused on characterizing the part of the distribution of PM 2.5 concentrations in which we had the most confidence in the associations reported in the epidemiological studies and conversely where our confidence in the as sociation became appreciably lower. The most direct approach to address this issue, consistent with CASAC advice (Samet, 2010c, p.10), was to consider epidemiological studies reporting confidence intervals around concentration

- response relationships ( U.S. EPA, 2011a, p. 2

- 63). Based on a thorough search of the available evidence, the Policy Assessment identified only one study (Schwartz et al., 2008) that conducted a multi

- model analysis to characterize confidence intervals around the estimated concentratio n - response relationship. The Policy Assessment concluded that this single relevant analysis was too limited to serve as the principal basis for identifying alternative standard levels in this review ( U.S. EPA, 2011a, p. 2

- 70). The Policy Assessment explore d other approaches that considered different statistical metrics to identify to characterize the part of the distributions of long

- term mean PM 2.5 concentrations that were most influential in generating health effect estimates in long

- and short

- term epidem iological studies, and placed greatest weight on those studies that reported positive and statistically significant associations ( U.S. EPA, 2011a, p. 2

- 63). First, as discussed in section III.A.3 above, the Policy Assessment considered the***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 175 of 790 Formatted: Left statistical metr ic used in previous reviews. This approach recognized the EPA’s views that the strongest evidence of associations occurs at concentrations around the long

- term mean concentration. Thus, in earlier reviews, the EPA focused on identifying standard levels that were somewhat below the long

- term mean concentrations reported in PM 2.5 exposure e pidemiological studies. The long

- term mean concentrations represented air quality data typically used in epidemiological analyses and provided a direct link between PM 2.5 concentrations and the observed health effects. Further, these data were available for all long

- and short

- term exposure studies analyzed and, therefore, represented the data set available for the broadest set of epidemiological studies. However, consist ent with CASAC’s comments on the second draft Policy Assessment 81 (Samet, 2010d, p. 2), in preparing the final Policy Assessment, the EPA staff explored ways to take into account additional information from epidemiological studies, when available (Rajan et al., 2011). These analyses focused on evaluating different statistical metrics, beyond the long

- term mean concentration, to characterize the part of the distribution of PM 2.5 concentrations in which staff continued to have confidence in the associations ob served in epidemiological studies and below which there was a comparative lack of data such that the staff’s confidence in the relationship was appreciably less. This would also be the part of the distribution of PM 2.5 concentrations which had the most inf

luence on generating the health effect estimates reported in epidemiological studies. As discussed in section III.A.3 above, the Policy Assessment recognized there was no one percentile value within a given distribution that was the

81 While CASAC expressed the view that it would be most desirable to have information on concentration

- response relationships, they recogn ized that it would also be “preferable to have information on the concentrations that were most influential in generating the health effect estimates in individual studies” (Samet, 2010d, p. 2).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 176 of 790 Formatted: Left most appropriate or “co rrect” way to characterize where our confidence in the associations becomes appreciably lower. The Policy Assessment concluded that focusing on concentrations within the lower quartile of a distribution, such as the range from the 25 th to the 10 th percenti le, was reasonable to consider as a region within which we begin to have appreciably less confidence in the associations observed in epidemiological studies. 82 In the EPA staff’s view, considering lower PM 2.5 concentrations, down to the lowest concentration observed in a study, would be a highly uncertain basis for selecting alternative standard levels ( U.S. EPA, 2009a, p. 2

- 71). As outlined in section III.A.3 above, the Policy Assessment recognized that there were two types of population

- level information t o consider in identifying the range of PM 2.5 concentrations which have the most influence on generating the health effect estimates reported in epidemiological studies. The most relevant information to consider was the number of health events (e.g., deaths , hospitalizations) occurring within a study population in relation to the distribution of PM 2.5 concentrations likely experienced by study participants. However, in recognizing that access to health event data may be restricted, and consistent with advice from CASAC (Samet 2010d, p.2), EPA staff also considered the number of participants within each study area, in relation to the
82 In the last review, staff believed it was appropriate to c onsider a level for an annual PM 2.5 standard that was somewhat below the averages of the long

- term concentrations across the cities in each of the key long

- term exposures studies, recognizing that the evidence of an association in any such study was strong est at and around the long

- term average where the data in the study are most concentrated. For example, the interquartile range of long

- term average concentrations within a study and a range within one standard deviation around the study mean were consider ed reasonable approaches for characterizing the range over which the evidence of association is strongest (U.S. EPA, 2005, pp. 5

- 22 to 5

- 23). In this review, the Policy Assessment noted the interrelatedness of the distributional statistics and a range of o ne standard deviation around the mean which contains approximately 68 percent of normally distributed data, in that one standard deviation below the mean falls between the 25 th and 10 th percentiles (U.S. EPA, 2011a, p. 2

- 71).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 177 of 790 Formatted: Left distribution of PM 2.5 concentrations (i.e., study population data), as a surrogate for health event data. In applying this appr oach, the Policy Assessment focused on identifying the part of the distribution of PM 2.5 concentrations which had the most influence on generating health effect estimates in epidemiological studies, as discussed in section III.A.3 above. As discussed below , in working with study investigators, the EPA staff was able to obtain health event data for three large multi

- city studies (Krewski et al., 2009; Zanobetti and Schwartz, 2009; Bell et al., 2008) and population data for the same three studies and one addi tional long

- term exposure study (Miller et al., 2007) , as documented in a staff memorandum (Rajan et al., 2011). 83 For the three studies for which both health event and study population data were available, the EPA staff analyzed the reliability of using st udy population data as a surrogate for health event data. Based on these analyses, the EPA staff recognized that the 10 th and 25 th percentiles of the health event and study population distributions are nearly identical and concluded that the distribution o f population data can be a useful surrogate for event data, providing support for consideration of the study population data for Miller et al. (2007), for which health event data were not available (Rajan et al., 2011, Analysis 1 and Analysis 2, in particu lar, Table 1 and Figures 1 and 2). With regard to the long

- term mean PM 2.5 concentrations which are relevant to the first approach, Figures 1 through 3 ( U.S. EPA, 2011a, Figures 2

- 4, 2

- 5, 2

- 6, and 2

- 8) summarize data available for multi

- city, long

- and short

- term exposure studies that evaluated endpoints classified in the Integrated Science Assessment as having evidence

83 The distributional statistical analysis of population

- level data built upon an earlier analysis that evaluated the distributions of air quality and associated population data for three long

- term exposure studies and three short

- term exposure studies (Schm idt et al., 2010, Analysis 2).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 178 of 790 Formatted: Left of a causal or likely causal relationshi p or evidence suggestive of a causal relationship, showing the studies with long

- term mean PM 2.5 concentrations below 17 μg/m 3

. 84 As discussed in more detail in section III.E.4.b of the proposal, Figures 1 and 3 summarize the health outcomes evaluated, rela tive risk estimates, air quality data, and geographic scope for long

- and short

- term exposure studies, respectively, that evaluated mortality (evidence of a causal relationship); cardiovascular effects (evidence of a causal relationship); and respiratory e ffects (evidence of a likely causal relationship) in the general population, as well as in older adults, an at

- risk population. Figure 2 provides this same summary information for long

- term exposure studies that evaluated respiratory effects (evidence of a likely causal relationship) in children, an at

- risk population, as well as developmental effects (evidence suggestive of a causal relationship).

84 Additional studies presented and assessed in the Integrated Science Assessment report effects at higher long

- term mean PM 2.5 concentrations (e.g., U.S. EPA, 2009a, Figures 2

- 1, 2

- 2, 7

- 6, and 7

- 7).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 179 of 790 Formatted: Left 

### Figure 1. Summary of Effect Estimates (per 10 μg/m 3 

### ) and Air Quality Distributions for Multi - City, Long - term PM 2.5 

### Exposure Studies of the General Population and Older Adults 85 

### , 86

85 

### The air quality data lon g - term mean PM 2.5 

### concentrations reported by the study authors for the Miller et al. (2007) study is and Lipfert et al. (2006a) studies are discussed more fully in the Response to Comments document
. (U.S. EPA, 2012a)
. 86 

### The Goss et al. (2004) study patients over the age of 6 years enrolled in the Cystic Fibrosis Foundation National Patient Reg istry in 1999 and 2000. The average age of the study participants was 18.4 (SD 10). Formatted: Font: 12 pt***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 180 of 790 Formatted: Left



### Source: U.S. EPA, 2011a, Figure 2

- 4 Formatted: Font: 12 pt***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 181 of 790 Formatted: Left 

### Figure 2. Summary of Effect Estimates (per 10 μg/m 3 

### ) and Air Quality Distributions for Multi - City, Long - term PM 2.5 

### Exposure Studies of Children

Source: U.S. EPA, 2011a, Figure 2

- 5***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 182 of 790 Formatted: Left 

### Figure 3. Summary of Effect Estimates (per 10 μg/m 3 

### ) and Air Quality Distributions for Multi - City, Short - term PM 2.5 

### Exposure Studies of the General Population and Older Adults

Source: U.S. EPA, 2011a, Figure 2

- 6***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 183 of 790 Formatted: Left With regard to consideration of additional information from epidemiological studies which was relevant to the second approach, the EPA staff compiled a summary of the range of PM 2.5 concentrations corresponding with the 25 th to 10 th percentiles of health event or study population data from the four multi

- city studies, for which distributional statistics are avail able 87 ( U.S. EPA, 2011a, Figure 2

- 7; Rajan et al., 2011, Table 1). By considering this approach, one could focus on the range of PM 2.5 concentrations below the long

- term mean ambient concentrations over which we continue to have confidence in the associatio ns observed in epidemiological studies (e.g., above the 25 th percentile) where commensurate public health protection could be obtained for PM 2.5 - related effects and, conversely, identify the range in the distribution below which our confidence in the assoc iations is appreciably less, to identify alternative annual standard levels. The mean PM 2.5 concentrations associated with the studies summarized in Figures 1, 2, and 3 and with the distributional statistics analyses (Rajan et al., 2011) are based on concentrations averaged across ambient monitors within each area included in a given study and t hen averaged across study areas to calculate an overall study mean concentration, as discussed above. Figure 4, discussed in more detail in section III.E.4.a of the proposal, summarizes statistical metrics for those key studies 88 included in

87 The EPA staff obtained health event data (e .g., number of deaths, hospitalizations) occurring in a study population for three multi

- city studies (Krewski et al., 2009; Zanobetti and Schwartz, 2009; Bell et al., 2008) and study population data were obtained for the same three studies and one additio nal study (Miller et al., 2007) (U.S. EPA, 2011a, p.2

- 71). If health event or study population data were available for additional studies, the EPA could employ distributional statistics to identify the broader range of PM 2.5 concentrations that were most i nfluential in generating health effect estimates in those studies. 88 Long

- and short

- term exposure studies considered “key” studies for consideration are summarized in Figure 4 and include those studies observing effects for which the evidence supported a causal or likely causal association. This figure represents the subset of multi

- city studies included in Figures 1 through 3 that provided evidence of positive and generally statistically significant effects associated in whole or in part with more recent air quality data, generally representing health effects associated with lower PM 2.5 concentrations than had previously been considered in the last review. The EPA notes that many of these studies evaluated multiple health endpoints, and not all of the eff ects evaluated provided evidence of positive and statistically significant effects. For purposes of informing the Administrator’s decision on the appropriate standard levels, the Agency considers the full body of scientific evidence and focuses on those as pects of the key studies that provided evidence of positive and generally statistically significant effects.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 184 of 790 Formatted: Left 

### Figure 4. Translating Epidemiological Evidence from Multi - City Exposure Studies into an Annual PM 2.5 

### Standard 89

89 

### The air quality data long

- term mean PM 2.5 

### concentrations reported by the study authors for the Miller et al. (2007) study is and Lipfert et al. ( 2006a) studies are discussed more fully in the Response to Comments document
. (U.S. EPA, 2012a)
. Formatted: Font: 12 pt***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 185 of 790 Formatted: Left



### Source: U.S. EPA, 2011a, Figure 2

-***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 186 of 790 Formatted: Left Figures 1, 2, and 3 that provide evidence of positive and generally statistically significant PM 2.5 - related effects, which are relevant to the two approaches for translating epidemiological evidence into potential standard levels as discussed above. The top of Figure 4 includes information for long

- term exposure studies e valuating health outcomes classified as having evidence of a cau s al or likely cau s al relationship with PM 2.5 exposures (long

- term mean PM 2.5 concentrations indicated by diamond symbols). The middle of Figure 4 includes information for short

- term exposure s tudies evaluating health outcomes classified as having evidence of a cau s al or likely cau s al relationship with PM 2.5 exposures (long

- term mean PM 2.5 concentrations indicated by triangle symbols). The bottom of Figure 4 includes information for long

- term exposures studies evaluating health outcomes classified as having evidence suggestive of a causal relationship (long

term mean PM 2.5 concentrations indicated by square symbols). Figure 4 also summarizes the range of PM 2.5 concentrations corresponding with the 25 th (indicated by solid circles) to 10 th (indicated by open circles) percentiles of the health event or study population data from the four multi

- city studies (highlighted in bold text) for which distributional statistics are available. In considerin g the evidence, the Policy Assessment recognized that NAAQS are standards set so as to provide requisite protection, neither more nor less stringent than necessary to protect public health, with an adequate margin of safety. This judgment, ultimately made by the Administrator, involves weighing the strength of the evidence and the inherent uncertainties and limitations of that evidence. Therefore, depending on the weight placed on different aspects of the evidence and inherent uncertainties, consideration o f different alternative standard levels could be supported.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 187 of 790 Formatted: Left Given the currently available evidence discussed in more detail in section III.E.4.b of the proposal and considering the various approaches discussed above, the Policy Assessment concluded it was appropriate to focus on an annual standard level within a range of about 12 to 11 μg/m 3 ( U.S. EPA, 2011a, pp. 2

- 82, 2

- 101, and 2

- 106). As illustrated in Figure 4, the Policy Assessment recognized that a standard level of 12 μg/m 3 , at the upper end of this range, was somewhat below the long

- term mean PM 2.5 concentrations reported in all the multi

- city, long

- and short

- term exposure studies that provided evidence of positive and statistically significant associations with health effects classified as having evidence of a causal or likely causal relationship, including premature mortality and hospitalizations and emergency department visits for cardiovascular and respiratory effects as well as respiratory effects in children. Further, a level of 12 μg/m 3 would reflect consideration of additional population

- level information from such epidemiological studies in that it generally corresponded with approximately the 25 th percentile of the available distributions of health events data in the studies for which popul ation

- level information was available. In addition, a level of 12 μg/m 3 would reflect some consideration of studies that provided more limited evidence of reproductive and developmental effects, which were suggestive of a causal relationship, in that it wa s about at the same level as the lowest long

- term mean PM 2.5 concentrations reported in such studies (see Figure 4). Alternatively the Policy Assessment recognized that an annual standard level of 11 μg/m 3 , at the lower end of this range, was well below t he lowest long

- term mean PM 2.5 concentrations reported in all multi

- city long

- and short

- term exposure studies that provide evidence of positive and statistically significant associations with health effects***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 188 of 790 Formatted: Left classified as having evidence of a causal or lik ely causal relationship. A level of 11 μg/m 3 would reflect placing more weight on the distributions of health event and population data, in that this level was within the range of PM 2.5 concentrations corresponding to the 25 th and 10 th percentiles of all t he available distributions of such data. In addition, a level of 11 μg/m 3 was somewhat below the lowest long

- term mean PM 2.5 concentrations reported in reproductive and developmental effects studies that are suggestive of a causal relationship. Thus, a lev el of 11 μg/m 3 would reflect an approach to translating the available evidence that places relatively more emphasis on margin of safety considerations and less certain causal relationships than would a standard set at a higher level. Such a policy approach would tend to weigh uncertainties in the evidence in such a way as to avoid potentially underestimating PM 2.5 - related risks to public health. Further, recognizing the uncertainties inherent in identifying any particular point at which our confidence in re ported associations becomes appreciably less, the Policy Assessment concluded that the available evidence did not provide a sufficient basis to consider alternative annual standard levels below 11 μg/m 3 ( U.S. EPA, 2011a, p. 2

- 81). The Policy Assessment al so considered the extent to which the available evidence provided a basis for considering alternative annual standard levels above 12 μg/m 3 . As discussed below, the Policy Assessment concluded that it could be reasonable to consider a standard level up to 13 μg/m 3 based on a policy approach that weighed uncertainties in the evidence in such a way as to avoid potentially overestimating PM 2.5 - related risks to public health, especially to the extent that primary emphasis was placed on long

- term exposure studie s as a basis for an annual standard level. A level of 13 μg/m 3 was somewhat below the long

- term mean PM 2.5 concentrations reported in all but one of the***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 189 of 790 Formatted: Left long

- term exposure studies providing evidence of positive and statistically significant associations with PM 2.5 - related health effects classified as having a causal or likely causal relationship. As shown in Figure 4, the one long

- term exposure study with a long

- term mean PM 2.5 concentration just below 13 μg/m 3 was the Miller et al ., ( ., ( 2007) study
. Howe ver, as noted in section III.D.1.a of the proposal and discussed in more detail in the Response to Comments document , the Policy Assessment observed that in comparison to other long

- term exposure studies, the Miller et al. study was more limited in that it was based on only one year of air quality data and the one year was after the health outcomes were reported ( U.S. EPA, 2011a, pp. 2

- 81 to 2

- 82). Thus, to the extent that less weight was placed on the Miller et al. study than on other long

- term exposure st udies with more robust air quality data, a level of 13 μg/m 3 could be considered as being protective of long

- term exposure related effects classified as having a causal or likely causal relationship. In also considering short

- term exposure studies, however , the Policy Assessment noted that a level of 13 μg/m 3 was below the long

- term mean PM 2.5 concentrations reported in most but not all such studies . In particular , two studies

-- Burnett et al. (2004) and Bell et al. (2008)

-- reported long

- term mean PM 2.5 concentration s of 12.8 and 12.9 μg/m 3 , respectively. In considering these studies, the Policy Assessment found no basis to conclude that these two studies were any more limited or uncertain than the other short

- term exposure studies shown in Figures 3 and 4 ( U.S. EPA, 2011a, p. 2

- 82). On this basis, as discussed below, the Policy Assessment concluded that consideration of an annual standard level of 13 μg/m 3 would have implications for the degree of protection that would need to be provided by the 24

- hour

s tandard, in order that the suite of PM 2.5 standards, taken together, would provide***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 190 of 790 Formatted: Left appropriate protection from effects on public health related to short

- term exposure to PM 2.5 ( U.S. EPA, 2011a, p. 2

- 82). The Policy Assessment also noted that a standard level of 13 μg/m 3 would reflect a judgment that the uncertainties in the epidemiological evidence as summarized in section III.B above and discussed in more detail in section III.B.2 of the proposal, including uncertainties related to the heterogeneity obs erved in the epidemiological studies in the eastern versus western parts of the U.S., the relative toxicity of PM 2.5 components, and the potential role of co

- pollutants, are too great to warrant placing any weight on the distributions of health event and p opulation data that extend down below the long

- term mean concentrations into the lower quartile of the data. This level would also reflect a judgment that the evidence from reproductive and developmental effects studies that is suggestive of a causal relat ionship was too uncertain to support consideration of any lower level. Beyond evidence

- based considerations, the Policy Assessment also considered the extent to which the quantitative risk assessment supported consideration of these alternative standard le vels or provided support for lower levels. In considering simulations of just meeting alternative annual standard levels within the range of 13 to 11 μg/m 3 (in conjunction with the current 24

- hour standard level of 35 μg/m 3 ), the Policy Assessment conclude d that important public health improvements are associated with risk reductions estimated for standard levels of 13 and 12 μg/m 3 and noted that the level of 11 μg/m 3 was not included in the quantitative risk assessment. The Policy Assessment noted that the overall confidence in the quantitative risk estimates varied for the different alternative standard levels evaluated and was stronger for the higher levels and***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 191 of 790 Formatted: Left substantially lower for the lowest level evaluated (i.e., 10 μg/m 3 ). Based on the above conside rations, the Policy Assessment concluded that the quantitative risk assessment provided support for considering alternative annual standard levels within a range of 13 to 11 μg/m 3 , but did not provide strong support for considering lower alternative standa rd levels ( U.S. EPA, 2011a, pp. 2

- 102 to 2

- 103). Taken together, the Policy Assessment concluded that consideration of alternative annual standard levels in the range of 13 to 11 μg/m 3 may be appropriate. Furthermore, the Policy Assessment concluded that t he currently available evidence most strongly supported consideration of an alternative annual standard level in the range of 12 to 11 μg/m 3 ( U.S. EPA, 2011a, p. 2

- 82). The Policy Assessment concluded that an alternative level within the range of 12 to 11 μg/m 3 would more fully take into consideration the available information from all long

- and short

- term PM 2.5 exposure studies, including studies of at

- risk populations, than would a higher level. This range also reflected placing weight on information from studies that helped to characterize the range of PM 2.5 concentrations over which we continue to have confidence in the associations observed in epidemiological studies, as well as the extent to which our confidence in the associations was appreciably less at lower concentrations. As recognized in sections III.A.3 and III.E.4.a above, an annual standard intended to serve as the primary means for providing protection from effects associated with both long

- and short

- term PM 2.5 exposures is not expected to p rovide appropriate protection against the effects of all short

- term PM 2.5 exposures (unless established at a level so low as to undoubtedly provide more protection than necessary for long

- term exposures). Of particular concern are areas with high peak

- to
- m ean ratios possibly associated with***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 192 of 790 Formatted: Left strong local or seasonal sources, or PM 2.5 - related effects that may be associated with shorter

- than

- daily exposure periods. As a result, the Policy Assessment concluded that it was appropriate to consider alternative 24

- hour PM 2.5 standard levels that would supplement the protection provided by an annual standard. As outlined in section III.A.3 above, the Policy Assessment considered the available evidence from short

- term PM 2.5 exposure studies, as well as the uncertaint ies and limitations in that evidence, to assess the degree to which alternative annual and 24

- hour PM 2.5 standards can be expected to reduce the estimated risks attributed to short

term fine particle exposures. In considering the available epidemiological evidence, the Policy Assessment took into account information from multi

- city studies as well as single

- city studies. The Policy Assessment considered the distributions of 24

- hour PM 2.5 concentrations reported in short

- term exposure studies, focusing on th e 98 th percentile concentrations to match the form of the 24

- hour standard as discussed in section III.E.3.b above. In recognizing that the annual and 24

- hour standards work together to provide protection from effects associated with short

- term PM 2.5 expos ures, the Policy Assessment also considered information on the long

- term mean PM 2.5 concentrations from these studies. In addition to considering the epidemiological evidence, the Policy Assessment considered air quality information, specifically peak

- to
- mean ratios using county

- level 24

- hour and annual design values, to characterize air quality patterns in areas possibly associated with strong local or seasonal sources. These patterns helped in understanding the extent to which different combinations of a nnual and 24

- hour standards would be consistent with the policy goal of setting a generally controlling annual standard with a***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 193 of 790 Formatted: Left 24

- hour standard that provides supplemental protection especially for areas with high peak

- to
- mean ratios ( U.S. EPA, 2011a, p. 2

- 14). In considering the information provided by the short

- term exposure studies, the Policy Assessment recognized that to the extent these studies were conducted in areas that likely did not meet one or both of the current standards, such studies did not help inform the characterization of the potential public health improvements of alternative standards set at lower levels. Therefore, in considering the short

- term exposure studies to inform staff conclusions regarding levels of the 24

- hour standard that a re appropriate to consider, the Policy Assessment placed greatest weight on studies conducted in areas that likely met both the current annual and 24

- hour standards. With regard to multi

- city studies that evaluated effects associated with short

- term PM 2.5 exposures, as summarized in Figure 3 above and discussed in more detail in section III.E.4.c of the proposal, the Policy Assessment noted that, to the extent air quality distributions were reduced to reflect just meeting the current 24

- hour standard, addit ional protection would be anticipated for the effects observed in the three multi

- city studies with 98 th percentile values greater than 35 μg/m 3 (Burnett et al., 2004; Burnett and Goldberg, 2003; Franklin et al., 2008). In the three additional studies with 98 th percentile values below 35 μg/m 3 , specifically 98 th percentile concentrations of 34.2, 34.3, and 34.8 μg/m 3 , the Policy Assessment noted that these studies reported long

- term mean PM 2.5 concentrations of 12.9, 13.2, and 13.4 μg/m 3 , respectively (Bell et al., 2008; Zanobetti and Schwartz, 2009; Dominici et al., 2006a). To the extent that consideration was given to revising the level of the annual standard, as discussed in section III.E.4.b of the proposal, the Policy Assessment reco gnized that potential changes associated with***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 194 of 790 Formatted: Left meeting such an alternative annual standard would result in lowering risks associated with both long

- and short

- term PM 2.5 exposures. Consequently, in considering a 24

- hour standard that would operate in conjun ction with an annual standard to provide appropriate public health protection, the Policy Assessment noted that to the extent that the level of the annual standard was revised to within a range of 13 to 11 μg/m 3 , in particular in the range of 12 to 11 μg/ m 3 , additional protection would be provided for the long

- term effects observed in these multi

- city studies ( U.S. EPA, 2011a, p. 2

- 84). Based on this information, the Policy Assessment concluded that the multi

- city, short

- term exposure studies generally pro vided support for retaining the 24

- hour standard level at 35 μg/m 3 so long as the standard is in conjunction with an annual standard level revised to within a range of 12 to 11 μg/m 3 ( U.S. EPA, 2011a, p. 2

- 84). Alternatively, in conjunction with an annual standard level of 13 μg/m 3 , the Policy Assessment concluded that the multi

- city studies provided limited support for revising the 24

- hour standard level somewhat below 35 μg/m 3 , such as down to 30 μg/m 3 , based on one study (Bell et al., 2008) that reported positive and statistically significant effects with an overall 98 th percentile value below the level of the current 24

- hour standard and an overall long

- term mean concentration slightly less than 13 μg/m 3 (Figure 3; U.S. EPA, 2011a, p. 2

- 84). In reachin g staff conclusions regarding alternative 24

- hour standard levels that were appropriate to consider, the Policy Assessment also took into account relevant information from single

- city studies that evaluated effects associated with short

- term PM 2.5 exposure s. The Policy Assessment recognized that these studies may provide additional insights regarding impacts on at

- risk populations and/or on areas with isolated peak concentrations.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 195 of 790 Formatted: Left As discussed in more detail in section III.E.4.c of the proposal, although a number of single

- city studies reported effects at appreciably lower PM 2.5 concentrations than multi

- city short

- term exposure studies, the uncertainties and limitations associated with the single

- city studies were considerably greater than those associated with the multi

- city studies and, thus, the Policy Assessment concluded there was less confidence in using these studies as a basis for setting the level of a standard. Therefore, the Policy Assessment concluded that the multi

- city short

- term exposure stud ies provided the strongest evidence to inform decisions on the level of the 24

- hour standard, and the single

- city studies did not warrant consideration of 24

- hour standard levels different from those supported by the multi

- city studies ( U.S. EPA, 2011a, p. 2

- 88). In addition to considering the epidemiological evidence, the Policy Assessment took into account air quality information based on county

- level 24

- hour and annual design values to understand the public health implications of the alternative standar d levels supported by the currently available scientific evidence, as discussed in section III.E.4.b above. Consistent with the general approach discussed in section III.A.3 above, the Policy Assessment considered the extent to which different combinations of alternative annual and 24

- hour standard levels based on the evidence would support the policy goal of lowering annual and 24

- hour air quality distributions by using the annual standard to be the “generally controlling” standard in conjunction with set ting the 24

- hour standard to provide supplemental protection ( U.S. EPA, 2011a, pp 2

- 88 to 2

- 91, Figure 2

- 10). Using information on the relationship of the 24

- hour and annual design values, the Policy Assessment examined the implications of three alternati ve suites of PM 2.5***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 196 of 790 Formatted: Left standards identified as appropriate to consider based on the currently available scientific evidence, as discussed above. The Policy Assessment concluded that an alternative suite of PM 2.5 standards that would include an annual standard level of 11 or 12 μg/m 3 and a 24

- hour standard with a level of 35 μg/m 3 (i.e., 11/35 or 12/35) would result in the annual standard being the generally controlling standard in most areas although the 24

- hour standard would continue to be the generally contr olling standard in the Northwest ( U.S. EPA, 2011a, pp. 2

- 89 to 2

- 91 and Figure 2

- 10). These Northwest counties generally represented areas where the annual mean PM 2.5 concentrations have historically been low but where relatively high 24

- hour concentration s occur, often related to seasonal wood smoke emissions. Alternatively, combining an alternative annual standard of 13 μg/m 3 with a 24

- hour standard of 30 μg/m 3 would result in many more areas across the country in which the 24

- hour standard would likely b ecome the controlling standard (the standard driving air quality distributions lower) than if an alternative annual standard of 12 or 11 μg/m 3 were paired with the current level of the 24

- hour standard (i.e., 35 μg/m 3 ). The Policy Assessment concluded tha t consideration of retaining the 24

- hour standard level at 35 μg/m 3 would reflect placing greatest weight on evidence from multi

city studies that reported positive and statistically significant associations with health effects classified as having a causa l or likely causal relationship. In conjunction with lowering the annual standard level, especially within a range of 12 to 11 μg/m 3 , this alternative recognized additional public health protection against effects associated with short

- term PM 2.5 exposures which would be provided by lowering the annual standard such that revision to the 24

- hour standard would not be warranted ( U.S. EPA, 2011a, p. 2

- 91).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 197 of 790 Formatted: Left Beyond evidence

- based considerations, the Policy Assessment also considered the extent to which the quan titative risk assessment supported consideration of retaining the current 24

- hour standard level or provided support for lower standard levels. In considering simulations of just meeting the current 24

- hour standard level of 35 μg/m 3 or alternative levels of 30 or 25 μg/m 3 (in conjunction with alternative annual standard levels within a range of 13 to 11 μg/m 3 ), the Policy Assessment noted that the overall confidence in the quantitative risk estimates varied for the different standard levels evaluated and w as stronger for the higher levels and substantially lower for the lowest level evaluated (i.e., 25 μg/m 3 ). Based on this information, the Policy Assessment concluded that the quantitative risk assessment provided support for considering a 24

- hour standard level of 35 or 30 μg/m 3 (in conjunction with an alternative standard level within a range of 13 to 11 μg/m 3 ) but did not provide strong support for considering lower alternative 24

- hour standard levels ( U.S. EPA, 2011a, pp. 2

- 102 to 2

- 103). Taken together, the Policy Assessment concluded that while it was appropriate to consider an alternative 24

- hour standard level within a range of 35 to 30 μg/m 3 , the currently available evidence most strongly supported consideration for retaining the current 24

- hour stan dard level at 35 μg/m 3 in conjunction with lowering the level of the annual standard within a range of 12 to 11 μg/m 3 ( U.S. EPA, 2011a, p. 2

- 92). ii. CASAC Advice Based on its review of the second draft Policy Assessment, CASAC agreed with the general approach for translating the available epidemiological evidence, risk information, and air quality information into the basis for reaching conclusions on alternative standards for consideration. Furthermore, CASAC agreed “that it is***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 198 of 790 Formatted: Left appropriate to return to the st rategy used in 1997 that considers the annual and the short

term standards together, with the annual standard as the controlling standard, and the short

- term standard supplementing the protection afforded by the annual standard” and “considers it appropria

te to place the greatest emphasis” on health effects judged to have evidence supportive of a causal or likely causal relationship as presented in the Integrated Science Assessment (Samet, 2010d, p. 1). CASAC concluded that the range of levels presented in the second draft Policy Assessment (i.e., alternative annual standard levels within a range of 13 to 11 μg/m 3 and alternative 24

- hour standard levels within a range of 35 to 30 μg/m 3 ) “are supported by the epidemiological and toxicological evidence, as we ll as by the risk and air quality information compiled” in the Integrated Science Assessment, Risk Assessment, and second draft Policy Assessment. CASAC further noted that “[a]lthough there is increasing uncertainty at lower levels, there is no evidence of a threshold (i.e., a level below which there is no risk for adverse health effects)” (Samet, 2010d, p. ii). Although CASAC supported the alternative standard level ranges presented in the second draft Policy Assessment, it did not express support for any specific levels or combinations of standards. Rather, CASAC encouraged the EPA to develop a clearer rationale in the final Policy Assessment for staff conclusions regarding annual and 24

- hour standards that were appropriate to consider, including consider ation of the combination of these standards supported by the available information (Samet, 2010d, p. ii). Specifically, in commenting on a distributional statistical analysis of air quality and associated population data presented in the second draft Polic y Assessment, CASAC encouraged staff to focus on information related to the concentrations that were most***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 199 of 790 Formatted: Left influential in generating the health effect estimates in individual studies to inform alternative standard levels. CASAC urged that the EPA redo that analysis using health event or study population data (Samet, 2010d, p. 2). CASAC also commented that the approach presented in the second draft Policy Assessment to identify alternative 24

- hour standard levels which focused on peak

- to
- mean ratios was not r elevant for informing the actual level (Samet 2010d, p. 4). Further, they expressed the concern that the combinations of annual and 24

- hour standard levels discussed in the second draft Policy Assessment (i.e., in the range of 13 to 11 μg/m 3 for the annual standard, in conjunction with retaining the current 24

- hour PM 2.5 standard level of 35 μg/m 3 ; alternatively, revising the level of the 24

- hour standard to 30 μg/m 3 in conjunction with an annual standard level of 11 μg/m 3 ) “may not be adequately inclusive” and “[i]t was not clear why, for example a daily standard of 30 μg/m 3 should only be considered in combination with an annual level of 11 μg/m 3 ” (Samet, 2010d, p. ii). CASAC encouraged the EPA to more clearly explain its rationale for identifying the 24

- h our/annual combinations that are appropriate for consideration (Samet 2010d, p. ii). In considering CASAC’s advice as well as public comment on the second draft Policy Assessment, the EPA staff conducted additional analyses and modified their conclusions regarding alternative standard levels that were appropriate to consider. The staff conclusions in the final Policy Assessment ( U.S. EPA, 2011a, section 2.3.4.4) differed somewhat from the alternative standard levels discussed in the second draft Policy Ass essment ( U.S. EPA, 2010f, section 2.3.4.3), upon which CASAC based its advice. Changes made in the final Policy Assessment were primarily focused on improving and clarifying the approach for translating the epidemiological evidence into a***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 200 of 790 Formatted: Left basis for staff c onclusions on the broadest range of alternative standard levels supported by the available scientific information and more clearly articulating the rationale for the staff’s conclusions (Wegman, 2011, pp. 1 to 2). Consistent with CASAC’s advice to consider more information from epidemiological studies, as discussed in section III.E.4.b.1 above, the EPA analyzed additional population

- level data obtained from several study authors (Rajan et al., 2011). In transmitting the final Policy Assessment to CASAC, the Agency notified CASAC that the final staff conclusions reflected consideration of CASAC’s advice and that those staff conclusions were based, in part, on the specific distributional analysis that CASAC had urged the EPA to conduct (Wegman, 2011, p.2). Thu s, CASAC had an opportunity to comment on the final Policy Assessment, but chose not to provide any additional comments or advice after receiving it. iii. Administrator’s Proposed Decisions on the Primary PM 2.5 Standard Levels In reaching her conclusions regar ding appropriate alternative standard levels to consider, the Administrator considered the epidemiological and other scientific evidence, estimates of risk reductions associated with just meeting alternative annual and/or 24

- hour standards, air quality ana lyses, related limitations and uncertainties, staff conclusions as presented in the Policy Assessment, and the advice of CASAC. As an initial matter, the Administrator agreed with the general approach discussed in the Policy Assessment as summarized in sec tions III.A.3 and III.E.4.a above, and supported by CASAC, of considering the protection afforded by the annual and 24

- hour standards taken together for mortality and morbidity effects associated with both long

- and short

term exposures to PM 2.5 ( 77 FR 389 39 ) . Furthermore, based on the evidence and***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 201 of 790 Formatted: Left quantitative risk assessment, the Administrator provisionally concluded it is appropriate to set a “generally controlling” annual standard that will lower a wide range of ambient 24

- hour concentrations, with a 24

- hour standard focused on providing supplemental protection, particularly for areas with high peak

- to
- mean ratios possibly associated with strong local or seasonal sources, or PM 2.5 - related effects that may be associated with shorter

- than daily exposure pe riods. The Administrator provisionally concluded this approach would likely reduce aggregate risks associated with both long

- and short

- term exposures more consistently than a generally controlling 24

- hour standard and would be the most effective and effic ient way to reduce total PM 2

- 5 - related population risk. Id. In reaching decisions on alternative standard levels to propose, the Administrator judged that it was most appropriate to examine where the evidence of associations observed in the epidemiological studies was strongest and, conversely, where she had appreciably less confidence in the associations observed in the epidemiological studies. Based on the characterization and assessment of the epidemiological and other studies presented and assessed in t he Integrated Science Assessment and the Policy Assessment, the Administrator recognized the substantial increase in the number and diversity of studies available in this review including extended analyses of the seminal studies of long

- term PM 2.5 exposure s (i.e., ACS and Harvard Six Cities studies) as well as important new long

- term exposure studies (as summarized in Figures 1 and 2). Collectively, the Administrator noted that these studies, along with evidence available in the last review, provided consis tent and stronger evidence of an association with premature mortality, with the strongest evidence related to cardiovascular

- related mortality, at lower ambient concentrations than previously observed. The Administrator also recognized the***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 202 of 790 Formatted: Left availability of stronger evidence of morbidity effects associated with long

- term PM 2.5 exposures, including evidence of cardiovascular effects from the WHI study and respiratory effects, including decreased lung function growth, from the extended analyses for the Southern California Children’s Health Study. Furthermore, the Administrator

re cognized new U.S. multi

- city studies that greatly expanded and reinforced our understanding of mortality and morbidity effects associated with short

- term PM 2.5 exposures, providing stronger evidence of associations at ambient concentrations similar to thos e previously observed (as summarized in Figure 3). Id. at 38939

- 40. The newly available scientific evidence built upon the previous scientific data base to provide evidence of generally robust associations and to provide a basis for greater confidence in t

he reported associations than in the last review. The Administrator recognized that the weight of evidence, as evaluated in the Integrated Science Assessment, was strongest for health endpoints classified as having evidence of a causal relationship. These relationships included those between long

- and short

- term PM 2.5 exposures and mortality and cardiovascular effects. She recognized that the weight of evidence was also strong for health endpoints classified as having evidence of a likely causal relationshi p, which included those between long

- and short

- term PM 2.5 exposures and respiratory effects. In addition, the Administrator made note of the much more limited evidence for health endpoints classified as having evidence suggestive of a causal relationship, including developmental, reproductive and carcinogenic effects. Id . at 38940. Based on information discussed and presented in the Integrated Science Assessment, the Administrator recognized that health effects may occur over the full***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 203 of 790 Formatted: Left range of concentratio ns observed in the long

- and short

- term epidemiological studies and that no discernible threshold for any effects can be identified based on the currently available evidence ( U.S. EPA, 2009a, section 2.4.3). She also recognized, in taking note of CASAC adv ice and the distributional statistics analysis discussed in section III.E.4.b.i above and in the Policy Assessment, that there was significantly greater confidence in observed associations over certain parts of the air quality distributions in the studies, and conversely, that there was significantly diminished confidence in ascribing effects to concentrations toward the lower part of the distributions. Consistent with the general approach summarized in section III.A.3 above, and supported by CASAC as discu ssed in section III.E.4.a above, the Administrator generally agreed that it was appropriate to consider a level for an annual standard that was somewhat below the long

- term mean PM 2.5 concentrations reported in long

- and short

term exposure studies. In rec ognizing that the evidence of an association in any such study was strongest at and around the long

- term average where the data in the study are most concentrated, she understood that this approach did not provide a bright line for reaching decisions about appropriate standard levels. The Administrator noted that long

term mean PM 2.5 concentrations were available for each study considered and, therefore, represented the most robust data set to inform her decisions on appropriate annual standard levels. She also noted that the overall study mean PM 2.5 concentrations were generally calculated based on monitored concentrations averaged across monitors in each study area with multiple monitors, referred to as a composite monitor concentration, in contrast to the highest concentration monitored in each study area, referred to as a maximum monitor concentration, which are used to determine whether an area meets a***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 204 of 790 Formatted: Left given standard. In considering such long

- term mean concentrations, the Administrator understood that it was appropriate to consider the weight of evidence for the health endpoints evaluated in such studies in giving weight to this information. Id
. Based on the information summarized in Figure 4 above and presented in more detail in the Policy Assessment ( U. S. EPA, 2011a, chapter 2) for effects classified in the Integrated Science Assessment as having a causal or likely causal relationship with PM 2.5 exposures, the Administrator observed an overall pattern of statistically significant associations reported in studies of long

- term PM 2.5 exposures with long

- term mean concentrations ranging from somewhat above the current standard level of 15 μg/m 3 down to the lowest mean concentration in such studies of 12.9 μg/m 3 (in Miller et al., 2007). 90 She observed a simila r pattern of statistically significant associations in studies of short

- term PM 2.5 exposures with long

- term mean concentrations ranging from around 15 μg/m 3 down to 12.8 μg/m 3 (in Burnett et al., 2004). With regard to effects classified as providing eviden ce suggestive of a causal relationship, the Administrator observed a small number of long

- term exposure studies related to developmental and reproductive effects that reported statistically significant associations with overall study mean PM 2.5

90 The EPA notes that the Miller et al., (2007) study provides strong evidence of cardiovascular related effects associated with long

- term PM 2.5 exposures. At the time of the proposal, the EPA recognized the limited nature of the air quality data considered in this study (77 FR 38918, fn. 62). The EPA has reviewed those limitations, in conjunction with consideration of public comments received on the proposal as discussed in section III.E.4.c, in conjunction with reaching a final decision on the level of the annual standard. Formatted: Font: 12 pt***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 205 of 790 Formatted: Left concentrati ons down to 11.9 μg/m 3 (in Bell et al., 2007). 91 Id. The Administrator also considered additional information from epidemiological studies, consistent with CASAC advice, to take into account the broader distribution of PM 2.5 concentrations and the degree of confidence in the observed associations over the broader air quality distribution. In considering this additional information, she understood that the Policy Assessment presented information on the 25 th and 10 th percentile s of the distributions of PM 2.5 concentrations available from four multi

- city studies to provide a general frame of reference as to the part of the distribution in which the data become appreciably more sparse and, thus, where her confidence in the associa tions observed in epidemiological studies would become appreciably less. As summarized in Figure 4 above, the Administrator took note of additional population

- level data that were available for four studies (Krewski et al., 2009; Miller et al., 2007; Bell et al., 2008; Zanobetti and Schwartz, 2009), each of which reported statistically significant associations with health endpoints classified as having evidence of a causal relationship. In considering the long

- term PM 2.5 concentrations associated with the 25 th percentile values of the population

- level data for these four studies, she observed that these values ranged from somewhat above to somewhat below 12 μg/m 3 . The Administrator recognized that these four studies represented include some of the strongest evidence available within the overall body of scientific evidence and noted that three of these studies (Krewski et al., 2009; Bell et al., 2008; Zanobetti and Schwartz, 2009) were
91 With respect to suggestive evidence related to cancer, mutagenic, and genotoxic effects, the PM 2.5 concentrations reported in studies generally included ambient concentrations that are equal to or greater than ambient concentrations observed in studies that reported mortality and cardiovascular and respiratory effects (U.S. EPA, 2009a, section 7.5), such that in selecting alt ernative standard levels that provide protection from mortality and cardiovascular and respiratory effects, it is reasonable to anticipate that protection will also be provided for carcinogenic effects.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 206 of 790 Formatted: Left used as the basis for concentration

- response functions used in the quantita tive risk assessment ( U.S. EPA, 2010a, section 3.3.3). In considering this information, the Administrator noted that CASAC advised that information about the long

- term PM 2.5 concentrations that were most influential in generating the health effect estimates in epidemiological studies can help to inform selection of an appropriate annual standard level. However, t he Administrator also recognized that additional population

- leve l data were available for only these four studies and, therefore, she believed that these studies comprised a more limited data set than one based on long

- term mean PM 2.5 concentrations for which data were available for all studies considered, as discussed above. The Administrator recognized, as summarized in section III.B.2 above, that important uncertainties remain in the evidence and information considered in this review of the primary fine particle standards. These uncertainties are generally related t o understanding the relative toxicity of the different components in the fine particle mixture, the role of PM 2.5 in the complex ambient mixture, exposure measurement errors inherent in epidemiological studies based on concentrations measured at fixed moni tor sites, and the nature, magnitude, and confidence in estimated risks related to increasingly lower ambient PM 2.5 concentrations. Furthermore, the Administrator noted that epidemiological studies have reported heterogeneity in responses both within and b etween cities and geographic regions across the U.S. She recognized that this heterogeneity may be attributed, in part, to differences in fine particle composition in different regions and cities. The Administrator also recognized that t here are additional limitations associated with evidence for reproductive and developmental effects,***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 207 of 790 Formatted: Left identified as being suggestive of a causal relationship with long

- term PM 2.5 exposures, including: the limited number of studies evaluating such effects; uncertainties relate d to identifying the relevant exposure time periods of concern; and limited toxicological evidence providing little information on the mode of action(s) or biological plausibility for an association between long

- term PM 2.5 exposures and adverse birth outco mes. Id . at 38941. The Administrator was mindful that considering what standards were requisite to protect public health with an adequate margin of safety required public health policy judgments that neither overstated nor understated the strength and limi tations of the evidence or the appr opriate inferences to be drawn from the evidence. In considering how to translate the available information into appropriate standard levels, the Administrator weighed the available scientific information and associated u ncertainties and limitations. For the purpose of determining what standard levels were appropriate to propose, the Administrator recognized, as did EPA staff in the Policy Assessment, that there was no single factor or criterion that comprised the sole “co rrect” approach to weighing the various types of available evidence and information, but rather there were various approaches that are appropriate to consider. The Administrator further recognized that different evaluations of the evidence and other inform ation before the Administrator could reflect placing different weight on the relative strengths and limitations of the scientific information, and different judgments could be made as to how such information should appropriately be used in making public he alth policy decisions on standard levels. This recognition led the Administrator to consider various approaches to weighing the evidence so as to identify appropriate standard levels to propose. In so doing, the***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 208 of 790 Formatted: Left Administrator encouraged extensive public c omment on alternative approaches to weighing the evidence and other information so as to inform her public health policy judgments before reaching final decisions on appropriate standard levels. In considering the available information, the Administrator n oted the advice of CASAC that the currently available scientific information, including epidemiological and toxicological evidence as well as risk and air quality information, provided support for considering an annual standard level within a range of 13 t o 11 μg/m 3 and a 24

- hour standard level within a range of 35 to 30 μg/m 3 . In addition, the Administrator recognized that the Policy Assessment concluded that the available evidence and risk

- based information support consideration of annual standard levels in the range of 13 to 11 μg/m 3 , and that the Policy Assessment also concluded that the evidence most strongly supported consideration of an annual standard level in the range of 12 to 11 μg/m 3 . In considering how the annual and 24

- hour standards work toget her to provide appropriate public health protection, the Administrator observed that CASAC did not express support for any specific levels or combinations of standards within these ranges . Nor did CASAC choose to comment on additional information and analy ses presented in the final Policy Assessment prepared in response to CASAC’s recommendations on the second draft Policy Assessment (Wegman, 2011)
. In considering the extent to which the currently available evidence and information provided support for specific standard levels within the ranges identified by CASAC and the Policy Assessment as appropriate for consideration, the Administrator initially considered standard levels within the range of 13 to 11 μg/m 3 for the annual standard. In so doing, the A dministrator first considered the long

- term mean PM 2.5***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 209 of 790 Formatted: Left concentrations reported in studies of effects classified as having evidence of a causal or likely causal relationship, as summarized in Figure 4 above and discussed more broadly above. She noted that a level at the upper end of this range would be below most but not all the overall study mean concentrations from the multi

- city studies of long

- and short

term exposures, whereas somewhat lower levels within this range would be below all such overall study mean concentrations. In considering the appropriate weight to place on this information, the Administrator again noted that the evidence of an association in any such study was strongest at and around the long

- term average where the data in the study

are most concentrated, and that long

- term mean PM 2.5 concentrations were available for each study considered and, therefore, represented the most robust data set to inform her decisions on appropriate annual standard levels. Further, she was mindful that this approach did not provide a bright line for reaching decisions about appropriate standard levels. Id. In considering the long

- term mean PM 2.5 concentrations reported in studies of effects classified as having evidence suggestive of a causal relationship, as summarized in Figure 4 for reproductive and developmental effects, the Administrator noted that a level at the upper end of this range would be below the overall study mean concentration in one of the three studies, while levels in the mid

- to lower part of this range would be below the overall study mean concentrations in two or three of these studies. In considering the appropriate weight to place on this information, the Administrator noted the very limited nature of this evidence of such effects and th e additional uncertainties in these epidemiological studies relative to the studies that provide evidence of causal or likely causal relationships.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 210 of 790 Formatted: Left The Administrator also considered the distributional analyses of population

- level information that were avai lable from four of the epidemiological studies that provide evidence of effects identified as having a causal relationship with long

- or short

- term PM 2.5 concentrations for annual standard levels within the same range of 13 to 11 μg/m 3

. In so doing, the Ad ministrator first noted that a level in the mid

- part of this range generally corresponds with approximately the 25 th percentile of the distributions of health events data available in three of these studies. The Administrator also noted that standard level s toward the upper part of this range would reflect placing substantially less weight on this information, whereas standard levels toward the lower part of this range would reflect placing substantially more weight on this information. In considering this information, the Administrator noted that there was no bright line that delineates the part of the distribution of PM 2.5 concentrations within which the data become appreciably more sparse and, thus, where her confidence in the associations observed in epi demiological studies became appreciably less. In considering mean PM 2.5 concentrations and distributional analyses from the various sets of epidemiological studies noted above, the Administrator was mindful, as noted above, that such studies typically repo rt concentrations based on composite monitor distributions, in which concentrations may be averaged across multiple ambient monitors that may be present within each area included in a given study. Thus, a policy approach that used data based on composite m onitors to identify potential alternative standard levels would inherently build in a margin of safety of some degree relative to an alternative standard level based on measurements at the monitor within an area that records the highest concentration, or t he maximum monitor, since once a standard was***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 211 of 790 Formatted: Left set, concentrations at appropriate maximum monitors within an area were generally used to determine whether an area meets a given standard. The Administrator also recognized that judgments about the appropriate weight to place on any of the factors discussed above should reflect consideration not only of the relative strength of the evidence but also on the important uncertainties that remained in the evidence and information being considered in this review. The Administrator noted that the extent to which these uncertainties influenced judgments about appropriate annual standard levels within the range of 13 to 11 μg/m 3 would likely be greater for standard levels in the lower part of this range which would neces sarily be based on fewer available studies than would higher levels within this range. Based on the above considerations, the Administrator concluded that it was appropriate to propose to set a level for the primary annual PM 2.5 standard within the range o f 12 to 13 μg/m 3 . The Administrator provisionally concluded that a standard set within this range would reflect alternative approaches to appropriately placing the most weight on the strongest available evidence, while placing less weight on much more limi ted evidence and on more uncertain analyses of information available from a relatively small number of studies. Further, she provisionally concluded that a standard level within this range would reflect alternative approaches to appropriately providing an adequate margin of safety for the populations at risk for the serious health effects classified as having evidence of a causal or likely causal relationship, depending in part on the emphasis placed on margin of safety considerations. The Administrator rec ognized that setting an annual standard level at the lower end of this range would reflect an approach that placed more emphasis on the entire body of the evidence, including the***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 212 of 790 Formatted: Left analysis of the distribution of air quality concentrations most influential i n generating health effect estimates in the studies, and on margin of safety considerations, than would setting a level at the upper end of the range. Conversely, an approach that would support a level at the upper end of this range would place more emphas is on the remaining uncertainties in the evidence to avoid potentially overestimating public health improvements, and would generally support a view that the uncertainties remaining in the evidence are too great to such that the evidence does not warrant se tting a lower annual standard level. Id . at 38942
. At the time of the proposal, while the Administrator recognized that CASAC advised, and the Policy Assessment concluded, that the available scientific information provided support for considering a range that extended down to 11 μg/m 3 , she concluded that proposing such an extended range would reflect a public health policy approach that placed more weight on relatively limited evidence and more uncertain information and analyses than she considered appropr iate at this time. Nonetheless, the Administrator solicited comment on a level down to 11 μg/m 3 as well as on approaches for translating scientific evidence and rationales that would support such a level. Such an approach might reflect a view that the unce rtainties associated with the available scientific information warrant a highly precautionary public health policy response that would incorporate a large margin of safety. The Administrator recognized that potential air quality changes associated with

mee ting an annual standard set at a level within the range of 12 to 13 μg/m 3 will result in lowering risks associated with both long

- and short

- term PM 2.5 exposures. However, the Administrator recognized that such an annual standard intended to serve as the p rimary***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 213 of 790 Formatted: Left means for providing protection from effects associated with both long

- and short

- term PM 2.5 exposures would not by itself be expected to offer requisite protection with an adequate margin of safety against the effects of all short

- term PM 2.5 exposur es. As a result, in conjunction with proposing an annual standard level in the range of 12 to 13 μg/m 3 , the Administrator provisionally concluded that it was appropriate to continue to provide supplemental protection by means of a 24

- hour standard set at t he appropriate level, particularly for areas with high peak

- to
- mean ratios possibly associated with strong local or seasonal sources, or for PM 2.5 - related effects that may be associated with shorter

than

- daily exposure periods. Based on the approach discussed in section III.A.3 above, at the time of the proposal the Administrator relied upon evidence from the short

- term exposure studies as the principal basis for selecting the level of the 24

- hour standard. In considering these studies as a basis for the level of a 24

- hour standard, and having selected a 98 th percentile form for the standard, the Administrator agreed with the focus in the Polic y Assessment of looking at the 98 th percentile values, as well as at the long

- term mean PM 2.5 concentrations i n these studies. In considering the information provided by the short

- term exposure studies, the Administrator recognized that to the extent these studies were conducted in areas that likely did not meet one or both of the current standards, such studies d id not help inform the characterization of the potential public health improvements of alternative standards set at lower levels. By reducing the PM 2.5 concentrations in such areas to just meet the current standards, the Administrator anticipated that addi tional public health protection would occur. Therefore, the Administrator focused on studies that reported positive and***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 214 of 790 Formatted: Left statistically significant associations in areas that would likely have met both the current 24

- hour and annual standards. She also consi dered whether or not these studies were conducted in areas that would likely have met an annual standard level of 12 to 13 μg/m 3 to inform her decision regarding an appropriate 24

- hour standard level. As discussed in section III.E.4.a, consistent with the Policy Assessment, the Administrator concluded that multi

- city, short

- term exposure studies provided the strongest data set for informing her decisions on appropriate 24

- hour standard levels. The Administrator viewed the single

city, short

- term exposure st udies as a much more limited data set providing mixed results and, therefore, she had less confidence in using those studies as a basis for setting the level of a 24

- hour standard. With regard to the limited number of single

- city studies that reported posi tive and statistically significant associations for a range of health endpoints related to short

- term PM 2.5 concentrations in areas that would likely have met the current suite of PM 2.5 standards, the Administrator recognized that many of those studies had significant limitations (e.g., limited statistical power, limited exposure data) or equivocal results (mixed results within the same study area) that made them unsuitable to form the basis for setting the level of a 24

- hour standard. With regard to multi

- city studies that evaluated effects associated with short

- term PM 2.5 exposures, the Administrator observed an overall pattern of positive and statistically significant associations in studies with 98 th percentile values averaged across study areas in the range of 45.8 to 34.2 μg/m 3 (Burnett et al., 2004; Zanobetti and Schwartz, 2009; Bell et al., 2008; Dominici et al., 2006a, Burnett and Goldberg, 2003; Franklin et al., 2008). The Administrator noted that, to the extent air quality distributions were reduced to reflect just meeting the current 24

- hour standard, additional protection***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 215 of 790 Formatted: Left would be anticipated for the effects observed in the three multi

- city studies with 98 th percentile values greater than 35 μg/m 3 (Burnett et al., 2004; Burnett and Goldberg, 2003; Franklin et al., 2008). I n the three additional studies with 98 th percentile values below 35 μg/m 3 , specifically 98 th percentile concentrations of 34.2, 34.3, and 34.8 μg/m 3 , the Administrator noted that these studies reported long

- term mean PM 2.5 concentrations of 12.9, 13.2, and 13.4 μg/m 3 , respectively (Bell et al., 2008; Zanobetti and Schwartz, 2009; Dominici et al., 2006a). In proposing to revise the level of the annual standard to within the range of 12 to 13 μg/m 3 , as discussed above, the Administrator recognized that additi onal protection would be provided for the short

- term effects observed in these multi

- city studies in conjunction with an annual standard level of 12 μg/m 3 , and in two of these three studies in conjunction with an annual standard level of 13 μg/m 3 . She note d that the study

- wide mean concentrations were based on averaging across monitors within study areas and that compliance with the standard would be based on concentrations measured at the monitor reporting the highest concentration within each area. The Ad ministrator believed it would be reasonable to conclude that revision to the 24

- hour standard would not be appropriate in conjunction with an annual standard within this range. Based on the above considerations related to the epidemiological evidence, the Administrator provisionally concluded that it was appropriate to retain the level of the 24

- hour standard at 35 μg/m 3 , in conjunction with a revised annual standard level in the proposed range of 12 to 13 μg/m 3

. In addition to considering the epidemiologic al evidence, the Administrator also took into account air quality information based on county

- level 24

- hour and annual***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 216 of 790 Formatted: Left design values to understand the public health implications of retaining the 24

- hour standard level at 35 μg/m 3 in conjunction with an ann ual standard level within the proposed range of 12 to 13 μg/m 3 . She considered whether these suites of standards would meet a public health policy goal which included setting the annual standard to be the “generally controlling” standard in conjunction wit h setting the 24

- hour standard to provide supplemental protection to the extent that additional protection is warranted. As discussed above, the Administrator provisionally concluded that this approach was the most effective and efficient way to reduce tot al population risk associated with both long

and short

- term PM 2.5 exposures, resulting in more uniform protection across the U.S. than the alternative of setting the 24

- hour standard to be the controlling standard. In considering the air quality informat ion, the Administrator first recognized that there was no annual standard within the proposed range of levels, when combined with a 24

- hour standard at the proposed level of 35 μg/m 3 , for which the annual standard would be the generally controlling standar d in all areas of the country. She further observed that such a suite of PM 2.5 standards with an annual standard level of 12 μg/m 3 would result in the annual standard as the generally controlling standard in most regions across the country, except for cert ain areas in the Northwest, where the annual mean PM 2.5 concentrations have historically been low but where relatively high 24

- hour concentrations occur, often related to seasonal wood smoke emissions ( U.S. EPA, 2011a, pp. 2

- 89 to 2

- 91, Figure 2

- 10). Altho ugh not explicitly delineated on Figure 2

- 10 in the Policy Assessment, an annual standard of 13 μg/m 3 would be somewhat less likely to be the generally controlling standard in some regions of the U.S. outside the Northwest in conjunction with a 24

- hour sta ndard level of 35 μg/m 3

.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 217 of 790 Formatted: Left Taking the above considerations into account, the Administrator proposed to revise the level of the primary annual PM 2.5 standard from 15.0 μg/m 3 to within the range of 12.0 to 13.0 μg/m 3 and to retain the 24

- hour standard level at 35 μg/m 3 . In the Administrator’s judgment, such a suite of primary PM 2.5 standards and the rationale supporting such levels could reasonably be judged to reflect alternative approaches to the appropriate consideration of the strength of the available evid ence and other information and their associated uncertainties and the advice of CASAC. The Administrator recognized that the final suite of standards selected from within the proposed range of annual standard levels, or the broader range of annual standard levels on which public comment was solicited, must be clearly responsive to the issues raised by the D.C. Circuit’s remand of the 2006 primary annual PM 2.5 standard. Furthermore, at the time of the proposal, she recognized that the final suite of standard s will reflect her ultimate judgment in the final rulemaking as to the suite of primary PM 2.5 standards that would be requisite to protect the public health with an adequate margin of safety from effects associated with fine particle exposures. The final j udgment to be made by the Administrator will appropriately consider the requirement for a standard that is neither more nor less stringent than necessary and will recognize that the CAA does not require that primary standards be set at a zero

- risk level, b ut rather at a level that reduces risk sufficiently so as to protect public health with an adequate margin of safety. At the time of the proposal, having reached her provisional judgment to propose revising the annual standard level from 15.0 to within a range of 12.0 to 13.0 μg/m 3 and to propose retaining the 24

- hour standard level at 35 μg/m 3 , the Administrator solicite d public comment on this range of levels and on approaches to considering the available***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 218 of 790 Formatted: Left evidence and information that would support the choice of levels within this range. The Administrator also solicited public comment on alternative annual standard level s down to 11 μg/m 3 and on the combination of annual and 24

- hour standards that commenters may believe is appropriate, along with the approaches and rationales used to support such levels. In addition, given the importance the evidence from epidemiologic st udies played in considering the appropriate annual and 24

- hour levels, the Administrator solicited public comment on issues related to translating epidemiological evidence into standards, including approaches for addressing the uncertainties and limitation s associated with this evidence.

c. Comments on Standard Levels This section addresses comments that relate to consideration of the appropriate levels of the primary annual and 24

- hour PM 2.5 standards , including c omments on the general approach used by the EP A to translate the available scientific information into standard levels and how specific PM 2.5 exposure studies should be considered as a basis for the standard level s. These comments on standard levels expand upon the more general comments that either su pport ed or oppose d any change to the current suite of primary PM 2.5 standards , which are addressed above in section III.D.2. 92 As explained there, one group of commenters generally opposed any change to the current primary PM 2.5 standards and more specifically disagreed with the basis for the EPA’s proposal to revise the annual standard level. Another group of commenters supported revising the current suite of primary PM 2.5 standards to provide increased public health protection. Some commenters in this second group argued that both the annual and 24

- hour standard levels

92 Specific comments on the forms of the annual and 24

- hour standards are addressed in section III.E.3.a and III.E.3.b, respectively.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 2 19 of 790 Formatted: Left should be lowered while other commenters in this group agreed with the EPA’s proposal to retain the level of the 24

- hour standard in conjunction with revising the level of the annual standard. While generally supporting the EPA’s proposal to lower the level of the annual standard, many commenters in this group disagreed that a level within the EPA’s proposed range was adequately protective and supported a level of 11 μg/m 3 or below. i. Annual Standard Level The group of commenters opposed to any change to the current suite of primary PM 2.5 standards generally raised questions regarding the underlying scientific evidence, including the causal determinations reached i n the Integrated Science Assessment, and focused strongly on the uncertainties they saw in the scientific evidence as a basis for their conclusion that no changes to the current standard levels were warranted. In commenting on the proposed standard levels, these commenters typically relied on the arguments summarized and addressed above in section III.D.2 as to why they believed it was inappropriate for the EPA to make any revisions to the suite of primary PM 2.5 standards. That is, they asserted that the EP A’s causal determinations were not adequately supported by the underlying scientific information; the biological plausibility of health effects observed in epidemiologic al studi es has not been demonstrated in controlled human exposure and toxicological stu dies ; uncertainties in the underlying health science are as great or greater than in 2006; there is no evidence of greater risk since the last review to justify tightening the current annual PM 2.5 standard; and “new” studies not included in the Integrated Science Assessment continue to increase uncertainty about possible health risks associated with exposure to PM 2.5 . With regard to the level of the annual standard, these commenters strongly***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 220 of 790 Formatted: Left disagreed with the Agency’s proposed decision to revise the level to within a range of 12 to 13 μg/m 3 and argued that the current standard level of 15 μg/m 3 should be retained
. For example, UARG, API, and other commenters in this group raised a number of issues that they asserted called into question the EPA’s interpreta tion of the epidemiological evidence to support revising the annual standard level. These commenters raised specific questions related to the general approach used by the EPA to translate the air quality and other information from specific epidemiological studies into standard levels, including : (1) the EPA’s approach for using composite monitor air quality distributions reported in epidemiological studies to select a standard level that would be compared to measurements at the monitor recording the highest value in an area to determine compliance with the standard; (2) the appropriate exposure period for effects observed in long

- term exposure mortality studies; and (3) the use of the EPA’s analysis of distribution s of underlying population

- level data (i.e., health event and study population data) for those epidemiological studies for which such information was available. These commenters also raised questions regarding the EPA’s consideration of specific scientific evidence as a basis for setting a standard level, including : (4) evidence of respiratory morbidity effects in long

- term exposure studies and (5) more limited evidence of health effects which have been categorized in the Integrated Science Assessment as suggestive of a causal relationship (i.e., dev elopmental and reproductive outcomes ). These comments are discussed in turn below. (1) Some commenters in this group argued that one reason why they believe there is no basis for setting a standard level below 15 μg/m 3 is that the air quality metric from

e pidemiological studies that the EPA relied on in the proposal is not the same metric that***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 221 of 790 Formatted: Left will be compared to the level of the standard to determine compliance with the standard. That is, commenters noted that the long

- term mean PM 2.5 concentrations that t he EPA considered, shown in Figure 4 above, are composite monitor mean concentrations (i.e., concentrations averaged across multiple monitors within areas with more than one monitor), whereas the PM 2.5 concentrations that will be compared to the level of t he standard are maximum monitor concentrations (i.e., the concentration measured by the monitor within an area reporting the highest concentration). This comment was presented most specifically in UARG’s comments (UARG, 2012, Attachment 1, pp. 2 to 6), whi ch raised two overarching issues as discussed below. First, the commenter noted that the EPA’s approach of considering composite monitor mean PM 2.5 concentrations in selecting a standard level, and then comparing the maximum monitor mean PM 2.5 concentratio n in each area to the standard level when the standard is implemented, was characterized in the proposal as inherently having the potential to build in a margin of safety (UARG, 2012, Attachment 1, p. 4, citing 77 FR 38905). The commenter asserted that the Administrator is ignoring this distinction between composite and maximum monitor concentrations, and that this approach creates an unwarranted case for lowering the standard level, since in the commenter’s view, it would result in a margin of safety that would be arbitrary, not based on evidence, and unquantified (UARG, 2012, Attachment 1, p. 4). In support of this view, the commenter asserted that there is a significant difference between composite monitor mean PM 2.5 concentrations and maximum monitor mea n PM 2.5 concentrations. The commenter asserted that the maximum monitor value will always be higher than the composite monitor value (except in areas that contain only a single monitor), such that when an area***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 222 of 790 Formatted: Left just attains the NAAQS, that area’s composite monitor long

- term mean PM 2.5 concentration will be lower than the level of the standard (UARG, 2012, Attachment 1, p. 3). Second, the commenter asserted that a more “reasoned and consistent approach would be to decide on a mean composite monitor PM 2.5 leve l that should be achieved and then identify the maximum monitor level that would result in that composite value” (UARG, 2012, Attachment 1, p. 4). The commenter conducted an analysis of maximum monitor versus composite monitor annual mean PM 2.5 concentrati ons using monitoring data 93 from 2006 to 2008 and presented results averaged across areas within two groups (i.e., those with design values 94 above the current standard level and those with design values just below the current standard level) to illustrate their suggested alternative approach. The commenter interpreted this analysis as showing that the composite monitor long

- term mean PM 2.5 con centrations from the subset of the epidemiological studies shown in Figure 4 (of the proposal and above) that the commenter considered to be an appropriate focus for this analysis would be achieved across the U.S. if the current annual NAAQS of 15 μg/m 3 is retained and attained
. The commenter considered the subset of epidemiological studies that included only long

- term exposures studies of effects for which the evidence is categorized as causal or likely causal, but did not consider short

term exposure stud ies. On this basis, the commenter asserted that attaining the current annual PM 2.5 standard would result in composite monitor long

- term mean concentrations in all areas that would be generally within or below the range of the composite monitor

93 The commenter indicated that this analysis was based on monitoring data for every core based statistical area (CBSA) in the EPA’s Air Quality System (AQS) database. 94 The des ign value is the air quality statistic that is compared to the level of the NAAQS to determine the attainment status of a given area. Formatted: Font: 12 pt Formatted: Font: 12 pt, Not Superscript/ Subscript Formatted: Font: 12 pt Formatted: Font: 12 pt, Not Superscript/ Subscript***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 223 of 790 Formatted: Left long

- term me an concentrations from such studies and, as a result, there is no reason to lower the level of the current annual NAAQS. In considering the first issue related to the EPA’s approach, the EPA notes that in proposing to revise both the form and level of the annual standard, the Administrator clearly took into account the distinction between the composite monitor long

- term mean PM 2.5 concentrations from the epidemiological studies, considered as a basis for selecting an annual standard level, and maximum monit or long

- term mean PM 2.5 concentrations. In deciding to focus on the composite monitor long

- term mean concentrations in selecting the standard level, and on the maximum monitor concentrations in selecting the form of the standard (i.e., consistent with prop osing to eliminate the option for spatial averaging across monitors within an area when implementing the standard 95 ), the Administrator reasonably considered the distinction between these metrics in a manner that was consistent with advice from CASAC (Samet et al., 2010d, pp. 2 to 3). As noted above in section III.A.3, the EPA recognizes that a statistical metric (e.g., the mean of a distribution) based on maximum monitor concentrations may be identical to or above the same statistical metric based on composite monitor concentrations. More specifically, many areas have only one monitor, in which case the composite and maximum monitor concentrations are identical. Based on the most recent data from the EPA’s AQS from 2009 to 2011 in the 331 CBSAs in whic h valid PM 2.5 data are available, as discussed in Frank (2012a, Table 5), there were 20 8 such areas (with design values ranging up to about 15 μg/m 3 ). Frank (2012a) also observed that other areas have multiple monitors with composite and maximum monitor me an PM 2.5 concentrations that were the same or relatively close, with 5 7 areas in which the
95 As discussed above in section III.E.3.a. Formatted: Font: 12 pt Formatted: Font: 12 pt, Not Superscript/ Subscript***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 224 of 790 Formatted: Left maximum monitor mean concentration was no more than 0.5 μg/m 3 higher than the composite monitor mean concentration and 56 areas in which the difference was between 0 .6 and 2 μg/m 3 . Further, there were only a few other areas in which the maximum monitor mean concentration was appreciably higher than the composite monitor mean concentration, such as areas in which some monitors may be separately impacted by local

source s. There were only 10 such areas in the country in which the maximum monitor mean concentration was between 2 to 6 μg/m 3 higher than the composite monitor concentration (Frank, 2012a, Table 4). 96 Thus, the EPA does not agree that there is a significant diff

erence between composite monitor mean PM 2.5 concentrations and maximum monitor mean PM 2.5 concentrations in the large majority of areas across the country. In proposing to revise the form of the annual PM 2.5 standard, as discussed above in section III.E.3. a, the EPA noted that when an annual PM 2.5 standard was first set in 1997, the form of the standard included the option for averaging across measurements at appropriate monitoring sites within an area, generally consistent with the composite monitor approa ch used in epidemiological studies, with some constraints intended to ensure that spatial averaging would not result in inequities in the level of protection for communities within large metropolitan areas. In the last review the EPA tightened the constrai nts on spatial averaging, and in this review has eliminated the option altogether, on the basis of analyses in each review that showed that such constraints may be inadequate to avoid substantially greater exposures for people living in locations around

96 The average difference between the maximum and composite design value among t he 123 CBSAs with two or more monitors is 0.8 μg/m 3 and the median difference is 0.6 μg/m 3 . The 25 th and 75 th percentiles are 0.3 and 1.0 μg/m 3 , respectively (Frank, 2012a, p. 4).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 225 of 790 Formatted: Left th e monitors recording the highest PM 2.5 concentrations in some areas, potentially resulting in disproportionate impacts on at

- risk populations of persons with lower SES levels as well as minorities . In light of these analyses, and consistent with the Admini strator’s decision to revise the form of the annual PM 2.5 standard by eliminating the option for spatial averaging, the EPA continues to conclude that a standard level based on consideration of long

- term mean concentrations from composite monitors, and app lied at each monitor within an area including the monitor measuring the highest concentration, is the appropriate approach to use in setting a standard that will protect public health, including the health of at

- risk populations, with an adequate margin of safety, as required by the CAA. The EPA acknowledges that at proposal, the Agency characterized the approach of using maximum monitor concentrations to determine compliance with the standard, while selecting the standard level based on consideration of co mposite monitor concentrations, as one that inherently had the potential to build in a margin of safety (77 FR 38905), and CASAC reiterated that view in supporting the EPA’s approach (Samet, 2010d, p. 3). Nonetheless, in light of the discussion above, the EPA more specifically recognizes that this approach does not build in any margin of safety in the large number of areas across the country with only one monitor. Further, based on the analyses done to inform consideration of the form of the standard (Schmi dt, 2011, Analysis A), the EPA concludes that this approach does not provide a margin of safety for the at

- risk populations that live around the monitor measuring the highest concentration, such as in those few areas in which the maximum monitor concentrat ion is appreciably higher than the composite monitor concentration. Rather, this approach properly treats those at

- risk***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 226 of 790 Formatted: Left populations the same way it does the broader populations that live in areas with only one monitor, by providing the same degree of prote ction for those at

- risk populations that would otherwise be disproportionately impacted as it does for the broader populations in other areas, While the EPA recognizes that this approach can result in some additional margin of safety for the subset of area s with multiple monitors in which at

- risk populations may not be disproportionately represented in areas around the maximum monitor, which may be the case in areas with relatively small differences between the maximum and composite monitor concentrations, the EPA notes that this margin would be relatively small in such areas. Based on the above considerations, the EPA does not agree that the Agency’s approach of using maximum monitor concentrations to determine compliance with the standard, while selecting the standard level based on consideration of composite monitor concentrations creates an unwarranted case for lowering the standard level based on a margin o f safety that would be arbitrary, not based on evidence, or lack quantification. The EPA recognizes that setting a standard to protect public health, including the health of at

- risk populations, with an adequate margin of safety, depends upon selecting a

s tandard level sufficiently below where there is clear the EPA has found the strongest evidence of health effects so as to provide such protection, and that the EPA’s approach regarding consideration of composite and maximum monitor concentrations is intende d to, and does, serve to address this requirement as part of and not separate from the selection of an appropriate standard level based on the health effects evidence. In considering the second issue related to the commenter’s suggested alternative approac h, the EPA strongly disagrees with the commenter’s view that a more “reasoned***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 227 of 790 Formatted: Left and consistent approach would be to decide on a mean composite monitor PM 2.5 level that should be achieved and then identify the maximum monitor level that would result in that c omposite value” (UARG, 2012, Attachment 1, p. 4). As discussed above, the EPA notes that for areas with only one monitor, or with multiple monitors that measure concentrations that are very close in magnitude, the maximum monitor level that would limit the composite monitor PM 2.5 level to be no greater than the level that should be achieved to protect public health with an adequate margin of safety, would essentially be the same as that composite monitor level. Further, as discussed above, even for areas in which the maximum monitor concentration is appreciably higher than other monitor concentrations within the same area, public health would not be protected with an adequate margin of safety if the disproportionately higher exposures of at

- risk, susceptible populations around the monitor measuring the highest concentration were in essence averaged away with measurements from monitors in other locations within large urban areas. Further, the commenter’s suggested approach would be based on annual average PM 2. 5 concentrations that have been measured over some past time period. Such an approach would reflect the air quality that existed in the past, but it would not necessarily provide appropriate constraints on the range of concentrations that would be allowed by such a standard in the future, when relationships between maximum and composite monitor concentrations in areas across the country may be different. For these reasons, the EPA fundamentally rejects the commenter’s suggested approach because it results i n a standard that demonstrably in the EPA’s views it would not protect public health, including providing protection for at

- risk populations, with an adequate margin of safety in areas across the country.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 228 of 790 Formatted: Left More specifically, in further considering the commen ter’s analysis of design values based on maximum versus composite monitor annual mean PM 2.5 concentrations using monitoring data from 2006 to 2008 which they assert supports retaining the current standard level of 15 μg/m 3 , the EPA finds flaws with the num erical results and the scope of the analysis, as well as flaws in the commenter’s translation of the analysis results into the basis for selecting an annual standard level. In considering the commenter’s analysis, the EPA notes that the analysis compared m aximum versus composite monitor annual mean PM 2.5 concentrations, averaged over 3 years, for two groups of areas: (1) areas with design values that exceed the current annual standard level (i.e., greater than 15.0 μg/m 3 ) and (2) areas with design values th at are just attaining the current annual standard (i.e., between 14.5 and 15.0 μg/m 3 ). 97 The commenter indicated that they used the full body of PM 2.5 monitoring data from the EPA’s AQS database (UARG, 2012, Attachment 1, p. 4), In attempting to reproduce t

he commenter’s results, the EPA repeated the calculations using only valid air quality data (i.e., data that meet data completeness and monitor siting criteria) from the AQS database for the same time period (Frank, 2012a). 98 Based on this corrected analysi s, the EPA finds that the composite monitor concentrations averaged across the areas within each group are somewhat higher than those calculated by the commenter,
97 For the first group of areas (which included 33 areas), this analysis calc ulated an average across the areas of maximum monitor annual mean PM 2.5 concentrations, averaged over 3 years, of 17.2 μg/m 3 compared to an average of composite monitor concentrations of 14.3 μg/m 3 . For the second group of areas (which included 11 areas), this analysis calculated an average across the areas of maximum monitor annual mean concentrations, averaged over 3 years, of 14.8 μg/m 3 compared to an average of composite monitor concentrations of 13.6 μg/m 3 (UARG, 2012, Attachment 1, Table 1). 98 The EPA notes that the Frank (2012a) analysis is similar to an earlier EPA staff analysis (Hassett

- Sipple et al., 2010), which used air quality data from EPA’s AQS database to compare maximum versus composite monitor long

- term mean PM 2.5 concentrations across the study areas in six selected multi

- city epidemiological studies. Formatted: Font: 12 pt

Formatted: Font: 12 pt Formatted: Font: 12 pt, Not Superscript/ Subscript***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 229 of 790 Formatted: Left and the average differences between the maximum and composite monitor concentrations

are some what smaller (Frank, 2012a, Table 3). 99 Notably, the difference between the maximum and composite monitor average concentrations for the second group of areas is substantially reduced in the corrected analysis, such that the difference (averaged across the 10 areas with valid data in the second group) is approximately 0.5 μg/m 3 , not 1.2 μg/m 3 as in the commenter’s analysis. In addition, the commenter’s analysis compared the average of the composite monitors to the average of the maximum monitors for each sub set of areas. This comparison of averages across all the areas in each subset masks the fact that the large majority of areas across the country have only one monitor, with the composite monitor and maximum monitor values the same for such areas, and many other areas have a maximum monitor value that is close to the composite monitor value. As discussed above, these circumstances have a major impact on the protection that would be achieved by the approach suggested by the commenter. With regard to the scope of the commenter’s analysis, the EPA finds that by limiting the scope to a small subset of areas with design values above or just below the current annual standard level of 15 μg/m 3 , the analysis ignores the large number of areas across the country with l ower design values that are relevant to consider in light of the epidemiological evidence of serious health effects at lower concentrations, well below the level of the current standard.
99 The EPA’s analysis was intended to repeat the commenter’s analysis, but using only valid air quality data (from 2006 to 2008). For the first group of areas (which included 21 areas with valid data), the EPA’s analysis calculated an average across the areas of maximum monitor annual mean concentrations, averaged of 3 years, of 16.8 μg/m 3 compared to an average of composite monitor concentrations of 14.8 μg/m 3 . For the second group of areas (which included 10 areas with valid data), the EPA’s analysis calculated an average across the areas of maximum monitor annual mean concentrations, averaged over 3 years, of 14.8 μg/m 3 compared to an average of composite monitor concentrations of 14.2 μg/ m 3 (Frank, 2012a, Table 3). Formatted: Font: 12 pt Formatted: Font: 12 pt, Not Superscript/ Subscript***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 230 of 790 Formatted: Left In translating the analysis results into the basis for selecting an a nnual standard level, the commenter’s translation is premised on the view that the “natural focal point” for setting an annual PM 2.5 standard level should be somewhere within the range of the long

- term mean PM 2.5 concentrations from the subset of epidemiol ogical studies that included only long

- term exposure studies of effects for which the evidence is categorized as causal or likely causal, but not for effects categorized as suggestive of causality, nor did it include short

- term exposure studies (which are included in Figure 4 of the proposal notice and above). Such a view is not consistent with setting a standard that would provide sufficient protection from the serious health effects reported even in the limited subset of studies considered by the commente r, including protecting public health with an adequate margin of safety. As discussed below, the EPA does not agree with the commenter’s view as to the appropriate focal point for selecting the level of an annual PM 2.5 standard, or with the limited set of studies considered by the commenter as a basis for selecting the level of the annual PM 2.5 standard. Regarding an appropriate focal point for selecting the level of the annual standard, as discussed in the proposal and as advised by CASAC, the EPA has focu sed on PM 2.5 concentrations somewhat below the lowest long

- term mean concentrations from each of the key studies of both long

- and short

- term exposures of effects for which the evidence is causal or likely causal, as considered by the EPA (i.e., the first two sets of studies shown in Figure 4). If the level of the annual standard was set just some where within the range of the long

- term mean concentrations from the various long

- term exposure studies, then one or more of the stud ie s would have a long

- term mean concentration below the selec ted level of the standard. Absent some reason to ignore or dis count these studies,***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 231 of 790 Formatted: Left which the commenter does not provide (and of which the EPA is unaware) , setting such a standard would allow that level of air quality , where the evidence of health effects is strongest, and its associated risk of PM 2.5 - related mortalit y and /or morbidity effects to continue. Selecting such a standard level that would explicitly allow such projected PM 2.5 - related mortality and morbidity effects to continue to occur could not be considered sufficient to protect the public health with an ad equate margin of safety. Further, focusing on just the long

- term mean PM 2.5 concentrations in the key epidemiological studies

– even the lowest long

- term mean concentration from the set of key studies

-- is not appropriate. Concentrations at and around the long

- term mean concentration s represent the part of the air quality distribution where the data in any given study are most concentrated and, thus, where the confidence in the magnitude and significance of an associati on in such study is strongest. However , the evidence of an association with adverse health effects in the studies is not limited to the PM 2.5 concentrations just at and around the long

- term mean, but rather extends more broadly to a lower p art of the distribution, recognizing that no discernible population

- level threshold for any such effects can be identified based on the available evidence . This broader region of the distribution of PM 2.5 concentrations should be considered to the extent

r elevant information is available , recognizing that the degree of confidence in the association identified in a study would change become lower as one moves away from below concentrations at and around the long

- term mean concentration in any given study. The commenter’s approach ignores this fundamental consideration. Regarding the set of studies that is appropriate to inform the selection of the level of the annual PM 2.5 standard, the EPA finds that limiting consideration only to the long

-***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 232 of 790 Formatted: Left term exposure studie s, as this commenter suggests, would be tantamount to ignoring the short

- term exposure studies , 100 which provide some of the strongest evidence from the entire body of ep idemiological studies. Thus, s e lecting a n annual standard level using the limited set of studies suggested by the commenter would fail to provide a degree of protection that would be sufficient to protect public health with an adequate margin of safety. For all the reasons discussed above, the EPA finds the commenter’s concerns with the EPA’s approach to considering composite and maximum monitor PM 2.5 concentrations in selecting the level of the annual PM 2.5 standard to be without merit. Further, the EPA finds no support in the commenter’s analysis for their suggested alternative approach. (2) With respect to the appropriate exposure period for mortality effects observed in long

- term exposure studies, some commenters in this group generally expressed views consistent with comments from UARG that argued that these studies “are most likely detect ing health risk from earlier, higher PM 2.5 levels and misattributing those risks to more recent, lower PM 2.5 levels” (UARG, 2012, Attachment 1, p 7). Further, this commenter asserted that “there is no knowledge or evidence indicating whether
100 The commenter suggests that the EPA should not place significant reliance on the long

- term mean concentrations from short

- term exposure studies because “[T]he short
‐ term studies did not use the annual average of PM 2.5 to devel op their associations; they used the daily 24
‐ hour averages of PM 2.5 . Thus, short
‐ term studies do not provide a natural indicator for the appropriate level of an annual standard....” (UARG, 2012, Attachment 1, p. 3). The EPA finds this argument unpersuasive. Quite simply, effects were observed in these studies with an air quality distribution that can meaningfully be characterized by these long

- term mean concentrations. Indeed, in remanding the 2006 standard, the D.C. Circuit discussed at length the interrela tionship of the long

- and short

term standards and studies, and remanded the 2006 standard to the EPA, in part, for ignoring those relationships without adequate explanation. American Farm Bureau Federation v. EPA. 559 F. 3d at 522

- 24.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 233 of 790 Formatted: Left premature deat

hs are the result of PM 2.5 exposures in the most recent year; or due to physical damages incurred from PM 2.5 exposures much earlier in life (with the impact on lifespan only emerging later in life); or due to total accumulated PM 2.5 exposure over many year s.” Id
. Further In addition , the commenter asserted that the long

- term exposure studies of mortality are central to the EPA’s basis for proposing to set a lower annual standard level, since most of the estimated benefits associated with a lower annual PM 2.5 standard are based on reductions in mortality related to long

- term exposures to PM 2.5 . As an initial matter, the EPA has recognized t he challenge in distinguishing between PM 2.5 - associated effects due to past and recent long

- term exposures , and in identif ying the relevant latency period for long

- term exposure to PM and resultant health effects (U.S. EPA, 2009a, section 7.6.4 ; 77 FR 38941/1). While the EPA has acknowledged that there remain important uncertainties related to characterizing the most relevant exposure periods in long

- term exposure studies, the assertion that there is “no knowledge or evidence” that helps to inform this issue is not correct, as discussed below. Both in the last review and in the current review , the EPA has assessed studies that used different air quality periods for estimating long

- term exposure and tested associations with mortality for the different exposure periods ( U.S. EPA, 2004, section 8 .2.3.5; U.S. EPA 2009a, section 7.6.4)
. In this review, the Integrate d Science Assessm ent discussed studies available since the last review that have assessed the relationship between long

- term exposure to PM 2.5 and mortality to explore the issue of the latency period between exposure to PM 2.5 and death ( U.S. EPA, 2009 a , s ection 7.6.4 ). Not ably, i n a recent analys i s of the extended Harvard Six Cities Study, Schwartz et al. (2008) used model averaging (i.e., multiple models were averaged and weighted by***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 234 of 790 Formatted: Left probability of accuracy) to assess exposure periods prospectively (77 FR 38907/1

- 2) . The

e xposure periods were estimated across a range of unconstrained distributed lag models (i.e., same ye ar, one year prior, two years prior to death ). In comparing lags , the authors reported that the effects of changes in exposure to PM 2.5 on mortality we re st rongest within a 2

- year period prior to death ( U.S. EPA, 2009a, p. 7

- 92, Figure 7

- 9 )
. Similarly, a large multi

- city study of the elderly found that the mortality risk associated with long

term exposure to PM 10 reported cumulative effect s that extended over the year s that deaths were observed in the study population (i.e., the follow

- up period) and for the 3

- year period prior to death (Zanobetti et al., 2008). Further, i n a study of two locations that experienced an abrupt decline in PM 2 .5 concentrations (i.e. , Utah Steel Strike, coal ban in Ireland), Röösli et al. (2005) reported that approximately 75 percent of health benefits were observed in the first 5 years ( U.S. EPA, 2009a , Table 7

- 9). Schwartz et al. (2008) and Puett et al. (2008) found, in a comparison of exposure periods ranging from 1 month to 48 months prior to death , that exposure to PM 10 24 months prior to death exhibited the strongest association, and the weakest association was reported for exposure in the time period of 1 month prior to death. Overall, the EPA notes that the available evidence for determining the exposure period that is causally related to the mortality effects of long

- term PM 2.5 exposures , as discussed above, cannot specifically disentangle the effects ob served in long

- term exposure studies associated with more recent air quality measurements from effects that may have been associated with earlier, and most likely higher, PM 2.5 exposures. While the evidence suggests that a latency period of up to five year s would account for the***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 235 of 790 Formatted: Left majority of deaths , it does not provide a basis for concluding that it is solely recent PM 2.5 concentrations that account for the mortality risk observed in such studies. Nonetheless, the more recent air quality data does well at explaining the relationships observed between long

- term exposures to PM 2.5 and mortality , with the strongest association observed in the two years prior to death. Further, the EPA recognizes that there is no discernible population

- level threshold below whi ch effects would not occur, such that it is reasonable to consider that health effects may occur over the full range of concentrations observed in the epidemiological studies, including the lower concentrations in the latter years. In light of this eviden ce and these considerations, the EPA concludes that it is appropriate to consider air quality concentrations that are generally contemporaneous with the collection of health event data (i.e., collected over the same time period) as being causally associate d with at least some proportion of the deaths assessed in a long

- term exposure study. This would include long

- term mean PM 2.5 concentrations from most of the key long

- term exposure studies of effects with causal or likely causal evidence shown in Figure 4 above, which reported long

- term mean PM 2.5 concentrations ranging from 13.6 μg/m 3 to 14.3 μg/m 3

. These studies include studies of mortality by Eftim et al. (2008), which separately analyzed the ACS and Harvard Six City sites, Zeger et al. (2008), and Lipfe rt et al. ( 2006 2006a ), as well as studies of morbidity endpoints by Goss et al. (2004), McConnell et al. (2003) and Gauderman et al. (2004), and Dockery et al. (1996) and Razienne et al. (1996). The EPA acknowledges that uncertainty in the relevant exposur e period is most notable in two other long

- term exposure studies of mortality. The Miller et al. (2007) reported a long

- term mean PM 2.5 concentration for a 1

-***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 236 of 790 Formatted: Left year exposure period that post

- dated the follow

- up period in which health event data were collecte d by two years. Also, the Krewski et al. (2009) study reported a long

- term mean PM 2.5 concentration for an exposure period that included only the last two years of the 18

- year follow

- up period. Based on these considerations, the EPA does not now consider i t appropriate to put weight on the reported long

- term mean concentrations from these two studies for the purpose of translating the information from the long

- term mortality studies into a basis for selecting the level of the annual PM 2.5 standard. 101 In addi tion, the EPA acknowledges that exposure periods that extend at least a couple years prior to the follow

- up period in which health event data were collected would likely more fully capture the PM

- related deaths in such studies. To explore how much higher t

he long

- term mean PM 2.5 concentrations would likely have been had air quality data prior to the follow

- up years of the studies been included, the EPA conducted a sensitivity analysis of long

- term mean PM 2.5 concentrations (Schmidt, 2012 2012a ) particularly considering studies that only included deaths from a relatively recent follow

up period. As examples of such studies, this analysis considered the Eftim et al. (2008) study of mortality in 51 the ACS sites and the Harvard Six Cities sites, as well as sites in the eastern region in the Zeger et al. (2008) study. Using data from the EPA’s AQS database, the analysis added the two years of air quality data just prior to the follow

- up period in each study, which was 2000 to 2002 in Eftim et al. (2008) and 2000 to 2005 in Zeger et al. (2008). The analysis then calculated the extended long

- term mean PM 2.5 concentration for each study. As discussed in Schmidt ( 2012 2012a ), in each case the

101 Nonetheless, the EPA notes that the Krewski et al. (2009) and Miller et al. (2007) studies provide strong evidence of mortality and cardiovascular

- related effects associated with long

- term PM 2.5 exposures to inform causality determinations reached in the Integrated Science Assessment (U.S. EPA, 2009a, sections 7.2.11 and 7.6).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 237 of 790 Formatted: Left long

- term mean PM 2.5 concentration averaged over the extended exposure period was less than 0. 3 4 μg/m 3 higher than the long

- term mean PM 2.5 concentration averaged over the follow

- up period. The EPA finds it reasonable to conclude that such a relatively small difference in lon g - term mean PM 2.5 concentrations would likely apply for other long

- term exposure studies that used similarly recent follow

- up periods as well (e.g., Goss et al., 2004; Lipfert et al., 2006 2006a ). Based on the above considerations, the EPA concludes that it is appropriate to consider the available air quality information from the long

- term exposure studies, while taking into account the uncertainties in the relevant long

- term exposure periods in weighing the information from these studies. The EPA recognizes that considering such information in selecting an appropriate annual standard level has the potential to build in some margin of safety. The EPA further concludes that it is appropriate to consider the air quality information from the set of long

- term exp osure studies discussed above in the context of the broader array of epidemiological studies that inform the EPA’s consideration of the level of the annual PM 2.5 standard. The EPA also notes that while the long

- term exposure studies are an important compon ent of the epidemiological evidence that informs the Agency’s consideration of the level of the annual standard, they do not provide the only relevant information, nor are they the set of studies for which the relevant long

- term mean PM 2.5 concentrations a re the lowest. As discussed in the proposal, the EPA also considers the long

- term mean PM 2.5 concentrations from the short

- term mortality and morbidity studies as providing important information in considering the level of the annual standard. As discussed above, a large proportion of the aggregate risk associated with short

- term exposures***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 238 of 790 Formatted: Left results from the large number of days during which the 24

- hour average concentrations are in the low

- to mid

- range of the concentrations observed in the studies. Thus, se tting the level of the annual standard based on long

- term mean concentrations, as well as the distribution of concentrations below the mean, in the short

- term exposure studies is the most effective and efficient way to reduce total PM 2.5 - related risk from the broad array of mortality and morbidity effects associated with short

- term exposures. Further, the EPA notes that the relevant exposure period for the short

- term exposure studies is the period contemporaneous with the collection of health event data,

an d that this exposure period is not subject to the uncertainties discussed above related to the long

- term exposure studies. Recognizing that the long

- term mean PM 2.5 concentrations from several of the multi

- city short

- term exposure studies shown in Figure 4 are below the long

- term mean PM 2.5 concentrations from the long

- term exposure studies (with the exception of Miller et al., 2007). 102 it It is reasonable that in selecting the level of the annual standard primary consideration should be given to the informat ion from this set of short

- term exposure studies. There is no reasonable basis to discount the long

- term mean concentrations of the short

- term exposure studies for purposes of setting the level of the annual standard. Thus, the commenter is incorrect in as serting that the long

- term exposure studies, not the short

- term exposure studies, would be central in the Administrator’s decision on the level of the annual standard. The standard is ultimately intended to protect not just against the single type of effec t that contributes the most to quantitative estimates of risk to public health, but rather to the broad array of effects,
102 As noted above, the EPA is not placing weight on the reported long

- term mean concentrations from the Miller et al. (2007) study for the purpose of translating the information from the long

- term mort ality studies into a basis for selecting the level of the annual PM 2.5 standard. Formatted: Font: 12 pt Formatted: Font: 12 pt, Not Superscript/ Subscript Formatted: Font: 12 pt***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 239 of 790 Formatted: Left including mortality and morbidity effects from long

- and short

- term exposures across the range of at

- risk populations impacted by PM 2. 5 - related effects. (3) With regard to the EPA’s analysis of distribution s of underlying population

level data (i.e., health event and study population data) and corresponding air quality data from each study area in certain key multi

- city epidemiological studies (Rajan et al., 2011), some commenters in this group raised a number of issues related to this analysis
. (API, 2012, Attachment 1 pp. 5 to 6; McClellan, 2012, pp.2 to 4). Some commenters noted the limited number of studies for which health event and study population data were available, and questioned whether these distributions would apply to other studies. Commenters expressed concerns that this analysis had not been formally reviewed by CASAC and was not published in the peer

- review literature. Ba sed on such concerns, some commenters asserted that the EPA should not consider this information as a basis for selecting a standard level. As an initial matter, as discussed in section III.E.4.b above, the EPA agrees with CASAC’s advice that it is appropr iate to consider additional data beyond the mean PM 2.5 concentrations in key multi

- city studies to help inform selection of the level of the annual PM 2.5 standard. As both the EPA and CASAC recognize, in the absence of a discernible threshold, health effec ts may occur over the full range of concentrations observed in the epidemiological studies , . Nonetheless, the EPA recognizes that confidence in the magnitude and there significance of an association is a high degree of confidence that the observed effects a

re associated with concentrations that extend below highest at and around the long

- term mean PM 2.5 concentrations reported in the studies and the degree of confidence becomes lower at lower concentrations within any given study . Following***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 240 of 790 Formatted: Left CASAC’s advice (Sa met, 2010d, p.2), the EPA used additional population

- level and air quality data made available by study authors to conduct an analysis of the distributions of such data, to help provide information on inform consideration of how the degree of confidence in the magnitude and significance of observed associations varies across the range of long

- term mean PM 2.5 concentrations in study areas within key multi

- city epidemiological studies. In the EPA’s view, such consideration is important in selecting a level fo r an annual standard that will protect public health with an adequate margin of safety. With regard to the number of multi

- city studies for which an analysis of the distributions of population

- level data across the study areas and the corresponding annual mean PM 2.5 concentrations was done, the EPA noted at proposal that data for such an analysis were made available from study authors for four studies, including two long

term exposure studies and two short

- term exposure studies. 103 The EPA recognized that

acc ess to health event data can be restricted due to confidentiality issues, such that it is not reasonable to expect that such information could be made available from all studies. In considering the information from these four studies, the EPA has further t aken into consideration uncertainties discussed in response to the above comment related to the appropriate exposure period for long

- term exposure studies. Based on these considerations, as noted above, the EPA concludes that such uncertainties are an impo rtant factor in evaluating the usefulness of the air quality information from the two long

- term exposure studies in this analysis (Krewski et al., 2009; Miller et al., 2007) and

103 Health event data and study population data were available from two short

- term exposure studies (Bell et al. 2008; Zanobetti and Schwartz, 2009) and one long

- term exposure study (Krewski et al., 2009). Only study population data were available from another long

- term exposure study (Miller et al., 2007).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 241 of 790 Formatted: Left that it would not be appropriate to place weight on the distributional analysi s of health event and air quality data from these two studies specifically for the purpose of translating the information from the long

- term mortality studies into a basis for selecting the level of the annual PM 2.5 standard. Such uncertainties are not rel evant to the short

term exposure studies, and thus, the Agency focuses on the two short

- term exposure studies in this analysis (Bell et al., 2008; Zanobetti and Schwartz, (2009). In focusing on these two short

- term exposure studies, the EPA first notes tha t these studies are key multi

- city studies that reported positive and statistically significant associations between mortality and cardiovascular

- related hospital admissions across a large number of areas throughout the U.S. (112 U.S. cities in Zanobetti a nd Schwartz, 2009; 202 U.S. counties in Bell et al., 2008) using relatively recent air quality and health event data (i.e., 1999 through 2005 in both studies). The EPA considers this to be a modest but important data set to use for this distributional anal ysis to help inform consideration of how much below the long

- term mean PM 2.5 concentrations in key multi

city long

- and short

- term exposure studies the annual PM 2.5 standard level should be set. While the EPA acknowledges that having such data available fr om more studies would have been useful, the Agency finds the information from this limited set of studies to be an important consideration in selecting an annual standard level, consistent with CASAC advice to consider such information. The results of this distributional analysis are shown below in Figure 5 (adapted from Figure 3 in Rajan et al., 2011). For each study, this figure shows the cumulative frequency of the number of health events in each study area and the corresponding long

term mean PM 2.5 conc entrations in each area. Consistent with CASAC advice (Samet,***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 242 of 790 Formatted: Left 2010d, p.2), such an analysis helps to inform the EPA’s understanding of the long

- term mean PM 2.5 concentrations that were most influential in generating the health effect estimates in individua l studies. In particular, the EPA recognizes that there is significantly greater confidence in the magnitude and significance of observed associations in that part of the air quality distribution corresponding to where the bulk of the health events evaluat ed in each study have been observed. With regard to the part of the distribution in which confidence in the magnitude and significance of associations observed may become appreciably lower In considering the results of this distributional analysis, as discu ssed more fully in the Response to Comments document , the EPA considers PM 2.5 concentrations between the 25 th and 10 th percentiles of the distribution of health events to be a reasonable range for providing a general frame of reference for that part of the distribution in which confidence may become in the magnitude and significance of the association may be appreciably lower . As highlighted in Figure 5, than confidence at and around the long

- ter m mean PM 2.5 concentrations corresponding with study areas contributing to the 25 th and 10 th percentiles of the distribution of deaths and cardiovascular

- related hospitalizations in concentration. For the two short

- term exposure studies included in this an alysis, the EPA notes that the PM 2.5 concentrations corresponding to the 25 th percentiles of the distributions of health events were 12.5 μg/m 3 and 10.3 11.5 μg/m 3 , respectively, for Zanobetti and Schwartz (2009 ), ) and 11.5 μg/m 3 and 9.8 μg/m 3 , respectively, for Bell et al. (2008 ) . The EPA also ) , with the 10 th percentiles being lower by approximately 2 μg/m 3 in each study (Rajan et al., 2011, Table 1). In considering this information, the EPA recognizes, however, that there is no clear dividing line or single percentile within a given distribution (including both above and Formatted: Font color: Auto***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 243 of 790 Formatted: Left below the 25 th percentile) provided by the scientific evidence that is most appropriate or ‘correct’ to use to characterize where the degree of confidence in the associations warrants setting the annual standard level. The decision as to the appropriate standard level below the long

- term mean concentrations of the key studies is largely a public health policy judgment to be made by the Administrator, taking into account all of the evidence and its related uncertainties, as discussed in section III.E.4.d below.

In response to concerns that this analysis was not reviewed by CASAC nor Formatted: Font: 12 pt***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 244 of 790 Formatted: Left published in the peer

- reviewed literature, the EPA notes that this analysis was conducted to dir ectly respond to advice from CASA C , as discussed in section III.E.4.b.1 above, in conjunction with their review of the Policy Assessment. The EPA notes that the same type of distributional analysis was presented in the second draft Policy Assessment based on air quality data, as well as population

- weighted air quality data, rather than health event or study population data. In considering that distributional information, CASAC urged that the EPA redo the analysis using health event or study population data, which is exactly what the EPA did and presented in the final Policy Assessment. The EPA provided CASAC with the final Policy Assessment and communicated how the final staff conclusions reflected consideration of its advice and that those staff conclusions were based in part on the specific distributional analysis that CASAC had urged the EPA to conduct (Wegman, 2011, Attachment p. 2). CASAC did not choose to provide any additional comments or advice after receiving the final Policy Assessment. The EPA

cons iders this distributional analysis to be the product of the peer review conducted by CASAC of the Policy Assessment, and thus does not agree with commenters’ characterization that the analysis lacked appropriate peer review. The EPA’s final analysis was ba sed on the comments provided by CASAC, the pe e r review committee established pursuant to the CAA , on the draft analysis, such that the final analysis stems directly from CASAC’s advice and the EPA’s response to its comments. Based on the above consideratio ns, the EPA continues to conclude that its analysis of distributions of health event and air quality data from two key multi

- city epidemiological studies provides important information related to understanding the associations between health events observe d in each city (e.g., deaths, hospitalizations)***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 245 of 790 Formatted: Left and the corresponding long

- term mean PM 2.5 concentrations observed in the studies. While recognizing that this is a relatively modest data set, the EPA further concludes that such information can appropriatel y help to inform the selection of the level of an annual standard that will protect public health with an adequate margin of safety from these types of health effects which are causally related to long

- and short

- term exposures to PM 2.5 . (4) Some commenter s in this group asserted there were limitations in the long

term exposure studies of morbidity, including studies evaluating respiratory effects in children. For example, one commenter (UARG, 2012, p. 12, Attachment 1, pp. 14 to 16) asserted there were ser ious limitations in the long

- term exposure studies of respiratory morbidity in each of the studies considered by the EPA (including McConnell et al., 2003; Gauderman et al., 2004; Dockery et al., 1996; Raizenne et al., 1996; and Goss et al., 2004) and argu ed that this evidence provides only a “weak association” with PM 2.5 exposures. This commenter asserted that many of these long

- term exposure studies evaluating respiratory effects were considered at the time the EPA reaffirmed the current annual standard l evel of 15 μg/m 3 in 2006, that the Administrator in the last review determined that the information they provided “was too limited to serve as the basis for setting a level of a national standard,” and that they should be given little weight in setting the level of the an nual standard in this review (UARG, 2012, Attachment 1, p. 14). More specifically, this commenter asserted that the McConnell et al. (2003) and Gauderman et al. (2004) stud ies reported mixed results for associations with PM 2.5 and stronger associations wi th NO 2 (API, 2012, Attachment 1, pp. 14 to 15). Similarly, this***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 246 of 790 Formatted: Left commenter argued that the Dockery et al. (1 996) and Raizenne et al. (1996) studies show ed stronger associations with acidity than with fine particles (measured as PM 2.1 ). Id. pp. 15 to 16. Wi th regard to the cystic fibrosis study, this commenter noted that the association between pulmonary exacerbations and PM 2.5 in this study was no longer statistically significant when the model adjusted for each individual’s baseline lung function. The comm enters referred to the data on lung function as an “important explanatory variable,” and suggested that the EPA should rely on results from the model that included individual baseline lung function information. Id . p. 16. For the reasons discussed below an d in more detail in the Response to Comments document, t he EPA disagrees with the commenters’ interpretation of these studies
. As an initial matter, the EPA notes that three of these studies (McConnell et al., 2003; Dockery et al., 1996; Raizenne et al., 1996) as well as the initial studies from the Southern California Children’s Health Study ( Peters et al., 1999; McConnell et al., 1999’ 1999; Gauderman et al., 2000, 2002 ; Avol et al., 2001 ) were discussed and considered in the 2004 Air Quality Criteria Doc ument ( U.S. EPA, 2004) and , thus, considered within the air quality criteria supporting the EPA’s final decisions in the review completed in 2006. Two additional studies (Gauderman et al., 2004; Goss et al., 2004) were discussed and considered in the provisional science assessment conduct ed for the last review ( U.S. EPA, 2006a). The EPA concluded that “new” studies considered in the provisional assessment completed in 2006 did not materially change any of the broad scientific conclusions regarding the health effects of PM exposure made in the Criteria Document (71 FR 61148 to 61149, October 17, 2006). All of these studies were considered in the Integrated Science Assessment that informs the current review ( U.S.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 247 of 790 Formatted: Left EPA, 2009a). With regard to the Southern California Children’s Health Study, ex tended analyses considered in the Integrated Science Assessment provided evidence that clinically important deficits in lung function 104 associated with long

- term exposure to PM 2.5 persist into early adulthood (U.S. EPA, 2009a, p. 7

- 27; Gauderman et al., 200 4). These effects remained positive in copollutant models. 105 Additional analyses of the Southern California Children’s Health Study cohort reported an association between long

- term PM 2.5 exposure and bronchitic symptoms ( U.S. EPA, 2009a, p. 7

- 23 to 7

- 24; Mc Connell et al., 2003, long

- term mean concentration of 13.8 μg/m 3 ) that remained positive in co

- pollutant models, with the PM 2.5 effect estimates increasing in magnitude in some models and decreasing in others, and a strong modifying effect of PM 2.5 on the association between lung function and asthma incidence ( U.S. EPA, 2009 a , 7

- 24; Islam et al., 2007). T he outcomes observed in the more recent reports from the Southern California Children’s Health Study, including evaluation of a broader range of endpoints and longer follow

- up periods, were larger in magnitude and more precise than reported in the initial version of the study . Supporting these results were new longitudinal cohort studies conducted by other researchers in varying locations using different met hods ( U.S. EPA, 2009a, section 7.3.9.1). The EPA, therefore, disagrees with the commenters that the

104 Clinical significance was defined as an FEV 1 below 80 percent of the predicted value, a criterion commonly used in clinical settings to identify persons at increased risk for adverse respiratory conditions (U.S. EPA, 2009a, p. 7

- 29 to 7

- 30). The primary NAAQS for sulfur dioxide (SO 2 ) also included this interpretation for FEV 1 (75 FR 35525, June 22, 2010). 105 Gauderman et al. (2004) clearly stated throughout their analysis that NO 2 was one component of a highly correlated mixture that contains PM 2.5 . Gauderman et al. (2004) did not present the results from copollutants models but stated “two

- pollutant models for any pair of pollutants did not provide a significantly better fit to the data than the corresponding single

- pollutant models.”***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 248 of 790 Formatted: Left studies by McConnell et al. (2003) and Gauderman et al. (2004) are flawed and should not be used in the PM NAAQS review process. The 24

- City study 106 by Docke ry et al. (1996) (long

- term mean concentration of 14.5 μg/m 3 ) was considered in the current as well as two previous reviews ( U.S. EPA, 2009a; U.S. EPA, 2004; U.S. EPA, 1996). This study observed that PM, specifically “particle strong acidity” and sulfate p articles (indicators of fine particles), were associated with reports of bronchitis in the previous year. Similarly, the magnitude of the associations between bronchitis and PM 10 and PM 2.1 were similar to those for acidi c aerosols and sulfate particles, th ough the confidence intervals for the PM 10 and PM 2.1 associations were slightly wider and the associations were not statistically significant. Acid aerosols , sulfate, and fine particles are formed in secondary reactions of the emissions from incomplete combustion and these pollutants have similar regional and temporal distributions . As noted by the study authors, “the strong correlations of several pollutants in this study, especially particle strong acidity with sulfate (r=0.90) and PM 2.1 (r=0.82), make it difficult to di stinguish the agent of interest ” (Dockery et al., 1996, p. 505). Overall, Dockery et al. (1996) (and, similarly, Raizenne et al., 1996) observed similar associations between respiratory health effects and acid aerosols , sulfate, PM 10 and PM 2.1 concentrations. The commenters noted that the associations with particle acidity were sensitive to the inclusion of the six Canadian sites. The EPA notes that none of these Canadian cities were in the “sulfate belt” where particle strong acidity was highest. Thus, the change in the effect estimate when the six Canadian cities were excluded from the analysis is likely due to the lower prevalence of bronchitis and the
106 The 24

- City study conducted by Dockery et al. (1996) included 18 sites in the U.S. and 6 sites in Canada. The Raizenne et al. (1996) study considered 22 of these 24 study areas. Athens, OH and South Brunswick, NJ were not included in this study.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 249 of 790 Formatted: Left lower concentrations of acid aerosols in these cities, and not due to some difference in susceptibility to bronchitis between the U.S. and Canadian populations that is not due to air pollution, as suggested by the commenters (UARG, 2012, Attachment 1, p. 15). In fact, contrary to the statements made by the commenters, the authors did not o bserve any subgroups that appeared to be markedly more susceptible to the risk of bronchitis. The Goss et al. (2004) study considered a U.S. cohort of cystic fibrosis patients and provided evidence of association between long

- term PM 2.5 exposures and

exac erbations of respiratory symptoms resulting in hospital admissions or use of home intravenous antibiotics ( U.S. EPA, 2009a, p. 7

- 25; long

- term mean concentration of 13.7 μg/m 3 ). The commenters noted that the association between pulmonary exacerbations and PM 2.5 in this study was no longer statistically significant when the model adjusted for each individual’s baseline lung function. The commenters referred to the data on lung function as an “important explanatory variable,” and suggested that the EPA should rely on results from the model that included individual baseline lung function information. The EPA disagrees with the commenters’ interpretation of this study. The Agency concludes it is unlikely that lung function is a potential confounder or an importa nt explanatory variable in this study. In fact, the authors noted that “it is more likely that lung function decline may be intimately associated with chronic exposure to air pollutants and may be part of the causal pathway in worsening prognosis in CF [cy stic fibrosis]; in support of this explanation, we found both cross

- sectional and longitudinal strong inverse relationships between FEV 1 and PM levels” (Goss et al., 2004, p. 819). The EPA notes that adjusting for a variable that is on the causal pathway c an lead to overadjustment bias, which is likely to attenuate the association (Schisterman et al. 2009); this is likely what***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 250 of 790 Formatted: Left was observed by the authors. Thus, the EPA continues to believe it is appropriate to focus on the results reported in Goss et al. (2 004) that did not include individual baseline lung function in the model. In addition, the EPA disagrees with commenters’ reliance solely on statistical significance when interpreting the study results from individual study results and the collective evide nce across studies. As discussed in section III.D.2 above, statistical significance of individual study findings has played an important role in the EPA’s evaluation of the study’s results and the EPA has placed greater emphasis on studies reporting statis tically significant results. However, in the broader evaluation of the evidence from many epidemiological studies, and subsequently during the process of forming causality determinations in the Integrated Science Assessment by integrating evidence from acr oss epidemiological, controlled human exposure, and toxicological studies, the EPA has emphasized the pattern of results across epidemiological studies and whether the effects observed were coherent across the scientific disciplines for drawing conclusions on the relationship between PM 2.5 and different health outcomes. As noted in section III.B.1.a of the proposal, with regard to respiratory effects, the Integrated Science Assessment concluded that extended analyses of studies available in the last review as well as new epidemiological studies conducted in the U.S. and abroad provided stronger evidence of respiratory

- related morbidity associated with long

- term PM 2.5 exposure (77 FR 38918). The strongest evidence for respiratory

- related effects available in this review was from epidemiological studies that evaluated decrements in lung function growth in children and increased respiratory symptoms and disease***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 251 of 790 Formatted: Left incidence in adults (U.S. EPA, 2009a, sections 2.3.1.2, 7.3.1.1, and 7.3.2.1). 107 In considering the co llective evidence from epidemiological, toxicological, and controlled human exposure studies, including the studies discussed above, the EPA recognizes that the Integrated Science Assessment concluded that a causal relationship is likely to exist between l ong - term PM 2.5 exposures and respiratory effects ( U.S. EPA, 2009a, p. 2

- 12, pp. 7

- 42 to 7

- 43). CASAC concurred with this causality determination (Samet, 2009f, p.9). The commenter’s assertion that the EPA should adhere to its assessment of these studies as it did in the review completed in 2006 is significantly mistaken. Most obviously, the EPA’s final decision in the last review was held to be deficient by the D.C. Circuit in remanding the 2006 primary annual PM 2.5 standard. As discussed in section III.A.2 above, the D.C. Circuit specifically held that the EPA did not provide a reasonable explanation of why certain morbidity studies, including an earlier study from the Southern California Children’s Health Study (Gauderman et al., 2000 , long

- term mean PM 2.5 concentration approximately 15 μg/m 3 ) and the 24

- Cities Study (Raizenne et al., 1996 , long

- term mean concentrations approximately 14.5 μg/m 3 ) did not warrant a more stringent annual PM 2.5 standard when the long

- term mean PM 2.5 concentrations reported in t

hose studies were at or lower than the level of the annual standard. American Farm Bureau Federation v. EPA . 559 F. 3d at 525. Indeed, the court found that, viewed together, the Gauderman et al. (2000) and Raizenne et al., (1996) studies “are related and t ogether indicate a significant public health risk...On this record, therefore, it appears the EPA too hastily discounted the Gauderman and 24

- Cities studies as lacking in
107 Supporting evidence comes from studies “that observed associations betw een long

term exposure to PM 10 and an increase in respiratory symptoms and reductions in lung function growth in areas where PM 10 is dominated by PM 2.5 ” ( U.S. EPA, 2009a, p. 2

- 12)
.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 252 of 790 Formatted: Left significance.” Id. In this review, the EPA recognizes a significant amount of evidence beyond these two studies that expands our understanding of respiratory effects associated with long

term PM 2.5 exposures. This body of scientific evidence includes an extended and new analyses from the Southern California Children’s Health Study (Gauderma n et al., 2004; Islam et al., 2007; Stanojevic et al., 2008) as well as additional studies that examined these health effects (Kim et al., 2004; Goss et al., 2004). Thus, even more so than in the last review, the evidence indicates a “significant public he alth risk” to children from long

- term PM 2.5 exposures at concentrations below the level of the current annual standard. A standard that does not reflect appropriate consideration of this evidence would not be requisite to protect public health with an adeq uate margin of safety. (5) With regard to the use of studies of health effects for which the EPA finds the evidence to be “suggestive” of a causal relationship, some commenters argued that such studies “do not merit any weight in the setting of the annual NAAQS” (e.g., UARG, 2012, Appendix 1, p. 3). The EPA disagrees with the commenter’s view that studies of health effects for which the evidence is suggestive of a causal relationship, rather than studies of health effects for which the evidence supports a c ausal or likely causal relationship, merit no weight at all in setting the NAAQS. To place no weight at all on such evidence would in essence treat such evidence as though it had been categorized as “not likely to be a causal relationship.” To do so would ignore the important distinctions in the nature of the evidence supporting these different causality determinations in the Integrated Science Assessment. It would also ignore the CAA requirement that primary standards are to be***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 253 of 790 Formatted: Left set to provide protection wi th an adequate margin of safety, including providing protection for at

- risk populations. Thus, ignoring this information in making decisions on the appropriate standard level would not be appropriate. 108 Nonetheless, in considering studies of health effects for which the evidence is suggestive of a causal relationship, the EPA does believe that it is appropriate to place less weight on such studies than on studies of health effects for which there is evidence of a causal or likely causal relationship. A secon d group of commenters supported revising the suite of primary PM 2.5 standards to provide increased public health protection. These commenters found the available scientific information and technical analyses to be stronger and more compelling than in the l ast review. These commenters generally placed substantial weight on CASAC advice and on the EPA staff analyses presented in the final Policy Assessment, which concluded that the evidence most strongly supported an annual standard level within a range of 11 to 12 μg/m 3 ( U.S. EPA, 2011a, p. 2

- 206). While some of these commenters felt that the level should be set within the proposed range (12 to 13 μg/m 3 ), most of these commenters advocated a level of 11 μg/m 3

. 109 For example, ALA et al., asserted: The EPA’s pro posed PM 2.5 standards, while a step in the right direction are insufficient to protect public health, including the health of susceptible populations, with an adequate margin of safety as required by the Clean Air Act...we will discuss the enormous gap in public health protection afforded by an
108 As discussed in section II.A above, the requirement that primary standar ds provide an adequate margin of safety was intended to address uncertainties associated with inconclusive scientific and technical information available at the time of standard setting. I was also intended to provide a reasonable degree of protection agai nst hazards that research has not yet identified. This certainly encompasses consideration of effects for which there is evidence suggestive of a causal relationship. 109 As discussed in section III.E.4.c.ii, many of these commenters also supported lowering the level of the primary 24

- hour PM 2.5 standard.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 254 of 790 Formatted: Left annual standard of 13 μg/m 3 , at the upper end of the proposed range, compared to the more protective 11 μg/m 3 , as advocated by our organizations (ALA et al., 2012, p. 6). In general, these commenters expressed the view that given the strength of the available scientific evidence, the serious nature of the health effects associated with PM 2.5 exposures, the large size of the at

- risk populations, the risks associated with long

- and short

- term PM 2.5 exposures, and the important uncertainties inherently present in the evidence, the EPA should follow a highly precautionary policy response by selecting an annual standard level that incorporates a large margin of safety. More specifically, these commenters offered a range of comments related to the general approach used by the EPA to select standard levels, including: (1) the EPA’s approach for setting a generally controlling annual standard; (2) the importance of the greatly expanded and stronger overall scientific data ba se; (3) consideration of the distributional statistical analysis conducted by the EPA and other approaches for translating the air quality information from specific epidemiological studies into standard levels; and (4) the significance of the PM 2.5 - related public health impacts, especially potential impacts on at

- risk populations, including children, in reaching judgments on setting standards that provide protection with an adequate margin of safety. These comments are discussed in turn below. (1) Some of t

hese commenters disagreed with the EPA’s approach for setting a “generally controlling” annual standard in conjunction with a 24

- hour standard providing supplemental protection particularly for areas with high peak

- to
- mean ratios. These commenters argued t

his approach would lead to “regional inequities” as demonstrated in the EPA’s analyses contained in Appendix C of the Policy Assessment (ALA et al., pp. 26 to 27). Specifically, these commenters argued:***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 255 of 790 Formatted: Left There is no basis in the Clean Air Act for such a det ermination. The Clean Air Act requires only that the NAAQS achieve public health protection with an adequate margin of safety. It is well

- documented that both long

- and short

- term exposures to PM 2.5 have serious and sometimes irreversible health impacts. T here is no health protection reason to argue tha t one standard should be “controlling” as a matter of policy without regard to the health consequences of such a policy. To adopt such a policy ignores the obligation to provide equal protection under the law to all Americans because it would result in uneven protection from air pollution in different localities and regions of the country (ALA et al., 2012, p. 26). The EPA believes these commenters misunderstood the basis for the EPA’s policy goal of setting a “generally controlling” annual standard. This approach relates exclusively to setting standards that will provide requisite protection against effects associated with both long

- and short

- term PM 2.5 exposures. It does so by lowering the overall air qualit y distributions across an area, recognizing that changes in PM 2.5 air quality designed to meet an annual standard would likely result not only in lower annual mean PM 2.5 concentrations but also in fewer and lower peak 24

- hour PM 2.5 concentrations. As discu ssed in section III.A.3 in the proposal and above, the EPA recognizes that there are various ways to combine the two primary PM 2.5 standards to achieve an appropriate degree of public health protection. Furthermore, the extent to which these two standards are interrelated in any given area depends in large part on the relative levels of the standards, the peak

- to
- mean ratios that characterize air quality patterns in an area, and whether changes in air quality designed to meet a given suite of standards are likely to be of a more regional or more localized nature. In focusing on a

n approach of setting a generally controlling annual standard, the EPA’s intent is in fact to avoid the potential “regional inequities” that are of concern to the commenters. The EP A judges that the most appropriate way to set standards that provide more consistent public health protection is by using the approach of setting a***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 256 of 790 Formatted: Left generally controlling annual standard. This judgment builds upon information presented in the Policy Assessm ent as discussed in section III.A.3 above. More specifically, the Policy Assessment recognized that the short

- term exposure studies primarily evaluated daily variations in health effects with monitor(s) that measured the variation in daily PM 2.5 concentrat ions over the course of several years. The strength of the associations observed in these epidemiological studies was demonstrably in the numerous “typical” days within the air quality distribution, not in the peak days ( U.S. EPA, 2011a, p. 2

- 9). In additi on, the quantitative risk assessments conducted for this and previous reviews demonstrated the same point, that is, much, if not most , of the aggregate risk associated with short

- term PM 2.5 exposures results from the large number of days during which the 2 4

- hour average concentrations are in the low

- to mid

- range, below the peak 24

- hour concentrations ( U.S. EPA, 2011a, section 2.2.2; U.S. EPA, 2010a, section 3.1.2.2). In addition, there was no evidence suggesting that risks associated with long

- term exposure s were likely to be disproportionately driven by peak 24

- hour concentrations. 110 For these reasons, the Policy Assessment concluded that strategies that focused primarily on reducing peak days were less likely to achieve reductions in the PM 2.5 concentratio ns that were most strongly associated with the observed health effects. Furthermore, the Policy Assessment concluded that a n approach that focused on reducing peak exposures would most likely result in more uneven public health protection across the U.S. b y either providing inadequate protection in some areas or overprotecting in other areas ( U.S. EPA, 2011a, p. 2

- 9; U.S. EPA, 2010a, section 5.2.3). This is because

110 In confirmation, a number of studies have presented analyses excluding higher PM concentration days and reported a limited effect on the magnitude of the effect estimates or statistical significance of the association (e.g., Dominici, 2006b; Schwartz et al., 1996; Pope and Dockery, 1992).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 257 of 790 Formatted: Left reductions based on control of peak days are less likely to control the bulk of the air quali ty distribution. As a result, the EPA believes a n approach that focuses on a generally controlling annual standard would likely reduce aggregate risks associated with both long

- and short

term exposures more consistently than a generally controlling 24

- hour standard and, therefore, would be the most effective and efficient way to reduce total PM 2

- 5 - related population risk. The CASAC agreed with this approach and considered it was “appropriate to return to the strategy used in 1997 that considers the annu al and the short

term standards together, with the annual standard as the controlling standard, and the short

- term standard supplementing the protection afforded by the annual standard” (Samet, 2010d, p. 1). For the reasons discussed above, the EPA disagre es with the comments that this approach will result in the concerns raised by the commenters; rather the EPA concludes that this approach will help to address these concerns. (2) Many of these commenters asserted that the currently available scientific inf ormation is greatly expanded and stronger compared to the last review. Some of these commenters highlighted the availability of multiple, multi

- city long

- and short

- term exposure studies providing “repeated, consistent evidence of effects below the current annual standard level” (ALA et al., 2012, pp. 39 to 49) and, more specifically, “significant evidence of harm with strong confidence well below EPA’s proposed annual standard range of 12

- 13 μg/m 3 ” (AHA et al., 2012, pp. 10 to 12). The EPA recognizes that in setting standards that are requisite to protect public health with an adequate margin of safety, the Administrator must weigh the various types of available scientific information in reaching public health policy judgments that neither***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 258 of 790 Formatted: Left
overstate nor un derstate the strength and limitations of this information or the appropriate inferences to be drawn from the available science. In general, the EPA agrees with these commenters’ views that the currently available scientific evidence is stronger “because o f its breadth and the substantiation of previously observed health effects” (77 FR 38906/2) and provides “greater confidence in the reported associations than in the last review” (77 FR 38940/1). The EPA also agrees with the commenters’ position that it is appropriate to consider the regions within the broader air quality distributions where we have the strongest confidence in the associations reported in epidemiological studies in setting the level of the annual standard. However, as discussed in section I II.E.4.d below, in weighing the available evidence and technical analyses, as well as the associated uncertainties and limitations in that information, the EPA disagrees with the commenters’ views regarding the extent to which the available scientific info rmation provides support for considering an annual standard level below the proposed range (i.e., below 12 to 13 μg/m 3 ). In particular, the EPA disagrees with the degree to which these commenters place more weight on the relatively more uncertain evidence that is suggestive of a causal relationship (e.g., low birth weight). Consistent with CASAC advice (Samet, 2010d, p. 1), the Agency concludes it is appropriate and reasonable to place the greatest emphasis on health effects for which the Integrated Science Assessment concluded there is evidence of a causal or likely causal relationship and to place less weight on the health effects that provide evidence that is only suggestive of a causal relationship
. . . (3) With regard to us ing the air quality information from epidemiological studies to inform decisions on standard levels, commenters in this group generally supported the***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 259 of 790 Formatted: Left EPA’s efforts to explore different statistical metrics from epidemiological studies to inform the Administrator’s decisions. These commen ters argued that by considering different analytic measures

-- either concentrations one standard deviation below the long

- term means reported in the epidemiological studies or the EPA’s d istributional statistical analysis of population

- level data that ext ends the approach used in previous PM NAAQS reviews to consider information beyond a single statistical metric

-- “the annual standard must be significantly lower than EPA has proposed” (ALA et al., 2012, pp. 50 to 61). Furthermore, with regard to characte rizing the PM 2.5 air quality at which associations have been observed, some of these commenters highlighted CASAC’s recommendation that “[f]urther consideration should be given to using the 10 th percentile as a level for assessing various scenarios of leve ls for the PM NAAQS” (Samet, 2010c, p. 11) (ALA et al., 2012, p. 55). Other commenters urged that the EPA extend the distributional analysis to include additional studies. For example, CHPAC urged the EPA to also conduct distributional analysis for childre n’s health studies to better inform standards that would protect both children and adults from adverse health outcomes (CHPAC, 2012, p. 3 ) )
. The EPA agrees with these commenters’ views that it is appropriate to take into account different statistical metri cs from epidemiological studies to inform the decisions on standard levels that are appropriate to consider
. in setting a standard that will protect public health with an adequate margin of safety
. In the development of the Policy Assessment, the EPA staff explored various approaches for us ing information from epidemiological studies in setting the standards. The general approach used in the final Policy Assessment, discussed in sections III.A.3 and III.E.4.a above, reflects consideration of CASAC advice (Samet, 2010c, d) and public comments on multiple***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 260 of 790 Formatted: Left drafts of the Policy Assessment
. With regard t o using the distributional statistical analysis to characterize the confidence in the associations , the EPA emphasizes that there is no clear dividing line provided by the scientific evidence, and that choosing how far below the long

- term mean concentratio ns from the epidemiological studies is appropriate to identify a standard level that will provide protection for the public health with an adequate margin of safety is largely a public health policy judgment. The EPA considers the region from approximately the 25 th to 10 th percentiles to be a reasonable range for providing a general frame of reference as to the part of the distribution over which our confidence in the magnitude and significance of the associations observed in epidemiological studies becomes is appreciably lower. However Based on these considerations, t he EPA concludes that it is not appropriate to place as much confidence in the magnitude and significance of the associations over the lower percentiles of the distributions in each study as at and around the long

- term mean concentrations. Thus , the EPA disagrees with the commenters’ views that the available information this analysis compels placing more emphasis on the lower part of this range in selecting a level for an annual standard that will protect public health with an adequate margin of safety
. The EPA recognizes that this information comes primarily from two short

- term exposure studies, a relatively modest data set. In light of the limited nature of this information, and in recognition of more general uncertainties inherent in the epidemiological evidence, the Administrator deems it reasonable not to place more emphasis on concentrations in the lower part of this range, as discussed below in section III.E.4.d. With regard to the scope of t he distributional statistical analysis, the EPA***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 261 of 79 0 Formatted: Left requested additional population

- level data from the study authors for a group of six multi

city studies for which previous air quality analyses had been conducted (Hassett

- Sipple et al., 2010; Schmidt et al., 2010, Analysis 2). These six studies were originally selected because they considered multiple locations representing varying geographic regions across multiple years. Thus, these studies provided evidence on the influence of different particle mixtures o n health effects associated with long

- and short

- term PM 2.5 exposures. In addition, these multi

- city studies considered relatively more recent health events and air quality conditions (1999 to 2005). As discussed in section III.E.4.b.i above, the EPA recei ved and analyzed population

- level data for four of the six studies (Rajan et al., 2011). T hree of these four studies (Krewski et al., 2009; Bell et al., 2008; Zanobetti and Schwartz, 2009) served as the basis for the concentration

- response functions used t o develop the core risk estimates ( U.S. EPA, 2010a, section 3.3.3). While, the EPA agrees that it would be useful to have such data from more studies, the Agency believes that the additional data that was requested and received from study authors provide u seful information to help inform the Administrator’s selection of the annual standard level. (4) Many commenters in this group highlighted PM 2.5 - related impacts on at

- risk populations, including potential impacts on children, older adults, persons with pr e existing heart and lung disease, and low

- income populations, to support their views that the annual standard should be revised to a level of 11 μg/m 3 or lower (CHPAC, 2012; AHA et al., 2012; ALA, 2012, pp. 29 to 38; Rom et al., 2012; Air Alliance Houston , et al, 2012). These commenters urged the EPA to adopt a policy approach that placed less weight on the remaining uncertainties and limitations in the evidence and placed more emphasis on margin of safety considerations, including providing protection aga inst***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 262 of 790 Formatted: Left effects for which there is more limited scientific evidence. For example, CHPAC urged the EPA “to place the same weight on studies examining impacts on children’s health as that of adult studies. ... The fact that there may be stronger evidence from adu lt studies does not mean that standards based on adult studies will be protective for children and consequently will meet the standard requisite to protect public health with an adequate margin of safety” (CHPAC, 2012 p. 3). Furthermore, with regard to the EPA’s approach for weighing uncertainties, some of these commenters stated that “we find no justification in the preamble for an annual standard level as high as 13 μg/m 3 , other than the vague assertion that uncertainties increase at lower concentrations. Further, the final proposal completely failed to address the Policy Assessment recommendations that if 13 μg/m 3 was proposed, the 24

- hour standard should be strengthened as well” (ALA et al., p. 7). The EPA has carefully evaluated and considered evidence of effects in at

- risk populations. With regard to effects classified as having evidence of a causal or likely causal relationship with long

- or short

- term PM 2.5 exposures (i.e., premature mortality, cardiovascular effects, and respiratory effects), the Age ncy takes note that it considered the full range of studies evaluating these effects, including studies of at

- risk populations, to inform its review of the primary PM 2.5 standards. Specific multi

- city studies summarized in Figures 1, 2, and 3 above highlig ht evidence of effects observed in two different lifestages

– children and older adults

– that have been identified as at

- risk populations. Thus, the EPA places as much weight on studies that explored effects in children for which the evidence is causal or likely causal in nature as on studies of such effects in adults, including older adults
. . As discussed above in responses to commenters supporting the retention of the current standards, in setting the standard, the EPA has***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 263 of 790 Formatted: Left focused on considering PM 2.5 co ncentrations somewhat below the lowest long

- term mean concentrations from each of the key studies of both long

- and short

- term exposures of effects for which the evidence supports a causal or likely causal relationship (i.e., the first two sets of studies shown in Figure 4). Absent some reason to ignore or discount these studies, which the commenter does not provide (and of which the EPA is unaware) , the EPA considers the available evidence of effects in children as well as other at

- risk populations. With r espect to the EPA’s consideration of more limited studies providing evidence suggestive of a causal relationship (e.g., developmental and reproductive effects), as noted above in responding to comments from the first group of commenters, the Agency agrees that it is important to place some weight on this body of evidence in setting standards that provide protection for at

- risk populations, as required by the CAA. However, the Agency does not agree that the same weight must be placed on this information as o n the body of scientific information for which there is evidence of a causal or likely causal relationship. To do so would ignore the difference in the breadth and strength of the evidence supporting the different causality determinations reached in the In tegrated Science Assessment. With regard to weighing the uncertainties and limitations remaining in the evidence and technical analyses, as discussed in section II.A above, the EPA recognizes that in setting a primary NAAQS that provides an adequate margi n of safety, the Administrator must consider a number of factors including the nature and severity of the health effects involved, the size of sensitive population(s) at risk, and the kind and degree of the uncertainties that remain. As discussed in sectio n III.E.4.d below, the Agency***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 264 of 790 Formatted: Left agrees with these commenters that, in weighing the available evidence and technical analyses including the uncertainties and limitations in this scientific information, there is no justification for setting a primary PM 2.5 ann ual standard level as high as 13 μg/m 3

. Finally, some commenters in both groups also identified “new” studies that were not included in the Integrated Science Assessment as providing further support for their views on the level of the annual standard. As d iscussed in section II.B.3 above, the EPA completed a provisional review and assessment of “new” studies published since the close of the Integrated Science Assessment, including “new” studies submitted by commenters (U.S. EPA, 2012a 2012 b ). The provisional assessment found that the “new” studies expand the scientific information considered in the Integrated Science Assessment and provide important insights on the relationship between PM 2.5 exposure and health effects of PM (U.S. EPA, 2012b) . However, the EP A notes that the provisional assessment found that the “new” science did not materially change the conclusions reached in the Integrated Science Assessment. The EPA notes that, as in past NAAQS reviews, the Agency is basing the final decisions in this revi ew on the studies and related information included in the Integrated Science Assessment that have undergone CASAC and public review, and will consider newly published studies for purposes of decision making in the next PM NAAQS review. ii. 24

- Hour Standard Level With respect to the level of the 24

- hour standard, the EPA received comments on the proposal from two distinct groups of commenters. One group that included virtually all commenters representing industry associations , businesses , and many States agreed with the Agency’s proposed decision to retain the level of the 24

- hour PM 2.5 standard.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 265 of 790 Formatted: Left The other group of commenters included many medical groups, numerous physicians and academic researchers, many public health organizations, some State and local agencies, five State Attorneys General, and a large number of individual commenters. These commenters disagreed with the Agency’s proposed decision and argued that EPA should lower the level of the 24

- hour standard to 30 or 25 μg/m 3 . Commen ts from these groups

on the level of the 24

- hour PM 2.5 standard are a ddressed below and in the Response to Comments Document
. As noted above, o f the public commenters who addressed the level of the 24

- hour PM 2.5 standard, all industry commenters and most S tate and l ocal commenters supported the proposed decision to retain the current level of 35 g/m 3 . In many cases, these groups agreed with the rationale supporting the Administrator’s proposed decision to retain the current 24

- hour PM 2.5 standard, includin g her emphasis on the annual standard as the generally controlling standard with the 24

- hour standard providing supplementary protection, and her conclusion that multi

- city, short

- term exposure studies provide the strongest data set for informing decisions on the appropriate 24

- hour standard level. Many of these commenters agreed with the Administrator’s view that the single

- city, short

- term studies provided a much more limited data set (e.g., limited statistical power, limited exposure data) and more equiv ocal results (e.g., mixed results within the same study area), making them an unsuitable basis for setting the level of the 24

- hour standard. While these commenters agreed with the EPA’s proposed decision to retain the current 24

- hour PM 2.5 standard, some did not agree with the EPA’s approach to considering the evidence from short

- term multi

- city studies. For example, a commenter representing UARG pointed out that the 98 th percentile concentrations reported in the***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 266 of 790 Formatted: Left proposal for multi

- city studies reflect th e averages of 98 th percentile concentrations across the cities included in those studies (UARG, 2012; Attachment 1; p. 25). This commenter contended that such averaged 98 th percentile PM 2.5 concentrations do not provide information that can appropriately inform a decision on the adequacy of the public health protection provided by the current or alternative 24

- hour standards. While the EPA agrees that there is uncertainty in linking effect s reported in multi

city studies to specific air quality concentrations (U.S. EPA, 2011 2011a , section 2.3.4.1), the EPA disagrees with this commenter’s view that such uncertainty precludes the use of averaged 98 th percentile PM 2.5 concentrations to inform a decision on the appropriateness of the protection provided by the 24

- hour PM 2.5 standard. In particular, the EPA notes that averaged 98 th percentile concentrations do provide information on the extent to which study cities contributing to reported associ ations would likely have met or violated the current 24

- hour PM 2.5 standard during the study period. As evidence of this, the EPA notes the three multi

- city studies specifically highlighted by this commenter as having averaged 98 th percentile 24

- hour PM 2.5 concentrations below 35 g/m 3 (Dominici et al., 2006 2006a ; Bell et al., 2008; Zanobetti and Schwartz, 2009). Based on the 98 th percentiles of 24

- hour PM 2.5 concentrations in the individual cities evaluated in these studies, the EPA notes that the majority of these study cities would likely have met the current standard during the study periods (Hassett

- Sipple et al., 2010). Therefore, regardless of whether the averaged 98 th percentile concentrations or the 98 th percentile concentrations in each city are co nsidered, these studies provide evidence for associations between short

- term PM 2.5 and mortality or morbidity across a large number of U.S. cities, the majority of which would likely have met the current 24

- hour PM 2.5 standard during***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 267 of 790 Formatted: Left study periods. In thei r review of the PM Policy Assessment, CASAC endorsed the conclusions drawn from analyses of averaged 98 th percentile 24

- hour PM 2.5 concentrations, and the EPA continues to conclude that this type of information can appropriately inform the Administrator’s decision on the current 24

- hour PM 2.5 standard. 111 A nother group of commenters argued that the 24

- hour standard level should be lowered . Many of these commenters supported setting the level of the 24

- hour PM 2.5 standard at either 25 or 30 g/m 3 . In support of their position, the ALA et. al. , AHA et al., five state Attorneys General, and a number of additional groups pointed to 98 th percentile PM 2.5 concentrations in locations of multi

- city and single

- city epidemiological studies. For example, the ALA and oth ers pointed to multi

- city studies by Dominici et al. ( 2006 2006a ), Zanobetti and Schwartz (2009), Burnett et al. (2000), and Bell et al. (2008) as providing evidence for associations with mortality and morbidity in study locations with averaged (i.e., avera ged across cities) 98 th percentile 24

- hour PM 2.5 concentrations below 35 g/m 3 . These commenters also pointed to several single

- city and panel studies reporting associations between short

- term PM 2.5 and mortality or morbidity in locations with relatively l ow 24

- hour PM 2.5 concentrations. Because some of these multi

- and single

- city studies have reported associations with health effects in locations with 98 th percentile PM 2.5 concentrations below 35 g/m 3 , commenters maintained that the current

111 This is not to say that the EPA’s decision on whether to revise the 24

- hour PM 2.5 standard should be based on or only be informed by considerations of whether studies reported associations with mortality or morbidity in areas with averaged 98 th percentile PM 2.5 concentrations less than 35 mg/m 3 . As discussed below, in reaching a decisi on in this final notice on the most appropriate approach to strengthen the suite of PM 2.5 standards, the Administrator considers the degree of public health protection provided by the combination of the annual and 24

- hour standards together.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 268 of 790 Formatted: Left
24

- hour PM 2.5 standard (i.e., with its level of 35 g/m 3 ) does not provide an appropriate degree of protection in all areas. In further support of their position that the level of the current 24

- hour standard should be lowered , these commenters pointed out the variabil ity across the U.S. in ratios of 24

- hour to annual PM 2.5 concentrations. They noted that some locations, including parts of the northwestern U.S., experience relatively low annual PM 2.5 concentrations but can experience relatively high 24

- hour concentratio ns at certain times of the year. In order to provide protection against effects associated with short

- term PM 2.5 exposures, especially in locations with high ratios of 24

- hour to annual PM 2.5 concentrations, these commenters advocated setting a lower level for the 24

- hour standard. The EPA agrees with these commenters that it is appropriate to maintain a 24

- hour PM 2.5 standard in order to supplement the protection provided by the revised annual standard, particularly in locations with relatively high ratio s of 24

- hour to annual PM 2.5 concentrations. However, in highlighting 98 th percentile PM 2.5 concentrations in study locations without also considering the impact of a revised annual standard on short

- term concentrations, these commenters ignore the fact th at many areas would be expected to experience decreasing short

- and long

- term PM 2.5 concentrations in response to a revised annual standard. In considering the specific multi

- city studies highlighted by public commenters who advocated a more stringen t 24

- hour standard, the EPA notes that such studies have reported consistently positive and statistically significant associations with short

- term PM 2.5 exposures in locations with averaged 98 th percentile PM 2.5 concentrations ranging from 45.8 to 34.2 μg/m 3 a nd long

- term mean PM 2.5 concentrations rang ing from 13.4 to***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 269 of 790 Formatted: Left 12.9 (Burnett and Goldberg, 2003; Burnett et al., 2004; Dominici et al., 2006 a ; Bell et al., 2008; Franklin et al., 2008; Zanobetti and Schwartz, 2009). 112 The EPA notes that to the extent air quali ty distributions are reduced to meet the current 24

- hour standard with its level of 35 g/m 3 and/or the revised annual standard with its level of 12 g/m 3 , additional protection would be anticipated against the effects reported in these short

- term , multi

- city studies. Put another way, to attain an annual standard with a level below the long

- term means in the locations of these short

- term studies (as EPA is adopting here), the overall air quality distributions in the majority of study cities will nec essarily be reduced, resulting in lower daily PM 2.5 ambient concentrations. We therefore expect that the revised annual standard will result in 98 th percentile PM 2.5 concentrations in these cities that are lower than those measured in the studies, and that the overall distributions of PM 2.5 concentrations will be lower than those reported to be associated with health effects. Thus, even for effects reported in multi

- city studies with averaged 98 th percentile concentrations below 35 μ g/m 3 , additional protect ion from the risks associated with short

- term exposures is anticipated from the revised annual standard, without revising the 24

- hour standard, because long

- term average PM 2.5 concentrations in multi

- city study

112 Commenters a lso highlighted associations with short

- term PM 2.5 concentrations reported in sub

- analyses restricted to days with 24

- hour concentrations at or below 35 g μ g /m 3 (Dominici, 2006b). These sub

- analyses were not included in the original publication by Dominici et al. (2006a). Authors provided results of sub

- analyses for the Administrator’s consideration in a letter to the docket following publication of the proposed rule in January 2006 (personal communication with Dr. Francesca Dominici, 2006b). As noted in se ction III.A.3, these sub

- analyses are part of the basis for the conclusion that there is no evidence suggesting that risks associated with long

- term exposures are likely to be disproportionately driven by peak 24

- hour concentrations. Because the sub

- analys es did not present long

- term average PM 2.5 concentrations, it is not clear whether they reflected PM 2.5 air quality that would have been allowed by the revised annual PM 2.5 standard being established in this notice.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 270 of 790 Formatted: Left locations were above the level of the revised annual standard (i.e., 12 μ g/m 3 ). 113 As discussed above, reducing the annual standard is the most efficient way to reduce the risks from short

- term exposures identified in these studies, as the bulk of the risk comes from the large number of days across the bulk of the air quality distribution, not the relatively small number of days with peak concentrations. In considering the single

- city studies highlighted by public commenters who advocated a more stringen t 24

- hour standard, the EPA first notes that, ove rall, these single

- city studies reported mixed results. Specifically, some studies reported positive and statistically significant associations with PM 2.5 , some studies reported positive but

non - significant associations, and several studies reported negati ve associations or a mix of positive and negative associations with PM 2.5 . In light of these inconsistent results, the proposal noted that the overall body of evidence from single

- city studies is mixed, particularly in locations with 98 th percentile s of 24

- hour concentrations below 35 μg/m 3

. Therefore, a lthough some single

- city studies report ed effects at appreciably lower PM 2.5 concentrations than short

- term multi

- city studies, the uncertainties and limitations associated with the single

- city studies were noted to be greater . In light of these greater uncertainties and limitations, the Administrator concluded in the proposal that she had less confidence in using these studies as a basis for setting the level of the standard (77 FR 38943). Given the conside rations and conclusions noted above, in the proposal the

113 It is also the case that additional pr otection is anticipated in locations with 98 th percentile 24

- hour PM 2.5 concentrations above 35 μg/m 3 , even if long

- term concentrations are below 12 μg/m 3 . As noted in the proposal and in the Policy Assessment (U.S. EPA, 2011 2011 a , Figure 2

- 10), parts of t he northwestern U.S. are more likely than other parts of the country to violate the 24

- hour standard and meet the revised annual standard.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 271 of 790 Formatted: Left Administrator concluded that the short

- term multi

- city studies provide the strongest evidence to inform decisions on the level of the 24

- hour stan dard. F urther , she viewed single

- city, short

- term exp osure studies as a much more limited data set providing mixed results, and she had less confidence in using these studies as a basis for setting the level of a 24

- hour standard (77 FR 38942)
. . In highlighting specific single

- city studies, public health, en vironmental, and State and local commenters appear to have selectively focused on studies reporting associations with PM 2.5 and to have overlooked studies that reported more equivocal results (e.g., Ostro et al., 2003; Rabinovitch et al., 2004; Slaughter e t al., 2005; Villeneuve et al., 2006) (U.S. EPA, 2011, Figure 2

- 9). As such, these commenters have not presented new information that causes the EPA to reconsider its decision to emphasize multi

- city studies over single

- city studies when identifying the ap propriate level of the 24

- hour PM 2.5 standard. In further considering the single

- city studies highlighted by public commenters, the EPA notes that some commenters advocating for a lower level for the 24

- hour PM 2.5 standard also discussed short

- term studies that have been published since the close of the Integrated Science Assessment. These recent studies were conducted in single cities or in small panels of volunteers. As in prior NAAQS reviews and as discussed above in more detail (section II.B.3) , the EPA is basing its decisions in this review on studies and related information assessed in the Integrated Science Assessment. The studies assessed in the Integrated Science Assessment, and the conclusions based on those studies, have undergone extensive critic al review by the EPA, CASAC, and the public. The rigor of that review makes the studies assessed in the Integrated Science Assessment, and the conclusions based on those studies, the most reliable source of scientific information on***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 272 of 790 Formatted: Left which to base decisions on the NAAQS. However, as discussed above (section II.B.3) , the EPA recognizes that ‘‘new studies” may sometimes be of such significance that it is appropriate to delay a decision on revision of a NAAQS and to supplement the pertinent air quality criteri a so the studies can be taken into account. In the present case, the EPA’s provisional consideration of ‘‘new studies” concludes that, taken in context, the “new” information and findings do not materially change any of the broad scientific conclusions made in the air quality criteria regarding the health effects of PM 2.5 ( U.S. EPA , 2012a 2012 b ). For this reason, reopening the air quality criteria review would not be warranted , even if there were time to do so under the court order governing the schedule for completing this review . Accordingly, the EPA is basing its final decisions in this review on the studies and related information included in the PM Integrated Science Assessment (i.e., the air quality criteria) that has undergone CASAC and public revi ew. The EPA will consider the “new studies” in the next periodic review of the PM NAAQS, which will provide an opportunity to fully assess these studies through a more rigorous review process involving the EPA, CASAC, and the public. Some p ublic health, m edical , and env ironmental commenters also criticized the EPA’s interpretation of PM 2.5 risk results. These commenters presented risk estimates for combinations of annual and 24

- hour standards using more recent air quality data than that used in the EPA’s Risk Assessment (U.S. EPA, 2010a). Based on these additional risk analyses, the ALA and other commenters contended that public health benefits could continue to increase as annual and 24

- hour standard levels decrease below 13 g/m 3 and 35 g/m 3 , respectively
.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 273 of 790 Formatted: Left The EPA agrees with commenters that important public health benefits are expected as a result of revising the level of the annual standard to 12 g/m 3 , as is done in this notice, rather than 13 g/m 3 . The Agency also acknowledges that estimated PM 2.5 - associated health risks continue to decrease with annual standard levels below 12 g/m 3 and/or with 24

- hour standard levels below 35 g/m 3 . However, the EPA disagrees with the commenters’ views regarding the extent to which risk estimates support setting standard levels below 12 μg/m 3 (annual standard) and 35 g/m 3 (24

- hour standard). 114 The CAA charges the Administrator with setting NAAQS that are “requisite” (i.e., neither more nor less stringent than necessary) to protect public health with an adequate margin of safety . In setting such standards the Administrator must weigh the available sc ientific evidence and information, including associated uncertainties and limitations . As described above, in reaching her proposed decisions on the PM 2.5 standards that would provide “requisite” protection , the Administrator carefully considered the avail able scientific evidence and risk information , making public health policy judgments that , in her view, neither overstate d nor understate d the strengths and limitations of that evidence and information. In contrast, a s discussed more fully above , public he alth, medical, and environmental commenters who recommended levels below 35 g/m 3 for the 24

- hour PM 2.5 standard have not provided new information or analyses to suggest that such standard levels are appropriate, given the uncertainties and limitations in the available health evidence , particularly uncertainties in studies conducted in locations with 98 th percentile 24

- hour PM 2.5 concentrations below 35 g/m 3 and long

- term average concentrations below 12 g/m 3

. 114 This section focuses on the 24

- hour standard. Section III.E.4.c.i above also discusses these commenters’ recommenda tions within the context of the annual PM 2.5 standard.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 274 of 790 Formatted: Left d. A dministrator’s Final Conclusions on the Primary PM 2.5 Standard Levels In reaching her conclusions regarding appropriate standard levels, the Administrator has considered the epidemiological and other scientific evidence, estimates of risk reductions associ ated with just meeting alternative annual and/or 24

- hour standards, air quality analyses, related limitations and uncertainties, the advice of CASAC, and extensive public comments on the proposal. After careful consideration of all of these, the Administra tor has decided to revise the level of the primary annual PM 2.5 standard from 15.0 μg/m 3 to 12.0 μg/m 3 and to retain the level of the primary 24

- hour standard at 35 μg/m 3

. As an initial matter, the Administrator agrees with the approach supported by CASAC and discussed in the Policy Assessment as summarized in sections III.A.3 and III.E.4.a above, of considering the annual and 24

- hour standards together in determining the protection afforded against mortality and morbidity effects associated with both long

and short

- term exposures to PM 2.5 . This approach is consistent with the approach taken in the review completed in 1997, in contrast to the approach used in the review completed in 2006 where each standard was considered independently of the other (i.e., o nly data from long

- term exposure studies were used to inform the level of the annual standard and only data from short

- term exposure studies were used to inform the level of the 24

- hour standard). 115 Based on the evidence and quantitative risk assessment, the Administrator concludes that it is appropriate to set an annual standard that is generally controlling, which will lower the broad distribution of 24

- hour average concentrations in an area as well as the annual average concentration, so as to provide p rotection from both long

- and
115 See 71 FR 61148 and 61168, October 17, 2006.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 275 of 790 Formatted: Left short

- term PM 2.5 exposures. In conjunction with this, it is appropriate to set a 24

- hour standard focused on providing supplemental protection, particularly for areas with high peak

- to
- mean ratios of 24

- hour concentrations, po ssibly associated with strong local or seasonal sources, and for PM 2.5 - related effects that may be associated with shorter

- than daily exposure periods. The Administrator concludes this approach will reduce aggregate risks associated with both long

- and sho rt
- term exposures more consistently than a generally controlling 24

- hour standard and is the most effective and efficient way to reduce total PM 2

- 5 - related population risk and so provide appropriate protection to protect public health with an adequate margi n of safety
. Based In selecting the level of the annual PM 2.5 standard, b ased on the characterization and assessment of the epidemiological and other studies presented and assessed in the Integrated Science Assessment and the Policy Assessment, the Administrator recognizes the substantial increase in the number and diversity of stu dies available in this review , including . This expanded body of evidence includes extended analyses of the seminal studies of long

- term PM 2.5 exposures (i.e., ACS and Harvard Six Cities studies) as well as important new long

- term exposure studies (as summa rized in Figures 1 and 2). Collectively, the Administrator notes that these studies, along with evidence available in the last review, provide consistent and stronger evidence than previously observed of an association between long

- term PM 2.5 exposures and premature mortality in areas with lower long

- term ambient concentrations than previously observed, with the strongest evidence related to cardiovascular

- related mortality. The Administrator also recognizes the availability of stronger evidence of morbidit y effects associated with long

- term PM 2.5 exposures, including evidence of respiratory effects such as decreased***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 276 of 790 Formatted: Left lung function growth, from the extended analyses for the Southern California Children’s Health Study and evidence of cardiovascular effects fro m the WHI study. Furthermore, the Administrator recognizes new U.S. multi

- city studies that greatly expand and reinforce our understanding of mortality and morbidity effects associated with short

- term PM 2.5 exposures, providing stronger evidence of associa tions in areas with ambient concentrations similar to those previously observed in short

- term exposure studies considered in the previous review (as summarized in Figure 3). The Administrator recognizes the strength of the scientific evidence for evaluati ng health effects associated with fine particles, noting that the newly available scientific evidence builds upon the previous scientific data base to provide evidence of generally robust associations and a basis for greater confidence in the reported asso ciations than in the last review. She notes the conclusion of the Integrated Science Assessment that this body of evidence supports a causal relationship between long

- and short

- term PM 2.5 exposures and mortality and cardiovascular effects and a likely cau sal relationship between long

- and short

- term PM 2.5 exposures and respiratory effects. In addition, the Administrator notes additional, but more limited evidence, for a broader range of health endpoints including evidence suggestive of a causal relationshi p for developmental and reproductive effects as well as for carcinogenic effects. Based on information discussed and presented in the Integrated Science Assessment, the Administrator recognizes that health effects may occur over the full range of concentra tions observed in the epidemiological studies of both long

- term and short

- term exposures, since no discernible population

- level threshold for any such effects can be identified based on the currently available evidence (U.S. EPA, 2009a, section***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 277 of 790 Formatted: Left 2.4.3). To inform her decisions on an appropriate level for the annual standard levels that will protect public health with an adequate margin of safety, in the absence of any discernible population

- level thresholds, the Administrator judges that it is appropriate to consider the relative degree to which the evidence of an association confidence in the magnitude and significance of the associations observed in an epidemiological study is supported stud ies across the range of long

- term PM 2.5 concentrations in the study, a nd therefore the degree to which the study provides confidence in the effects across this range of concentrations such studies . Further, she recognizes, in taking note of CASAC advice and the distributional statistics analysis discussed in the Policy Assess ment and in section III.E.4.a above, that there is significantly greater confidence in the magnitude and significance of observed associations for certain parts the part of the air quality distribution corresponding to where the bulk of the health events ev aluated in each study have been observed
. , generally at and around the long

- term mean concentrations
. Conversely, she also recognizes that there is significantly diminished confidence in the magnitude and significance of observed associations in the lowest low er part of the air quality distribution corresponding to where a relatively small proportion of the health events were observed. Based on the above considerations, the Administrator takes into account information that characterizes the part of the air q uality distributions that corresponds to the large proportion of health event data that was most influential in defining the association between PM 2.5 and the health endpoints evaluated in each study. In so doing Further , the Administrator recognizes that the long

- term mean concentrations, or any other specific point in the air quality distribution of each study, do not represent a “bright line” at and above which effects have been observed and below***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 278 of 790 Formatted: Left which effects have not been observed. As just noted, no discernible population

- level threshold for any such effects can be identified based on the currently available evidence. The Administrator notes that the concentrations at and around the long

- term mean concentrations, for both the long

- and short

- term expo sure studies, represents a part of the air quality distribution in which the health event data in any given study are generally most concentrated and, thus, where these data have the most influence on the magnitude and significance of the association obser ved in such study. The Administrator notes that long

- term mean PM 2.5 concentrations are generally available for each published study and, therefore, represent the most comprehensive data set to inform her decisions on the appropriate annual standard level. Nonetheless, in I n considering the long

- term mean concentrations reported in epidemiological studies, the Administrator recognizes that in setting an selecting a level of the annual standard level that will protect public health with an adequate margin of safety , it is not sufficient to focus on a concentration generally somewhere within the range of long

- term mean concentrations from the key long

- term and short

- term exposure studies that reported lower concentrations than had been observed in earlier revi ews. These key studies provide information for various types of serious health endpoints (including mortality and morbidity effects), different study populations (which may include at

- risk populations such as children and older adults), and different air q uality distributions that are specific to each study. A level somewhere within the range of long

term mean concentrations of the full set of key studies would be higher than the long

term mean of at least one of the studies being considered and therefore w ould fail to protect not provide a sufficient degree of protection against the health effects associated***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 279 of 790 Formatted: Left with the air quality distribution observed in that study. Absent some reasoned basis to place less weight on the evidence in the epidemiological study wi th the lowest long

- term mean concentration among these key studies, this approach would fail to provide sufficient protection not be consistent with the requirement to set a standard that will protect public health with an adequate margin of safety. 116 Thus, the Administrator recognizes it is important to protect against the serious effects observed in each of these studies
. so as to protect public health with an adequate margin of safety
. In so doing, she looks to identify the study with the lowest long

- term mean concentration within the full set of key studies to help inform her decision of the appropriate standard level which will provide protection for the broad array of health outcomes observed in all of the studies, including effects observed in at

- risk p opulations. Further, consistent with the general approach summarized in section III.E.4.a above and supported by CASAC as discussed in section III.E.4.b.ii above, the Administrator recognizes that it is appropriate to consider a level for an annual standar d that is not just at but rather is somewhat below the long

- term mean PM 2.5 concentrations reported in each of the key long

- and short

- term exposure studies. In so doing, she focuses especially on multi

- city studies that evaluated health endpoints for which the associations are causal or likely causal (i.e., mortality and cardiov ascular and respiratory effects associated with both long

- and short

- term PM 2.5 exposures). As discussed above, the importance of considering a level somewhat below the lowest long

- term mean concentrations in this set of key studies is to establish a stand ard that would be protective against the observed effects in all of the studies, and that takes into account the relative

116 See American Farm Bureau Federation v. EPA , 559 F. 3d 512, 525

- 26 (D.C. Cir. 2009). Formatted: Font: 12 pt***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 280 of 790 Formatted: Left degree of confidence in the magnitude and significance of observed associations across the air quality distributions in these studies. The Administrator recognizes that there is no clear way to identify how much below the long

- term mean concentrations of key studies to set a standard that would provide requisite protection with an adequate margin of safety. She therefore must use her ju dgment to weigh the available scientific and technical information, and associated uncertainties, to reach a final decision on the appropriate standard level. In considering the information in Figures 1

- 4 for effects classified as having evidence of a ca usal or likely causal relationship with long

- or short

- term PM 2.5 exposures, she observes a cluster of short

- term exposure studies with long

- term mean concentrations within a range of 13.4 μg/m 3 down to 12.8 μg/m 3 (Dominici et al., 2006 2006 a ; Burnett and Go ldberg, 2003; Zanobetti and Schwartz, 2009; Bell et al., 2008; Burnett et al., 2004). She also observes a cluster of long

- term exposure studies with long

- term mean concentrations within a range of 14.5 μg/m 3 to 13.6 μg/m 3 (Dockery et al., 1996; Lipfert et al., 2006 2006 a ; Zeger et al., 2008; McConnell et al., 2003; Goss et al., 2004; Eftim et al., 2008). For the reasons discussed in response to public comments in section III.E.4.c above, the Administrator is less influenced by the long

- term mean PM 2.5 concen trations from the Miller et al. (2007) and Krewski et al. (2009) studies with reported long

- term mean PM 2.5 concentrations of 12.9 and 14.0 μg/m 3 , respectively. In each case, the most relevant exposure periods would likely have had higher mean PM 2.5 concen trations than those reported in the studies. 117 Thus, the Administrator considers the long

- term mean PM 2.5 concentrations from these

117 In the case of Miller et al. (2007), the mean concentration is based on a single year of air quality data which post

- dated by two years the period for which the health events data were collected. In the case of Krewski et al. (2009),the air quality data w ere based on the last two years of the 18

- year period for which the health event data were collected. Formatted: Font: 12 pt***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 281 of 790 Formatted: Left two studies to be a highly uncertain basis for informing her selection of the annual standard level. 118 To help guide her judg ment of the appropriate level below the long

- term mean concentrations in the epidemiological studies at which to set the standard, the Administrator considered additional information from epidemiological studies concerning the broader distribution of PM 2.5 concentrations which correspond to the health events observed in these studies (e.g., deaths, hospitalizations). The Administrator observes that the development and use of this information in considering standard levels is consistent with CASAC’s advice, as discussed in section III.E.4.b.ii above, to focus on understanding the concentrations that were most influential in generating the health effect estimates in individual studies (Samet, 2010d, p. 2). In considering this additional population

- level infor mation, the Administrator recognizes that, in general, the confidence in the magnitude and significance of an association identified in a study is strongest at and around the long

- term mean concentration for the air quality distribution, as this represents the part of the distribution in which the data in any given study are generally most concentrated. She also recognizes that the degree of confidence decreases as one moves towards the lower part of the distribution. Consistent with the approach used in th e Policy Assessment, the Administrator believes that the range from approximately the 25 th to 10 th percentiles is a reasonable range for providing a general frame of reference as to the part of the distribution in which her confidence in the associations observed in epidemiological

118 Nonetheless, as noted above, the EPA notes that the Krewski et al. (2009) and Miller et al. (2007) studies provide strong evidence of mortality and car diovascular

- related effects associated with long

- term PM 2.5 exposures to inform causality determinations reached in the Integrated Science Assessment (U.S. EPA, 2009a, sections 7.2.11 and 7.6).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 282 of 790 Formatted: Left studies becomes is appreciably lower. However , as noted above , it is imp ortant to emphasize that there is no clear dividing line or single percentile within a given distribution provided by the scientific evidence that is most appropriate or ‘correct’ to use to characterize where the degree of confidence in the associations wa rrants setting the annual standard level. The decision of the appropriate standard level below the long

- term mean concentrations of the key studies , which in conjunction with the other elements of the standard would protect public health with an adequate m argin of safety, is largely a public health policy judgment, taking into account all of the evidence and its related uncertainties. As discussed in section III.E.4.b, the Administrator takes note of additional population

- level data that were made availabl e to the EPA by study authors. 119 In considering this information, the Administrator particularly focuses on the analysis of the distributions of the health event data for each area within these studies and the corresponding air quality data for the two shor t
- term exposure studies (Zanobetti and Schwartz, 2009; Bell et al., 2008). These short

- term exposure studies evaluate the relationship between daily changes (one or more days) in PM 2.5 concentrations and daily changes in health events (e.g., deaths, hospit alizations), such that the air quality concentrations that comprise the most relevant exposure periods in these studies are

119 As summarized in section III.E.4.a, population

- level data w ere provided to the EPA for four studies. These four studies represent some of the strongest evidence showing associations between health effects and PM 2.5 within the overall body of scientific evidence and include three studies (Krewski et al., 2009; Bell et al., 2008; and Zanobetti and Schwartz, 2009) that were used as the basis for concentration

- response functions in the quantitative risk assessment (U.S. EPA, 2010a, section 3.3.3). T he Administrator recognizes that the additional population

- level data a vailable for these four multi

- city studies represents a more limited data set compared to the set of long

- term mean PM 2.5 concentrations which were available in the published literature for all studies considered in the Integrated Science Assessment. Formatted: Font: 12 pt***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 283 of 790 Formatted: Left contemporaneous with the health event data. In addition, these studies considered more recent air quality data, representing general ly lower PM 2.5 concentrations, in a large number of study areas across the U.S. Thus, such studies provide the most useful evidence for an analysis evaluating the distribution of health event data and the corresponding long

- term mean PM 2.5 concentrations a cross the areas included in each multi

- city study. The Administrator also considered the additional population

- level data that were made available to EPA for two long

- term exposure studies (Krewski et al., 2009; Miller et al., 2007). She re cognizes that i n long

- term exposure studies investigators follow a specific group of study participants (i.e., cohort) over time and across urban study areas, and evaluate how PM 2.5 concentrations averaged over a period of years are associated with specific health endpoi nts (e.g., deaths) across cities. As discussed in response to public comments in section III.E.4.c, disentangling the effects observed in long

- term exposure studies associated with more recent air quality measurements from effects that may have been associ ated with earlier, and most likely higher, PM 2.5 exposures introduces some uncertainty with regard to understanding the appropriate exposure window associated with the observed effects. This is in contrast to the short

- term exposure studies where the relev ant exposure period is contemporaneous to the period for which the health data were collected. In light of these considerations, as noted above, the Administrator considers the analysis of air quality concentrations that correspond to the distribution of p opulation

- level data in these two studies to be a highly uncertain basis for informing her selection of the annual standard level. Based on the above considerations, the Administrator views the additional***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 284 of 790 Formatted: Left population

- level data for the two short

- term expos ure studies as appropriate to help inform her judgment of how much below the long

- term mean concentrations to set the level of the annual standard. The Administrator notes that the long

- term mean PM 2.5 concentrations corresponding with study areas contribu ting to the 25 th and 10 th percentiles of the distribution of deaths and cardiovascular

- related hospitalizations in these two short

- term exposure studies were 12.5 μg/m 3 and 10.3 11.5 μg/m 3 , respectively, for Zanobetti and Schwartz (2009 ), ) and 11.5 μg/m 3 and 9.8 μg/m 3 , respectively, for Bell et al. (2008 ) (Figure 5 above; Rajan et al., 2011, Table 1). ) , with the 10 th percentiles being lower by approximately 2 μg/m 3 in each study.
. The Administrator recognizes, as summarized in section III.B above and discussed more fully in section III.B.2 of the proposal, that important uncertainties remain in the evidence and information considered in this review of the primary fine particle standards. These uncertainties are generally related to understanding the re lative toxicity of the different components in the fine particle mixture, the role of PM 2.5 in the complex ambient mixture, exposure measurement errors, and the nature and magnitude of estimated risks related to increasingly lower ambient PM 2.5 concentrati ons. Furthermore, the Administrator notes that epidemiological studies have reported heterogeneity in responses both within and between cities and geographic regions across the U.S. She recognizes that this heterogeneity may be attributed, in part, to diff erences in fine particle composition in different regions and cities. 120

120 No netheless, as explained in section III.E.1, the currently available evidence is not sufficient to support replacing or supplementing the PM 2.5 indicator with any other indicator defined in terms of a specific fine particle component or group of components associated with any source categories of fine particles. Furthermore, the evidence is not sufficient to support eliminating any component or group of components associated with any source categories of fine particles from the mix of fine particles included in the PM 2.5 Formatted: Font color: Black

Formatted: Font: 12 pt***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 285 of 790 Formatted: Left With regard to evidence for reproductive and developmental effects identified as being suggestive of a causal relationship with long

- term PM 2.5 exposures, the Administrator recognizes t hat t here are a number of limitations associated with this body of evidence including: the limited number of studies evaluating such effects; uncertainties related to identifying the relevant exposure time periods of concern; and limited toxicological evid ence providing little information on the mode of action(s) or biological plausibility for an association between long

- term PM 2.5 exposures and adverse birth outcomes. Nonetheless, the Administrator believes that this more limited body of evidence provides some support for considering that serious effects may be occurring in a susceptible population at concentrations lower than those associated with effects classified as having a causal or likely causal relationship with long

- term PM 2.5 exposures (i.e., mort ality, cardiovascular, and respiratory effects). Overall, the Administrator believes that the available evidence interpreted in light of the remaining uncertainties, as summarized above and discussed more fully in the Integrated Science Assessment and the Policy Assessment, provides increased confidence relative to information available in the last review and provides a strong basis for informing her final decisions in the current review. The Administrator is mindful that considering what standards are requ isite to protect public health with an adequate margin of safety requires public health policy judgments that neither overstate nor understate the strength and limitations of the evidence or the appropriate inferences to be drawn from the evidence. In cons idering how to translate the available information into appropriate standard levels, the Administrator weighs the available scientific information and associated uncertainties and limitations. For the purpose of determining what annual indicator.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 286 of 790 Formatted: Left standard level is ap propriate the Administrator recognizes that there is no single factor or criterion that comprises the ‘‘correct’’ approach to weighing the various types of available evidence and information. In considering this information, the Administrator notes the adv ice of CASAC that “there are significant public health consequences at the current levels of the standards that justify consideration of lowering the PM 2.5 NAAQS further” (Samet, 2010c, p. 12). In addition, she recognizes that CASAC concluded, “although th ere is increasing uncertainty at lower levels, there is no evidence of a threshold (i.e., a level below which there is no risk for adverse effects)” (Samet, 2010 2010 d , p.ii) and that the final decisions on standard levels must reflect a judgment of the ava ilable scientific information with respect to her interpretation of the CAA’s requirement to set primary standards that provide requisite protection to public health with an adequate margin of safety (Samet, 2010d, p. 4). The Administrator recognizes CASAC ’s advice that the currently available scientific information provided support for considering an annual standard level within a range of 13 to 11 μg/m 3 and a 24

- hour standard level within a range of 35 to 30 μg/m 3 . In considering how the annual and 24

- hou r standards work together to provide appropriate public health protection, the Administrator observes that CASAC did not express support for any specific levels or combinations of standards within these ranges. She also notes that CASAC encouraged the EPA staff to consider additional data from epidemiological studies to help quantify the characterization of the PM 2.5 concentrations that were most influential in generating the health effect estimates in these studies (Samet, 2010d, p. 2). In response to CAS AC’s advice, the Administrator recognizes that the EPA staff***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 287 of 790 Formatted: Left acquired additional data from authors of key epidemiological studies and analyzed these data to characterize the distribution of PM 2.5 concentrations in relation to health events data to better u nderstand the degree of confidence in the associations observed in the studies as discussed above. The Administrator recognizes that the final Policy Assessment included consideration of these additional analyses in reaching final staff conclusions with re gard to the broadest range of alternative standard levels supported by the science. She takes note that the final Policy Assessment concluded that while alternative standard levels within the range of 13 to 11 μg/m 3 were appropriate to consider, the eviden ce most strongly supported consideration of an annual standard level in the range of 12 to 11 μg/m 3 . The Administrator is aware that, in transmitting the final Policy Assessment to CASAC, the Agency notified CASAC that the final staff conclusions reflected consideration of CASAC’s advice and that those staff conclusions were based, in part, on the specific distributional analysis that CASAC had urged the EPA to conduct (Wegman, 2011). Thus, CASAC had an opportunity to comment on the final Policy Assessment, but chose not to provide any additional comments or advice after receiving it. In selecting the annual standard level, the Administrator has considered many factors including the nature and severity of the health effects involved, the strength of the
ove rall body of scientific evidence as considered in reaching causality determinations, the size of the at

- risk populations, and the estimated public health impacts. She has also considered the kind and degree of the uncertainties that remain in the available scientific information. She recognizes that the association between PM 2.5 and serious health effects is well established, including at concentrations below those allowed by the current***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 288 of 790 Formatted: Left standard. Further, she recognizes the CAA requirement that requires primary standards to provide an adequate margin of safety was intended to address uncertainties associated with inconclusive scientific and technical information as well as to provide a reasonable degree of protection against hazards that research has not yet identified. In considering the currently available evidence, as summarized and discussed more broadly above, the information on risk, CASAC advice, the conclusions of the Policy Assessment, and public comments on the proposal, the Administrator strongl y believes that a lower annual standard level is needed to protect public health with an adequate margin of safety. In this instance, the association between PM 2.5 and serious health effects is well established, including at concentrations below those allo wed by the current standard. In reaching her final decision on the appropriate annual standard level to set, the Administrator is mindful that the CAA does not require that primary standards be set at a

zero - risk level, but rather at a level that reduces risk sufficiently so as to protect public health, including the health of at

- risk populations, with an adequate margin of safety. On balance, the Administrator concludes that an annual standard level of 12 μg/m 3 would be requisite to protect the public hea lth with an adequate margin of safety from effects associated with long

- and short

- term PM 2.5 exposures, while still recognizing that uncertainties remain in the scientific information. In the Administrator’s judgment, an annual standard of 12 μg/m 3 appro priately reflects placing greatest weight on evidence of effects for which the Integrated Science Assessment determined there is a causal or likely causal relationship with long

- and short

- term PM 2.5 exposures. An annual standard level of 12 μg/m 3 is below the long

- term mean PM 2.5 concentrations reported in each of the key multi

- city, long

- and short

- term***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 289 of 790 Formatted: Left exposures studies providing evidence of an array of serious health effects (e.g., premature mortality, increased hospitalization for cardiovascular and re spiratory effects). As noted above, the importance of considering a level somewhat below the lowest long

- term mean concentration in the full set of studies considered is to set a standard that would be protective provide appropriate protecti on against the o bserved effects in all such studies. In reaching her decision, the Administrator has taken into account that at and around the mean PM 2.5 concentration in any given study represents a part of the air quality distribution in which the health event data in that study are generally most concentrated. Furthermore, in identifying an appropriate annual standard level below the long

- term mean concentrations, she recognizes that there is no evidence to support the existence of any discernible threshold, and, there fore, she has a high degree of confidence that the observed effects are associated with concentrations not just at but extending somewhat below the long

- term mean concentration. To further inform her judgment in setting the annual standard level so as to p rotect public health with an adequate margin of safety , the Administrator has placed weight on additional population

- level information available from a subset of these epidemiological studies, consistent with CASAC advice. In particular, she has drawn from two short

- term exposure studies, which provide the most relevant information for evaluating the distribution of health events and corresponding long

- term PM 2.5 concentrations. As explained above, this provides information on helps inform her judgment as to the degree of confidence in the observed associations in the epidemiological studies. In this regard, the Administrator generally judges the region around the 25 th percentile as a reasonable part of the distribution to help guide her decision on the appro priate standard level. Since this evidence comes primarily***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 290 of 790 Formatted: Left from two studies, a relatively modest data set, the Administrator deems it reasonable not to draw further inferences from air quality and health event data in the lower part of the distribution for the purpose of setting a standard level. The Administrator notes that the long

- term mean PM 2.5 concentrations around the 25 th percentile of the distributions of deaths and cardiovascular

- related hospitalizations were approximately around 12 .5 μg/m 3 and 11.5 μg/m 3 in Zanobetti and Schwartz (2009) and in Bell et al. (2008), respectively (Figure 5; Rajan et al., 2011, Table 1). these two studies
. The Administrator views this information as helpful in guiding her determination as to where she continues t o have sufficient her confidence in the magnitude and significance of the associations to warrant setting an annual is reduced to such a degree that a standard set at a lower level would not be warrant ed to provide requisite protection that is neither more n or less than needed to provide an adequate margin of safety
. The Administrator also recognizes that a level of 12 μg/m 3 places some weight on studies which provide evidence of reproductive and developmental effects (e.g., infant mortality, low birth weight ). These studies were identified in the Integrated Science Assessment as having evidence suggestive of a causal relationship with long

- term PM 2.5 concentrations. A level of 12 μg/m 3 is approximately the same level as the lowest long

term mean concentration reported in such studies (Figures 2 and 4; 11.9 μg/m 3 for Bell et al., 2007). 121 While the Administrator acknowledges that this evidence is limited, she

121 With respect to cancer, mutagenic, and genotoxic effects, the Administrator observes that the PM 2.5 concentrations reported in studies evaluating these effects generally included ambient concentrations that are equal to or great er than ambient concentrations observed in studies that reported mortality and cardiovascular and respiratory effects (U.S. EPA, 2009a, section 7.5). Therefore, the Administrator concludes that in selecting alternative standard levels that provide protecti on from mortality and cardiovascular and respiratory effects, it is reasonable to anticipate that protection will also be provided for carcinogenic effects. Formatted: Font: 12 pt***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 291 of 790 Formatted: Left believes it is appropriate to place some weight on these studies in order to set a standard that provide s protection with an adequate margin of safety, including providing protection for at

- risk populations, as required by the CAA. Due to the limited nature of this evidence, she has determined it is not necessary to set a standard below the lowest long

- term mean concentration in these studies. In reflecting on extensive public comments received on the proposal as discussed in section III.E.4.c above, the Administrator recognizes that some commenters have offered different evaluations of the evidence and othe r information available in this review and would make different judgments about the weight to place on the relative strengths and limitations of the scientific information and about how such information could be used in making public health policy decision s on the annual standard level. One group of such commenters who supported a higher annual standard level (e.g., above 13 μg/m 3 ) would place greater weight on the remaining uncertainties in the evidence as a basis for discounting the overall strength of th e evidence supporting a higher standard level than the Administrator judges to be appropriate. Such an approach is based on these commenters’ judgment that the uncertainties remaining in the evidence are too great to warrant setting a lower a n annual standar d below the current level. The Administrator does not agree. As an initial matter, an annual standard level of 13 μg/m 3 or higher would be above the long

- term mean concentrations reported in two well

- conducted, multi

- city short

- term exposure studies reporting positive and statistically significant associations of serious effects (Burnett et al., 2004 and Bell et al., 2008) . These important studies are fully consistent with the pattern of evidence presented by the large body of evidence in***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 292 of 790 Formatted: Left this review. As the Administrator recognized in the proposal, and as advised by CASAC, the appropriate focus for selecting the level of t he annual PM 2.5 standard is on concentrations somewhat below the lowest long

- term mean concentrations from the set of key studies of both long

- term and short

- term PM 2.5 exposures considered by the EPA (i.e., as shown in Figure 4). Thus, a standard level se t at 13 μg/m 3 or higher would clearly not provide protection for the effects observed in the full set epidemiological studies and, therefore, this standard level could not be judged to be requisite with an adequate margin of safety. 122 In addition, as noted above, in recognizing that there is no evidence to support the existence of a discernible threshold below which an effect would not occur, the Administrator is mindful that effects occur around and below the long

- term mean concentrations reported in both the short

- term and long

- term the epidemiological studies. A standard level of 13 μg/m 3 or higher would place essentially no weight on not appropriately take into account evidence from the two well

- conducted, multi

- city, short

term exposure studies reporting serious effects with long

- term mean concentrations below 13 μg/m 3 noted above (Burnett et al, 2004; Bell et al., 2008). Such a standard level would also place essentially no weight on not appropriately take into account additional population

- level data fro m a limited number of epidemiological studies. This approach would ignore CASAC’s advice to consider such information in order to better understand

122 T he Administrator is mindful that, in reviewing the 2006 final PM NAAQS decisions, the D.C. Circu it Court of Appeals concluded that the EPA failed to adequately explain why that annual standard provided requisite protection from effects associated with both long

- and short

- term exposures or from morbidity effects in children and other at

- risk populati ons when long

- term means of important short

- term studies were below the level the Administrator selected for the annual standard. See American Farm Bureau v. EPA. 559 F. 3d 512, 524

- 26. There is no reasonable basis to discount these two studies for purpose s of setting the level of the annual standard. Formatted: Font: 12 pt***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 293 of 790 Formatted: Left the concentrations that were most influential in generating over which there is a high degree of confidence r egarding the health effect estimates magnitude and significance of the associations observed in individual epidemiological studies and where there is appreciably less confidence
. Furthermore, a standard level of 13 μg/m 3 or higher would place no weight on not appropriately take into account the more limited evidence of effects in some at

- risk populations (e.g., low birth weight). In the Administrator’s view, placing no weight on a standard set at this information level would fail to not provide protection with an adequate margin of safety, including providing protection for at

- risk populations. The Administrator is mindful that the CAA requirement that primary standards provide an adequate margin of safety, discussed in section II.A above, was intended to addre ss uncertainties associated with inconclusive scientific and technical information available at the time of standard setting as well as to provide a reasonable degree of protection against hazards that research has not yet identified. In light of the enti re body of evidence as discussed above, the Administrator judges that an annual standard level set above 12 μg/m 3 would not be sufficient to protect public health with an adequate margin of safety from the serious health effects associated with long

- and s hort

- term exposure to PM 2.5. The Administrator also recognizes that a second group of commenters supported a lower annual standard level (e.g., no higher than 11 μg/m 3 ). Such a standard level would reflect placing essentially as much weight on the relativ ely more limited data providing evidence suggestive of a causal relationship for effects observed in some at

- risk populations (e.g., low birth weight) as on more certain evidence of effects classified as***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 294 of 790 Formatted: Left having a causal or likely causal relationship with P M 2.5 exposures. In the Administrator’s view, while it is important to place some weight on such suggestive evidence, it would not be appropriate to place as much weight on it as the commenters would do. An annual standard level of 11 μg/m 3 would also reflect these commenters’ judgment that it is appropriate to focus on a lower part of the distributions of health event data from the small number of epidemiological studies for which this information was made available than the Administrator b elieves is warranted. In the Administrator’s view, using this type of information to set a standard level of 11 μg/m 3 or below would assume too high a degree of confidence in the magnitude and significance of the associations observed in the lower part of the distributions of health events observed in these studies. Given the uncertainties in the evidence and the limited set of studies for which the EPA has information on the distribution of health event data and corresponding air quality data, the Administ

rator believes it is not appropriate to focus on the lower part of the distributions of health events data. On balance, the Administrator finds that the available evidence interpreted in light of the remaining uncertainties does not justify a standard lev el set below 12 μg/m 3 as necessary to protect public health with an adequate margin of safety. After carefully considering the above considerations and the public comments summarized in section III.E.4.c above, the Administrator has decided to set the lev el of the primary annual PM 2.5 standard at 12 μg/m 3 . In her judgment, a standard set at this level provides the requisite degree of public health protection, including the health of at

risk populations, with an adequate margin of safety and is neither more nor less stringent than necessary for this purpose.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 295 of 790 Formatted: Left As discussed above, the Administrator concludes that an approach that focuses on setting a generally controlling annual standard is the most effective and efficient way to reduce total population risk as sociated with both long

- and short

- term PM 2.5 exposures. Such an approach would result in more uniform protection across the U.S. than the alternative of setting the levels of the 24

- hour and annual standard such that the 24

- hour standard would generally b e the controlling standard in areas across the country (see section III.A.3). The Administrator recognizes that potential air quality changes associated with meeting an annual standard level of 12.μg/m 3 will result in lowering risks associated with both l ong - and short

- term PM 2.5 exposures by lowering the overall air quality distribution. However, the Administrator recognizes that such an annual standard alone would not be expected to offer sufficient protection with an adequate margin of safety against th e effects of all short

- term PM 2.5 exposures . in all parts of the country
. As a result, in conjunction with an annual standard level of 12 μg/m 3 , the Administrator concludes that it is appropriate to continue to provide supplemental protection by means of a 24

- hour standard set at the appropriate level, particularly for areas with high peak

- to
mean ratios possibly associated with strong local or seasonal sources and for areas with PM 2.5 - related effects that may be associated with shorter

- than

- daily exposure periods. In selecting the level of a 24

- hour standard meant to provide such supplemental protection, the Administrator relies upon evidence and air quality information from key short

- term exposure studies. In considering these studies, the Administrator n otes that to the extent air quality distributions in the study areas considered are reduced to meet the current 24

- hour standard (at a level of 35 μg/m 3 ) or to meet the revised annual standard***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 296 of 790 Formatted: Left discussed above (at a level of 12 μg/m 3 ), additional protection would be anticipated against the effects observed in these studies. In light of this, when selecting the appropriate level for the 24

- hour standard, the Administrator considers both the 98 th percentiles of 24

- hour PM 2.5 concentrations and the long

- term me an PM 2.5 concentrations in the locations of the short

- term exposure studies. She notes that such consideration of both short

- and long

- term PM 2.5 concentrations can inform her decision on the extent to which a given 24

- hour standard, in combination with th e revised annual standard established in this notice, would provide protection against the health effects reported in short

- term studies. As discussed in section III.E.4.a above, the Administrator concludes that multi

city short

- term exposure studies provide the strongest data set for informing her decisions on appropriate 24

- hour standard levels. With regard to the limited number of single

- city studies that reported positive and statistically significant associations for a range of health endpoints related to short

- term PM 2.5 concentrations in areas that would likely have met the current suite of PM 2.5 standards, the Administrator recognizes that many of these studies had significant limitations (e.g., limited statistical power, limited exposure data) or equivocal results (mixed results within the same study area) that make them unsuitable to form the basis for setting the level of a 24

- hour standard. With regard to multi

- city studies that evaluated effects associated with short

- term PM 2.5 exposures, the Administrator observes an overall pattern of positive and statistically significant associations in studies with 98 th percentile 24

- hour val ues averaged across study areas within the range of 45.8 to 34.2 μg/m 3 (Burnett et al., 2004; Zanobetti and Schwartz, 2009; Bell et al., 2008; Dominici et al., 2006a, Burnett and***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 297 of 790 Formatted: Left Goldberg, 2003; Franklin et al., 2008). The Administrator notes that, to the extent air quality distributions are reduced to reflect just meeting the current 24

- hour standard, additional protection would be provided for the effects observed in the three multi

- city studies with 98 th percentile values greater than 35 μg/m 3 (Burnett e t al., 2004; Burnett and Goldberg, 2003; Franklin et al., 2008). In the three additional multi

- city studies with 98 th percentile values below 35 μg/m 3 , specifically 98 th percentile concentrations of 34.2, 34.3, and 34.8 μg/m 3 , the Administrator notes that these studies reported long

- term mean PM 2.5 concentrations of 12.9, 13.2, and 13.4 μg/m 3 , respectively (Bell et al., 2008; Zanobetti and Schwartz, 2009; Dominici et al., 2006a). In revising the level of the annual standard to 12 μg/m 3 , as discussed above, the Administrator recognizes that additional protection would be provided for the short

- term effects observed in these multi

- city studies such that revision to the 24

- hour standard would not be warranted. That is, by lowering the level of the annual standa rd to 12 μg/m 3 , the 98 th percentile of the distribution would be lowered as well such that additional protection from effects associated with short

- term exposures would be afforded. Therefore, the epidemiological evidence supports a conclusion that it is a ppropriate to retain the level of the 24

- hour standard at 35 μg/m 3 , in conjunction with a revised annual standard level of 12 μg/m 3

. In addition to considering the epidemiological evidence, the Administrator also has taken into account air quality informa tion based on county

- level 24

- hour and annual design values to understand the implications of revising the annual standard level from 15 to 12 μg/m 3 in conjunction with retaining the 24

- hour standard level at 35 μg/m 3 . She has considered this information t o evaluate the public health protection provided by the two standards in combination and to evaluate the most appropriate means of developing a***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 298 of 790 Formatted: Left suite of standards providing requisite public health protection with an adequate margin of safety. In consideri ng the air quality information, the Administrator observes that a suite of PM 2.5 standards that includes an annual standard level of 12 μg/m 3 and a 24

- hour standard level of 35 μg/m 3 would result in the annual standard as the generally controlling standard in most regions across the country, except for certain areas in the Northwest, where the annual mean PM 2.5 concentrations have historically been low but where relatively high 24

- hour concentrations occur, often related to seasonal wood smoke emissions (U. S. EPA, 2011a, pp. 2

- 89 to 2

- 91, Figure 2

- 10). In fact, these are the type of areas for which the supplemental protection afforded by the 24

- hour standard is intended, such that the two standards together provide the requisite degree of protection. The Adm inistrator concludes the current 24

- hour standard at a level of 35 μg/m 3 , in conjunction with a revised annual standard level of 12 μg/m 3 , will provide appropriate protection from effects observed in studies in such areas in which the long

- term mean
concen trations were below 12 μg/m 3 and the 98 th percentile 24

- hour concentrations were above 35 μg/m 3 (e.g., areas in the Northwest U.S.). After carefully taking the public comments and above considerations into account, the Administrator has decided to retain the current level of the primary PM 2.5 24

- hour standard at 35 μg/m 3 in conjunction with revising the annual standard level from 15.0 μg/m 3 to 12.0 μg/m 3

. 123 In the Administrator’s judgment, this suite of primary PM 2.5 standards and the rationale supporting t hese levels appropriately reflects consideration of the strength of the available evidence and other information and its associated
123 As noted in section II.B.1, Table 1 and section III.E.4.a above, the annual standard level is defined to one decimal place. Throughout this section, the annual standard levels discussed have been denoted as i nteger values (e.g., 12 μg/m 3 ) for simplicity. Formatted: Font: 12 pt***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 299 of 790 Formatted: Left uncertainties as well as the advice of CASAC and consideration of public comments. In the Administrator’s judgment, this sui te of primary PM 2.5 standards is sufficient but not more protective than necessary to protect the public health, including at

- risk populations, with an adequate margin of safety from effects associated with long

- and short

- term exposures to fine particles. This suite of stan dards will provide significant protection from serious health effects including premature mortality and cardiovascular and respiratory morbidity effects that are causally or likely causally related to long

- and short

term PM 2.5 exposures. These standards w ill also provide an appropriate degree of protection against other health effects for which there is more limited evidence of effects and causality, such as reproductive and developmental effects. This judgment by the Administrator appropriately considers the requirement for a standard that is requisite to protect public health but is neither more nor less stringent than necessary. 124 D. Administrator’s Final Decisions on Primary PM 2.5 Standards For the reasons discussed above, and taking into account the info rmation and assessments presented in the Integrated Science Assessment, Risk Assessment, and Policy Assessment, the advice and recommendations of CASAC, and public comments to date, the Administrator revises the current suite of primary PM 2.5 standards. S pecifically, the Administrator revises: (1) the level of the primary annual PM 2.5 standard to 12.0 μg/m 3 and (2) the form of the primary annual PM 2.5 standard to one based on the highest appropriate area

- wide monitor in an area, with no option for spatial averaging. In conjunction with revising the primary annual PM 2.5 standard to provide protection from effects associated with long

- and short

- term PM 2.5 exposures, the Administrator retains
124 The Administrator also judges that this suite of standards addresses the issues raised by the D.C. Circuit’s remand of the 2006 primary annual PM 2.5 standard by appropriately revising that standard. Formatted: Font: 12 pt***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 300 of 790 Formatted: Left the level of 35 μg/m 3 and the 98 th percentile form of the primary 2 4

- hour PM 2.5 standard to continue to provide supplemental protection for areas with high peak PM 2.5 concentrations. The Administrator is not revising the current PM 2.5 indicator or the annual and 24

- hour averaging times for the primary PM 2.5 standards. The Administrator concludes that this suite of standards would be requisite to protect public health with an adequate margin of safety against health effects potentially associated with long

- and short

- term PM 2.5 exposures. IV. Rationale for Final Decision on Pri mary PM 10 Standard Th is section presents the rationale for the Administrator’s final decision to retain the current 24

- hour primary PM 10 standard in order to continue to provide public health protection against short

- term exposures to inhalable particles in the size range of 2.5 to 10 μ m ( i.e., PM 10

- 2.5 or thoracic coarse particles). These are particles capable of reaching the most sensitive areas of the lung, including the trachea, bronchi, and deep lungs. The current st andard uses PM 10 as the indicator for thoracic coarse particles, and thus is referred to as a PM 10 standard. 125 As discussed more fully in the proposal and below, this rationale is based on a thorough review of the latest scientific evidence , published thr ough mid

- 2009 and assessed in the Integrated Science Assessment (U.S. EPA, 2009a) , evaluating human health effects associated with long

- and short

- term expo sures to thoracic coarse particles. The Administrator’s final decision also takes into account: (1) the EPA staff analyses of air quality information and health evidence and staff conclusions regarding the current and potential alternative standards, as presented in the Policy Assessment for the PM

125 Through out this section of the preamble, we are using the terms ‘thoracic coarse particles’, ‘inhalable coarse particles’, and ‘PM 10

- 2.5 ’ synonymously.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 301 of 790 Formatted: Left NAAQS (U.S. EPA , 2011 2011 a ); (2) CASAC advice and recommendations, as reflected in discussions at public meetings of drafts of the Integrated Science Assessment and Policy Assessment, and in CASAC’s letters to the Administrator; (3) the multiple rounds of public comments received d uring the development of the Integrated Science Assessment and Policy Assessment , both in connection with CASAC meetings and separately; and (4) public comments (including testimony at the public hearings) received on the proposal. In presenting the rationale for the final decision to retain the current primar y PM 10 standard, this section discusses the EPA’s past reviews of the PM NAAQS and the general approach taken to review the current standard (section I V .A), the health effects associated with ex posures to ambient PM 10

- 2.5 (section I V .B), the consideration of the current and potential alternative standards in the Policy Assessment (section I V .C), CASAC recommendations regarding the current and potential alternative standards (section I V .D), the Ad ministrator’s proposed decision to retain the current primary PM 10 standard (section I V .E) , public comments received in response to the Administrator’s proposed decision (section IV.F), and the Administrator’s final decision to retain the current primary P M 10 standard (section I V
. G )
. A. Background The following sections discuss previous reviews of the PM NAAQS (section I V .A.1), the litigation of the EPA’s 2006 decision on the PM 10 standards (section I V .A.2), and the general approach taken to review the primary PM 10 standard in the current review (section I V .A.3)
. 1. Previous Reviews of the PM NAAQS***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 302 of 790 Formatted: Left

a. Reviews Completed in 1987 and 1997 The PM NAAQS have always included some type of a primary standard to protect against effects associated with exposures to thoracic coarse particles
. In 1987, when the EPA first revised the PM NAAQS, the EPA changed the indicator for PM from TSP to focus on inhalable particles, those which can penetrate into the trachea, bronchi, and deep lungs (52 FR 24634, July 1, 1987). In that review, the EPA changed the PM indicator to PM 10 based on evidence that the risk of adverse health effects associated with particles with a nominal mean aerodynamic diameter less than or equal to 10 μm was significantly greater than risks associate d with larger particles (52 FR 24639, July 1, 1987). In the 1997 review, in conjunction with establishing new fine particle (i.e., PM 2.5 ) standards (discussed above in section s II.B.1 and I II.A.1), the EPA concluded that continued protection was warranted against potential effects associated with thoracic coarse particles in the size range of 2.5 to 10 μm
. This conclusion was based on particle dosimetry, toxicological information, and on limited epidemiological evidence from studies that measured PM 10 in a reas where the coarse fraction was likely to dominate PM 10 mass (62 FR 38677, July 18, 1997) . The EPA concluded there that a PM 10 standard could provide requisite protection against effects associated with particles in the size range of 2.5 to 10 μm. 126 Alth ough the EPA considered a more narrowly defined indicator for thoracic coarse particles in that review (i.e., PM 10

- 2.5 ), the EPA concluded that it was more appropriate, based on existing evidence, to continue to use PM 10 as the indicator
. This decision was based, in part, on the recognition that the only studies of
126 With regard to the 24

- hour PM 10 standard, the EPA retained the indicator, averaging time, and level (150 μg/m 3 ), but revised the form (i.e., from one

- expected

- exceedance to the 99 th percentile).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 303 of 790 Formatted: Left clear quantitative relevance to health effects most likely associated with thoracic coarse particles used PM 10 . These were two studies conducted in areas where the coarse fraction was the dominan t fraction of PM 10 , and which substantially exceeded the 24

- hour PM 10 standard (62 FR 38679)
. In addition, there were only very limited ambient air quality data then available specifically for PM 10

- 2.5 , in contrast to the extensive monitoring network alrea dy in place for PM 10 . Therefore, the EPA considered it more administratively feasible to use PM 10 as an indicator
. The EPA also stated that the PM 10 standards would work in conjunction with the PM 2.5 standards by regulating the portion of particulate poll ution not regulated by the then newly adopted PM 2.5 standards
. In May 1998, a three

-

judge panel of the U.S. Court of Appeals for the District of Columbia Circuit found "ample support" for the EPA 's decision to regulate coarse particle pollution, but vacat ed the 1997 PM 10 standards, concluding that the EPA had failed to adequately explain its choice of PM 10 as the indicator for thoracic coarse particles American Trucking Associations v. EPA , 175 F. 3d 1027, 1054

- 56 (D.C. Cir. 1999)
. In particular, the court held that the EPA had not explained the use of an indicator under which the allowable level of coarse particles varied according to the amount of PM 2.5 present, and which, moreover, potentially double regulated PM 2.5 . The court also rejected consideration s of administrative feasibility as justification for use of PM 10 as the indicator for thoracic coarse PM, since NAAQS (and their elements) are to be based exclusively on health and welfare considerations
. Id. at 1054
. Pursuant to the court’s decision, the EPA removed the vacated 1997 PM 10 standards from the CFR (69 FR 45592, July 30, 2004) and deleted the regulatory provision (at 40 CFR 50.6(d)) that controlled the transition from the pre

- existing 1987 PM 10 standards to the 1997 PM 10***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 304 of 790 Formatted: Left standards (65 FR 80776, December 22, 2000)
. The pre

- existing 1987 PM 10 standards thus remained in place
. Id. at 80777
. b. Review Completed in 2006 In the review of the PM NAAQS that concluded in 2006, the EPA considered the growing, but still limited, body of evidence supporting associations between health effects and thoracic coarse particles measured as PM 10

- 2.5 . 127 The new studies available in the 2006 review included epidemiological studies that reported associations with health effects using direct measurements of PM 10

- 2.5 , as well as dosimetric and toxicological studies
. In considering this growing body of PM 10

- 2.5 evidence, as well as evidence from studies that measured PM 10 in locations where the majority of PM 10 was in the PM 10

- 2.5 fraction (U.S. EPA , 2005, sectio n 5.4.1), staff concluded that the level of protection afforded by the existing 1987 PM 10 standard remained appropriate (U.S. EPA , 2005, p. 5

- 67) but recommended that the indicator for the standard be revised
. Specifically, staff recommended replacing the PM 10 indicator with an indicator of urban thoracic coarse particles in the size range of 10

- 2.5 μm (U.S. EPA , 2005, pp. 5

- 70 to 5

- 71)
. The agency proposed to retain a standard for a subset of thoracic coarse particles, proposing a qualified PM 10

- 2.5 indica tor to focus on the mix of thoracic coarse particles generally present in urban environments
. More specifically, the proposed revised thoracic coarse particle standard would have applied only to an ambient mix of PM 10

- 2.5 dominated by resuspended dust from high

- density traffic on paved roads and/or by industrial and construction sources
. The proposed revised standard would not have applied to any
127 The PM Staff Paper (U.S. EPA, 2005) also presented results of a quantitative assessment of health risks for PM 10

- 2.5 . However, staff concl uded that the nature and magnit ude of the uncertainties and concerns associated with this risk assessment weighed against its use as a basis for recommending specific levels for a thoracic coarse particle standard (U.S. EPA, 2005, p. 5

- 69).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 305 of 790 Formatted: Left ambient mix of PM 10

- 2.5 dominated by rural windblown dust and soils
. In addition, agricultural sources, mining s ources, and other similar sources of crustal material would not have been subject to control in meeting the standard (71 FR 2667 to 2668, January 17, 2006)
. The Agency received a large number of comments overwhelmingly and persuasively opposed to the prop osed qualified PM 10

- 2.5 indicator (71 FR 61188 to 61197, October 17, 2006)
. After careful consideration of the scientific evidence and the recommendations contained in the 2005 Staff Paper, the advice and recommendations from CASAC, and the public comments received regarding the appropriate indicator for coarse particles, and after extensive evaluation of the alternatives available to the Agency, the Administrator decided it would not be appropriate to adopt the proposed qualified PM 10

- 2.5 indicator, or any qualified indicator
. Underlying this determination w as the Administrator’s decision that it was requisite to provide protection from exposure to all thoracic coarse PM, regardless of its origin. The Administrator thus rejected arguments that there are no health effects from community

- level exposures to coarse PM in non

- urban areas (71 FR 61189). The EPA concluded that dosimetric, toxicological, occupational and epidemiological evidence supported retention of a primary standard for short

- term exposures that included all thoracic coarse particles (i.e., particles of both urban and non

- urban origin), consistent with the Act’s requirement that primary NAAQS must be requisite to protect the public health and provide an adequate margin of safety. At the same time , the Agency concluded that the standard should target protection toward urban areas, where the evidence of health effects from exposure to PM 10

- 2.5 was strongest (71 FR at 61193, 61197). The proposed indicator was not suitable for that purpose
. Not***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 306 of 790 Formatted: Left only did it inappropriately provide no protection at all to many areas, but it failed to identify many areas where the ambient particle mix was dominated by coarse particles contaminated with urban/industrial types of coarse particles for which evidenc e of health effects was strongest (71 FR 61193)
. The Agency ultimately concluded that the existing indicator, PM 10 , was most consistent with the evidence
. Although PM 10 includes both coarse and fine PM, the Agency concluded that it remained an appropriate indicator for thoracic coarse particles because, as discussed in the PM Staff Paper (U.S. EPA , 2005, p. 2

– 54, Figures 2

– 23 and 2

– 24), fine particle levels are generally higher in urban areas and, therefore, a PM 10 standard set at a single unvarying level will generally result in lower allowable concentrations of thoracic coarse particles in urban areas than in non

- urban areas (71 FR 61195 96)
. The EPA considered this to be an appropriate targeting of protection given that the strongest evidence for effect s associated with thoracic coarse particles came from epidemiological studies conducted in urban areas and that eleva ted fine particle concentrations in urban areas could result in increased contamination of coarse fraction particles by PM 2.5 , potentially increasing the toxicity of thoracic coarse particles in urban areas ( id
. ). Given the evidence that the existing (i.e. 1987) PM 10 standard was established at a level and form which afforded requisite protection with an adequate m argin of safety, the Agency retained the level and form of the 24

- hour PM 10 standard. 128 The Agency also revoked the annual PM 10 standard, in light of the conclusion in
128 Thus, the standard is met when a 24

- hour ave rage PM 10 concentration of 150 μg/m 3 is not exceeded more than one day per year, on average over a three

- year period. As noted above, the 1987 PM 10 standard was not adopted solely to control thoracic coarse particles. However, when reviewing this standard in the 2006 review, EPA determined that the level and form of the standard being reviewed (i.e., the 1987 PM 10 standard) provided requisite protection with an adequate margin of safety from short

- term exposures to thoracic coarse particles.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 307 of 790 Formatted: Left the PM Criteria Document (U.S. EPA , 2004, p. 9

- 79) that the available evidence does not suggest an association with long

- term exposure to PM 10

- 2.5 and the conclusion in the Staff Paper (U.S. EPA , 2005, p. 5

- 61) that there is no quantitative evidence that directly supports retention of an annual standard . This decision was consistent with CASAC advice and recommendations (Henderson, 2005 2005a,b ). In the same rulemaking, the EPA also included a new FRM for the measurement of PM 10

- 2.5 in the ambient air (71 FR 61212 to 61213, October 17, 2006)
. Although the standard for thoracic coarse particles does not use a PM 10

- 2.5 indicator, the new FRM for PM 10

- 2.5 was established to provide a basis for approving FEMs and to promote the gathering of scientific data to support future reviews of the PM NAAQS (71 FR 61202/3, October 17, 2006). 129 2. Litigation Related to the 2006 Prim ary PM 10 Standards A number of groups filed suit in response to the final decisions made in the 2006 review
. See American Farm Bureau Federation v. EPA , 559 F. 3d 512 (DC Cir. 2009)
. Among the petitions for review were challenges from industry groups on th e decision to retain the PM 10 indicator and the level of the PM 10 standard and from environmental and public health groups on the decision to revoke the annual PM 10 standard
. The court upheld both the decision to retain the 24

- hour PM 10 standard and the de cision to revoke the annual standard
. First, the court upheld the EPA ’s decision for a standard to encompass all thoracic coarse PM, both of urban and non

- urban origin
. The court rejected arguments that the

129 As noted below, however, with this notice the EPA is revoking the requirement for PM 10

- 2.5 speciation at NCore monitoring sites due to technical issues related to the development of appropriate monitoring methods (section VIII.B.3.c). The requirement for P M 10

- 2.5 mass measurements at NCore sites is being retained.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 308 of 790 Formatted: Left evidence showed there are no risks from exposure to non
- urban coarse PM
. The court further found that the EPA had a reasonable basis not to set separate standards for urban and non

- urban coarse PM, namely the inability to reasonably define what ambient mixes would be included under either ‘urban’ or ‘no n - urban;’ and the evidence in the record that supported the EPA ’s appropriately cautious decision to provide “some protection from exposure to thoracic coarse particles... in all areas.” 559 F. 3d at 532

- 33
. S pecifically, the court stated, Although the evid ence of danger from coarse PM is, as EPA recognizes, “inconclusive,” (71 FR 61193, October 17, 2006), the agency need not wait for conclusive findings before regulating a pollutant it reasonably believes may pose a significant risk to public health
. The ev idence in the record supports the EPA’s cautious decision that “some protection from exposure to thoracic coarse particles is warranted in all areas.” Id. As the court has consistently reaffirmed, the CAA permits the Administrator to “err on the side of ca ution” in setting NAAQS. 559 F. 3d at 533. The court also upheld the EPA ’s decision to retain the level of the standard at 150 μg/m 3 and to use PM 10 as the indicator for thoracic coarse particles
. In upholding the level of the standard, the court referred to the conclusion in the Staff Paper that there is “little basis for concluding that the degree of protection afforded by the current PM 10 standards in urban areas is greater than warranted, since potential mortality effects have been associated with air q uality levels not allowed by the current 24

- hour standard, but have not been associated with air quality levels that would generally meet that standard, and morbidity effects have been associated with air quality levels that exceeded the current 24

- hour st andard only a few times.” 559 F. 3d at 534

. The court also rejected arguments that a PM 10 standard established at an unvarying level will result in arbitrarily varying levels of protection given that the level of coarse PM would vary based on the amount of fine PM present
. The court agreed that the variation in allowable coarse PM***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 309 of 790 Formatted: Left was in accor d with the strength of the evidence: typically less coarse PM would be allowed in urban areas (where levels of fine PM are typically higher), in accord with the strongest evidence of health effects from coarse particles
. 559 F. 3d at 535

- 36
. In addition, s uch regulation would not impermissibly double regulate fine particles, since any additional control of fine particles (beyond that afforded by the primary PM 2.5 standard) would be for a different purpose: to prevent contamination of coarse particles by fin e particles
. 559 F. 3d at 535, 536
. These same explanations justified the choice of PM 10 as an indicator and provided the reasoned explanation for that choice lacking in the record for the 1997 standard
. 559 F. 3d at 536. With regard to the challenge from environ mental and public health groups, the court upheld the EPA ’s decision to revoke the annual PM 10 standard. The court rejected the argument that the EPA is required by law to have an annual PM 10 standard, holding that section 109 (d)(1) of the Act all ows the EPA to revoke a standard no longer warranted by the cu rrent scientific understanding. 559 F. 3d at 538. The court further held that the EPA ’s decision to revoke the annual standard was supported by the science: The EPA reasonably decided that an a nnual coarse PM standard is not necessary because, as the Criteria Document and the Staff Paper make clear, the latest scientific data do not indicate that long

- term exposure to coarse particles poses a health risk. The CASAC also agreed that an annual coa rse PM standard is unnecessary. 559 F. 3d at 538

- 39. 3. General Approach Used in the Current Review The approach taken to considering the existing and potential alternative primary PM 10 standards in the current review builds upon the approaches used in previous PM NAAQS reviews
. This approach is based most fundamentally on using information from epidemiological studies and air quality analyses to inform the identification of a range of***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 310 of 790 Formatted: Left
p olicy options for consideration by the Administrator
. The Administrator considers the appropriateness of the current and potential alternative standards, taking into account the four elements of the NAAQS: indicator, averaging time, form, and level. Evide nce - based approaches to using information from epidemiological studies to inform decisions on PM standards are complicated by the recognition that no population threshold, below which it can be concluded with confidence that PM

- related effects do not occur , can be discerned from the available evidence (U.S. EPA , 2009a, section s 2.4.3 and 6.5.2.7 )
. 130 As a result, any approach to reaching decisions on what standards are appropriate requires judgments about how to translate the information available from the ep idemiological studies into a basis for appropriate standards, which includes consideration of how to weigh the uncertainties in reported associations across the distributions of PM concentrations in the studies
. The approach taken to informing these decisi ons in the current review recognizes that the available health effects evidence reflects a continuum consisting of ambient levels at which scientists generally agree that health effects are likely to occur through lower levels at which the likelihood and

m agnitude of the response become increasingly uncertain
. Such an approach is consistent with setting standards that are neither more nor less stringent than necessary, recognizing that a zero

- risk standard is not required by the CAA. Because the purpose of the PM 10 standard is to protect against exposures to PM 10

- 2.5 , it is most appropriate to focus on PM 10

- 2.5 health studies when considering the degree of public health protection provided by the current PM 10 standard. Compared to health studies of PM 10 , studies that evaluate associations with PM 10

- 2.5 provide clearer
130 Studies that have characterized the concentration

- response relationships for PM exposures have evaluated PM 10 , which includes both coarse and fine particles, and PM 2.5 (U.S. EPA, 2009a, sections 2.4.3 and 6.5.2.7).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 311 of 790 Formatted: Left evidence for health effects following exposures to thoracic coarse particles. In contrast, i t is difficult to interpret PM 10 studies within the context of a standard meant to protect against exposures to PM 10

- 2.5 because PM 10 is comprised of both fine and coarse particles, even in locations with the highest concentrations of PM 10

- 2.5 (U.S. EPA , 2011a, Figure 3

- 4) . Therefore, the extent to which PM 10 effect estimates reflect associations with P M 10

- 2.5 versus PM 2.5 can be highly uncertain. In light of this uncertainty, it is preferable to consider PM 10

- 2.5 studies when such studies are available. Given the availability in this review of a number of studies that evaluated associations with PM 10

- 2.5 , and given that the Integ rated Science Assessment weight

- of

- evidence conclusions for thoracic coarse particles were based on studies of PM 10

- 2.5 , in this review the EPA focuses primarily on studies that have specifically evaluated PM 10

- 2.5 . 131 As disc ussed in more detail in the Risk Assessment (U.S. EPA , 2010a , Appendix H ), the EPA did not conduct a quantitative assessment of health risks associated with PM 10

- 2.5 . The Risk Assessment concluded that limitations in the monitoring network and in the healt

h studies that rely on that monitoring network, which would be the basis for estimating PM 10

- 2.5 health risks, would introduce significant uncertainty into a PM 10

- 2.5 risk assessment such that the risk estimates generated would be of limited value in infor ming revie w of the standard. Therefore, it was judged that a quantitative assessment of PM 10

- 2.5 risks is not supportable at this time (U.S. EPA , 2010a, p. 2

- 6). This decision does not indicate that health effects are not associated with exposure to thoracic coarse particles. Rather, as noted above, it reflects the conclusion that limitations in the available health studies and air quality information would introduce significant
131 It should also be noted that CASAC endorsed the approach adopted in the Integrated Science Assessment, which draws weight

- of

- evidence conclusions for PM 2.5 and PM 10

- 2.5 , but not for PM 10 (Samet, 2009f).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 312 of 790 Formatted: Left
uncerta inty into a quantitative assessment of PM 10

- 2.5 risks such that the risk estimates generated would be of limited value in informing review of the standard
. B. Health Effects Related to Exposure to Thoracic Coarse Particles This section briefly outlines the k ey information presented in section I V .B of the proposal (77 FR 389 47 to 389 51 , June 29, 2012) , and discussed more fully in the Integrated Science Assessment (U.S. EPA, 2009a, Chapters 2, 4, 5, 6, 7, and 8) and the Policy Assessment (U.S. EPA, 2011 2011a , C hapter 3 ) , related to health effects associated with thoracic coarse particle exposures. In looking across the new scientific evidence available in this review, our overall understanding of health effects associated with thoracic coarse particle exposures has been expanded, though important uncertainties remain. Some highlights of the key policy

- relevant scientific evidence available in this review include the following : (1) A number of multi

- city and single

- city epidemiological studies have evaluated associations between short

- term PM 10

- 2.5 and mortality, cardiovascular effects (e.g., including hospital admissions and emergency department visits), and/or respiratory effects
. D espite differences in the approaches used to estimate ambient PM 10

- 2.5 concentrations, the majority of these studies have reported positive , though often not statistically significant, associations with short

- term PM 10

- 2.5 concentrations. M ost PM 10

- 2.5 ef fe ct estimates remained positive in co

- pollutant models that included either gaseous or particulate co

- pollutants. In U.S. study locations likely to have met the current PM 10 standard during the study period, a few PM 10

- 2.5 effect estimates were statistically significant and remained so in co

pollutant models
. 132 (2) A small number of controlled human exposure studies have reported alterations in heart rate variability or increased pulmonary inflammation following short

- term expo sure to PM 10

- 2.5 , providing some support for the associations reported in
132 The statistical significance of effect estimates provides important information on their statistical precision. However, when a group of studies report effect estimates that are similar in direction and magnitude, such a pattern of results warrants consideration of those studies even if not all reported statistically significant associations in single

- or co pollutant models (section III.D.2, above). In considering the PM 10

- 2.5 epidemiologic studies below, the Administrator considers both the pattern of results across studies and the statistical significance of those results.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 313 of 790 Formatted: Left epidemiological studies. T oxicological studies that have examined the effect s of PM 10

- 2.5 have used intratracheal instillation and, because these studies do not directly mirror any r eal

- world mode of exposure , they provide only limited evidence for the biological plausibility of PM 10

- 2.5 - induced effects. (3) Using a more formal framework for reaching causal determinations than used in previous reviews, t

he Integrated Science Assessment c onclude d that the existing evidence is “suggestive” of a causal relationship between short

- term PM 10

- 2.5 exposures and mortality, cardiovascular effects , and respiratory effects (U.S. EPA , 2009a, section 2.3.3). 133 In contrast, the Integrated Science Assessment conclude d that available evidence is “inadequate” to infer a causal relationship between long

- term PM 10

- 2.5 exposures and various health effects. (4) T here are several at

- risk populations that may be especially susceptible or vulnerable to PM

- related effects , including effects associated with exposures to coarse particles . These groups include those with preexisting heart and lung diseases, specific genetic differences, and lower socioeconomic status as well as t he lifestages of childhood and older adulthood. Evidence for PM

- related effects in these at

- risk populations has expanded and is stronger than previously observed. There is emerging, though still limited, evidence for additional potentially at

- risk populat ions, such as those with diabetes, people who are obese, pregnant women, and the developing fetus. (5) T he Integrated Science Assessment concludes that currently available evidence is insufficient to draw distinctions in particle toxicity based on composition and notes that recent studies have reported that PM (both PM 2.5 and PM 10

- 2.5 ) from a variety of sources , including sources likely to be present in urban and non

- urban locations, is associated with adverse health effects. Although new PM 10

- 2.5 scientifi c studies have become available since the last review and have expanded our understanding of the association between PM 10

- 2.5 and adverse health effects (see above and U.S. EPA , 2009a, Chapter 6), important
133 The causal framework draws upon the assessment and integration of evidence fro m across epidemiological, controlled human exposure, and toxicological studies, and the related uncertainties that ultimately influence our understanding of the evidence. This framework employs a five

- level hierarchy that classifies the overall weight

- of

- evidence using the following categorizations: causal relationship, likely to be causal relationship, suggestive of a causal relationship, inadequate to infer a causal relationship, and not likely to be a causal relationship (U.S. EPA, 2009a, Table 1

- 3). I n the case of a “suggestive” determination, “the evidence is suggestive of a causal relationship with relevant pollutant exposures, but is limited because chance, bias and confounding cannot be ruled out. For example, at least one high

- quality epidemiologi c study shows an association with a given health outcome but the results of other studies are inconsistent” (U.S. EPA, 2009a, Table 1

- 3).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 314 of 790 Formatted: Left uncertainties remain
. These uncertainties, and their implications for interpreting the scientific evidence, include the following: (1) The potential for confounding by co

- occurring pollutants, especially PM 2.5 , has been addressed with co

- pollutant models in only a relatively small number of PM 10

- 2.5 epidemiological studies (U.S. EPA , 2009a, section 2.3.3). This is a particularly important limitation given the relatively small body of experimental evidence (i.e., controlled human exposure and animal toxicological studies) available to support the associations between PM 10

- 2.5 and adverse health effects. The net impact of such limitations is to increase uncertainty in characterizations of the extent to which PM 10

- 2.5 itself, rather than one or more co

- occurring pollutants, is responsi ble for the mortality and morbidity effects reported in epidemiological studies. (2) T here is greater spatial variability in PM 10

- 2.5 concentrations than PM 2.5 concentrations, resulting in increased exposure error for PM 10

- 2.5 (U.S. EPA , 2009a, p. 2

- 8) . A vai lable measurements do not provide sufficient information to adequately characterize the spatial distribution of PM 10

- 2.5 concentrations (U.S. EPA , 2009a, section 3.5.1.1). The net effect of these uncertainties on PM 10

- 2.5 epidemiological studies is to bias the results of such studies toward the null hypothesis. That is, as noted in the Integrated Science Assessment, these limitations in estimates of ambient PM 10

- 2.5 concentrations “would tend to increase uncertainty and make it more difficult to detect effe cts of PM 10

- 2.5 in epidemiologic studies” (U.S. EPA , 2009a, p. 2

- 21). (3) Only a relatively small number of PM 10

- 2.5 monitoring sites are currently operating and such sites have been in operation for a relatively short period of time, limiting the spatial and temporal coverage for routine measurement of PM 10

- 2.5 concentrations. Given these limitations in routine monitoring, epidemiological studies have employed different approaches for estimating PM 10

- 2.5 concentrations. Given the relatively small number of PM 10

- 2.5 monitoring sites, the relatively large spatial variability in ambient PM 10

- 2.5 concentrations (see above), the use of different approaches to estimating ambient PM 10

- 2.5 concentrations across epidemiological studies, and the limitations inherent in such estimates, the distributions of thoracic coarse particle concentrations over which reported health outcomes occur remain highly uncertain (U.S. EPA , 2009a, sections 2.2.3, 2.3.3, 2.3.4, and 3.5.1.1). (4) There is relatively little information on the chemical and biological composition of PM 10

- 2.5 and the effects associated with the various components (U.S. EPA , 2009a, section 2.3.4). W ithout more information on the chemical speciation of PM 10

- 2.5 , the apparent variability in associations with health e ffects across locations is difficult to characterize (U.S. EPA , 2009a, section 6.5.2.3).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 315 of 790 Formatted: Left (5) One of the implications of the uncertainties and limitations discussed above is that the Risk Assessment concluded it would not be appropriate to conduct a quantitat ive assessment of health risks associated with PM 10

- 2.5 . The lack of a quantitative PM 10

- 2.5 risk assessment in the current review adds to the uncertainty in any conclusions about the extent to which revision of the current PM 10 standard would be expected to improve the protection of public health, beyond the protection provided by the current standard. 134 C. Consideration of the Current and Potential Alternative Standards in the Policy Assessment The following sections discuss the Policy Assessment’s consideration of the current and potential alternative standards to protect against exposures to thoracic coarse particles (U.S. EPA , 2011a, chapter 3)
. Section I V .C.1 discusses the consideration of the current standard while section I V .C.2 discusses the c onsideration of potential alternative standards in terms of the basic elements of a standard: indicator, averaging time, form, and level
. 1. Consideration of the Current Standard in the Policy Assessment As discussed above the 24

- hour PM 10 standard is mea nt to protect the public health against exposures to thoracic coarse particles (i.e., PM 10

- 2.5 )
. In considering the adequacy of the current PM 10 standard, the Policy Assessment considered the health effects evidence linking short

- term PM 10

- 2.5 exposures wi th mortality and morbidity (U.S. EPA , 2009a, chapters 2 and 6), the ambient PM 10 concentrations in PM 10

- 2.5 study locations (U.S. EPA , 2011a, section 3.2.1), the uncertainties and limitations associated with this health evidence (U.S. EPA , 2011a, section 3 .2.1), and the consideration of these uncertainties and limitations as part of the weight of evidence conclusions in the Integrated Science Assessment (U.S. EPA , 2009a)
.

134 As noted above , the EPA’s decision not to conduct a quantitative risk assessment reflects uncertainty regarding the value of such an assessment, but does not indicate that health effects are not associated with exposure to thoracic coarse particles.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 316 of 790 Formatted: Left In considering the health evidence, air quality information, and associated uncertain ties as they relate to the current PM 10 standard, the Policy Assessment noted that a decision on the adequacy of the public health protection provided by that standard is a public health policy judgment in which the Administrator weighs the evidence and in formation, as well as its uncertainties
. Therefore, depending on the emphasis placed on different aspects of the evidence, information, and uncertainties, consideration of different conclusions on the adequacy of the current standard could be supported
. Fo r example, the Policy Assessment noted that one approach to considering the evidence, information, and its associated uncertainties would be to place emphasis on the following (U.S. EPA , 2011a, section 3.2. 3 ): (1) While most of PM 10

- 2.5 effect estimates repor ted for mortality and morbidity were positive, many were not statistically significant, even in single

- pollutant models
. This includes effect estimates reported in study locations with PM 10 concentrations above those allowed by the current 24

- hour PM 10 sta ndard
. (2) The number of epidemiological studies that have employed co

- pollutant models to address the potential for confounding, particularly by PM 2.5 , remains limited
. Therefore, the extent to which PM 10

- 2.5 itself, rather than one or more co

pollutants, contributes to reported health effects remains uncertain
. (3) Only a limited number of experimental studies provide support for the associations reported in epidemiological studies, resulting in further uncertai nty regarding the plausibility of a causal link between PM 10

- 2.5 and mortality and morbidity
. (4) Limitations in PM 10

- 2.5 monitoring and the different approaches used to estimate PM 10

- 2.5 concentrations across epidemiological studies result in u ncertainty as to the ambient PM 10

- 2.5 concentrations at which the reported effects occur
. (5) The chemical and biological composition of PM 10

- 2.5 , and the effects associated with the various components, remains uncertain
. Without more information on the chemical speciation of PM 10

- 2.5 , the apparent variability in associations across locations is difficult to interpret. (6) In considering the available evidence and its associated uncertainties, the Integrated Science Assessment concluded that the evidence is “suggestive” of a c ausal relationship between short

- term PM 10

- 2.5 exposures and mortality, cardiovascular effects, and respiratory effects
. These weight

- of

- evidence conclusions contrast with those for the relationships between PM 2.5 exposures and***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 317 of 790 Formatted: Left adverse health effects, whic h were judged in the Integrated Science Assessment to be either “causal” or “likely causal” for mortality, cardiovascular effects, and respiratory effects
. The Policy Assessment conclude d that, to the extent a decision on the adequacy of the current 24

- ho ur PM 10 standard were to place emphasis on the considerations noted above, it could be judged that, although it remains appropriate to maintain a standard to protect against short

- term exposures to thoracic coarse particles, the available evidence suggests that the current 24

- hour PM 10 standard appropriately protects public health and provides an adequate margin of safety against effects that have been associated with PM 10

- 2.5 exposures. Although such an approach to considering the adequacy of the current

s tandard would recognize the positive, and in some cases statistically significant, associations between all types of PM 10

- 2.5 and mortality and morbidity, it would place relatively greater emphasis on the limitations and uncertainties noted above, which te nd to complicate the interpretation of that evidence
. In addition, the Policy Assessment note d the judgment that , given the uncertainties and limitations in the PM 10

- 2.5 health evidence and air quality information, it would not have been appropriate to conduct a quantitative assessment of health risks associated with PM 10

- 2.5 (U.S. EPA, 2011a, p. 3

- 6; U.S. EPA, 2010a , pp. 2

- 6 to 2

- 7, Appendix H)
. As discussed above, the lack of a quantitative PM 10

- 2.5 risk assessment adds to the uncertain ty associated with any characterization of potential public health improvements that would be realized with a revised standard. The Policy Assessment also note d an alternative approach to considering the evidence and its uncertainties would place emphasis on the following ( U.S. EPA , 2011a, section 3.2. 3 ) :***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 318 of 790 Formatted: Left (1) Several multi

- city epidemiological studies conducted in the U.S., Canada, and Europe, as well as a number of single

- city studies, have reported generally positive, and in some cases statistically significant, associations between short

term PM 10

- 2.5 concentrations and adverse health endpoints including mortality and cardiovascular

- related and respiratory

- related hospital admissions and emergency department visits
. (2) Both single

- city and multi

- city analyses, using different approaches to estimate ambient PM 10

- 2.5 concentrations, have reported positive PM 10

- 2.5 effect estimates in locations that would likely have m et the current 24

- hour PM 10 standard. In a few cases, these PM 10

- 2.5 effect estimates were statistically significant. (3) While limited in number, studies that have evaluated co

- pollutant models have generally reported that PM 10

- 2.5 effect estimates remain p ositive, and in a few cases statistically significant, when these models include gaseous pollutants or fine particles
. (4) Support for the plausibility of the associations reported in epidemiological studies is provided by a small number of controlled human exposure studies reporting that short

- term (i.e., 2

- hour) exposures to PM 10

- 2.5 decrease heart rate variability and increase markers of pulmonary inflammation. T his approach to considering the health evidence, air quality information, and the associated uncertainties would place substantial weight on the generally positive PM 10

- 2.5 effect estimates that have been reported for mortality and morbidity, even those effect estimates that are not statistically significant
. The Policy Assessment conclude d that t his could be judged appropriate given that consistent results have been reported across multiple studies using different approaches to estimate ambient PM 10

- 2.5 concentrations and that exposure measurement error, which is likely to be larger for PM 10

- 2.5 t han for PM 2.5 , tends to bias the results of epidemiological studies toward the null hypothesis, making it less likely that associations will be detected
. Such an approach would place less weight on the uncertainties and limitations in the evidence that res ulted in the Integrated Science Assessment conclusions that the evidence is only suggestive of a causal relationship
.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 319 of 790 Formatted: Left Given all of the above, the Policy Assessment conclude d that it would be appropriate to consider either retaining or revising the current 24

- hour PM 10 standard, depending on the approach taken to considering the available evidence, air quality information, and the uncertainties and limitations associated with that evidence and information (U.S. EPA , 2011a, section 3.2. 3 )
. 2. Consideration of Potential Alternative Standards in the Policy Assessment Given the conclusion that it would be appropriate to consider either retaining or revising the current PM 10 standard, the Policy Assessment also considered what potential alternative standards, if any , could be supported by the available scientific evidence in order to increase public health protection against exposures to PM 10

- 2.5 . The Policy Assessment considered such potential alternative standards defined in terms of the elements of a standard (i.e., indicator, averaging time, form, and level). Key conclusions from the Policy Assessment regarding indicator, averaging time, and form included the following: (1) A PM 10 indicator would continue to appropriately target protection against thoracic coarse particle exposures to those locations where the evidence is strongest for associations with adverse health effects ( i.e., urban areas ). (2) The available evidence supports the importance of maintaining a standard that protects against short

- term exposures to all thoracic coarse particles. Given that the majority of th is evidence is based on 24

- hour average thoracic coarse particle concentrations, consideration of a 24

- hour a veraging time remains appropriate. (3) Given the limited body of evidence supporting PM 10

- 2.5 - related effects following long

- term exposures, which resulted in the Integrated Science Assessment conclu sion that the available evidence is “inadequate” to infer a causal relationship between long

- term PM 10

- 2.5 exposures and a variety of health effects, consideration of an annual thoracic coarse particle standard is not supported at this time. (4) T o the extent it is judged appropriate to revise the current 24

- hour PM 10 standard, it would be appropriate to consider revising the form to the 3

- year average of the***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 320 of 790 Formatted: Left 98 th percentile of the annual distribution of 24

- hour PM 10 concentrations
. In considering the available evidence and air quality information within the context of identifying potential alternative standard levels for consideration (assuming a decision were made that it is appropriate to amend the standard) , the Policy Assessment first note d that a standard level as h igh as about 85 μg/m 3 , for a 24

- hour PM 10 standard with a 98 th percentile form, could be supported . Based on considering air quality concentrations in study locations, the Policy Assessment noted that s uch a standard level would be expected to maintain PM 1 0 and PM 10

- 2.5 concentrations below those present in U.S. locations of single

- city studies where PM 10

- 2.5 effect estimates have been reported to be positive and statistically significant and below those present in some locations where single

- city studies r eported PM 10

- 2.5 effect estimates that were positive, but not statistically significant
. These include some locations likely to have met the current PM 10 standard during the study periods (U.S. EPA, 2011a, section 3.3.4). T he Policy Assessment also note d that, b ased on analysis of the number of people living in counties that could violate the current and potential alternative PM 10 standards, a 24

- hour PM 10 standard with a 98 th percentile form and a level between 75 and 80 μg/m 3 would provide a level of pu blic health protection that is generally equivalent, across the U.S., to that provided by the current standard . Given this, the Policy Assessment concluded that it would be appropriate to consider standard levels in the range of approximately 75 to 80 μg/m 3 (with a 98 th percentile form) , t o the extent population counts we re emphasized in comparing the public health protection provided by the current and potential alternative standards and to the extent it wa s judged appropriate to set a revised standard pr oviding at least the level of public health protection that is***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 321 of 790 Formatted: Left provided by the current standard , based on such population counts (U.S. EPA, 2011a, section 3.3.4)
. The Policy Assessment also conclude d that alternative approaches to considering the evidence could lead to consideration of standard levels below 75 μg/m 3 for a standard with a 98 th percentile form. For example, a number of single

- city epidemiological studies have reported positive, though not statistically significant, PM 10

- 2.5 effect estimates in locations with 98 th percentile PM 10 concentrations below 75 μg/m 3

. Given that exposure error is particularly important for PM 10

- 2.5 epidemiological studies and can bias the results of these studies toward the null hypothesis (see section I V.B above), th e Policy Assessment noted that it could be judged appropriate to place more weight on positive associations reported in these epidemiological studies, even when those associations are not statistically significant
. In addition, the Policy Assessment noted that multi

- city averages of 98 th percentile PM 10 concentrations in the locations evaluated by U.S. multi

city studies of thoracic coarse particles (Zanobetti and Schwartz, 2009; Peng et al., 2008) were near or below 75 ppb. Despite uncertainties in the ext ent to which effects reported in multi

- city studies are associated with the short

- term air quality in any particular location, the Policy Assessment noted that emphasis could be placed on these multi

- city averaged concentrations. The Policy Assessment conc lude d that, to the extent more weight is placed on single

- city studies reporting positive, but not statistically significant, PM 10

- 2.5 effect estimates and on multi

- city studies, it could be appropriate to consider standard levels as low as 65 μg/m 3 with a 98 th percentile form (U.S. EPA, 2011a, section 3.3.4). In considering potential alternative standard levels below 65 μg/m 3 , the Policy***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 322 of 790 Formatted: Left Assessment note d that the overall body of PM 10

- 2.5 health evidence is relatively uncertain, with somewhat stronger supp ort in U.S. studies for associations with PM 10

- 2.5 in locations with 98 th percentile PM 10 concentrations above 85 μg/m 3 than in locations with 98 th percentile PM 10 concentrations below 65 μg/m 3

. In light of the limitations in the evidence for a relationshi p between PM 10

- 2.5 and adverse health effects in locations with relatively low PM 10 concentrations, along with the overall uncertainties in the body of PM 10

- 2.5 health evidence as described above and in the Integrated Science Assessment, the Policy Assessm ent conclude d that consideration of standard levels below 65 μg/m 3 was not appropriate (U.S. EPA, 2011a, section 3.3.4). D
. CASAC Advice Following their review of the first and second draft Policy Assessments, CASAC provided advice and recommendations re garding the current and potential alternative standards for thoracic coarse particles (Samet, 2010c ,d )
. With regard to the existing PM 10 standard, CASAC concluded that “the current data, while limited, is sufficient to call into question the level of protection afforded the American people by the current standard” (Samet, 2010d, p. 7). In drawing this conclusion, CASAC noted the positive a ssociations in multi

- city and single

- city studies, including in locations with PM 10 concentrations below those allowed by the current standard
. In addition, CASAC gave “significant weight to studies that have generally reported that PM 10

- 2.5 effect estimat es remain positive when evaluated in co

- pollutant models” and concluded that “controlled human exposure PM 10

- 2.5 studies showing decreases in heart rate variability and increases in markers of pulmonary inflammation are deemed adequate to support the plaus ibility of***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 323 of 790 Formatted: Left the associations reported in epidemiologic studies” (Samet, 2010d, p. 7)

. 135 Given all of the above conclusions CASAC recommended that “the primary standard for PM 10 should be revised” (Samet, 2010d, p. ii and p. 7)

. In discussing potential revisi ons, while CASAC noted that the scientific evidence supports adoption of a standard at least as stringent as the current standard, they recommended revising the current standard in order to increase public health protection
. In considering potential altern ative standards, CASAC drew conclusions and made recommendations in terms of the major elements of a standard: indicator, averaging time, form, and level
. The CASAC agreed with the EPA staff’s conclusions that the available evidence supports consideration in the current review of retaining the current PM 10 indicator and the current 24

- hour averaging time (Samet, 2010c, Samet, 2010d)
. Specifically, with regard to indicator, CASAC concluded that “[w] hile it would be preferable to use an indicator that reflec ts the coarse PM directly linked to health risks (PM 10

- 2.5 ), CASAC recognizes that there is not yet sufficient data to permit a change in the indicator from PM 10 to one that directly measures thoracic coarse particles” (Samet, 2010d, p. ii)
. In addition, C ASAC “vigorously recommends the implementation of plans for the deployment of a network of PM 10

- 2.5 sampling systems so that future epidemiological studies will be able to more thoroughly explore the use of PM 10

- 2.5 as a more appropriate indicator for thor acic coarse particles” (Samet, 2010d, p. 7). The CASAC also agreed that the evidence supports consideration of a potential alternative form
. Specifically, CASAC “felt strongly that it is appropriate to change the

135 Nonetheless, CASAC endorsed the Integrated Science Assessment weight of evidence conclusions for PM 10

- 2.5 (i.e., that th e evidence is only “suggestive” of a causal relationship between short

- term exposures and mortality, respiratory effects, and cardiovascular effects) (Samet, 2009e; Samet, 2009f).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 324 of 790 Formatted: Left statistical form of the PM 10 standard to a 98 th percentile” (Samet, 2010d, p.7)

. In reaching this conclusion, CASAC noted that “[p]ublished work has shown that the percentile form has greater power to identify non

- attainment and a smaller probability of misclassification relative to the expected exceedance form of the standard” (Samet, 2010d. p. 7)
. With regard to standard level, in conjunction with a 98 th percentile form, CASAC concluded that “alternative standard levels of 85 and 65 μg/m 3 (based on consideration of 98 th percentile PM 10 concentr ation) could be justified” (Samet, 2010d, p.8)

. However, in considering the evidence and uncertainties, CASAC recommended a standard level from the lower part of the range discussed in the Policy Assessment, recommending a level “somewhere in the range of 75 to 65 μg/m 3 ” (Samet, 2010d, p. ii)

. In making this recommendation, CASAC noted that the number of people living in counties with air quality not meeting the current standard is approximately equal to the number living in counties that would not meet a 98 th percentile standard with a level between 75 and 80 μg/m 3

. CASAC used this information as the basis for their conclusion that a 98 th percentile standard between 75 and 80 μg/m 3 would be “comparable to the degree of protection afforded to the current PM 10 standard” (Samet, 2010d, p. ii)

. Given this conclusion regarding the comparability of the current and potential alternative standards, as well as their conclusion on the public health protection provided by the current standard (i.e., that available evi dence is sufficient to call it into question), CASAC recommended a level within a range of 75 to 65 μg/m 3 in order to increase public health protection, relative to that provided by the current standard (Samet 2010d, p. ii).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 325 of 790 Formatted: Left
E. Administrator’s Proposed Co nclusions Concerning the Adequacy of the Current Primary PM

10 Standard In considering the evidence and information as they relate to the adequacy of the current 24

- hour PM 10 standard , the Administrator first note d in the proposal that this standard is meant to protect the public health against effects associated with short

- term exposures to PM 10

- 2.5 . In the last review, it was judged appropriate to maintain such a standard given the “ growing body of evidence suggesting causal associations between short

- term exposure to thoracic coarse particles and morbidity effects, such as respiratory symptoms and hospital admissions for respiratory diseases, and possibly mortality” (71 FR 61185, October 17, 2006)
. Given the continued expansion in the body of scientifi c evidence linking short

- term PM 10

- 2.5 to health outcomes such as premature death and hospital visits, discussed in detail in the Integrated Science Assessment (U.S. EPA , 2009a, Chapter 6) and summarized in the proposal , the Administrator provisionally

con clude d that the available evidence continue d to support the appropriateness of maintaining a standard to protect the public health against effects associated with short

term (e.g., 24

- hour) exposures to all PM 10

- 2.5 . In drawing provisional conclusions in t he proposal as to whether the current PM 10 standard remains requisite (i.e., neither more nor less stringent than necessary) to protect public health with an adequate margin of safety against such exposures, the Administrator considered the following : (1) The extent to which it is appropriate to maintain a standard that provides some measure of protection against all PM 10

- 2.5 , regardless of composition or source of origin ; (2) The extent to which it is appropriate to retain a PM 10 indicator for a standard meant to protect against exposures to ambient PM 10

- 2.5 ; and (3) The extent to which the current PM 10 standard provides an appropriate degree of public health protection
.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 326 of 790 Formatted: Left With regard to the first point, the proposal noted the conclusion from the last review that dos imetric, toxicological, occupational, and epidemiological evidence supported retention of a primary standard to provide some measure of protection against short

- term exposures to all thoracic coarse particles, regardless of their source of origin or locati on, consistent with the Act’s requirement that primary NAAQS provide requisite protection with an adequate margin of safety (71 FR 61197)
. In that review, the EPA concluded that PM from a number of source types, including motor vehicle emissions, coal comb ustion, oil burning, and vegetative burning, are associated with health effects (U.S. EPA , 2004) . This information formed part of the basis for the D.C. Circuit’s holding that it was appropriate for the thoracic coarse particle standard to provide “some protection from exposure to thoracic coarse particles...in all areas” ( American Farm Bureau Federation v. EPA , 559 F. 3d at 532

- 33)
. I n considering this issue in the proposal , the Administrator judge d that the expanded body of scientific evidence in this r eview provides even more support for a standard that protects against exposures to all thoracic coarse particles, regardless of their location or source of origin
. Specifically, the Administrator note d that epidemiological studies have reported positive as sociations between PM 10

- 2.5 and mortality or morbidity in a large number of cities across North America, Europe, and Asia, encompassing a variety of environments where PM 10

- 2.5 sources and composition are expected to vary widely
. See 77 FR 38959. In cons idering this evidence, the Integrated Science Assessment conclude d that “ many constituents of PM can be linked with differing health effects ” (U.S. EPA , 2009a, p. 2

- 26)
. While PM 10

- 2.5 in most of these study areas is of largely urban origin, the Administra tor note d that some recent studies have also linked mortality***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 327 of 790 Formatted: Left and morbidity with relatively high ambient concentrations of thoracic coarse particles of

non - urban crustal origin
. In considering these studies, she note d the Integrated Science Assessment’s co nclusion that “PM (both PM 2.5 and PM 10

- 2.5 ) from crustal, soil or road dust sources or PM tracers linked to these sources are associated with cardiovascular effects” (U.S. EPA , 2009a, p. 2

- 26)
. In light of this body of available evidence reporting PM 10

- 2. 5 - associated health effects across different locations with a variety of sources, as well as the Integrated Science Assessment’s conclusions regarding the links between adverse health effects and PM sources and composition, the Administrator provisionally conclude d in the proposal that it is appropriate to maintain a standard that provides some measure of protection against exposures to all thoracic coarse particles, regardless of their location, source of origin, or composition (77 FR 38959

- 60). With regar d to the second point, in considering the appropriateness of a PM 10 indicator for a standard meant to provide such public health protection, the Administrator note d that the rationale used in the last review to support the unqualified PM 10 indicator (see a bove) remains relevant in the current review
. Specifically, as an initial consideration, she note d that PM 10 mass includes both coarse PM (PM 10

- 2.5 ) and fine PM (PM 2.5 )
. As a result, the concentration of PM 10

- 2.5 allowed by a PM 10 standard set at a single level declines as the concentration of PM 2.5 increases
. At the same time, the Administrator note d that PM 2.5 concentrations tend to be higher in urban areas than in rural areas (U.S. EPA , 2005, p. 2

– 54, and Figures 2

– 23 and 2

– 24) and, therefore, a PM 10 standard will generally allow lower PM 10

- 2.5 concentrations in urban areas than in rural

areas . 77 FR 38960.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 328 of 790 Formatted: Left In considering the appropriateness of this variation in allowable PM 10

- 2.5 concentrations, the Administrator consider ed the relative strength of t he evidence for health effects associated with PM 10

- 2.5 of urban origin versus non

- urban origin
. She specifically note d that, as described above and similar to the scientific evidence available in the last review, the large majority of the available eviden ce for thoracic coarse particle health effects comes from studies conducted in locations with sources more typical of urban and industrial areas than of rural areas . Although as just noted, associations with adverse health effects have been reported in s ome study locations where PM 10

- 2.5 is largely non

- urban in origin (i.e., in dust storm studies), particle concentrations in these study areas are typically much higher than reported in study locations where the PM 10

- 2.5 is of urban origin
. Therefore, the A dministrator note d that the strongest evidence for a link between PM 10

- 2.5 and adverse health impacts, particularly for such a link at relatively low particle concentrations, comes from studies where exposure is to PM 10

- 2.5 of urban or industrial origin. 7 7 FR 38960. The Administrator also note d that chemical constituents present at higher levels in urban or industrial areas, including byproducts of incomplete combustion ( e.g. polycyclic aromatic hydrocarbons) emitted as PM 2.5 from motor vehicles as well as metals and other contaminants emitted from anthropogenic sources, can contaminate PM 10

- 2.5 (U.S. EPA , 2004, p. 8

– 344; 71 FR 2665)
. While the Administrator acknowledge d the uncertainty expressed in the Integrated Science Assessment regarding the extent to which, based on available evidence , particle composition can be linked to health outcomes, she also consider ed the possibility that PM 10

- 2.5 contaminants typical of urban or industrial areas could increase the toxicity of thoracic coarse particles in urban locations (77 FR 38960).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 329 of 790 Formatted: Left Given that the large majority of the evidence for PM 10

- 2.5 toxicity, particularly at relatively low particle concentrations, comes from study locations where thoracic coarse particles are of urban origin, and given the possibility that PM 10

- 2.5 contaminants in urban areas could increase particle toxicity, the Administrator provisionally conclude d in the proposal that it remains appropriate to maintain a standard that targets public health protection to urban locations
. Specifically, she conclude d at proposal that it is appropriate to maintain a standard that allows lower ambient concentrations of PM 10

- 2.5 in urban areas, where the evidence is strongest that thoracic coarse particles are linked to mortality and morbidity, and higher concentrations in non

- urban areas, where the public health concerns are less certain
. Id. Given all of the above considerations and conclusions, the Administrator judge d that the available evidence support ed retaining a PM 10 indicator for a sta ndard that is meant to protect against exposure to thoracic coarse particles
. In reaching this initial judgment, she note d that, to the extent a PM 10 indicator results in lower allowable concentrations of thoracic coarse particles in some areas compared to others, lower concentrations will be allowed in those locations (i.e., urban or industrial areas) where the science has shown the strongest evidence of adverse health effects associated with exposure to thoracic coarse particles and where we have the most concern regarding PM 10

- 2.5 toxicity
. Therefore, the Administrator provisionally conclude d that the varying amounts of coarse particles that are allowed in urban vs. non

- urban areas under the 24

- hour PM 10 standard, based on the varying levels of PM 2.5 pres ent, appropriately reflect the differences in the strength of evidence regarding coarse particle effects in urban and

non - urban areas (77 FR 38960).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 330 of 790 Formatted: Left In reaching this provisional conclusion, the Administrator also note d that, i n their review of the second d raft Policy Assessment, CASAC concluded that “[w] hile it would be preferable to use an indicator that reflects the coarse PM directly linked to health risks (PM 10

- 2.5 ), CASAC recognizes that there is not yet sufficient data to permit a change in the indica tor from PM 10 to one that directly measures thoracic coarse particles” (Samet, 2010d, p. ii)
. In addition, CASAC “vigorously recommends the implementation of plans for the deployment of a network of PM 10

- 2.5 sampling systems so that future epidemiological studies will be able to more thoroughly explore the use of PM 10

- 2.5 as a more appropriate indicator for thoracic coarse particles” (Samet, 2010d, p. 7)

. Given this recommendation, the Administrator further judge d that, although current evidence is not suff icient to identify a standard based on an alternative indicator that would be requisite to protect public health with an adequate margin of safety across the United States, consideration of alternative indicators (e.g., PM 10

- 2.5 ) in future reviews is desir able and could be informed by additional research, as described in the Policy Assessment (U.S. EPA , 2011a, section 3.5)
. With regard to the third point, in evaluating the degree of public health protection provided by the current PM 10 standard, the Administrator note d that the Policy Assessment discusse d two different approaches to considering the scientific evidence and air quality information (U.S. EPA , 2011a, section 3.2.3)
. These different approaches, which are described above (sec tion I V .C .1 ), lead to different conclusions regarding the appropriateness of the degree of public health protection provided by the current PM 10 standard
. The Administrator further note d that the primary difference between the two approaches lies in the ex tent to which weight is placed on the following (U.S. EPA ,***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 331 of 790 Formatted: Left 2011a, section 3.2.3) : (1) The PM 10

- 2.5 weight

- of

- evidence classifications presented in the Integrated Science Assessment concluding that the existing evidence is suggestive of a causal relationship b etween short

- term PM 10

- 2.5 exposures and mortality, cardiovascular effects, and respiratory effects (a classification supported by CASAC); (2) Individual PM 10

- 2.5 epidemiological studies reporting associations in locations that meet the current PM 10 standard, including associations that are not statistically significant ; (3) The limited number of PM 10

- 2.5 epidemiological studies that have evaluated co

pollutant models ; (4) The limited number of PM 10

- 2.5 controlled human exposure studies ; (5) Uncertainties in the PM 10

- 2.5 air quality concentrations reported in epidemiological studies, given limitations in PM 10

- 2.5 monitoring data and the different approaches used across studies to estimate ambient PM 10

- 2.5 concentrations ; and (6) Uncertainties and limitations in the evidence that tend to call into question the presence of a causal relationship between PM 10

- 2.5 exposures and mortality/morbidity
. In evaluating the different possible approaches to considering the public health protection provided by the current PM 10 standard, the Administrator first note d that when the available PM 10

- 2.5 scientific evidence and its associated uncertainties are considered, the Integrated Science Assessment conclude d that the evidence is suggestive of a causal relationship between short

- term PM 10

- 2. 5 exposures and mortality, cardiovascular effects, and respiratory effects
. As discussed in section I V .B.1 above and in more detail in the Integrated Science Assessment (U.S. EPA , 2009a, section 1.5), a suggestive determination is made when the “[e]vidence is suggestive of a causal relationship with relevant pollutant exposures, but is limited because chance, bias and confounding cannot be ruled out.” In contrast, the Administrator note d that she proposed to strengthen the annual fine particle standard base d on a body of scientific evidence judged sufficient to***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 332 of 790 Formatted: Left conclude that a causal relationship exists (i.e., mortality, cardiovascular effects) or is likely to exist (i.e., respiratory effects) (section I II.B) . 77 FR 38961. The suggestive judgment for PM 10

- 2 .5 reflects the greater degree of uncertainty associated with this body of evidence, as discussed above (sections I V.B and I V .C ) and summarized below. In the proposal ( 77 FR 38961) , t he Administrator note d that the important uncertainties and limitations associated with the scientific evidence and air quality information raise questions as to whether public health benefits would be achieved by revising the existing PM 10 standard
. Such uncertainties and limitations include the following: (1) While PM 10

- 2.5 eff ect estimates reported for mortality and morbidity were generally positive, most were not statistically significant, even in single

- pollutant models
. This includes effect estimates reported in some study locations with PM 10 concentrations above those allow ed by the current 24

- hour PM 10 standard
. (2) The number of epidemiological studies that have employed co

- pollutant models to address the potential for confounding, particularly by PM 2.5 , remains limited
. Therefore, the extent to which PM 10

- 2.5 itself, rather than one or more co

pollutants, contributes to reported health effects is less certain. (3) Only a limited number of experimental studies (i.e., controlled human exposure and animal toxicological) provide support for the associations reported in epidemiological studies, resulting in further uncertainty regarding the plausibility of the associations between PM 10

- 2.5 and mortality and morbidity reported in epidemiological studies
. (4) Limitations in PM 10

- 2.5 monitoring data and the different approac hes used by epidemiological study researchers to estimate PM 10

- 2.5 concentrations across epidemiological studies result in u ncertainty in the ambient PM 10

- 2.5 concentrations at which the reported effects occur, increasing uncertainty in estimates of the ex tent to which changes in ambient PM 10

- 2.5 concentrations would likely impact public health. (5) The lack of a quantitative PM 10

- 2.5 risk assessment further contributes to uncertainty regarding the extent to which any revisions to the current PM 10 standard wou ld be expected to improve the protection of public health, beyond the protection provided by the current standard (see section III.B.5 above).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 333 of 790 Formatted: Left (6) The chemical and biological composition of PM 10

- 2.5 , and the effects associated with the various components, rem ains uncertain
. Without more information on the chemical speciation of PM 10

- 2.5 , the apparent variability in associations across locations is difficult to interpret. In considering these uncertainties and limitations, the Administrator note d in particul ar the considerable degree of uncertainty in the extent to which health effects reported in epidemiological studies are due to PM 10

- 2.5 itself, as opposed to one or more

co - occurring pollutants
. As discussed above, this uncertainty reflects the fact that t here are a relatively small number of PM 10

- 2.5 studies that have utilized co - pollutant models, particularly co

- pollutant models that have included PM 2.5 , and a very limited body of controlled human exposure evidence supporting the biological plausibility of a causal relationship between PM 10

- 2.5 and mortality and morbidity at ambient concentrations
. The Administrator note d that these important limitations in the overall body of health evidence introduce uncertainty into the interpretation of individual epi demiological studies, particularly those studies reporting associations with PM 10

- 2.5 that are not statistically significant
. Given this, the Administrator reache d the provisional conclusion in the proposal that it is appropriate to place relatively little weight on epidemiological studies reporting associations with PM 10

- 2.5 that are not statistically significant in single

pollutant and/or co

- pollutant models. Id
. With regard to this provisional conclusion, the Administrator note d that, for single

- city mor tality studies conducted in the United States where ambient PM 10 concentration data were available for comparison to the current standard, positive and statistically significant PM 10

- 2.5 effect estimates were only reported in study locations that would lik ely have violated the current PM 10 standard during the study period (U.S. EPA , 2011a, Figure 3

- 2)
. In U.S. study locations that would likely have met the current***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 334 of 790 Formatted: Left standard, PM 10

- 2.5 effect estimates for mortality were positive, but not statistically signifi cant (U.S. EPA , 2011a, Figure 3

- 2)
. In considering U.S. study locations where single

- city morbidity studies were conducted, and which would likely have met the current PM 10 standard during the study period, the Administrator note d that PM 10

- 2.5 effect esti mates were both positive and negative, with most not statistically significant (U.S. EPA , 2011a, Figure 3

- 3). In addition, in considering single

- city analyses for the locations evaluated in a large U.S. multi

- city mortality study ( Zanobetti and Schwartz , 2 009), the Administrator note d that associations in most of the study locations were not statistically significant and that this was the only study to estimate ambient PM 10

- 2.5 concentrations as the difference between county

- wide PM 10 and PM 2.5 mass . As discussed in the Policy Assessment and in the proposal , it is not clear how computed PM 10

- 2.5 measurements, such as those used by Zanobetti and Schwartz (2009) , compare with the PM 10

- 2.5 concentrations obtained in other studies either by direct measurem ent or by calculating the difference using co

located samplers (U.S. EPA , 2009a, section 6.5.2.3). For these reasons, in the proposal the Administrator note d that “ there is considerable uncertainty in interpreting the associations in these single

- city anal yses ” (77 FR 38961

- 62). The Administrator acknowledge d that an approach to considering the available scientific evidence and air quality information that emphasizes the above considerations differs from the approach taken by CASAC
. Specifically, in its rev iew of the draft Policy Assessment CASAC placed a substantial amount of weight on individual studies, particularly those reporting positive health effects associations for PM 10

- 2.5 in locations that met the current PM 10 standard during the study period
. In emphasizing these studies,***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 335 of 790 Formatted: Left as well as the limited number of supporting studies that have evaluated co

- pollutant models and the small number of supporting experimental studies, CASAC concluded that “the current data, while limited, is sufficient to call in to question the level of protection afforded the American people by the current standard” (Samet, 2010d, p. 7) and recommended revising the current PM 10 standard (Samet, 2010d)
. The Administrator carefully considered CASAC’s advice and recommendations

. Sh e note d that in making its recommendation on the current PM 10 standard, CASAC did not discuss its approach to considering the important uncertainties and limitations in the health evidence, and did not discuss how these uncertainties and limitations we re reflected in its recommendation . Nor did CASAC discuss uncertainties in the reported concentrations of PM 10

- 2.5 in the epidemiological studies, or how reported concentrations in the various studies relate to one another when differing measurement methodolo gies are used. As discussed above, such uncertainties and limitations contributed to the conclusions in the Integrated Science Assessment that the PM 10

- 2.5 evidence is only suggestive of a causal relationship, a conclusion that CASAC endorsed (Samet, 2009 e,f)
. Given the importance of these uncertainties and limitations to the interpretation of the evidence, as reflected in the weight of evidence conclusions in the Integrated Science Assessment and as discussed above, the Administrator judge d it appropriate to consider and account for them when drawing conclusions about the potential implications of individual PM 10

- 2.5 health studies for the current standard
. In light of the above approach to considering the scientific evidence, air quality information, and associated uncertainties, the Administrator reache d the following provisional conclusions in the proposal :***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 336 of 790 Formatted: Left (1) W hen viewed as a whole the available evidence and information suggests that the degree of public health protection provided against short

- term expos ures to PM 10

- 2.5 does not need to be increased beyond that provided by the current PM 10 standard. This provisional conclusion noted the important uncertainties and limitations associated with the overall body of health evidence and air quality information for PM 10

- 2.5 , as discussed above and as reflected in the Integrated Science Assessment weight

- of

- evidence conclusions; that PM 10

- 2.5 effect estimates for the most serious health effect, mortality, were not statistically significant in U.S. locations that m et the current PM 10 standard and where coarse particle concentrations were either directly measured or estimated based on co

located samplers; and that PM 10

- 2.5 effect estimates for morbidity endpoints were both positive and negative in locations that met the current standard, with most not statistically significant
. (2) T he degree of public health protection provided by the current standard is not greater than warranted . This provisional conclusion noted that positive and statistically significant association s with mortality were reported in single

- city U.S. study locations likely to have violated the current PM 10 standard
. 136 In reaching these provisional conclusions, the Administrator note d that the Policy Assessment also discusse d the potential for a revised PM 10 standard (i.e., with a revised form and level) to be “generally equivalent” to the current standard, but to better target public health protection to locations where there is greater concern regarding PM 10

- 2.5 - associated health effects (U.S. EPA , 2011a, sections 3.3.3 and 3.3.4). In considering such a potential revised standard, the Policy Assessment discusse d the large amount of variability in PM 10 air quality correlations across monitoring locations and over time (U.S. EPA , 2011a, Figure 3

- 7) a nd the regional variability in the relative degree of public
136 There are similarities with the conclusions drawn by the Administrator in t he last review. There, the Administrator concluded that there was no basis for concluding that the degree of protection afforded by the current PM 10 standards in urban areas is greater than warranted, since potential mortality effects have been associated with air quality levels not allowed by the current 24

- hour standard, but have not been associated with air quality levels that would generally meet that standard, and morbidity effects have been associated with air quality levels that exceeded the current 24

- hour standard only a few times (71 FR 61202). In addition, the Administrator concluded that there was a high degree of uncertainty in the relevant population exposures implied by the morbidity studies suggesting that there is little basis for concludin g that a greater degree of protection is warranted. Id. The D.C. Circuit in American Farm Bureau Federation v EPA explicitly endorsed this reasoning. 559 F. 3d at 534.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 337 of 790 Formatted: Left health protection that could be provided by the current and potential alternative standards (U.S. EPA , 2011a, Table 3

- 2)
. In light of this variability, the Administrator note d the Policy Assessme nt conclusion that no single revised PM 10 standard (i.e., with a revised form and level) would provide public health protection equivalent to that provided by the current standard, consistently over time and across locations (U.S. EPA , 2011a, section 3.3.4 )
. That is, a revised standard, even one that is meant to be “generally equivalent” to the current PM 10 standard, could increase protection in some locations while decreasing protection in others (77 FR 38962). In considering the appropriateness of revisin g the current PM 10 standard in this way, the Administrator note d the following: (1) P ositive PM 10

- 2.5 effect estimates for mortality were not statistically significant in U.S. locations that met the current PM 10 standard and where coarse particle concentrations were either directly measured or estimated based on co

- located samplers, while positive and statistically significant associations with mortality were reported in locations likely to have violated the curr ent PM 10 standard. (2) E ffect estimates for morbidity endpoints in locations that met the current standard were both positive and negative, with most not statistically significant. (3) Important uncertainties and limitations associated with the overall body of h ealth evidence and air quality information for PM 10

- 2.5 , as discussed above and as reflected in the Integrated Science Assessment weight

- of

- evidence conclusions, call into question the extent to which the type of quantified and refined targeting of public health protection envisioned under a revised standard could be reliably accomplished
. Given all of the above considerations, the Administrator note d that there is a large amount of uncertainty in the extent to which public health would be improved by chan ging the locations to which the PM 10 standard targets protection
. Therefore, she reache d the provisional conclusion that the current PM 10 standard should not be revised in order to change that targeting of protection
. In considering all of the above, incl uding the scientific evidence, the air quality***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 338 of 790 Formatted: Left information, the associated uncertainties, and CASAC’s advice, the Administrator reache d the provisional conclusion that the current 24

- hour PM 10 standard is requisite (i.e., neither more protective nor less p rotective than necessary) to protect public health with an adequate margin of safety against effects that have been associated with PM 10

- 2.5 . In light of this provisional conclusion, t he Administrator propose d to retain the current PM 10 standard in order to protect against health effects associated with short

- term exposures to PM 10

- 2.5 (77 FR 38963). The Administrator recognize d that her proposed conclusions and decision to retain the current PM 10 standard differ ed from CASAC’s recommend ations, stemming from the differences in how the Administrator and CASAC considered and accounted for the evidence and its limitations and uncertainties
. In light of CASAC’s views and recommendation to revise the current PM 10 standard, the Administrator we lcome d the public’s views on these different approaches to considering and accounting for the evidence and its limitations and uncertainties, as well as on the appropriateness of revising the primary PM 10 standard, including revising the form and level of the standard. In doing so, t

he Administrator solicit ed comment on all aspects of th e proposed decision, including her rationale for reaching the provisional conclusion that the current PM 10 standard is requisite to protect public health with an adequate ma rgin of safety and the provisional conclusion that it is not appropriate to revise the current PM 10 standard by setting a “generally equivalent” standard with the goal of better targeting public health protection. F
. Public Comments on the Administrator’s Proposed Decision to Retain the Primary PM

10 Standard This section discusses the major public comments received on the Administrator’s Formatted: Indent: Left: 0", Hanging: 0.5", Space After: 12 pt, Line spacing: single***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 339 of 790 Formatted: Left proposed decision to retain the primary PM 10 standard. Additional comments are addressed in the Response to Comments Document (U.S. EPA, 2012 2012a ). Many public commenters agreed with the Administrator’s proposed decision to retain the current 24

- hour primary PM 10 standard. Among those expressing a position on this proposed decision, industry groups and most State and Local commenters endorsed the Administrator’s proposed rationale for retaining the current primary PM 10 standard, including her consideration of the available scientific evidence and associated uncertainties and her consideration of CASAC recomm endations. Although industry commenters generally agreed with the Administrator’s proposed decision to retain the current primary PM 10 standard, a few also some also contended that the current standard is “excessively precautionary” (NMA and NCBA, 2012, p. 4) and a few expressed support for a less stringent standard for coarse particles that are comprised largely of crustal material. For example, the Coarse Particulate Matter Coalition (CPMC) (2012) and several other industry commenters recommended that the final decision allow application of a 98 th percentile form for the current standard (i.e. with its level of 150 ug/m 3 ) in cases where coarse particles consist primarily of crustal material. Such an approach would allow more yearly exceedances of the exist ing standard level than are allowed with the current one

- expected

- exceedance form. These industry commenters contended that a 98 th percentile form applied in this way would provide appropriate regulatory relief for areas where the evidence for coarse particle

related health effects is relatively uncertain. In reaching her conclusion that the current primary PM 10 standard is requisite to protect public health with an adequate margin of safety, t he Administrator considered the***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 340 of 790 Formatted: Left degree of public health protection provided by the current standard as a whole, including all elements of that standard (i.e., indicator, averaging time, form, level). As discussed above and in the following section, this co nclusion reflects the Administrator’s judgments that (1) the current standard appropriately provides some measure of protection against exposures to all thoracic coarse particles, regardless of their location, source of origin, or composition and (2) the c urrent standard appropriately allows lower ambient concentrations of PM 10

- 2.5 in urban areas, where the evidence is strongest that thoracic coarse particles are linked to mortality and morbidity, and higher concentrations in non

urban areas, where the publ ic health concerns are less certain
. Because the considerations that led to these judgments, and to the conclusion that the current primary PM 10 standard is requisite to protect public health, took into account the degree of public health protection provi ded by the standard as a whole, it would not be appropriate to consider revising one element of the standard (e.g., the form, as suggested by commenters in this case) without considering the extent to which the other elements of the standard should also be revised. The change in form requested by industry commenters, without also lowering the level of the standard, would markedly reduce the public health protection provided against exposures to thoracic coarse particles. 137 However, i ndustry commenters have n ot presented new evidence or analyses

137 Based on regression analyses presented in the PA (U.S. EPA, 2011a, Figures 3

- 7 and 3

- 8) , PM 10 one - expected

- exceedance concentration

- equivalent design values were between approximately 175 and 300 g/m 3 at monitoring locations recording 3

- year averages of 98 th percentile 24

- hour PM 10 concentrations around 150 g/m 3 (i.e., the level of the current standard). This suggests that, depending on the location, a 24

- hour PM 10 standard with a 98 th percentile form in conjunction with the current level (i.e., as recommended by these commenters) could be “generally equivalent” to a 24

- hour PM 10 standard with a one

- expected

- exceedance form and a level as high as approximately 300 g/m 3 . Based on this analysis, a 24

- hour PM 10 standard with a 98 th percentile form and a level of 150 g/m 3 would be markedly less health protective tha n the current standard. Formatted: Font: Times New Roman Formatted: Font: Times New Roman

Formatted: Font: Times New Roman Formatted: Font: Times New Roman***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 341 of 790 Formatted: Left to support their conclusion that an appropriate degree of public health protection could be achieved by allowing the use of an alternative form (i.e., 98 th percentile) for some coarse particles, while retaining the oth er elements of the current standard. Nor have these commenters presented new evidence or analyses challenging the basis for the conclusion in the proposal that the varying amounts of coarse particles allowed in urban versus non urban areas under the curren t 24

- hour PM 10 standard, based on the varying levels of PM 2.5 present, appropriately reflect the differences in the strength of evidence regarding coarse particle effects in urban and non

- urban areas . In light of this, EPA does not believe that a reduction in public health protection, such as that requested by industry commenters, is warranted. In further considering these comments, it is to be remembered that epidemiologic studies have not de monstrated that coarse particles of non

- urban origin do not caus e health effects, and commenters have not provided additional evidence on this point. While there are fewer studies of non

- urban coarse particles than of urban coarse particles, several studies have reported positive and statistically significant associati ons between coarse particles of crustal, non

- urban origin and mortality or morbidity (Ostro et al., 2003; Bell et al., 2008; Chan et al., 2008; Middleton et al., 200 8; Perez et al., 2008). These studies formed part of the basis for the PM Integrated Scienc e Assessment conclusion that “ recent studies have suggested that PM (both PM 2.5 and PM 10

- 2.5 ) from crustal, soil or road dust sources or PM tracers linked to these sources are associated with cardiovascular effects” (U.S. EPA , 2009 2009 a , p. 2

- 26). Moreover, crustal coarse particles may be contaminated with toxic trace elements and other components from previously deposited fine PM from ubiquitous sources such as mobile source engine***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 342 of 790 Formatted: Left exhaust, as well as by toxic metals from smelters or other industri al activities, animal waste, or pesticides (U.S. EPA, 2004, p. 8

- 344). In the proposal, the Administrator acknowledged the potential for this type of contamination to increase the toxicity of coarse particles of crustal, non

- urban origin (77 FR 38960; see also 71 FR 61190). In suggesting a change in the form of the current standard, industry commenters also did not address the manifold difficulties noted above, and in the last review, associated with developing an indicator that could reliably identify ambi ent mixes dominated by particular types of sources of coarse particles. See above and 71 FR 61193. Yet such an indicator would be a prerequisite of the type of standard these commenters request. For all of the reasons discussed above, the EPA does not agr ee with industry commenters who recommended allowing the application of a 98 th percentile form for the current standard in cases where coarse particles consist primarily of crustal material. Some industry commenters contended that the uncertainties and li mitations that precluded a quantitative risk assessment also preclude revising the PM 10 standard. Although the EPA agrees that there are important uncertainties and limitations in the extent to which the quantitative relationships between ambient PM 10

- 2.5 and health outcomes can be characterized in risk models, the Agency does not agree that such limitations alone preclude the option of revising a NAAQS. As noted above, t he lack of a quantitative PM 10

- 2.5 risk assessment in the current review adds uncertain ty to conclusions about the extent to which revision of the current PM 10 standard would be expected to improve the protection of public health, beyond the protection provided by the current standard. However, the EPA does not agree that such uncertainties necessarily preclude***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 343 of 790 Formatted: Left revision of a NAAQS. Indeed, with respect to thoracic coarse particles, the D.C. Circuit noted that “[a]lthough the evidence of danger from coarse PM is, as the EPA recognizes, ‘inconclusive’, th e agency need not wait for conclusive findings before regulating a pollutant it reasonably believes may pose a significant risk to public health.” 559 F. 3d at 533. Thus, the Administrator’s conclusion that the current 24

- hour PM 10 standard provides requi site protection of public health relies on her consideration of the broad body of evidence, rather than solely on the uncertainties that led to the decision not to conduct a quantitative assessment of PM 10

- 2.5 health risks. Commenters representing a numbe r of environmental groups and medical organizations disagreed with the Administrator’s proposal to retain the current primary PM 10 standard. These commenters generally requested that the EPA revise the PM 10 standard to increase public health protection, co nsistent with the recommendations from CASAC. As discussed above and in the proposal, in reaching provisional conclusions in the proposal regarding the current standard, the Administrator carefully considered CASAC’s advice and recommendations. She speci fically note d that in making its recommendation on the current PM 10 standard, CASAC did not discuss its approach to considering the important uncertainties and limitations in the health evidence, and did not discuss how these uncertainties and limitations we re reflected in its recommendation s . S uch uncertainties and limitations contributed to the conclusions in the Integrated Science Assessment that the PM 10

- 2.5 evidence is only suggestive of a causal relationship, a conclusion that CA SAC endorsed (Samet, 2009e,f). These commenters also did not address the important uncertainties in the epidemiologic studies on which their comments are based. Given the importance of these uncertainties and limitations to the interpretation of the evidence, as reflected in the weight of evidence conclusions in the***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 344 of 790 Formatted: Left Integrated Science Assessment and as discussed in the proposal , the Administrator judge s that it is appropriate to consider and account for them when drawing conclusions about the implications of individual PM 10

- 2. 5 health studies for the current standard. Commenters have not provided new information that would change the Administrator’s views on the evidence and uncertainties. In recommending that the PM 10 standard be revised, some commenters supported their concl usions by referencing studies that evaluated PM 10 , rather than PM 10

- 2.5 . These commenters contended that “[t]he most relevant studies to the setting of a PM 10 standard are the thousands of studies that have reported adverse effects associated with PM 10 pollution” (ALA et al., 2012). As discussed in the Policy Assessment, the proposal, and above, since the establishment of the primary PM 2.5 standards, the purpose of the primary PM 10 standard has been to protect against health effects associated with exp osures to PM 10

- 2.5 . PM 10 is the indicator, not the target pollutant. With regard to the appropriateness of considering PM 10 health studies for the purpose of reaching conclusions on a standard meant to protect against exposures to PM 10

- 2.5 , the proposal noted that PM 10 includes both fine and coarse particles, even in locations with the highest concentrations of PM 10

- 2.5 . Therefore, the extent to which PM 10 effect estimates reflect associations with PM 10

- 2.5 versus PM 2.5 can be highly uncertain and it is often unclear how PM 10 health studies should be interpreted when considering a standard meant to protect against exposures to PM 10

- 2.5 . Given this uncertainty and the availability of a number of PM 10

- 2.5 health studies in this review, the Integrated Science Assessment considered PM 10

- 2.5 studies, but not PM 10***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 345 of 790 Formatted: Left studies, when drawing weight

- of

- evidence conclusions regarding the coarse fraction. 138 In light of the uncertainty in ascribing PM 10 - related health effects to the coars e or fine fractions, indicating that the best evidence for effects associated with exposures to PM 10

- 2.5 comes from studies evaluating PM 10

- 2.5 itself, and given CASAC’s support for the approach adopted in th e Integrated Science Assessment, which draws wei ght

- of

evidence conclusions for PM 2.5 and PM 10

- 2.5 but not for PM 10 (Samet, 2009 f ) , the EPA continues to conclude that it is appropriate to focus on PM 10

- 2.5 health studies when considering the degree of public health protection provided by the current primary PM 10 standard, a standard intended exclusively to provide protection against exposures to PM 10

- 2.5 . G
. Administrator’s Final Decision on the Primary PM 10 Standard In reaching a final decision on the primary PM 10 standard, the Administrator takes into account the available scientific evidence, and the assessment of that evidence, in the Integrated Science Assessment ; the analyses and staff conclusions presented in the P olicy Assessment; the advi ce and recommendations of CASAC; and public comments on the proposal. In particular, as in the proposal, the Administrator places emphasis on her consideration of the following issues : (1) The extent to which it is appropriate to main tain a standard that provides some measure of protection against all PM 10

- 2.5 , regardless of composition or source of origin ; (2) The extent to which it is appropriate to retain a PM 10 indicator for a standard meant to protect against exposures to ambient PM 1 0

- 2.5 ; and
138 Although EPA relied in the 1997 review on evidence from PM 10 studies, EPA did so out of necessity (i.e., there were as yet no reliable studies measuring PM 10

- 2.5 ). In the 2006 review, EPA placed primary reliance on epidemiologic s tudies measuring or estimating PM 10

- 2.5 , although there were comparatively few such studies. In this review, a larger body of PM 10

- 2.5 studies are available. EPA regards these studies as the evidence to be given principal weight in reviewing the adequacy o f the PM 10 standard.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 346 of 790 Formatted: Left
(3) The extent to which the current PM 10 standard provides an appropriate degree of public health protection. Each of these issues is discussed below. With regard to the first issue , as in the proposal the Administrator judges that the expanded b ody of scientific evidence available in this review provides ample support for a standard that protects against exposures to all thoracic coarse particles, regardless of their location or source of origin . There was already ample evidence for this position in the previous review, 139 and that evidence has since increased. Specifically, the Administrator notes that epidemiological studies have reported positive associations between PM 10

- 2.5 and mortality or morbidity in a large number of cities across North America, Europe, and Asia, encompassing a variety of environments where PM 10

- 2.5 sources and composition are expected to vary widely
. In considering this evidence, the Integrated Science Assessment concludes that “ many constituents of PM can be linked with differing health effects ” (U.S. EPA , 2009a, p. 2

- 26) . Although PM 10

- 2.5 in most of these study areas is of largely urban origin, the Administrator notes that some recent studies have als o linked mortality and morbidity with relatively high ambient concentrations of particles of non

- urban crustal origin
. In considering these studies, she notes the Integrated Science Assessment’s conclusion that “PM (both PM 2.5 and PM 10

- 2.5 ) from crustal, s oil or road dust sources or PM tracers linked to these sources are associated with cardiovascular effects” (U.S. EPA , 2009a, p. 2

- 26) . The Administrator likewise notes CASAC’s emphatic advice that a standard remains needed for all types of thoracic

139 The D.C. Circuit agreed. See 559 F. 3d at 532

- 33.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 3 47 of 790 Formatted: Left

coarse PM. 140 In light of this body of available evidence reporting PM 10

- 2.5 - associated health effects across different locations with a variety of sources, the Integrated Science Assessment’s conclusions regarding the links between adverse health effects and PM

so urces and composition, and CASAC’s advice, the Administrator concludes in the current review that it is appropriate to maintain a standard that provides some measure of protection against exposures to all thoracic coarse particles, regardless of their loca tion, source of origin, or composition
. With regard to the second issue , in considering the appropriateness of a PM 10 indicator for a standard meant to provide such public health protection, the Administrator notes that the rationale used in the last revi ew to support the unqualified PM 10 indicator remains relevant in the current review
. Specifically, as an initial consideration, she notes that PM 10 mass includes both coarse PM (PM 10

- 2.5 ) and fine PM (PM 2.5 )
. As a result, the concentration of PM 10

- 2.5 allo wed by a PM 10 standard set at a single level declines as the concentration of PM 2.5 increases
. At the same time, the Administrator notes that PM 2.5 concentrations tend to be higher in urban areas than rural areas (U.S. EPA , 2005, p. 2

– 54, and Figures 2

– 23 and 2

– 24) and, therefore, a PM 10 standard will generally allow lower PM 10

- 2.5 concentrations in urban areas than in rural areas
. In considering the appropriateness of this variation in allowable PM 10

- 2.5 concentrations, the Administrator considers the re lative strength of the evidence for health effects associated with PM 10

- 2.5 of urban origin versus non

- urban origin
. She specifically notes that , as discussed in the proposal, the large majority of the available evidence for thoracic coarse particle health effects comes from studies conducted in

140 Indeed, CASAC recommended making the standard for all types of thoracic coarse PM more stringent (Samet, 2010d).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 348 of 790 Formatted: Left locations with sources more typical of urban and industrial areas than rural areas
. While associations with adverse health effects have been reported in some study locations where PM 10

- 2.5 is largely non

- urban in or igin (i.e., in dust storm studies), particle concentrations in these study areas are typically much higher than reported in study locations where the PM is of urban origin
. Therefore, the Administrator notes that the strongest evidence for a link between P M 10

- 2.5 and adverse health impacts, particularly for such a link at relatively low particle concentrations, comes from studies of urban or industrial PM 10

- 2.5 . The Administrator also notes that chemical constituents present at higher levels in urban or in dustrial areas, including byproducts of incomplete combustion ( e.g. polycyclic aromatic hydrocarbons) emitted as PM 2.5 from motor vehicles as well as metals and other contaminants emitted from anthropogenic sources, can contaminate PM 10

- 2.5 (U.S. EPA , 2004 , p. 8

– 344; 71 FR 2665, January 17, 2006)
. While the Administrator acknowledges the uncertainty expressed in the Integrated Science Assessment regarding the extent to which particle composition can be linked to health outcomes based on available evidence, she also considers the possibility that PM 10

- 2.5 contaminants typical of urban or industrial areas could increase the toxicity of thoracic coarse particles in urban locations
. Given that the large majority of the evidence for PM 10

- 2.5 toxicity, particular ly at relatively low particle concentrations, comes from study locations where thoracic coarse particles are of urban origin, and given the possibility that PM 10

- 2.5 contaminants in urban areas could increase particle toxicity, the Administrator concludes that it remains appropriate to maintain a standard that provides some protection in all areas but targets public health protection to urban locations
. Specifically, she concludes that it is appropriate to maintain a standard that allows lower ambient conce ntrations of PM 10

- 2.5 in***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 349 of 790 Formatted: Left urban areas, where the evidence is strongest that thoracic coarse particles are linked to mortality and morbidity, and higher concentrations in non

- urban areas, where the public health concerns are less certain
. Given all of the a

bove considerations and conclusions, the Administrator judges that the available evidence supports retaining a PM 10 indicator for a standard that is meant to protect against exposures to thoracic coarse particles
. In reaching this judgment, she notes that, to the extent a PM 10 indicator results in lower allowable concentrations of thoracic coarse particles in some areas compared to others, lower concentrations will be allowed in those locations (i.e., urban or industrial areas) where the science has shown t he strongest evidence of adverse health effects associated with exposure to thoracic coarse particles and where we have the most concern regarding PM 10

- 2.5 toxicity
. Therefore, the Administrator concludes that the varying amounts of coarse particles that

a re allowed in urban vs. non

- urban areas under the 24

- hour PM 10 standard, based on the varying levels of PM 2.5 present, appropriately reflect the differences in the strength of evidence regarding coarse particle effects in urban and non

- urban areas. 141 , 142 In reaching this conclusion, the Administrator also notes that, i n their review of

141 As discussed in the proposal, the Administrator recognizes that t his relationship is qualitative. That is, the varying coarse particle concentrations allowed under the PM 10 standard do not precisely correspon d to the variable toxicity of thoracic coarse particles in different areas (insofar as that variability is understood). Although currently available information does not allow any more precise adjustment for relative toxicity, the Administrator believes th e standard will generally ensure that the coarse particle levels allowed will be lower in urban areas and higher in non

- urban areas. Addressing this qualitative relationship, the D.C. Circuit held that “[i]t is true that the EPA relies on a qualitative ana lysis to describe the protection the coarse PM NAAQS will provide. But the fact that the EPA’s analysis is qualitative rather than quantitative does not undermine its validity as an acceptable rationale for the EPA’s decision.” 559 F. 3d at 535. 142 The D.C. Circuit agreed with similar conclusions in the last review and held that this rationale reasonably supported use of an unqualified PM 10 indicator for thoracic coarse particles. American Farm Bureau Federation v. EPA , 559 F. 3d at 535

- 36.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 350 of 790 Formatted: Left the second draft Policy Assessment, CASAC concluded that “[w] hile it would be preferable to use an indicator that reflects the coarse PM directly linked to health risks (PM 1 0

- 2.5 ), CASAC recognizes that there is not yet sufficient data to permit a change in the indicator from PM 10 to one that directly measures thoracic coarse particles” (Samet, 2010d, p. ii) . Thus, consistent the considerations presented above and with CASAC advice, the Administrator concludes that it is appropriate to retain PM 10 as the indicator for thoracic coarse particles. 143 With regard to the third issue , in evaluating the degree of public health protection provided by the current PM 10 standard, the Admi nistrator first notes that when the available PM 10

- 2.5 scientific evidence and its associated uncertainties we re considered, the Integrated Science Assessment conclude d that the evidence is suggestive of a causal relationship between short

- term PM 10

- 2.5 ex posures and mortality, cardiovascular effects, and respiratory effects
. As discussed above and in more detail in the Integrated Science Assessment (U.S. EPA , 2009a, section 1.5), a suggestive determination is made when the “[e]vidence is suggestive of a ca usal relationship with relevant pollutant exposures, but is limited because chance, bias and confounding cannot be ruled out.” In contrast, the Administrator notes that she is strengthen ing the annual fine particle standard based on a body of scientific ev idence judged sufficient to conclude that a causal relationship exists (i.e., mortality, cardiovascular effects) or is likely to exist (i.e., respiratory effects)
. The suggestive judgment for PM 10

- 2.5 reflects the greater degree of uncertainty associated w ith

143 In addition, CAS AC “vigorously recommends the implementation of plans for the deployment of a network of PM 10

- 2.5 sampling systems so that future epidemiological studies will be able to more thoroughly explore the use of PM 10

- 2.5 as a more appropriate indicator for thorac ic coarse particles” (Samet, 2010d, p. 7). Consideration of alternative indicators (e.g., PM 10

- 2.5 ) in future reviews could be informed by additional research, as described in the Policy Assessment (U.S. EPA, 2011a, section 3.5).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 351 of 790 Formatted: Left this body of evidence, as discussed above and in more detail in the proposal, and as summarized below. The Administrator notes that the important uncertainties and limitations associated with the scientific evidence and air quality information raise questions as to whether public health benefits would be achieved by revising the existing PM 10 standard
. Such uncertainties and limitations include the following: (1) While PM 10

- 2.5 effect estimates reported for mortality and morbidity were generally positive , most were not statistically significant, even in single

- pollutant models
. This includes effect estimates reported in some study locations with PM 10 concentrations above those allowed by the current 24

- hour PM 10 standard
. (2) The number of epidemiological studies that have employed co

- pollutant models to address the potential for confounding, particularly by PM 2.5 , remains limited
. Therefore, the extent to which PM 10

- 2.5 itself, rather than one or more co

pollutants, contributes to reported health effects r emains uncertain
. (3) Only a limited number of experimental studies provide support for the associations reported in epidemiological studies, resulting in further uncertainty regarding the plausibility of the associations between PM 10

- 2.5 and mortality and mo rbidity reported in epidemiological studies
. (4) Limitations in PM 10

- 2.5 monitoring data and the different approaches used to estimate PM 10

- 2.5 concentrations across epidemiological studies result in u ncertainty in the ambient PM 10

- 2.5 concentrations at which the reported effects occur, increasing uncertainty in estimates of the extent to which changes in ambient PM 10

- 2.5 concentrations would likely impact public health. (5) The lack of a quantitative PM 10

- 2.5 risk assessment further contributes to uncertainty re garding the extent to which any revisions to the current PM 10 standard would be expected to improve the protection of public health, beyond the protection provided by the current standard (see section III.B.5 above). (6) The chemical and biological compositio n of PM 10

- 2.5 , and the effects associated with the various components, remains uncertain
. Without more information on the chemical speciation of PM 10

- 2.5 , the apparent variability in associations across locations is difficult to characterize
. In considering these uncertainties and limitations, the Administrator notes in particular the considerable degree of uncertainty in the extent to which health effects***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 352 of 790 Formatted: Left reported in epidemiological studies are due to PM 10

- 2.5 itself, as opposed to one or more

co - occurring pollutants
. As discussed above, this uncertainty reflects the fact that there are a relatively small number of PM 10

- 2.5 studies that have evaluated co

- pollutant models, particularly co

- pollutant models that have included PM 2.5 , and a very limite d body of controlled human exposure evidence supporting the plausibility of a causal relationship between PM 10

- 2.5 and mortality and morbidity at ambient concentrations
. The Administrator notes that these important limitations in the overall body of health evidence introduce uncertainty into the interpretation of individual epidemiological studies, particularly those studies reporting associations with PM 10

- 2.5 that are not statistically significant
. Given this, the Administrator reaches the conclusion that it is appropriate to place relatively little weight on epidemiological studies reporting associations with PM 10

- 2.5 that are not statistically significant in single

- pollutant and/or

co - pollutant models. 144 With regard to this conclusion, the Administrator notes that, for single

- city
144 The Administrator acknowl edges that this approach to interpreting the evidence differs in emphasis from the approach she has adopted for the evidence relating to PM 2.5 . As discussed above in section III.E.4, for fine particles the Administrator has considered not only whether stud y results are statistically significant (or remain so after application of co - pollutant models), but she also places emphasis on the overall pattern of results across the epidemiological literature. This includes giving some credence to studies that repor ted statistically non

- significant associations. This difference in emphasis stems from the much stronger overall body of evidence available for fine particles, compared to coarse particles. As discussed above, when the available PM 2.5 scientific evidence a nd its associated uncertainties were considered, the Integrated Science Assessment concluded that the evidence was sufficient to conclude that causal relationships exist with mortality and cardiovascular effects, and that a causal relationship is likely to exist with respiratory effects. In contrast, the Integrated Science Assessment concluded that the evidence is suggestive of a causal relationship between short

- term PM 10

- 2.5 exposures and mortality, cardiovascular effects, and respiratory effects. A sugge stive determination is made when the “[e]vidence is suggestive of a causal relationship with relevant pollutant exposures, but is limited because chance, bias and confounding cannot be ruled out” (U.S. EPA, 2009a, section 1.5). The suggestive judgment for PM 10

- 2.5 reflects the greater degree of uncertainty associated with this body of evidence.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 353 of 790 Formatted: Left mortality studies conducted in the United States where ambient PM 10 concentration data were available for comparison to the current standard, positive and statistically significant PM 10

- 2.5 effect estimates were only reported in study locations that would likely have violated the current PM 10 standard during the study period (U.S. EPA , 2011a, Figure 3

- 2)
. In U.S. study locations that would likely have met the current standard, PM 10

- 2.5 effect estimates for mortality were positive , but not statistically significant (U.S. EPA , 2011a, Figure 3

- 2)
. In considering U.S. study locations where single

- city morbidity studies were conducted, and which would likely have met the current PM 10 standard during the study period, the Administrator notes that PM 10

- 2.5 effect estimates were both positive and negative, with most not statistically significant (U.S. EPA , 2011a, Figure 3

- 3). In addition, in considering single

- city analyses for the locations evaluated in a large U.S. multi

- city mortality s tudy ( Zanobetti and Schwartz , 2009), the Administrator note s that associations in most of the study locations were not statistically significant and that this was the only study to estimate ambient PM 10

- 2.5 concentrations as the difference between county

- wide PM 10 and PM 2.5 mass . As discussed in the proposal , the Administrator notes that it is not clear how computed PM 10

- 2.5 measurements, such as those used by Zanobetti and Schwartz (2009) , compare with the PM 10

- 2.5 concentrations obtained in other studies either by direct measurement by calculating the difference using

co - located samplers (U.S. EPA , 2009a, section 6.5.2.3). For these reasons, as in the proposal, the Administrator note s that there is consider able uncertainty in interpreting the

assoc iations, and especially the concentrations at which such associations may have occurred, in these single

- city analyses. The Administrator acknowledges that an approach to considering the available***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 354 of 790 Formatted: Left scientific evide nce and air quality information that emphasizes the above considerations differs from the approach taken by CASAC
. Specifically, CASAC placed a substantial amount of weight on individual studies, particularly those reporting positive health effects associa tions in locations that met the current PM 10 standard during the study period
. In emphasizing these studies, as well as the limited number of supporting studies that have evaluated co

- pollutant models and the small number of supporting experimental studies , CASAC concluded that “the current data, while limited, is sufficient to call into question the level of protection afforded the American people by the current standard” (Samet, 2010d, p. 7) and recommended revising the current PM 10 standard (Samet, 2010d )
. The Administrator has carefully considered CASAC’s advice and recommendations
. She notes that in making its recommendation on the current PM 10 standard, CASAC did not discuss its approach to considering the important uncertainties and limitations in the health evidence, and did not discuss how these uncertainties and limitations are reflected in its recommendation
. As discussed above, such uncertainties and limitations contributed to the conclusions in the Integrated Science Assessment that the PM 10

- 2 .5 evidence is only suggestive of a causal relationship, a conclusion that CASAC endorsed (Samet, 2009e,f)
. Given the importance of these uncertainties and limitations to the interpretation of the evidence, as reflected in the weight of evidence conclusion s in the Integrated Science Assessment and as discussed above, the Administrator judges that it is appropriate to consider and account for them when drawing conclusions about the potential implications of individual PM 10

- 2.5 health studies for the current standard
.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 355 of 790 Formatted: Left In light of the above approach to considering the scientific evidence, air quality information, and associated uncertainties, the Administrator reaches the following conclusions: (1) W hen viewed as a whole the available evidence and information sugg ests that the degree of public health protection provided against short

- term exposures to PM 10

- 2.5 should be maintained but does not need to be increased beyond that provided by the current PM 10 standard. This conclusion emphasizes the important uncertaint ies and limitations associated with the overall body of health evidence and air quality information for PM 10

- 2.5 , as discussed above and as reflected in the Integrated Science Assessment weight

- of

- evidence conclusions; that PM 10

- 2.5 effect estimates for th e most serious health effect, mortality, were not statistically significant in U.S. locations that met the current PM 10 standard and where coarse particle concentrations were either directly measured or estimated based on co

located samplers; and that PM 10

- 2.5 effect estimates for morbidity endpoints were both positive and negative in locations that met the current standard, with most not statistically significant
. 145 (2) T he degree of public health protection provided by the current standard is not greater than warranted . This conclusion notes that positive and statistically significant associations with mortality were reported in single

- city U.S. study locations likely to have violated the current PM 10 standard
. 146

145 This is not to say that the EPA could not adopt or revise a standard for a pollutant for which the evidence is suggestive of a causal relationship. Indeed, with r espect to thoracic coarse particles itself, the D.C. Circuit noted that “[a]lthough the evidence of danger from coarse PM is, as the EPA recognizes, ‘inconclusive’, the agency need not wait for conclusive findings before regulating a pollutant it reasonabl y believes may pose a significant risk to public health.” American Farm Bureau Federation v EPA 559 F. 3d at 533. As explained in the text above, it is the Administrator’s judgment that significant uncertainties presented by the evidence and information be fore her in this review, both as to causality and as to concentrations at which effects may be occurring, best support a decision to retain rather than revise the current primary 24

- hour PM 10 standard. 146 There are similarities with the conclusions drawn by the Administrator in the last review. There, the Administrator concluded that there was no basis for concluding that the degree of protection afforded by the current PM 10 standards in urban areas is greater than warranted, since potential mortality effects have been associated with air quality levels not allowed by the current 24

- hour standard, but have not been associated with air quality levels that would generally meet that standard, and morbidity effects have been associated with air quality levels that exceeded the current 24

- hour standard only a few times. 71 FR 61202. In addition, the Administrator concluded that there was a high degree of uncertainty in the relevant population exposures implied by the morbidity studies suggesting that there is littl e basis for concluding that a greater degree of***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 356 of 790 Formatted: Left In reaching these conclusions, the Administrato r notes that the Policy Assessment also discusse d the potential for a revised PM 10 standard (i.e., with a revised form and level) to be “generally equivalent” to the current standard, but to better target public health protection to locations where there i s greater concern regarding PM 10

- 2.5 - associated health effects (U.S. EPA , 2011a, sections 3.3.3 and 3.3.4). 147 In considering such a potential revised standard, the Policy Assessment discusses the large amount of variability in PM 10 air quality correlations across monitoring locations and over time (U.S. EPA , 2011a, Figure 3

- 7) and the regional variability in the relative degree of public health protection that could be provided by the current and potential alternative standards (U.S . EPA , 2011a, Table 3

- 2)
. In light of this variability, the Administrator notes the Policy Assessment conclusion that no single revised PM 10 standard (i.e., with a revised form and level) would provide public health protection equivalent to that provided b y the current standard, consistently over time and across locations (U.S. EPA , 2011a, section 3.3.4)
. That is, a revised standard, even one that is meant to be “generally equivalent” to the current PM 10 standard, could increase protection in some locations while decreasing protection in other locations
. In considering the appropriateness of revising the current PM 10 standard in this way, the Administrator notes the following: protection is warranted. Id. The D.C. Circuit in American Farm Bureau Federation v EPA explicitly endorsed this reasoning. 559 F. 3d at 534. 147 As discussed in detail above (section IV.C.2.d) and in the Policy Assessment (U.S. EPA, 2011a, sections 3.3.3 and 3.3.4), a revised standard that is generally equivalent to the current PM 10 standard could provide a degree of public health protection that is similar to the degree of protection provided by the current stan dard, across the United States as a whole. However, compared to the current PM 10 standard, such a generally equivalent standard would change the degree of public health protection provided in some specific areas, providing increased protection in some loca tions and decreased protection in other locations.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 357 of 790 Formatted: Left (1) As discussed above, positive PM 10

- 2.5 effect estimates for mortality were not st atistically significant in U.S. locations that met the current PM 10 standard and where coarse particle concentrations were either directly measured or estimated based on co

- located samplers, while positive and statistically significant associations with mo rtality were reported in locations likely to have violated the current PM 10 standard. (2) Also as discussed above, effect estimates for morbidity endpoints in locations that met the current standard were both positive and negative, with most not statistically significant. (3) Important uncertainties and limitations associated with the overall body of health evidence and air quality information for PM 10

- 2.5 , as discussed above and as reflected in the Integrated Science Assessment weight

- of

- evidence conclusions, ca ll into question the extent to which the type of quantified and refined targeting of public health protection envisioned under a revised standard could be reliably accomplished
. Given all of the above considerations, the Administrator notes that there is a large amount of uncertainty in the extent to which public health would be improved by changing the locations to which the PM 10 standard targets protection
. Therefore, she reaches the conclusion that the current PM 10 standard should not be revised in orde r to change that targeting of protection
. In considering all of the above, including the scientific evidence, the air quality information, the associated uncertainties, CASAC’s advice, and public comments received on the proposed rule, the Administrator r eaches the conclusion in the current review that the existing 24

- hour PM 10 standard , with its one

- expected exceedance form and a level of 150 g/m 3 , is requisite (i.e., neither more protective nor less protective than necessary) to protect public health with an adequate margin of safety against effects that have been associated with PM 10

- 2.5 . In light of this conclusion, with this notice t he Administr ator retain s the current PM 10 standard. V. Communicati on of Public Health Information Sections 319(a)(1) and (3) of the CAA require the EPA to establish a uniform air***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 358 of 790 Formatted: Left quality index for reporting of air quality
. These sections specifically direct the Administrator to ‘‘promulgate regulations establishing an air quality monitoring system throughout the United States which utilizes uniform air quality monitoring criteria and methodology and measures such air quality according to a uniform air quality index’’ and ‘‘provides for daily analysis and reporting of air quality based upon such uniform air quality index...’’ In 1979, the EPA established requirements for index reporting (44 FR 27598, May 10, 1979)
. The requireme nt for State and local agencies to report the AQI appears in 40 CFR 58.50 , and the specific requirements (e.g., what to report, how to report, reporting frequency, calculations) are in appendix G to 40 CFR part 58. Information on the public health implicat ions of ambient concentrations of criteria pollutants is currently made available primarily by AQI reporting through EPA’s AIRNow website. 148 The current AQI has been in use since its inception in 1999. 149 It provides accurate, timely, and easily understandable information about daily levels of pollution (40 CFR 58.50)
. The AQI establishes a nationally uniform system of indexing pollution levels for ozone, carbon monoxide, nitrogen dioxide, PM, and sulfur d ioxide
. The AQI is also recognized internationally as a proven tool to effectively communicate air quality information to the public
. The AQI converts pollutant concentrations in a community’s air to a number on a scale from 0 to 500
. Reported AQI values enable the public to know whether air pollution levels in a particular location are characterized as good (0

– 50), moderate (51

– 100), unhealthy for sensitive groups (101

– 150), unhealthy (151

– 200), very unhealthy (201

– 148 See http://www.airnow.gov/
. 149 In 1976, the EPA established a nationally uniform air quality index, then called the Pollutant Standard Index (PSI), for use by State and local agencies on a voluntary basis (41 FR 37660, September 7, 1976). In August 1999, the EPA adopted revisions to this air quality index (64 FR 42530, August 4, 1999) and renamed the index the AQI. Formatted: Font: 12 pt***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 359 of 790 Formatted: Left 300), or hazardous (30 1

– 500)
. The AQI i ndex value of 100 typically corresponds to the level of the short

- term (e.g., daily or hourly standard) NAAQS for each pollutant
. Below an index value of 100, an intermediate value of 50 was defined either as the level of the annual standard if an annual s tandard has been established (e.g., PM 2.5 , nitrogen dioxide), or as a concentration equal to one

- half the value of the short

- term standard used to define an index value of 100 (e.g., carbon monoxide). An AQI value greater than 100 means that a pollutant is in one of the unhealthy categories (i.e., unhealthy for sensitive groups, unhealthy, very unhealthy, or hazardous) on a given day
. An AQI value at or below 100 means that a pollutant concentration is in one of the satisfactory categories (i.e., moderate

o r good) . The underlying health information that supports the NAAQS review also supports the selection of the AQI “breakpoints”

– the ambient concentrations that delineate the various AQI categories for each pollutant. Historically, s tate and local agencies have primarily used the AQI to provide general information to the public about air quality and its relationship to public health
. For more than a decade, many s tates and local agencies, as well as the EPA and other Federal agencies, have been developing n ew and innovative programs and initiatives to provide more information to the public in a more timely way
. These initiatives, including air quality forecasting, real

- time data repor ting through the Air Now website, and state and local air quality action day programs, can serve to provide useful, up

- to
- date, and timely information to the public about air pollution and its effects
. Such information will help individuals take actions to avoid or to reduce exposures to ambient pollution at levels of concern to t

hem
. Thus, these programs have significantly broadened the ways in which s tate and local agencies can meet the nationally uni form AQI reporting***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 360 of 790 Formatted: Left requirements and contribute to s tate and local efforts to provide community health protection
. With respect to an AQI value of 50, the historical approach is to set it at the same level of the annual primary standard, if there is one
. This is consistent with the previous AQI sub

- index for PM 2.5 , in which the AQI value of 50 was set at 15 μg/m 3 in 1999, consistent w ith the level of the annual PM 2.5 standard at that time. In recognition of the proposed change to the annual PM 2.5 standard summarized in section III.F of the proposal , the EPA propos ed a conforming change to the PM 2.5 sub

- index of the AQI to be consistent with the proposed change to the annual standard . As discussed below, no state or local agencies, or their organizations (e.g., NACAA), that commented on the proposed changes to the AQI disagreed with our proposed approach. Based on the se comments, the EPA continues to see no basis for deviating from this approach in this review. Thus, the EPA is taking final action to set an AQI value of 50 at 12.0 μg /m 3 , 24

- hour average, consistent with the final decision on the annual PM 2.5 standard l evel (section III.F). With respect to an AQI value of 100, which is the basis for advisories to individuals in sensitive groups , in the proposal we described two general approaches that could be used to select the associated PM 2.5 level
. By far the most c ommon approach, which has been used with all of the other sub

- indices, is to set an AQI value of 100 at the same level as the short

- term standard . In the proposal, the EPA recognize d that some

s tate and local air quality agencies have expressed a strong pr eference that the Agency set an AQI value of 100 equal to any short

- term standard (77 FR 38964). These agencies typically express the view that this linkage is useful for the purpose of communicating with the public about the standard, as well as providing consistent messages about the***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 361 of 790 Formatted: Left health impacts associated with daily air quality . The EPA propos ed to use this approach to set the AQI value of 100 at 35 μg/m 3 , 24

- hour average, consistent with the proposed decision to retain the current 24

- hour PM 2.5 standard
. Id
. An alternative approach discussed in the proposal ( 77 FR 38964 ), wa s to directly evaluate the health effects evidence to select the level for an AQI value of 100 . This was the approach used in the 1999 rulemaking to set the AQI value of 100 at a level of 40 μg/m 3 , 24

- hour average, 150 when the 24

- hour standard level was 65 μg/m 3 . This alternative approach was used in the case of the PM 2.5 sub

- index, because the annual and 24

- hour PM 2.5 standards set in 1997 were designed to work together, an d the intended degree of health protection against short

- term risks was not defined by the 24

- hour standard alone, but rather by the combination of the two standards working in concert. Indeed, at that time, the 24

- hour standard was set to provide suppleme ntal protection relative to the principal protection provided by the annual standard. In the proposal, the EPA solicited comment on this alternative approach in recognition that, as proposed, the 24

- hour PM 2.5 standard is intended to continue to provide supplemental protection against effects associated with short

- term exposures of PM 2.5 by working in conjunction with the annual standard to reduce 24

- hour exposures to PM 2.5 . The EPA recognized that in the past, some s tate and local air quality agencies ha ve expressed support for this alternative approach . Using this alternative approach could have result ed in c onsideration of a lower level for an AQI value of 100, based on the discussion of the health information pertaining to the level of the 24

- hour stan dard in section III.E.4 of the proposal. The EPA

150 C urrently, we are cautioning members of sensitive groups at the AQI value of 100 at 35 μg/m 3 , 24

- hour average, consistent with more recent guidance from the EPA with regard to the development of State emergency episode contingency plans (Harnett, 2009, Attachment B). Formatted: Font: 12 pt Formatted: Font: 12 pt, Not Superscript/ Subscript***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 362 of 790 Formatted: Left
encourage d s tate and local air quality agencies to comment on both the approach and the level at which to set an AQI value of 100 together with any supporting rationale. Of the state or local agencies, or th eir organizations (e.g., NACAA), that commented on the proposed changes to the AQI, only one organization, NESCAUM, expressed some support for this approach. In its comments, NESCAUM expressed support for a 24

- hour standard set at 30 μg/m 3 , 24

- hour average . NESCAUM also expressed the view that EPA should carefully consider how to set the breakpoint for an AQI value of 100. NESCAUM expressed the view that i f the EPA were to keep the 24

- hour PM 2.5 standard at 35 ug/m 3 , the annual standard would be controlling , and a 24

- hour breakpoint at that level (35 ug/m 3 ) would not be very effective for the purposes of public health messaging. However, other agencies, such as Georgia Department of Natural Resources (Georgia DNR), expressed the view that linkage between the short

- term standard and the AQI of 100 is useful for the purpose of communicating with the public about the standard as well as providing consistent messages about the health impacts associated with the daily air quality . Based on these comments, the EPA see s no basis for deviating from the approach proposed in this review. Thus, the EPA is taking final action to set an AQI value of 100 at 35 μg/m 3 , 24

- hour average, consistent with the final decision on the 24

- hour PM 2.5 standard level (section III.F). With respect to an AQI value of 150, this level is based upon the same health effects information that informs the selection of the level of the 24

- hour standard and the AQI value of 100 . The AQI value of 150 was set in the 1999 rulemaking at a level of 65 μg/m 3 , 24

- hour average. In considering what level to propose for an AQI value of 150,
we stated the view that the health effects evidence indicates that the level of 55 μg/m 3 ,***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 363 of 790 Formatted: Left 24

- hour average, is appropriate to use 151 in conjunction with an AQI value of 100 set at the level of 35 μg/m 3

. The Agency’s approach to selecting the levels at which to set the AQI values of 100 and 150 inherently recognizes that the epidemiological evidence upon which these decisions are based provides no evidence of discern i ble thre sholds, below which effects do not occur in either sensitive groups or in the general population, at which to set these two breakpoints . Therefore, the EPA concluded the use of a proportional adjustment would be appropriate . Commenters did not comment on t his proposed approach to revising the AQI value of 150; thus, the EPA is taking final action to set an AQI value of 150 at 55 μg/m 3 , 24

- hour average. Based on the air quality and health considerations discussed in section V of the proposal, the EPA conclud ed that it was appropriate to propose to retain the current level of 500 μg/m 3 , 24

- hour average, for the AQI value of 500 . In addition, the EPA solicited comment on alternative levels and approaches to setting a level for the AQI value of 500, as well as s upporting information and rationales for such alternative levels. The EPA also solicited any additional information, data, research or analyses that may be useful to inform a final decision on the appropriate level to set the AQI value of 500. Receiving no information with which to inform alternative approaches to setting an AQI value of 500, the EPA is taking final action to retain the current level of 500 μg/m 3 , 24

- hour average, for the AQI value of 500
. For the intermediate breakpoints in the AQI between the values of 150 and 500, the EPA propos ed PM 2.5 concentrations that generally reflect ed a linear relationship between increasing index values and increasing PM 2.5 values (77 FR 38965). The
151 We note that this level is consiste nt with the level recommended in the more recent EPA guidance (Harnett, 2009, Attachment B), which is in use by many State and local agencies.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 364 of 790 Formatted: Left available scientific evidence of health effects related to population exposures to PM 2.5 concentrations between the level of the 24

- hour standard and an AQI value of 500 suggest ed a continuum of effects in this range, with increasing PM 2.5 concentrations being associated with increasingly larger numbers of people likely to experience such effects
. The generally linear relationship between AQI values and PM 2.5 concentrations in this range is consistent with the health evidence
. This also is consistent with the Agency’s practice of setting breakpoints in symmetrical fashion where health effects information does not suggest particular levels. Table 2 below summarizes the finalized breakpoint s for the PM 2.5 sub

- index. 152 Table 2 shows the intermediate breakpoints for AQI values of 200, 300 and 400 based on a linear interp olation between the proposed levels for AQI values of 150 and 500. If a different level were to be set for an AQI value of 150 or 500, intermediate levels would be calculated based on a linear relationship between the selected levels for AQI values of 150 and 500. Table 2. Breakpoints for PM 2.5 Sub

- Index

AQI Category Index Values Proposed Breakpoints (μg/m 3 , 24

- hour average) Good 0

- 50 0.0

– (12.0) Moderate 51

- 100 (12.1)

– 35.4 Unhealthy for Sensitive Groups 101

- 150 35.5

– 55.4 Unhealthy 151

- 200 55.5

- 150.4 Very Unhealthy 201

- 300 150.5

- 250.4 Hazardous 301

- 400 250.5

- 350.4

152 As discussed in section VII.C below, the EPA is also updating the data handling procedures for reporting the AQ I and corresponding updates for other AQI

- sub

- indices presented in Table 2 of appendix G of 40 CFR part 58.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 365 of 790 Formatted: Left
401

- 500 350.5

- 500.4

I n retaining the 500 level for the AQI as described above , we note that the EPA is not establish ing a Significant Harm Level (SHL) for PM 2.5 . The SHL is an important part of air pollution Emergency Episode Plans, which are required for certain areas by CAA section 110(a)(2)(G) and associated regulations at 40 CFR 51.150, under the Prevention of Air Pollution Emergency Episodes program. The Age ncy believes that air quality responses established through an Emergency Episode Plan should be developed through a collaborative process working with State and Tribal air quality, forestry and agricultural agencies, Federal land management agencies, priva te land managers and the public. Therefore, if in future rulemaking the EPA proposes revisions to the Prevention of Air Pollution Emergency Episodes program, the proposal will include a SHL for PM 2.5 that is developed in collaboration with these organizati ons. As discussed in the 1999 Air Quality Index Reporting Rule (64 FR 42530), if a future rulemaking results in a SHL that is different from the 500 value of the AQI for PM 2.5 , the AQI will be revised accordingly. The EPA also received more general commen ts on AQI reporting, comments that did not pertain to setting specific breakpoints. One set of commenters (e.g., API and UARG), expressed the view that changes to the AQI are not appropriate. They noted that air quality is getting better, and in fact is be tter than when EPA established the AQI. These commenters stated that the proposed changes to the annual standard and the AQI would mean that the public would hear less often that air quality is good, and thereby would receive apparently inconsistent or mis leading messages that air quality is worse. The AQI has been revised several times in conjunction with revisions to the standards. State and local air quality agencies and organizations are proficient at communicating***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 366 of 790 Formatted: Left with the public about the reasons for changes to the AQI. Therefore, the EPA strongly disagrees with these commenters that the public will receive inconsistent or misleading messages. Recognizing the importance of the AQI as a communication tool that allows the public to take exposure reductio n measures when air quality may pose health risks, the EPA agrees with state and local air quality agencies and organizations that favored revising the AQI at the same time as the primary standard. A few state and local air quality agencies and organizatio ns recommended against using near

- roadway PM 2.5 monitors for AQI reporting. In support of this comment, they expressed the following views, that near

- roadway monitors are source

- oriented, represent micro

- scale conditions, and the agencies don’t have experi ence using them for AQI reporting. The EPA disagrees with the comment in that these monitors will be sited at existing near

- road stations sited to be representative of area

- wide PM 2.5 concentrations indicative of general population exposure. Accordingly, d ata from these near

- road monitors should be included in the AQI since they provide information about PM 2.5 levels that millions of people, who work, live and go to school near busy roadways, are exposed to. T he stations are representative of somewhat eleva ted concentrations in near road environments, but since these stations represent many such locations throughout a metropolitan area, they are appropriate for characterizing exposure in typical portions of major urban areas
. The EPA is committed to helping air quality agencies develop appropriate ways to report PM 2.5 levels from these monitors using the AQI. VI. Rationale for Final Decisions on the Secondary PM Standards This section presents the Administrator’s final decisions regarding the need to revise the current suite of secondary PM 2.5 and PM 10 standards to address visibility***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 367 of 790 Formatted: Left impairment and other welfare effects considered in this review. As discussed more fully bel ow, Specifically, t

his section describes the rationale for the Administrator’s final decision to retain the current suite of secondary PM standards to address PM

- related visibility impairment as well as other PM

- related welfare effects, including ecological effects, effects on materials, and climate impacts. This suite of standards includes an annual PM 2.5 standard of 15 μg/m 3 , a 24

- hour PM 2.5 standard of 35 μg/m 3 , and a 24

- hour PM 10 standard of 150 μg/m 3 . The Administrator is revising only the form of the secondary annual PM 2.5 standard to remove the option for spatial averaging consistent with this change to the primary annual PM 2.5 standard. C ontrary to what was proposed, the Administrator has decided not to establish a distinct standard to address PM

- rel ated visibility impairment . The rationale for this decision is presented below
. T he Administrator’s final decision s on the secondary standards are based on a thorough review , in the Integrated Science Assessment, of the latest scientific information , published through mid

- 2009 , on welfare effects associated with fine and coarse particles in the ambient air , as presented in the Integrated Science Assessment
. The final decisions also take into account: (1) staff assessments of the most policy

relevant i nformation presented and assessed in the Integrated Science Assessment and staff analyses of air quality and visibility effects presented in the Visibility Assessment and the Policy Assessment, upon which staff conclusions regarding appropriate considerati ons in this review are based; (2) CASAC advice and recommendations, as reflected in discussions of drafts of the Integrated Science Assessment, Visibility Assessment, and Policy Assessment at public meetings, in separate written comments, and in CASAC’s le tters to the Administrator; (3) the multiple rounds of public comments***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 368 of 790 Formatted: Left received during the development of these documents, either both in connection with CASAC meetings or and separately; and (4) public comments received on the proposal. In particular, this section presents background information on the EPA’s previous and current reviews of the secondary PM standards (section VI.A), a summary of the proposed decisions regarding the secondary PM standards (section VI.B), a summary discussion of significant publ ic comments received on those proposed decisions (section VI.C), and the Administrator’s final decisions on the secondary PM standards (section VI.D). A. Background The current suite of secondary PM standards is identical to the current suite of primary PM standards set in 2006 , including 24

- hour and annual PM 2.5 standards and a 24

- hour PM 10 standard. The current secondary PM 2.5 standards are intended to provide protection from PM

- related visibility impairment, whereas the entire suite of secondary PM standa

rds is intended to provide protection from other PM

- related effects on public welfare, including effects on sensitive ecosystems, materials damage and soiling, and climatic and radiative processes. The approach used for reviewing the current suite of secon dary PM standards built upon and broadened the approaches used in previous PM NAAQS reviews. The following discussion focuses particularly on the current secondary PM 2.5 standards related to visibility impairment and provides a summary of the approaches us ed to review and establish secondary PM 2.5 standards in the last two reviews (section VI.A.1); judicial review of the 2006 standards that resulted in the remand of the secondary annual and 24

- hour PM 2.5 NAAQS to the EPA (section VI.A.2); and the approach u sed in this review***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 369 of 790 Formatted: Left for evaluating the secondary PM 2.5 standards used in this review (section VI.A.3). 1. Approaches Used in Previous Reviews The original secondary PM 2.5 standards were established in 1997, and a revision to the 24

- hour standard was made in 2006. The approaches used in making final decisions on secondary standards in those reviews, as well as the current review, utilized different ways to consider the underlying body of scientific evidence. They also reflected an evolution in EPA’s understan ding of the nature of the effect on public welfare from PM

- related visibility impairment, from an approach focusing that focus ed only on Federal Class I area visibility impacts to a more multifaceted approach that also considers consider ed PM

- related impacts on visibility in non - Federal Class I area visibility area s , such as in urban areas. This evolution occurred in conjunction with the expansion of available PM data and information from associated visibility

- related studies of public perception, valuation, an d personal comfort and well

- being. In 1997, the EPA revised the PM NAAQS in part by establishing new identical primary and secondary PM 2.5 standards. In revising the secondary standards, the EPA recognized that PM produces adverse effects on visibility an d that impairment of visibility was being experienced throughout the U.S., in multi

- state regions, urban areas, and remote mandatory Federal Class I areas alike. However, in considering an appropriate level for a secondary standard to address adverse effec ts of PM 2.5 on visibility, the EPA concluded that the determination of a single national level was complicated by important regional differences influenced by factors such as background and current levels of PM 2.5 , composition of PM 2.5 , and average relativ e humidity. Variations in these factors across regions could thus result in situations where attaining***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 370 of 790 Formatted: Left an appropriately protective concentration of fine particles in one region might or might not provide adequate protection in a different region. The EPA a lso determined that there was insufficient information at that time to establish a level for a national secondary standard that would represent a threshold above which visibility conditions would always be adverse and below which visibility conditions woul d always be acceptable. Based on an assessment of the potential visibility improvements that would result from reaching attainment with the new primary standards for PM 2.5 , the EPA concluded that attainment of the annual and 24

- hour PM 2.5 primary standards would lead to visibility improvements in the eastern U.S. at both urban and regional scales, but little or no change in the western U.S., except in and near certain urban areas. The EPA also considered the potential effectiveness of a regional haze progra m, required by sections 169A and 169B of the CAA 153 to address those effects of PM on visibility that would not be addressed through attainment of the primary PM 2.5 standards. The regional haze program would be designed to address the widespread, regionally uniform type of haze caused by a multitude of sources. The structure and requirements of sections 169A and 169B of the CAA provide for visibility protection progr ams that can be more responsive to the factors contributing to regional differences in visibility than can programs addressing the kinds of nationally applicable secondary NAAQS considered in the 1997 review. The regional haze visibility goal is more prote ctive than a secondary NAAQS since the goal is to eliminate any anthropogenic impairment rather than to provide a level of protection from visibility impairment that is requisite to protect
153 In 1977, Congress established as a national goal ‘‘the prevention of any future, and the remedying of any existing, impairment of visibility in mandatory Federal Class I areas which impairment results from manmade air pollution,” section 169A(a)(1) of the CAA. The EPA is required by section 169A(a)(4) of the CAA to promulgate regulations to ensure that ‘‘reasonable progress’’ is achieved toward meeting the national goal.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 371 of 790 Formatted: Left the public welfare. Thus, an important factor considered in the 19 97 review was whether a regional haze program, in conjunction with secondary standards set identical to the suite of PM 2.5 primary standards, would provide appropriate protection for visibility in non

Federal Class I areas. The EPA concluded that the two p rograms and associated control strategies should provide such protection due to the regional approaches needed to manage emissions of pollutants that impair visibility in many of these areas. For these reasons, in 1997 the EPA concluded that a national reg ional haze program, combined with a nationally applicable level of protection achieved through secondary PM 2.5 standards set identical to the primary PM 2.5 standards, would be more effective for addressing regional variations in the adverse effects of PM 2. 5 on visibility than would be national secondary standards for PM with levels lower than the primary PM 2.5 standards. The EPA further recognized that people living in certain urban areas may place a high value on unique scenic resources in or near these ar eas and as a result might experience visibility problems attributable to sources that would not necessarily be addressed by the combined effects of a regional haze program and PM 2.5 secondary standards. The EPA concluded that in such cases, state or local regulatory approaches, such as past action in Colorado to establish a local visibility standard for the City of Denver, would be more appropriate and effective in addressing these special situations because of the localized and unique characteristics of th e problems involved. Visibility in an urban area located near a mandatory Federal Class I area could also be improved through state implementation of the then

- current visibility regulations, by which emission limitations can be imposed on a source or group of sources found to be contributing to ‘‘reasonably attributable’’ impairment in the mandatory Federal Class I area.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 372 of 790 Formatted: Left Based on these considerations, in 1997 the EPA set secondary PM 2.5 standards identical to the primary PM 2.5 standards, that would work in conjunction with a regional haze program

the R egional H aze P rogram to be established under sections 169A and 169B of the CAA, as the most appropriate and effective means of addressing the public welfare effects associated with visibility impairment. Togethe r, the two programs and associated control strategies were expected to provide appropriate protection against PM

related visibility impairment and enable all regions of the country to make reasonable progress toward the national visibility goal. In 2006, t he EPA revised the suite of secondary PM 2.5 standards to address visibility impairment by making the suite of secondary standards identical to the revised suite of primary PM 2.5 standards. The EPA’s decision regarding the need to revise the suite of second ary PM 2.5 standards reflected a number of new developments that had occurred and sources of information that had become available following the 1997 review. First, the EPA promulgated a Regional Haze Program in 1999 (65 FR 35713, July 1, 1999) which requir ed states to establish goals for improving visibility in Federal Class I areas and to adopt control strategies to achieve these goals. Second, extensive new information from visibility and fine particle monitoring networks had become available, allowing fo r updated characterizations of visibility trends and PM concentrations in urban areas, as well as Federal Class I areas. These new data allowed the EPA to better characterize visibility impairment in urban areas and the relationship between visibility and PM 2.5 concentrations. Finally, additional studies in the U.S. and abroad provided the basis for the establishment of standards and programs to address specific visibility concerns in a number of local areas. These studies (Denver, Phoenix, and British***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 373 of 790 Formatted: Left Colu mbia) utilized photographic representations of visibility impairment and produced reasonably consistent results in terms of the visual ranges found to be generally acceptable by study participants. The EPA considered the information generated by these stud ies useful in characterizing the nature of particle

- induced haze and for informing judgments about the acceptability of various levels of visual air quality in urban areas across the U.S. Based largely on this information, the Administrator concluded that it was appropriate to revise the secondary PM 2.5 standards to provide increased protection from visibility impairment principally in urban areas, in conjunction with the regional haze program for protection of visual air quality in Federal Class I areas. In so doing, the Administrator recognized that PM

- related visibility impairment is principally related to fine particle concentrations and that perception of visibility impairment is most directly related to short

- term, nearly instantaneous levels of visua l air quality. Thus, in considering whether the then

- current suite of secondary standards would provide the appropriate degree of protection, he concluded that it was appropriate to focus on just the 24

- hour secondary PM 2.5 standard to provide requisite pr otection. The Administrator then considered whether PM 2.5 mass remained the appropriate indicator for a secondary standard to protect visibility, primarily in urban areas. The Administrator noted that PM

- related visibility impairment is principally related to fine particle levels. H ygroscopic components of fine particles, in particular sulfates and nitrates, contribute disproportionately to visibility impairment under high humidity conditions. Particles in the coarse mode generally contribute only marginall y to visibility impairment in urban areas. With the substantial addition to the air quality and visibility data made possible by the national urban PM 2.5 monitoring networks, an analysis***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 374 of 790 Formatted: Left conducted for the 2006 review found that, in urban areas, visibility levels showed far less difference between eastern and western regions on a 24

- hour or shorter time basis than implied by the largely non

- urban data available in the 1997 review. In analyzing how well PM 2.5 concentrations correlated with visibility in urban locations across the U.S., the 2005 Staff Paper concluded that clear correlations existed between 24

- hour average PM 2.5 concentrations and calculated (i.e., reconstructed) light extinction, which is direct ly related to visual range (U.S. EPA, 2005, p. 7

- 6). These correlations were similar in the eastern and western regions of the U.S. These correlations were less influenced by relative humidity and more consistent across regions when PM 2.5 concentrations we re averaged over shorter, daylight time periods (e.g., 4 to 8 hours) when relative humidity in eastern urban areas was generally lower and thus more similar to relative humidity in western urban areas. The 2005 Staff Paper noted that a standard set at any specific PM 2.5 concentration would necessarily result in visual ranges that vary somewhat in urban areas across the country, reflecting the variability in the correlations between PM 2.5 concentrations and light extinction. The 2005 Staff Paper concluded th at it was appropriate to use PM 2.5 as an indicator for standards to address visibility impairment in urban areas, especially when the indicator is defined for a relatively short period (e.g., 4 to 8 hours) of daylight hours (U.S. EPA, 2005, p. 7

- 6). Based on their review of the Staff Paper, most CASAC Panel members also endorsed such a PM 2.5 indicator for a secondary standard to address visibility impairment (Henderson, 2005a, p. 9). Based on the above considerations, the Administrator concluded that PM 2.5 should be retained as the indicator for fine particles as part of a secondary standard to address visibility protection, in conjunction with averaging times from 4 to 24 hours.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 375 of 790 Formatted: Left In considering what level of protection against PM

- related visibility impairmen t would be appropriate, the Administrator took into account the results of the public perception and attitude surveys regarding the acceptability of various degrees of visibility impairment in the U.S. and Canada, state and local visibility standards withi n the U.S., and visual inspection of photographic representations of several urban areas across the U.S. In the Administrator’s judgment, these sources provided useful but still quite limited information on the range of levels appropriate for consideration in setting a national visibility standard primarily for urban areas, given the generally subjective nature of the public welfare effect involved. Based on photographic representations of varying levels of visual air quality, public perception studies, and local and state visibility standards, the 2005 Staff Paper had concluded that 30 to 20 μg/m 3 PM 2.5 represented a reasonable range for a national visibility standard primarily for urban areas, based on a sub

- daily averaging time (U.S. EPA, 2005, p. 7

- 13). The upper end of this range was below the levels at which illustrative scenic views are significantly obscured, and the lower end was around the level at which visual air quality generally appeared to be good based on observation of the illustrative views. This concentration range generally corresponded to median visual ranges in urban areas within regions across the U.S. of approximately 25 to 35 km, a range that was bounded above by the visual range targets selected in specific areas where state or local agencies placed particular emphasis on protecting visual air quality. In considering a reasonable range of forms for a PM 2.5 standard within this range of levels, the 2005 Staff Paper had concluded that a concentration

- based percentile form was appropriate , and that the upper end of the range of concentration percentiles for consideration should be consistent with the 98 th percentile used for the primary standard***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 376 of 790 Formatted: Left and that the lower end of the range should be the 92 nd percentile, which represented the

mean o f the distribution of the 20 percent most impaired days, as targeted in the regional haze program (U.S. EPA, 2005 pp. 7

- 11 to 7

- 13). While recognizing that it was difficult to select any specific level and form based on then

- currently available information (Henderson, 2005a, p. 9), the CASAC Panel was generally in agreement with the ranges of levels and forms presented in the 2005 Staff Paper. The Administrator also considered the level of protection that would be afforded by the proposed suite of primary PM 2.5 standards (71 FR 2681, January 17, 2006), on the basis that although significantly more information was available than in the 1997 review concerning the relationship between fine PM levels and visibility across the country, there was still little ava ilable information for use in making the relatively subjective value judgment needed in selecting the appropriate degree of protection to be afforded by such a standard. In so doing, the Administrator compared the extent to which the proposed suite of prim ary standards would require areas across the country to improve visual air quality with the extent of increased protection likely to be afforded by a standard based on a sub

- daily averaging time. Based on such an analysis, the Administrator observed that t he predicted percent of counties with monitors not likely to meet the proposed suite of primary PM 2.5 standards was actually somewhat greater than the predicted percent of counties with monitors not likely to meet a sub

- daily secondary standard with an
ave raging time of 4 daylight hours, a level toward the upper end of the range recommended in the 2005 Staff Paper, and a form within the recommended range. Based on this comparison, the Administrator tentatively concluded that revising the secondary 24

- hour P M 2.5 standard to be identical to the proposed revised primary PM 2.5 standard***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 377 of 790 Formatted: Left (and retaining the then

- current annual secondary PM 2.5 standard) was a reasonable policy approach to addressing visibility protection primarily in urban areas. In proposing this

a pproach, the Administrator also solicited comment on a sub

- daily (4

- to 8

- hour averaging time) secondary PM 2.5 standard (71 FR 2675 to 2781, January 17, 2006). In commenting on the proposed decision, the CASAC requested that a sub

- daily standard to protec t visibility “be favorably reconsidered” (Henderson, 2006a, p.6). The CASAC noted three cautions regarding the proposed reliance on a secondary PM 2.5 standard identical to the proposed 24

- hour primary PM 2.5 standard: (1) PM 2.5 mass measurement is a better indicator of visibility impairment during daylight hours, when relative humidity is generally low; the sub

- daily standard more clearly matches the nature of visibility impairment, whose adverse effects are most evident during the daylight hours; using a 24

- hour PM 2.5 standard as a proxy introduces error and uncertainty in protecting visibility; and sub

- daily standards are used for other NAAQS and should be the focus for visibility; (2) CASAC and its monitoring subcommittees had repeatedly commended EPA’s in itiatives promoting the introduction of continuous and near

continuous PM monitoring and recognized that an expanded deployment of continuous PM 2.5 monitors would be consistent with setting a sub

- daily standard to protect visibility; and (3) the analysis s howing a similarity between percentages of counties not likely to meet what the CASAC Panel considered to be a lenient 4

- to 8

- hour secondary standard and a secondary standard identical to the proposed 24

- hour primary standard was a numerical coincidence t

hat was not indicative of any fundamental relationship between visibility and health. The CASAC Panel further stated that “visual air quality is substantially impaired at PM 2.5 concentrations of 35 μg/m 3 ” and that “[i]t is not***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 378 of 790 Formatted: Left reasonable to have the visibi lity standard tied to the health standard, which may change in ways that make it even less appropriate for visibility concerns” (Henderson, 2006a, pp. 5 to 6). In reaching a final decision, the Administrator focused on the relative protection provided by the proposed primary standards based on the above

- mentioned similarities in percentages of counties meeting alternative standards and on the limitations in the information available concerning studies of public perception and attitudes regarding the accept ability of various degrees of visibility impairment in urban areas, as well as on the subjective nature of the judgment required. In so doing, the Administrator concluded that caution was warranted in establishing a distinct secondary standard for visibili ty impairment and that the available information did not warrant adopting a secondary standard that would provide either more or less protection against visibility impairment in urban areas than would be provided by secondary standards set equal to the pro posed primary PM 2.5 standards. 2. Remand of 2006 Secondary PM 2.5 Standards As noted above in section II.B.2 above, several parties filed petitions for review challenging EPA’s decision to set the secondary NAAQS for fine PM identical to the primary NAAQS. On judicial review, the D.C. Circuit remanded to the EPA for reconsideratio n the secondary NAAQS for fine PM because the Agency’s decision was unreasonable and contrary to the requirements of section 109(b)(2). American Farm Bureau Federation v. EPA , 559 F. 3d 512 (D.C. Cir., 2009). The petitioners argued that the EPA’s decision lacked a reasoned basis. First, they asserted that the EPA never determined what level of visibility was “requisite to protect***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 379 of 790 Formatted: Left the public welfare.” They argued that the EPA unreasonably rejected the target level of protection recommended by its staff, whil e failing to provide a target level of its own. The court agreed, stating that “the EPA’s failure to identify such a level when deciding where to set the level of air quality required by the revised secondary fine PM NAAQS is contrary to the statute and th erefore unlawful. Furthermore, the failure to set any target level of visibility protection deprived the EPA’s decision

- making of a reasoned basis.” 559 F. 3d at 530. Second, the petitioners challenged EPA’s method of comparing the protection expected from potential standards. They contended that the EPA relied on a meaningless numerical comparison, ignored the effect of humidity on the usefulness of a standard using a daily averaging time, and unreasonably concluded that the primary standards would achieve a level of visibility roughly equivalent to the level the EPA staff and CASAC deemed “requisite to protect the public welfare.” The court found that the EPA’s equivalency analysis based on the percentages of counties exceeding alternative standards “faile d on its own terms.” The same table showing the percentages of counties exceeding alternative secondary standards, used for comparison to the percentages of counties exceeding alternative primary standards to show equivalency, also included six other alter native secondary standards within the recommended CASAC range that would be more “protective” under EPA’s definition than the adopted primary standards. Two

- thirds of the potential secondary standards within the CASAC’s recommended range would be substanti ally more protective than the adopted primary standards. The court found that the EPA failed to explain why it looked only at one of the few potential secondary standards that would be less protective, and only slightly less so, than the primary***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 380 of 790 Formatted: Left standards. More fundamentally, however, the court found that the EPA’s equivalency analysis based on percentages of counties demonstrated nothing about the relative protection offered by the different standards, and that the tables offered no valid information about the relative visibility protection provided by the standards. 559 F. 3d at 530

- 31. Finally, the Staff Paper had made clear that a visibility standard using PM 2.5 mass as the indicator in conjunction with a daily averaging time would be confounded by regio nal differences in humidity. The court noted that the EPA acknowledged this problem, yet did not address this issue in concluding that the primary standards would be sufficiently protective of visibility. 559 F. 3d at 530. Therefore, the court granted the petition for review and remanded for reconsideration the secondary PM 2.5 NAAQS. 3. General Approach Used in the Policy Assessment for the Current Review The approach used in this review broadened the general approaches used in the last two PM NAAQS reviews by utilizing, to the extent available, enhanced tools, methods, and data to more comprehensively characterize visibility impacts. As such, the EPA took into account considerations based on both the scientific evidence (“evidence

based”) and a quantitative analysis of PM

- related impacts on visibility (“impact

- based”) to inform conclusions related to the adequacy of the current secondary PM 2.5 standards and alternative standards that were appropriate for consideration in this review. As in past reviews, the EPA also considered that the secondary NAAQS should address PM

- related visibility impairment in conjunction with the Regional Haze Program, such that the secondary NAAQS would focus on protection from visibility impairment principally in urban areas in con

junction with the Regional Haze Program that is focused on improving***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 381 of 790 Formatted: Left visibility in Federal Class I areas. The EPA again recognized that such an approach remains the most appropriate and effective means of addressing the public welfare effects associated wi th visibility impairment in areas across the country. The Policy Assessment drew from the qualitative evaluation of all studies discussed in the Integrated Science Assessment (U.S. EPA, 2009a). Specifically, the Policy Assessment considered the extensive n ew air quality and source apportionment information available from the regional planning organizations, long

- standing evidence of PM effects on visibility, and limited public preference studies stud y information from four urban areas (U.S. EPA, 2009a, chapt er 9), as well as the integration of evidence across disciplines (U.S. EPA, 2009a, chapter 2). In addition, limited information that had become available regarding the characterization of public preferences in urban areas provided some new perspectives on the usefulness of this information in informing the selection of target levels of urban visibility protection. On these bases, the Policy Assessment again focused assessments on visibility conditions in urban areas. The conclusions in the Policy Assessment reflected EPA staff’s understanding of both evidence

- based and impact

- based considerations to inform two overarching questions related to (1) the adequacy of the current suite of PM 2.5 standards and (2) what potential alternative standards, if any, should be considered in this review to provide appropriate protection from PM

- related visibility impairment. In addressing these broad questions, the discussions in the Policy Assessment were organized around a series of more specific questions reflecting differ ent aspects of each overarching question (U.S. EPA, 2011a, Figure 4

- 1). When evaluating the visibility protection afforded by the current or any alternative standards considered, the Policy Assessment took into account***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 382 of 790 Formatted: Left the four basic elements of the NAAQS: indicator, averaging time, level, and form. B. Proposed Decisions on Secondary PM Standards At the time of proposal, the Administrator proposed to revise the suite of secondary PM standards by adding a distinct standard for PM 2.5 to address PM

- related visibi lity impairment, focused primarily on visibility in urban areas. This proposed standard was to be defined in terms of a PM 2.5 visibility index, which would use measured PM 2.5 mass concentration, in combination with speciation and relative humidity data, to calculate PM 2.5 light extinction, translated into the deciview (dv) scale; a 24

- hour averaging time; a 90 th percentile form, averaged over 3 years; and a level of 28

- 30 dv. To address other non

- visibility welfare effects, the Administrator proposed to ret ain the current suite of secondary PM standards generally, while revising only the form of the secondary annual PM 2.5 standard to remove the option for spatial averaging consistent with this proposed change to the primary annual PM 2.5 standard. Each of the se proposed decisions is described in more detail in the proposal and below. 1. PM

- Related Visibility Impairment As discussed in Section VI.B
. of the proposal, the Administrator’s proposed decision regarding a distinct secondary standard to provide protection from visibility impairment reflected careful consideration of the following: (1) the latest scientific information on visibility effects a ssociated with PM as described in the Integrated Science Assessment (U.S. EPA, 2009a); (2) insights gained from assessments of correlations between ambient PM 2.5 and visibility impairment prepared by EPA staff in the Visibility Assessment (U.S. EPA, 2010b) ; and (3) specific conclusions regarding the need for revisions to the current standards (i.e., indicator, averaging time, form, and***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 383 of 790 Formatted: Left level) that, taken together, would be requisite to protect the public welfare from adverse effects on visual air quality. T his section summarizes key information from the proposal regarding the nature of visibility impairment, including the relationship between ambient PM and visibility, temporal variations in light extinction, periods during the day of interest for assessing visibility conditions, and exposure durations of interest (section VI.B.1.a); limited public perceptions and attitudes about visibility impairment and the impacts of visibility impairment on public welfare (section VI.B.1.b); CASAC advice regarding the nee d for, and design of, secondary standards to protect visibility (section VI.B.1.c); and the Administrator’s proposed conclusions regarding setting a distinct standard to address visibility impairment (section VI.B.1.d).

a. Nature of PM

- related Visibility I mpairment As noted at the time of proposal, the fundamental science characterizing the contribution of PM, especially fine particles, to visibility impairment is well understood. This science provides the basis for the Integrated Science Assessment designa tion of the relationship between PM and visibility impairment as causal. New research available in this review, discussed in chapter 9 of the Integrated Science Assessment, continues to support and refine EPA’s understanding of the effect of PM on visibili ty and the source contributions to that effect in rural and remote locations. This research provides new insights regarding the regional source contributions to urban visibility impairment and better characterization of the increment in PM concentrations a nd visibility impairment that occur in many cities (i.e., the urban excess) relative to conditions in the surrounding rural areas (i.e., regional background). Ongoing urban PM 2.5 speciated and aggregated mass monitoring has produced new information that ha s allowed for updated***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 384 of 790 Formatted: Left characterization of current visibility levels in urban areas. i. Relationship between Ambient PM and Visibility Visibility impairment is caused by the scattering and absorption of light by suspended particles and gases in the atmosph ere. When PM is present in the air, its contribution to light extinction typically greatly exceeds that of gases. The combined effect of light scattering and absorption by both particles and gases is characterized as light extinction, i.e., the fraction of light that is scattered or absorbed in the atmosphere. Light extinction can be quantified by a light extinction coefficient with units of 1/distance, which is often expressed as 1/(1 million meters) or inverse megameters (abbreviated Mm - 1 ) or in terms of an alternative scale known as the deciview scale, defined by the following equation: 154 Deciview (dv) = 10 ln ( b ext / 10 Mm - 1 ) The deciview scale is frequently used in the scientific literature on visibility, as well as in the Regional Haze Program. In particular, the deciview scale is used in the public perception studies that were considered in the past and current reviews to inform judgments about an appropriate degree of protection to be provided by a secondary NAAQS. The amount of light extinction c ontributed by PM depends on the particle concentration as well as on the particle size distribution and composition and also on the relative humidity. As described in detail in section VI.B.1.a of the proposal, visibility

154 As used in the Regional Haze Program, the term b ext refers to light extinction due t o PM 2.5 , PM 10

- 2.5 , and “clean” atmospheric gases. In the Policy Assessment, in focusing on light extinction due to PM 2.5 , the deciview values include only the effects of PM 2.5 and the gases. The “Rayleigh” term associated with clean atmospheric gases is re presented by the constant value of 10 Mm - 1 . Omission of the Rayleigh term would create the possibility of negative deciview values when the PM 2.5 concentration is very low.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 385 of 790 Formatted: Left scientists have developed an algor ithm, known as the IMPROVE algorithm, 155 to estimate light extinction using routinely monitored fine particle (PM 2.5 ) speciation and coarse particle mass (PM 10

– 2.5 ) data, as well as data on relative humidity. There is both an original and a revised version o f the IMPROVE algorithm (Pitchford et al., 2007). The revised version was developed to address observed biases in the predictions using the original algorithm under very low and very high light extinction conditions. 156 These IMPROVE algorithms are routinely used to calculate light extinction levels on a 24

- hour basis in Federal Class I areas under the Regional Haze Program. In either version of the IMPROVE algorithm, the concentration of each of the major aerosol components is multiplied by a dry extinction efficiency value and, for the hygroscopic components (i.e., ammoniated sulfate and ammonium nitrate), also multiplied by an additional factor to account for the water growth to estimate these components’ contribution to light extinction. Summing the contri bution of each component gives the estimate of total light extinction per unit distance denoted as the light extinction coefficient ( b ext ), as shown below for the original IMPROVE algorithm. b ext ≈ 3 x f

(RH) x [Sulfate] + 3 x f (RH) x [Nitrate] + 4 x [Organic Mass] + 10 x [Elemental Carbon] + 1 x [Fine Soil] + 0.6 x [Coarse Mass] + 10

155 The algorithm is referred to as the IMPROVE algorithm because it was developed sp ecifically to use the aerosol monitoring data generated at network sites and with equipment specifically designed to support the IMPROVE program and was evaluated using IMPROVE optical measurements at the subset of sites that make those measurements (Malm et al., 1994). 156 These biases were detected by comparing light extinction estimates generated from the IMPROVE algorithm to direct optical measurements in a number of rural Federal Class I areas.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 386 of 790 Formatted: Left Light extinction ( b ext ) is in units of Mm - 1 , the mass concentrations of the components indicated in brackets are in units of μg/m 3 , and f (RH) is the unitless wat er growth term that depends on relative humidity. The final term of 10 Mm - 1 is known as the Rayleigh scattering term and accounts for light scattering by the natural gases in unpolluted air. Despite the simplicity of this algorithm, it performs reasonably well and permits the contributions to light extinction from each of the major components (including the water associated with the sulfate and nitrate compounds) to be separately approximated. Inspection of the PM component

- specific terms in the simple orig inal IMPROVE algorithm shows that most of the PM 2.5 components contribute 5 times or more light extinction than a similar concentration of PM 10

– 2.5 . The f (RH ) term in the original algorithm reflects the increase in light scattering caused by particulate s ulfate and nitrate under conditions of high relative humidity. Particles with hygroscopic components (e.g., particulate sulfate and nitrate) contribute more light extinction at higher relative humidity than at lower relative humidity because they change si ze in the atmosphere in response to ambient relative humidity conditions
. For relative humidity below 40 percent the f (RH) value is 1, but it increases to 2 at approximately 66 percent, 3 at approximately 83 percent, 4 at approximately 90 percent, 5 at app roximately 93 percent, and 6 at approximately 95 percent relative humidity. The result is that both particulate sulfate and nitrate are more efficient per unit mass in light extinction than any other aerosol component for relative humidity above approximat ely 85 percent where their total light extinction efficiency exceeds the 10 m 2 /g associated with elemental carbon (EC). PM containing elemental or black carbon (BC) absorbs light as well as scattering it, making it the component with the greatest light ext inction***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 387 of 790 Formatted: Left contributions per unit of mass concentration, except for the hygroscopic components under these high relative humidity conditions. 157 Subsequent As noted above, s ubsequent to the development of the original IMPROVE algorithm, an alternative algorithm (variously referred to as the “revised algorithm” or the “new algorithm” in the literature) has been developed. It w as developed. The revised IMPROVE algorithm is different from the original algorithm in several important ways. First, the revised algorithm employs a more complex split

- component mass extinction efficiency to correct biases believed to be related to particle size distributions , a sea salt term that can be important for remote coastal areas,
. 158 Specifically, t

he revised algorithm incorporat es terms to account for particles representing the different dry extinction and water uptake from two size modes of sulfate, nitrate and organic mass
. 159 Second, the revised algorithm uses a different multiplier for

157 The IMPROVE algorithm does not explicitly separate the lig ht

- scattering and light

absorbing effects of elemental carbon. 158 In either version of the IMPROVE algorithm, the concentration of each of the major aerosol components is multiplied by a dry extinction efficiency value and, for the hygroscopic components (i.e., ammoniated sulfate and ammonium nitrate), also multiplied b y an additional factor to account for the water growth to estimate these components’ contribution to light extinction. Both the dry extinction efficiency and water growth terms have been developed by a combination of empirical assessment and theoretical ca lculation using typical particle size distributions associated with each of the major aerosol components. 159 The relative contributions of sulfate, nitrate and organic mass concentrations to visibility impairment with the revised algorithm are different tha n with the original algorithm due to the combination of the dry extinction coefficient and f(RH) functions for derived concentrations of small and large particles. The apportionment of the total fine particle concentration of each of the three PM 2.5 compon ents into the concentrations of the small and large size fractions was empirically developed for remote areas. The fraction of the fine particle component that is in the large mode is estimated by dividing the total concentration of the component by 20 ug/ m 3 . If the total concentration of a component exceeds 20 ug/m 3 , all of it is assumed to be in the large mode
.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 388 of 790 Formatted: Left organic carbon for purposes of estimating organic carbonaceous material , 160 to better represent aged aerosol found in remote areas
. 161 In addition, the revised algorithm includes a term for hygroscopic sea salt that can be important for remote coastal areas, and site

- specific Rayleigh light scattering terms in place of a universal Rayleigh light scattering value. As noted in section VI.B.1.a of the proposal, the revised IMPROVE algorithm can yield higher estimates of current light extinction levels in urban areas on days with relatively poor visibility as compared to the original algorithm (Pitchford, 2010). This difference is primarily attributable to the split

- component mass extinction efficiency treatment in the revised al gorithm. Th is revised algorithm was evaluated at 21 remote locations and is generally used by RPOs and States for implementation of the Regional Haze Rule
. ii. Temporal Variations of Light Extinction Particulate matter concentrations and light extinction in urban environments vary from hour to hour throughout the 24

- hour day due to a combination of diurnal changes in meteorological conditions and systematic changes in emissions activity (e.g., rush hour traffic). Various factors combine to make early morni ng the most likely time for peak urban light extinction; although the net effects of the systematic urban

- and larger

- scale variations mean that peak daytime PM light extinction levels can occur any time of day, in many areas they occur most often in early morning hours (U.S. EPA, 2010b, sections 3.4.2 and 3.4.3; Figures 3

- 9, 3

- 10, and 3

- 12). This temporal pattern in urban areas contrasts with the general lack of a strong diurnal pattern in PM concentrations and light

160 The revised IMPROVE algorithm uses a multiplier of 1.8 for rural areas instead of 1.4 as used in the original algorithm for the mean ratio of o rganic mass to organic carbon. 161 The revised IMPROVE algorithm uses a multiplier of 1.8 for rural areas instead of 1.4 as used in the original algorithm for the mean ratio of organic mass to organic carbon.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 389 of 79 0 Formatted: Left extinction in most Federal Class I area s, reflective of a relative lack of local sources as compared to urban areas. The use in the Regional Haze Program of 24

- hour average concentrations in the IMPROVE algorithm is consistent with this general lack of a strong diurnal pattern in Federal Class I areas. iii. Periods during the Day of Interest for Assessment of Visibility As noted in sections VI.B.1.b and VI.B.1.c of the proposal, daytime visibility has dominated the attention of those who have studied the visibility effects of air pollution, pa rticularly in urban areas. The EPA recognizes, however, that physically PM light extinction behaves the same at night as during the day and can contribute to nighttime visibility effects by enhancing the scattering of anthropogenic light, contributing to t he “skyglow” within and over populated areas, adding to the total sky brightness , and contributing to the reduction in contrast of stars against the background. However, l ittle research has been conducted on nighttime visibility, and the state of the scien ce is not comparable to that associated with daytime visibility impairment, particularly in terms of the impact on human welfare. T he Policy Assessment notes that the science is not available at this time to support adequate characterization specifically o f nighttime PM light extinction conditions and the related effects on public welfare (U.S. EPA, 2011a, p. 4

- 18). Therefore the EPA has focused its assessments of PM visibility impacts in urban areas on daylight hours during this review. iv. Exposure Durat ions of Interest As noted in section VI.B.1.d of the proposal, the roles that exposure duration and variations in visual air quality within any given exposure period play in determining the acceptability or unacceptability of a given level of visual air qu ality have not been***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 390 of 790 Formatted: Left investigated via preference studies. In the preference studies available for this review, subjects were simply asked to rate the acceptability or unacceptability of each image of a haze

- obscured scene, without being provided any suggest ion of assumed duration or of assumed conditions before or after the occurrence of the scene presented. Preference and/or valuation studies show that atmospheric visibility conditions can be quickly assessed and preferences determined. The EPA is unaware o f any studies that characterize the extent to which different frequencies and durations of exposure to visibility conditions contribute to the degree of public welfare impact that occurs. The Policy Assessment considered a variety of circumstances that ar e commonly expected to occur in evaluating the potential impact of visibility impairment on the public welfare based on available information (U.S. EPA, 2011a, pp. 4

- 19 to 4

- 20). In some circumstances, such as infrequent visits to scenic vistas in natural or urban environments, people are motivated specifically to take the opportunity to view a valued scene and are likely to do so for many minutes to hours to appreciate various aspects of the vista they choose to view. However, the public has many more oppo rtunities to notice visibility conditions on a daily basis in settings associated with performing daily routines (e.g., during commutes and while working, exercising, or recreating outdoors). As noted in the Policy Assessment, information regarding the fra ction of the public that has only one or a few opportunities to experience visibility during the day, or on the role the duration of the observed visibility conditions has on wellbeing effects associated with those visibility conditions, is not available ( U.S. EPA, 2011a, p. 4

- 20). However, it is possible that people with limited opportunities to experience visibility conditions on a daily basis would receive the entire impact of the day’s visual air quality based on the visibility***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 391 of 790 Formatted: Left conditions that occur dur ing the short time period when they can see it. Since this group could be affected on the basis of observing visual air quality conditions for periods as short as one hour or less, and because during each daylight hour there are some people outdoors, commu ting, or near windows, the Policy Assessment judged that it would be appropriate to use the maximum hourly value of PM light extinction during daylight hours for each day for purposes of evaluating the adequacy of the current suite of secondary standards. Other observers may have access to visibility conditions throughout the day. For this group, it might be that an hour with poor or “unacceptable” visibility can be offset by one or more other hours with clearer conditions. Therefore, the proposal acknowled ged that it might also be appropriate to consider a multi

- hour daylight exposure period.

v. Periods of Fog and Rain As discussed in section VI.C of the proposal, the EPA also recognized that it is appropriate to give special treatment to periods of fog and rain when considering whether current PM 2.5 standards adequately protect public welfare from PM

- related visibility impairment. Visibility impairment occurs during periods with fog or precipitation irrespective of the presence or absence of PM. Therefore, it is logical that periods with naturally im

paired visibility due to fog or precipitation should not be treated as having PM

- impaired visibility. There are multiple ways to adjust visibility data to reduce the effects of fog and precipitation. In the Visibility Assessment, following the advice of CA SAC, the EPA evaluated the effect of excluding daylight hours for which relative humidity was greater than 90 percent from analyses in order to avoid precipitation and fog confounding estimates of PM visibility impairment. For the 15 urban areas included***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 392 of 790 Formatted: Left i n the Visibility Assessment, the EPA found that a 90 percent relative humidity cutoff criterion was effective in that on average less than 6 percent of the daylight hours were removed from consideration, yet those hours had on average ten times the likelih ood of rain, six times the likelihood of snow/sleet, and 34 times the likelihood of fog compared with hours with 90 percent or lower relative humidity. In the Regional Haze program, the EPA utilizes monthly average relative humidity values based on 10 year s of climatological data to reduce the effect of fog and precipitation. This approach focuses on longer

- term averages for each monitoring site and thereby eliminates the effect of very high humidity conditions on visibility at those locations. b. Public P erception of Visibility Impairment As described in section VI.B.2 of the proposal, there are two main types of studies that evaluate the public perception of urban visibility impairment: urban visibility preference studies and urban visibility valuation st udies. As noted in the Integrated Science Assessment, “[b]oth types of studies are designed to evaluate individuals’ desire (or demand) for good visual air quality (VAQ) where they live, using different metrics to evaluate demand. Urban visibility preferen ce studies examine individuals’ demand by investigating what amount of visibility degradation is unacceptable while economic studies examine demand by investigating how much one would be willing to pay to improve visibility” (U.S. EPA, 2009a, p. 9

- 66). Bec ause of the limited number of new studies on urban visibility valuation, the Integrated Science Assessment cites to the discussion in the 2004 Criteria Document of the various methods one can use to determine the economic valuation of changes in visibility , which include hedonic valuation, contingent valuation and contingent choice, and travel cost.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 393 of 790 Formatted: Left Contingent valuation studies are a type of stated preference study that measures the strength of preferences and expresses that preference in dollar values. Con tingent valuation studies often include payment vehicles that require respondents to consider implementation costs and their ability to pay for visibility improvements in their responses. This study design aspect is critical because the EPA cannot consider implementations costs in setting either primary or secondary NAAQS. Therefore in considering the information available to help inform the standard

- setting process, the EPA has focused on the public perception studies that do not embed consideration of imp lementation costs. Nonetheless, the EPA recognizes that valuation studies do provide additional evidence that the public is experiencing losses in welfare due to visibility impairment. 162 The public perception studies are described in detail below. In order to identify levels of visibility impairment appropriate for consideration in setting secondary PM NAAQS to protect the public welfare, the Visibility Assessment comprehensively examined information that was available in this review regarding people’s state d preferences regarding acceptable and unacceptable visual air quality. Light extinction is an atmospheric property that by itself does not directly translate into a public welfare effect. Instead, light extinction becomes meaningful in the context of the impact of differences in visibility on the human observer. This has been
162 In the regulatory impact analysis (RIA) accompanying this rulemaking, the EPA describes a revised approach to estimate urban residential visibility benefits that applies the results of several contingent valuation studies. The EPA is unable to apply the p ublic perception studies to estimate benefits because they do not provide sufficient information on which to develop monetized benefits estimates. Specifically, the public perception studies do not provide preferences expressed in dollar values, even thoug h they do provide additional evidence that the benefits associated with improving residential visibility are not zero. As previously noted in this preamble, the RIA is done for informational purposes only, and the proposed decisions on the NAAQS in this ru lemaking are not in any way based on consideration of the information or analyses in the RIA.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 394 of 790 Formatted: Left studied in terms of the acceptability or unacceptability expressed for the visibility impact of a given level of light extinction by a human observer. The perception of the visibilit y impact of a given level of light extinction occurs in conjunction with the associated characteristics and lighting conditions of the viewed scene. 163 Thus, a given level of light extinction may be perceived differently by observers looking at different sce nes or the same scene with different lighting characteristics. Likewise, different observers looking at the same scene with the same lighting may have different preferences regarding the associated visual air quality. When scene and lighting characteristic s are held constant, the perceived appearance of a scene (i.e., how well the scenic features can be seen and the amount of visible haze) depends only on changes in light extinction. This has been demonstrated using the WinHaze model (Molenar et al., 1994) that uses image processing technology to apply user

- specified changes in light extinction values to the same base photograph with set scene and lighting characteristics. Much of what is known about the acceptability of levels of visibility comes from

surv ey studies in which participants were asked questions about their preference or the value they place on various visibility levels as displayed to them in scenic photographs and/or WinHaze images with a range of known light extinction levels. Urban visibili ty preference studies for four urban areas were reviewed in the The Visibility Assessment (U.S. EPA, 2010b, chapter 2 ) revi ew ed the limited number of urban visibility preference studies currently available (i.e., four studies ) to assess the light extinction levels judged

163 By “characteristics of the scene” the EPA means the distance(s) between the viewer and the object(s) of interest, the shapes and colors of the objects, the cont rast between objects and the sky or other background, and the inherent interest of the objects to the viewer. Distance is particularly important because at a given value of light extinction, which is a property of air at a given point(s) in space, more lig ht is actually absorbed and scattered when light passes through more air between the object and the viewer.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 395 of 790 Formatted: Left by the participant to have acceptable visibility for those particular scenes. The reanalysis of urban preference studies conducted in the Visibility Assessment for this review included three completed western urban visibility preference sur vey studies plus a pair of smaller focus studies designed to explore and further develop urban visibility survey instruments. The three western studies included one in Denver, Colorado (Ely et al., 1991), one in the lower Fraser River valley near Vancouver , British Columbia (BC), Canada (Pryor, 1996), and one in Phoenix, Arizona (BBC Research & Consulting, 2003). A pilot focus group study was also conducted for Washington, DC (Abt Associates Inc., 2001). In response to an EPA request for public comment on t he Scope and Methods Plan (74 FR 11580, March 18, 2009), comments were received (Smith, 2009) about the results of a new focus group study of scenes from Washington, DC, that had been conducted on subjects from both Houston, Texas, and Washington, DC, usin g scenes, methods and approaches similar to the method and approach employed in the EPA pilot study (Smith and Howell, 2009). When taken together, these studies from the four different urban areas included a total of 852 individuals, with each individual

r esponding to a series of questions while viewing a set of images of various urban visual air quality conditions. The approaches used in the four studies were similar and were all derived from the method first developed for the Denver urban visibility stud y. In particular, the studies all used a similar group interview type of survey to investigate the level of visibility impairment that participants described as “acceptable.” In each preference study, participants were initially given a set of “warm up” ex ercises to familiarize them with how the scene in the photograph or image appears under different VAQ conditions. The***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 396 of 790 Formatted: Left participants next were shown 25 randomly ordered photographs (images), and asked to rate each one based on a scale of 1 (poor) to 7 (excel lent). They were then shown the same photographs or images again, in the same order, and asked to judge whether each of the photographs (images) would violate what they would consider to be an appropriate urban visibility standard (i.e. whether the level o f impairment was “acceptable” or “unacceptable”). The term “acceptable” was not defined, so that each person’s response was based on his/her own values and preferences for VAQ. However, when answering this question, participants were instructed to consider the following three factors: (1) The standard would be for their own urban area, not a pristine national park area where the standards might be stricter; (2) The level of an urban visibility standard violation should be set at a VAQ level considered to be unreasonable, objectionable, and unacceptable visually; and (3) Judgments of standards violations should be based on visibility only, not on health effects. While the results differed among the four urban areas, results from a rating exercise show that wi thin each preference study, individual survey participants consistently distinguish between photos or images representing different levels of light extinction, and that more participants rate as acceptable images representing lower levels of light extincti on than they do images representing higher levels. Given the similarities in the approaches used, it is the EPA staff concluded that it
was reasonable to compare the results to identify overall trends in the study findings and to conclude that this compari son can usefully inform the selection of a range of levels for use in further analyses . However, the staff also noted that variations in the specific materials and methods used in each study introduce uncertainties that should also be considered when inter

preting the results of these comparisons. Key differences between***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 397 of 790 Formatted: Left the studies include the following: 1) scene characteristics; 2) image presentation methods (e.g., projected slides of actual photos, projected images generated using WinHaze (a significant t echnical advance in the method of presenting visual air quality conditions), or use of a computer monitor screen; 3) number of participants in each study; 4) participant representativeness of the general population of the relevant metropolitan area; and 5) specific wording used to frame the questions used in the group interview process. In the Visibility Assessment, each study was evaluated separately and figures developed to display the percentage of participants that rated the visual air quality depicted in each photograph as “acceptable.” Ely et al. (1991) introduced a “50% acceptability” criterion analysis of the Denver preference study results. The 50 percent acceptability criterion is designed to identify the visual air quality level (defined in terms of deciviews or light extinction) that best divides the photographs into two groups: those with a visual air quality rated as acceptable by the majority of the participants, and those rated not acceptable by the majority of participants. The Visibility As sessment adopted this criterion as a useful index for comparison between studies. The results of each analysis were then combined graphically to allow for visual comparison. This information was then carried forward into the Policy Assessment. Figure 6 5 presents the graphical summary of the results of the studies in the four cities and draws on results previously presented in Figures 2

- 3, 2

- 5, 2

- 7, and 2

- 11 of chapter 2 in the Visibility Assessment. Figure 6 5 also contains lines at 20 dv and 30 dv that g enerally identify a range where the 50 percent acceptance criteria occur across all four of the urban preference studies (U.S. EPA, 2011a, p. 4

- 24). Out of the 114 data points shown in Figure 6 5 , only one photograph (or image) with a visual air quality bel ow 20 dv was***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 398 of 790 Formatted: Left rated as acceptable by less than 50 percent of the participants who rated that photograph. 164 Similarly, only one image with a visual air quality above 30 dv was rated acceptable by more than 50 percent of the participants who viewed it. 165

Figur e 6 5 . Summary of Results of Urban Visibility Studies in Four Cities, Showing the

Identified Range of the 50% Acceptance Criteria 166

Source: U.S. EPA, 2011a, Figure 4

- 2; U.S. EPA 2010b, Figure 2

- 16 As Figure 6 5 above shows, each urban area has a separate and unique response

164 Only 47 percent of the British Columbia participants rated a 19.2 dv photograph as acceptable. 165 In the 2001 Washington, DC study, a 30.9 dv image was used as a repeated slide. The first time it was shown 56 percent of the participants rated it as acceptable, but only 11 percent rated it as acceptable the second time it was shown. The same visual air quality level was rated as acceptable by 4 percen t of the participants in the 2009 study (Test 1). All three points are shown in Figure X 5
. 166 Top scale shows light extinction in inverse megameter units; bottom scale in deciviews. Logit analysis estimated response functions are shown as the color

- coded cu rved lines for each of the four urban areas.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 399 of 790 Formatted: Left curve that appears to indicate that it is distinct from the others. 167 These curves are the result of a logistical regression analysis using a logit model of the greater than 19,000 ratings of haze images as acceptable or unacceptable. The model results can be used to estimate the visual air quality in terms of dv values where the estimated response functions cross the 50 percent acceptability level, as well as any alternative criteria levels. S elected examples of these are shown in Table 4

- 1 of the Policy Assessment (U.S. EPA, 2011a; U.S. EPA, 2010b, Table 2

- 4). This table shows that the logit model results also support the upper and lower ends of the range of 50 th percentile acceptability value s (e.g., near 20 dv for Denver and near 30 dv for Washington, DC) already identified in Figure 6 5
. Based on the composite results and the effective range of 50 th percentile acceptability across the four urban preference studies shown in Figure 6 5 and Tabl e 4

- 1 of the Policy Assessment, benchmark levels of (total) light extinction were selected in a range from 20 dv to 30 dv (75 to 200 Mm - 1 ) 168 for the purpose of provisionally assessing whether visibility conditions would be considered acceptable (i.e., less than the low end of the range), unacceptable (i.e., greater than the high end of the range), or potentially acceptable (within the range ). ) based on the very limited public preference information
. A

167 At present, data is only available for four urban areas, as presented in Figure 5 and discussed throughout this section. Additional research could help inform whether the range identified by combining the resu lts of the studies depicted in Figure 5 is more broadly representative. 168 These values were rounded from 74 Mm - 1 and 201 Mm - 1 to avoid an implication of greater precision than is warranted. Note that the middle value of 25 dv when converted to light extinc tion is 122 Mm - 1 is rounded to 120 Mm - 1 for the same reason. Assessments conducted for the Visibility Assessment and the first and second drafts of the Policy Assessment used the unrounded values. The Policy Assessment considered the results of assessment using unrounded values to be sufficiently representative of what would result if the rounded values were used that it was unnecessary to redo the assessments. That is why some tables and figures in the Policy Assessment reflected the unrounded values.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 400 of 790 Formatted: Left midpoint of 25 dv (120 Mm - 1 ) was also selected for use in the assessment. This level is also very near to the 50 th percentile criterion value from the Phoenix study (i.e., 24.2 dv), which is by far the best of the four studies in terms of the fit of the data to the response curve and the representativeness of st udy participants. Based on the currently available information, the Policy Assessment concluded that the use of 25 dv to represent the middle of the distribution of results seemed well supported (U.S. EPA, 2011a, p. 4

- 25). These three benchmark values prov ide a low, middle, and high set of light extinction conditions that are used to provisionally define daylight hours with urban haze conditions that have been judged unacceptable by at least 50 percent of the participants in one or more of these preference studies. As discussed above, PM light extinction is taken to be (total) light extinction minus the Rayleigh scatter, 169 such that the low, middle, and high levels correspond to PM light extinction levels of about 65 Mm - 1 , 110 Mm - 1 , and 190 Mm - 1 . In the Visib ility Assessment, these three light extinction levels were called Candidate Protection Levels (CPLs). This term was also used in the Policy Assessment and in the proposal notice. It is important to note, however, that the degree of protection provided by a secondary NAAQS is not determined solely by any one component of the standard but by all the components (i.e., indicator, averaging time, form, and level) being applied together. Therefore, the Policy Assessment noted that the term CPL is meant only to in dicate target levels of visibility within a range that the EPA staff felt appropriate for consideration that could, in conjunction with other elements of the standard, including indicator, averaging time, and form, potentially provide an appropriate degree of visibility protection.

169 Ra yleigh scatter is light scattering by atmospheric gases which is on average about 10 Mm - 1

.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 401 of 790 Formatted: Left In characterizing the Policy Assessment’s confidence in each CPL and across the range, a number of issues were considered (U.S. EPA, 2011a, p. 4

- 26). Looking first at the two studies that define the upper and lower bounds of the range, the Policy Assessment considered whether they represent a true regional distinction in preferences for urban visibility conditions between western and eastern U.S. There was little information available to help evaluate the possibility of a regional distinction especially given that there have been preference studies in only one eastern urban area. Smith and Howell (2009) found little difference in preference response to Washington, DC, haze photographs between the study participants from Washington, DC, and those from Houston, Texas. 170 This provides some limited evidence that the value judgment of the public in different areas of the country may not be an important factor in explaining the differences in these study results. In further considering wh at factors could explain the observed differences in preferences across the four urban areas, the Policy Assessment noted that the urban scenes used in each study had different characteristics (U.S. EPA, 2011a, p. 4

- 26). For example, each of the western ur ban visibility preference study scenes included mountains in the background while the single eastern urban study did not. It is also true that each of the western scenes included objects at greater distances from the camera location than in the eastern stu dy. There is no question that objects at a greater distance have a greater sensitivity to perceived visibility changes as light extinction is changed compared to otherwise similar scenes with objects at a shorter range. This alone might explain the
170 The first preference study using WinHaze images of a scenic vista from Washington, DC was conducted in 2001 using subjects who were residents of Washington, DC. M ore recently, Smith and Howell (2009) interviewed additional subjects using the same images and interview procedure. The additional subjects included some residents of the Washington, DC area and some residents of the Houston, Texas area.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 402 of 790 Formatted: Left differe nce between the results of the eastern study and those from the western urban studies. Having scenes with the object of greatest intrinsic value nearer and hence less sensitive in the eastern urban area compared with more distant objects of greatest intrin sic value in the western urban areas could further explain the difference in preference results. Another question considered was whether the high CPL value that is based on the eastern preference results is likely to be generally representative of urban a reas that do not have associated mountains or other valued objects visible in the distant background. Such areas would include the middle of the country, many areas in the eastern U.S., and possibly some areas in the western U.S. as well. 171 Based on the cur rently available information, the Policy Assessment concluded that the high end of the CPL range (30 dv) is an appropriate level to consider ( U.S. EPA, 2011a, p. 4

- 27). With respect to the low end of the range, the Policy Assessment considered factors that might further refine its understanding of the robustness of this level. The Policy Assessment concluded that additional urban preference studies, especially with a greater variety in types of scenes, could help evaluate whether the lower CPL value of 20 d v is generally supportable (U.S. EPA, 2011a, p. 4

- 27). Further, the reason for the noisiness in data points around the curves apparent in both the Denver and British Columbia results compared to the smoother curve fit of Phoenix study results could be expl ored. One possible explanation discussed in the Policy Assessment is that these older

171 In order to ex amine this issue, an effort would have to be made to see if scenes in such areas could be found that would be generally comparable to the western scenes (e.g., scenes that contain valued scenic elements at more sensitive distances than that used in the eas tern study). This is only one of a family of issues concerning how exposure to urban scenes of varying sensitivity affects public perception for which no preference study information is currently available.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 403 of 790 Formatted: Left studies use photographs taken at different times of day and on different days to capture the range of light extinction levels needed for the preference studies. In contra st, the use of WinHaze in the Phoenix (and Washington, DC) study reduced variations that affect scene appearance preference rating and avoided the uncertainty inherent in using ambient measurements to represent sight path

- averaged light extinction values. Reducing these sources of noisiness and uncertainty in the results of future studies of sensitive urban scenes could provide more confidence in the selection of a low CPL value. Based on the above considerations, and recognizing the limitations in the

curr ently available information, the Policy Assessment concluded that it is reasonable to consider a range of CPL values including a high value of 30 dv, a mid

- range value of 25 dv, and a low value of 20 dv (U.S. EPA, 2011a, p. 4

- 27). Based on its review of th e second draft Policy Assessment, CASAC also supported this set of CPLs for consideration by the EPA in this review. CASAC noted that these CPL values were based on all available visibility preference data and that they bound the study results as represent ed by the 50 percent acceptability criteria. While recommending that further visibility preference studies be conducted to reduce remaining uncertainties, 172 CASAC concluded that this range of levels is was “adequately supported by the evidence presented” (Sa met, 2010d, p. iii).

172 “CASAC has also identified needs for the next r eview cycle in terms of further research on a number of topics related to urban visibility; .... In particular, there is a need for the Agency to conduct additional urban visibility preference studies over a broad range of urban areas and viewing conditions, to further evaluate and refine the range of visibility levels considered to be acceptable in the current assessment.” (Samet, 2010a)***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 404 of 790 Formatted: Left

c. Summary of Proposed Conclusions i. Adequacy of the Current Standards for PM

- Related Visibility Impairment At the time of proposal, the Administrator provisionally concluded that the current suite of secondary PM standards are is not sufficiently protective of visual air quality, and that consideration should be given to an alternative secondary standard that would provide additional protection against PM

- related visibility impairment, with a focus primarily in urban areas. This p roposed conclusion was based on the information presented in the proposal with regard to the nature of PM

- related visibility impairment, the results of public perception surveys on the acceptability of varying degrees of visibility impairment in urban area s, analyses of the number of days that are estimated to exceed a range of candidate protection levels under conditions simulated to just meet the current standards, and the advice of CASAC. This section summarizes key points from section VI.C of the propos al regarding visibility under current conditions, the degree of protection afforded by the current standards, and CASAC’s advice regarding the adequacy of the current standards. As discussed in section VI.C.1 of the proposal, to evaluate visibility under current conditions the Visibility Assessment and Policy Assessment estimated PM

- related light extinction 173 levels for 15 urban areas 174 in the United States. Consistent with the emphasis in this review on the hourly or multi

- hour time periods that might reaso nably

173 PM

- related light extinction is used here to refer to the light extinction caused by PM regardless of particle size; PM 10 light extinction refers to the contribution by particles sampled through an inlet with a particle size 50 percent cutpoint of 10 μm diameter; and PM 2.5 light extinction refers to the contribution by particles sampled through an inlet with a particle size 50 percent cutpoint of 2.5 μm diameter. 174 The 15 urban areas are Tacoma, Fresno, Los Angeles, Phoenix, Salt Lake City, Dallas, Houston, St. Louis, Birmingham, Atlanta, Detroit, Pittsburgh, Baltimore, Philadelphia, and New York.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 405 of 790 Formatted: Left characterize the visibility effects experienced by various segments of the population, these analyses focused on using maximum 1

- hour of and 4

- hour values of PM light extinction during daylight hours for purposes of evaluating the degree of visibility impairment. Hourly average PM

- related light extinction was analyzed in terms of both PM 10 and PM 2.5 light extinction. For reasons discussed above, hours with relative humidity greater than 90 percent were excluded from consideration. Recent visibility

con ditions in these urban areas were then compared to the CPLs identified above. The Visibility Assessment, which focused on PM 10 light extinction in 14 of the 15 urban areas during the 2005 to 2007 time period, 175 found that all 14 areas had daily maximum hour ly PM 10 light extinction values estimated to exceed even the highest CPL some of the days. Except for the two Texas areas and the non

- California western urban areas, all of the other urban areas were estimated to have maximum hourly PM 10 concentrations tha t exceeded the high CPL on about 20 percent to over 60 percent of the days. All 14 of the urban areas were estimated to have maximum hourly PM 10 concentrations that exceeded the low CPL on about 40 percent to over 90 percent of the days. In general, areas in the East and in California tend to have a higher frequency of hourly visibility conditions estimated to be above the high CPL compared with those in the western U.S. The Policy Assessment repeated the Visibility Assessment

- type modeling based on PM 2.5 light extinction and data from the more recent 2007 to 2009 time period for the
175 Comments on the second dr aft Visibility Assessment from those familiar with the monitoring sites in St. Louis indicated that the site selected to provide continuous PM 10 monitoring, although less than a mile from the site of the PM 2.5 data, was not representative of the urban area and resulted in unrealistically large PM 10

- 2.5 values. The EPA staff considered these comments credible and set aside the St. Louis assessment results for PM 10 light extinction. Thus, results and statements in the Policy Assessment regarding PM 10 light ex tinction applied to only the other 14 areas. However, results regarding PM 2.5 light extinction in most cases applied to all 15 study areas because the St. Louis estimates for PM 2.5 light extinction were not affected by the PM 10 monitoring issue.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 406 of 790 Formatted: Left same 15 study areas (including St. Louis). While the estimates of the percentage of daily maximum hourly PM 2.5 light extinction values exceeding the CPLs were somewhat lower th an for PM 10 light extinction, the patterns of these estimates across the study areas was found to be similar. More specifically, except for the two Texas and the non

- California western urban areas, all of the other urban areas were estimated to have maximu m hourly PM 2.5 concentrations that exceeded the high CPL on about 10 percent up to about 50 percent of the days based on PM 2.5 light extinction, while all 15 areas were estimated to have maximum hourly PM 2.5 concentrations that exceeded the low CPL on over 10 percent to over 90 percent of the days. To evaluate how PM

- related visibility would be affected by just meeting the current suite of PM 2.5 secondary standards, t he Policy Assessment applied the proportional rollback approach described in section VI.C. 2 of the proposal to all the PM 2.5 monitoring sites in each study area. 176 After adjusting for composition, the Policy Assessment applied the original IMPROVE algorithm to calculate the PM 10 light extinction, using “rolled back” PM 2.5 component concentration s, the current conditions PM 10

- 2.5 concentration for the day and hour, and relative humidity for the day and hour. In these analyses, the Policy Assessment estimated both PM 2.5 and PM 10 light extinction in terms of both daily maximum 1

- hour average values and multi

- hour (i.e., 4

- hour) average values for daylight hours. Figure 4

- 7 and Table 4

- 6 of the Policy Assessment displayed the results of the rollback procedures as a box and whisker plot of daily maximum daylight 1

- hour PM 2.5 light extinction and the pe rcentage of daily maximum hourly PM 2.5 light extinction values estimated to exceed the CPLs when just

176 Phoenix and Salt Lake City met the current PM 2.5 NAAQS under current conditions and required no reduction.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 407 of 790 Formatted: Left meeting the current suite of PM 2.5 secondary standards for all 15 areas considered in the Visibility Assessment (including St. Louis) (excluding hours wit h relative humidity greater than 90 percent). These displays showed that the daily maximum 1

- hour average PM 2.5 light extinction values in all of the study areas other than the three western non

California areas were estimated to exceed the high CPL on abo ut 8 percent up to over 30 percent of the days and to exceed the middle CPL on about 30 percent up to about 70 percent of the days, while all areas except Phoenix were estimated to have daily maximum 1

- hour average PM 2.5 light extinction values that exceed ed the low CPL on over 15 percent to about 90 percent of the days. Figure 4

- 8 and Table 4

- 7 of the Policy Assessment present results based on daily maximum 4

- hour average values. These displays show that the daily maximum 4

- hour average PM 2.5 light extinct ion values in all of the study areas other than the three western non

- California areas and the two areas in Texas were estimated to exceed the high CPL on about 4 percent up to over 15 percent of the days and to exceed the middle CPL on about 15 percent up to about 45 percent of the days, while all areas except Phoenix were estimated to have daily maximum 4

- hour average PM 2.5 light extinction values that exceeded the low CPL on over 10 percent to about 75 percent of the days. A similar set of figures and tables were developed in terms of PM 10 light extinction (U.S. EPA, 2011a, Figures 4

- 5 and 4

- 6, Tables 4

- 4 and 4

- 5). Taking the results of these analyses focusing on 1

- hour and 4

- hour maximum light extinction values into account, the Policy Assessment concluded that the available information in this review clearly called into question the adequacy of the current suite of PM 2.5 standards in the context of public welfare protection from visibility impairment, primarily in urban areas, and supported consideration of alternative standards to provide***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 408 of 790 Formatted: Left appropriate protection (U.S. EPA, 2011a, p. 4

- 39). This conclusion was based in part on the large percentage of days, in many urban areas, that were estimated to have maximum 1

- hour or 4

- hour light extinction values that exceed the range of CPLs identified for consideration under simulations of conditions that would just meet the current suite of PM 2.5 secondary standards. In particular, for air quality that was simulated to just meet the current PM 2.5 standards, greater than 10 percent of the days were estimated to have peak light extinction values that exceed the highest, least protectiv e CPL of 30 dv in terms of PM 2.5 light extinction for 9 of the 15 urban areas, based on 1

- hour average values, and would thus likely fail to meet a 90 th percentile

- based standard at that level. For these areas, the percent of days estimated to have maximum 1

- hour values that exceed the highest CPL ranged from over 10 percent to over 30 percent. Similarly, when the middle CPL of 25 dv was considered, greater than 30 percent up to approximately 70 percent of the days were estimated to have peak light extincti on that exceeded that CPL in terms of PM 2.5 light extinction, for 11 of the 15 urban areas, based on 1

- hour average values. Based on a 4

- hour averaging time, 5 of the areas were estimated to have at least 10 percent of the days with peak light extinction e xceeding the highest CPL in terms of PM 2.5 light extinction, and 8 of the areas were estimated to have at least 30 percent of the days with peak light extinction exceeding the middle CPL in terms of PM 2.5 light extinction. For the lowest CPL of 20 dv, the percentages of days with 4

- hour maximum light extinction estimated to exceed that CPL are even higher for all cases considered. Based on all of the above, the Policy Assessment concluded that PM light extinction estimated to be associated with just meeting the current suite of PM 2.5 secondary standards in many areas across the country exceeded levels and percentages of days that***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 409 of 790 Formatted: Left could reasonably be considered to be important from a public welfare perspective (U.S. EPA, 2011a, p. 4

- 40). Further, the Policy Assessment concluded that use of the current indicator of PM 2.5 mass, in conjunction with the current 24

- hour and annual averaging times, is clearly called into question for a national standard intended to protect public welfare from PM

- related visibility impairment (U.S. EPA, 2011a, p. 4

- 40). This is because such a standard is inherently variable in the degree of protection provided because of regional differences in relative humidity and species composition of PM 2.5 , which are critical factors in the rela tionship between the mix of fine particles in the ambient air and the associated impairment of visibility. The Policy Assessment noted that this concern was one of the important elements in the court’s decision to remand the PM 2.5 secondary standards set i n 2006 to the Agency. Thus, in addition to concluding that the available information clearly calls into question the adequacy of the protection against PM

- related visibility impairment afforded by the current suite of PM 2.5 standards, the Policy Assessmen t also concluded that it clearly calls into question the appropriateness of each of the current standard elements: indicator, averaging time, form, and level (U.S. EPA, 2011a, p. 4

- 40). After reviewing the information and analysis in the second draft Polic y Assessment, CASAC concluded that the “currently available information clearly calls into question the adequacy of the current standards and that consideration should be given to revising the suite of standards to provide increased public welfare protecti on” (Samet, 2010d, p. iii). CASAC noted that the detailed estimates of hourly PM light extinction associated with just meeting the current standards “clearly demonstrate that***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 410 of 790 Formatted: Left current standards do not protect against levels of visual air quality which have been judged to be unacceptable in all of the available urban visibility preference studies.” Further, CASAC stated, with respect to the current suite of secondary PM 2.5 standards, that “[T]he levels are too high, the averaging times are too long, and the P M 2.5 mass indicator could be improved to correspond more closely to the light scattering and absorption properties of suspended particles in the ambient air” (Samet, 2010d, p. 9). After considering the available evidence and the advice of CASAC, the Admini strator concluded at the time of proposal that such information did provide an appropriate basis to inform a conclusion as to whether the current standards afford adequate protection against PM

- related visibility impairment in urban areas. The Administrato r took into account the information discussed above with regard to the nature of PM

- related visibility impairment, the results of public perception surveys on the acceptability of varying degrees of visibility impairment in urban areas, analyses of the

num ber of days on which peak 1

- hour or 4

- hour light extinction values are estimated to exceed a range of candidate protection levels under conditions simulated to just meet the current standards, and the advice of CASAC. She noted the clear causal relationshi p between PM in the ambient air and impairment of visibility, the evidence from the visibility preference studies, and the rationale for determining a range of candidate protection levels based on those studies. She also noted the relatively large number o f days when maximum 1

- hour or 4

- hour light extinction values were estimated to exceed the three candidate protection levels, including the highest level of 30 dv, under the current standards. While recognizing the limitations in the available information o n public perceptions of the acceptability of varying degree of visibility impairment and the***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 411 of 790 Formatted: Left information on the number of days estimated to exceed the CPLs, she concluded that such information provided an appropriate basis to inform a conclusion as to whet her the current standards provide adequate protection against PM

- related visibility impairment in urban areas. Based on these considerations, and placing great importance on the advice of CASAC, the Administrator provisionally concluded that the current st andards are not sufficiently protective of visual air quality, and that consideration should be given to an alternative secondary standard that would provide additional protection against PM

related visibility impairment, with a focus primarily in urban ar eas. Having reached this conclusion, the Administrator also stated at the time of proposal that the current indicator of PM 2.5 mass, in conjunction with the current 24

- hour and annual averaging times, is not well suited for a national standard intended to protect public welfare from PM

- related visibility impairment. As noted in the proposal, the current standards do not incorporate information on the concentrations of various species within the mix of ambient particles, nor do they incorporate information o n relative humidity, both of which play a central role in determining the relationship between the mix of PM in the ambient air and impairment of visibility. Such considerations were reflected both in CASAC’s advice to set a distinct secondary standard tha t would more directly reflect the relationship between ambient PM and visibility impairment and in the court’s remand of the current secondary PM 2.5 standards. Based on the above considerations, at the time of proposal the Administrator provisionally concl uded that the current secondary PM 2.5 standards, taken together, are neither sufficiently protective nor suitably structured to provide an appropriate degree of public welfare protection from PM

- related visibility impairment, primarily in urban areas. This led the EPA to consider***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 412 of 790 Formatted: Left alternative standards by looking at each of the elements of the standards

— indicator, averaging time, form, and level

— as discussed below. ii. Indicator At the time of proposal, the EPA considered three alternative indicators for a PM 2.5 standard designed to protect against visibility impairment: the current PM 2.5 mass indicator; directly measured PM 2.5 light extinction; and calculated PM 2.5 light extinction. Directly measured PM 2.5 light extinction is a measurement (or combination of measurements) of the light absorption and scattering caused by PM 2.5 under ambient conditions. Calculated PM 2.5 light extinction uses the IMPROVE algorithm to calculate PM 2.5 light extinction using measured PM 2.5 mass, speciated PM 2.5 mass, and measured relative humidity. The Policy Assessment evaluated each of these alternatives, finally concluding that consideration should be given to establishing a new calculated PM 2.5 light extinction indicator (U.S. EPA, 2011a, p. 4

- 51). As discus sed in section VI.D.1 of the proposal, the Policy Assessment concluded that consideration of the use of either directly measured PM 2.5 light extinction or calculated PM 2.5 light extinction as an indicator is justified because light extinction is a physical ly meaningful measure of the characteristic of ambient PM 2.5 that is most relevant and directly related to PM

- related visibility effects (U.S. EPA, 2011a, p. 4

- 41). Further, as noted above, PM 2.5 is the component of PM responsible for most of the visibilit y impairment in most urban areas. In these areas, the contribution of PM 10

– 2.5 is a minor contributor to visibility impairment most of the time. The Policy Assessment also indicated that the available evidence demonstrated a strong correspondence between

c alculated PM 2.5 light extinction and PM

- related visibility impairment, as well as the***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 413 of 790 Formatted: Left significant degree of variability in visibility protection across the U.S. allowed by a PM 2.5 mass indicator. The Policy Assessment recognized that while in the future it would be appropriate to consider a direct measurement of PM 2.5 light extinction it was not an appropriate option in this review because a suitable specification of the equipment and associated performance verification procedures cannot be developed in the time frame for this review. (a) PM 2.5 Mass In terms of utilizing a PM 2.5 mass indicator, the proposal noted that PM 2.5 mass monitoring methods are in widespread use, including the FRM involving the collection of periodic (usually 1

- day

- in

- 6 or 1

- day

- in

- 3) 24

- hour filter samples. However, these routine monitoring activities do not include measurement of the full water content of the ambient PM 2.5 that contributes, often significantly, to visibility impacts. 177 Further, the PM 2.5 mass concentration monitors do not provide information on the composition of the ambient PM 2.5 , which plays a central role in the relationship between PM

- related visibility impairment and ambient PM 2.5 mass concentrations. 178 Additional analyses discussed in the proposal that looked at the contribution of PM 2.5 to total PM

- related light extinction (defined in terms of hourly PM 10 calculated light extinction) indicate that there is a poor correlation between hourly PM 10 light extinction and hourly PM 2.5 mass principally due to the impact of the water content of the particles on light extinction, which depends on both the composition of the PM 2.5 and the ambient relative humidity. Both composition and especially relative humidity vary during a single day, as well as from day

- to
- day, at any site and time of year. Also, there are systematic regional and seasonal differences in***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 414 of 790 Formatted: Left the distribution of ambient humidity and PM 2.5 composition conditions that make it impossible to select a PM 2.5 concentration that generally would correspond to the sam e PM

- related light extinction levels across all areas of the nation. Analyses discussed in the proposal quantify the projected uneven protection that would result from the use of 1

- hour average PM 2.5 mass as the indicator. (b) Directly Measured PM 2.5 Lig ht Extinction PM light extinction has a nearly one

- to
- one relationship to light extinction, unlike PM 2.5 mass concentration. As explained above, PM 2.5 is the component responsible for the large majority of PM light extinction in most places and times. PM 2.5 light extinction can be directly measured using several instrumental methods, some of which have been used for decades to routinely monitor the two components of PM 2.5 light extinction (light scattering and absorption) or to jointly measure both as tot al light extinction (from which Rayleigh scattering is subtracted to get PM 2.5 light extinction). As noted at the time of proposal, there are a number of advantages to direct measurements of light extinction for use in a secondary standard relative to esti mates of PM 2.5 light extinction calculated using PM 2.5 mass and speciation data. These include greater accuracy of direct measurements with shorter averaging times and overall greater simplicity when compared to the need for measurements of multiple parame ters to calculate PM light extinction. In evaluating whether direct measurement of PM 2.5 or PM 10 light extinction is appropriate to consider in the context of this PM NAAQS review, the EPA solicited comment from the Ambient Air Monitoring and Methods Subco mmittee (AAMMS) of CASAC. The CASAC AAMMS recommended that consideration of direct measurement should be limited to PM 2.5 light extinction, and that although instruments suitable for this***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 415 of 790 Formatted: Left purpose are commercially available at present, research is expected to produce even better instruments in the near term. The CASAC AAMMS advised against choosing any currently available commercial instrument, or even a general measurement approach, as an FRM because to do so could discourage development of other potentiall y superior approaches. Instead, the CASAC AAMMS recommended that the EPA develop performance

- based approval criteria for direct measurement methods in order to put all approaches on a level playing field. At the present time, the EPA has not undertaken to develop and test such performance

- base approval criteria. The EPA anticipates that if an effort were begun it would take at least several years before such criteria would be ready for regulatory use. Thus, the Policy Assessment concluded that while in the future it would be appropriate to consider a direct measurement of PM 2.5 light extinction, or the sum of separate measurements of light scattering and light absorption, as the indicator for the secondary PM 2.5 standard, this is not an appropriate option in this review because a suitable specification of the equipment or appropriate performance

- based verification procedures cannot be developed in the time frame for this review (U.S. EPA, 2011a, p. 4

- 51,

- 52). (c) Calculated PM 2.5 Light Extinction For the r easons discussed above, the Policy Assessment concluded that a calculated PM 2.5 light extinction indicator would be the preferred approach. PM 2.5 light extinction can be calculated from PM 2.5 mass, combined with speciated PM 2.5 mass concentration data plus relative humidity data, as is presently routinely done on a 24

- hour average basis under the Regional Haze Program using data from the rural IMPROVE monitoring network. This same calculation procedure, using a 24

- hour average basis,***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 416 of 790 Formatted: Left could be used for a NAA QS focused on protecting against PM

- related visibility impairment primarily in urban areas. This approach would use the type of data that is routinely collected from the urban CSN 179 in combination with monthly average relative humidity data based on long

- te rm climatological means as used in the Regional Haze Program (U.S. EPA, 2011a, Appendix G, section G.2). The proposal discussed the complex approach utilized in the Visibility Assessment for calculating hourly PM 2.5 light extinction 180 and discussed various simplified approaches for calculating these hourly values that were analyzed in the Policy Assessment. The Policy Assessment concluded that each of these simplified approaches provided reasonably good estimates of PM 2.5 light extinction and each would be a ppropriate to consider as the indicator for a distinct hourly or multi

- hour secondary standard (U.S. EPA, 2011a, p. 4

- 48). The proposal also recognized that the Policy Assessment identified a number of variations on these simplified approaches that it woul d be appropriate to consider, including: (1) the use of the split

- component mass extinction efficiency approach from the revised IMPROVE algorithm 181

179 About 200 sites in the CSN routinely measure 24

- hour average PM 2.5 chemical components using filter

- based samplers and chemical analysis in a laboratory, on either a 1

- day

- in

- 3 or 1

- day

- in

- 6 schedule (U.S. EPA, 2011a, Appendix B, section B.1.3). 180 As noted at the time of proposal, the sheer size of the ambient air qualit y, meteorological, and chemical transport modeling data files involved with the Visibility Assessment approach would make it very difficult for state agencies or any interested party to consistently apply such an approach on a routine basis for the purpose of implementing a national standard defined in terms of the Visibility Assessment approach. 181 If the revised IMPROVE algorithm were used to define the calculated PM 2.5 mass based indicator, it would not be possible to algebraically reduce the revised algo rithm to a two
- factor version as described above and in Appendix F of the Policy Assessment for the simplified approaches. Instead, five component fractions would be determined from each day of speciated sampling, and then either applied to hourly measurem ents of PM 2.5 mass on the same day or averaged across a month and then applied to measurements of PM 2.5 mass on each day of the month.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 417 of 790 Formatted: Left (2) the use of more refined value(s) for the organic carbon multiplier 182 (3) the use of the reconstructed 24

- hour PM 2.5 mass (i.e., the sum of the five PM 2.5 components from speciated monitoring) as a normalization value for the hourly measurements from the PM 2.5 instrument as a way of better reflecting ambient nitrate concentrations (4) the use of historical monthly or seasona l, or regional, speciation averages Overall, the analyses conducted for the Visibility Assessment and Policy Assessment indicate indicate d that the use of a calculated PM 2.5 light extinction indicator would provide a much higher degree of uniformity in term s of the degree of protection from visibility impairment across the country than a PM 2.5 mass indicator, because a calculated PM 2.5 light extinction indicator would directly incorporate the effects of humidity and PM 2.5 composition differences between vari ous regions. Further, the proposal noted that the Policy Assessment concluded that consideration could be given to defining a calculated PM 2.5 light extinction indicator on either a 24

- hour or a sub

- daily basis (U.S. EPA, 2011a, p. 4

- 52). However, the Poli cy Assessment noted that approval of continuous FEM monitors has been based only on 24

- hour average, not hourly, PM 2.5 mass. In addition, there are mixed results of data quality assessments on a 24

- hour basis for these monitors, as well as the near absence of performance data for sub

- daily averaging periods. Thus, while it is possible to utilize data from PM 2.5 continuous FEMs on a 1

- hour or multi

- hour (e.g., 4

- hour) basis, these factors increase the uncertainty of utilizing continuous methods to support 1

- hour or 4

- hour PM 2.5 mass measurements as an input to the light extinction calculation. Therefore, as noted at the tim e of proposal, until issues regarding the comparability of 24

- hour PM 2.5 mass values derived from continuous

182 An organic carbon (OC)

- to
- organic mass (OM) multiplier of 1.6 was used for the assessment, which was found to produce a value of OM comparable to the one derived with the original, albeit more complex , Visibility Assessment method.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 418 of 790 Formatted: Left FEMs and filter

- based FRMs 183 are resolved, there is reason to be cautious about relying on a calculation procedure that uses hourly PM 2.5 mass value s reported by continuous FEMs in combination with speciated PM 2.5 mass values from 24

- hour filter

- based samplers. (d) CASAC Advice In reviewing the second draft Policy Assessment, CASAC stated that it “overwhelmingly ... would prefer the direct measurement of light extinction,” recognizing it as the property of the atmosphere that most directly relates to visibility effects (Samet, 2010d, p. iii). CASAC noted that “[I]t has the advantage of relating directly to the demonstrated harmful welfare effect of ambi ent PM on human visual perception.” However, CASAC also concluded that the calculated PM 2.5 light extinction indicator “appears to be a reasonable approach for estimating hourly light extinction” (Samet, 2010d, p. 11). Further, based on CASAC’s understandi ng of the time that would be required to develop an FRM for this indicator, CASAC agreed with the staff preference presented in the second draft Policy Assessment for a calculated PM 2.5 light extinction indicator. CASAC noted that “[I]ts reliance on proced ures that have already been implemented in the CSN and routinely collected continuous PM 2.5 data suggest that it could be implemented much sooner than a directly measured indicator” (Samet, 2010d, p. iii). 184 (e) Administrator's Proposed Conclusions on Indicator
183 Filter

- based FRMs are designed to adequately quantify the amount of PM 2.5 collected over 24

- hours. They cannot be presumed to be appropriate for quantifying average concentrations over 1

- hour or 4

- hour periods. 184 In commenting on the second draft Policy Assessment, CASAC did not have an opportunity to review the assessment of continuous PM 2.5 FEMs compared to collocated FRMs (Hanley and Reff, 2011) as presented and discussed in the final Policy Assessment (U.S. EPA, 2011a, p. 4

- 50).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 419 of 790 Formatted: Left At the time of proposal, while agreeing with CASAC that a directly measured PM light extinction indicator would provide the most direct link between PM in the ambient air and PM

- related light extinction, the Administrator provisionally concluded that this was not an appropriate option in this review because a suitable specification of currently available equipment or performance

- based verification procedures cannot be developed in the time frame of this review. Taking all of the above consideratio ns and CASAC advice into account, the Administrator provisionally concluded that a new calculated PM 2.5 light extinction indicator, similar to that used in the Regional Haze Program (i.e., using an IMPROVE algorithm as translated into the deciview scale), was the appropriate indicator to replace the current PM 2.5 mass indicator. Such an indicator, referred to as a PM 2.5 visibility index, would appropriately reflect the relationship between ambient PM and PM

- related light extinction, based on the analyses di scussed in the proposal and incorporation of factors based on measured PM 2.5 speciation concentrations and relative humidity data. In addition, selection of this type of indicator would address, in part, the issues raised in the court’s remand of the 2006 PM 2.5 standards. The Administrator also noted that such a PM 2.5 visibility index would afford a relatively high degree of uniformity of visual air quality protection in areas across the country by virtue of directly incorporating the effects of differences in PM 2.5 composition and relative humidity across the country. Based on these above considerations, the Administrator proposed to set a distinct secondary standard for PM 2.5 defined in terms of a PM 2.5 visibility index (i.e., a calculated PM 2.5 light ext inction indicator, translated into the deciview scale) to protect against PM

- related visibility impairment primarily in urban areas. The Administrator***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 420 of 790 Formatted: Left proposed that such an index be based on the original IMPROVE algorithm in conjunction with monthly averag e relative humidity data based on long

- term climatological means as used in the Regional Haze Program. The EPA solicited comment on all aspects of the proposed indicator, especially: (1) the proposed use of a PM 2.5 visibility index rather than a PM 10 visibilit y index which would include an additional term for coarse particles; (2) using the revised IMPROVE algorithm rather than the original IMPROVE algorithm; (3) the use of alternative values for the organic carbon multiplier in conjunction with either the original or revised IMPROVE algorithm; (4) the use of historical monthly, seasonal, or regional speciation averages; (5) alternative approaches to determining relative humidity; and (6) simplified approaches to generating hourly PM 2.5 light extinction values for purposes of calcu lating an hourly or multi

- hour indicator. iii. Averaging Times In this review, as discussed in section VI.D.2 of the proposal, consideration of appropriate averaging times for use in conjunction with a PM 2.5 visibility index was informed by information rel ated to the nature of PM visibility effects and the nature of inputs to the calculation of PM 2.5 light extinction, as discussed above. The EPA considered both sub

- daily (1

- and 4

- hour averaging times) and 24

- hour averaging times. In considering sub

- daily a veraging times, the EPA has also considered what diurnal periods and ambient relative humidity conditions would be appropriate to consider in conjunction with such an averaging time. As an initial matter, the Policy Assessment considered sub

- daily averagin g times. Taking into account what is known from available studies concerning how quickly people experience and judge visibility conditions, the possibility that some fraction of the public***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 421 of 790 Formatted: Left experiences infrequent or short periods of exposure to ambient visi bility conditions, and the typical rate of change of the path

- averaged PM light extinction over urban areas, the initial analyses conducted as part of the Visibility Assessment focused on a 1

- hour averaging time. In its review of the first draft Policy Ass essment, CASAC agreed that a 1

- hour averaging time would be appropriate to consider, noting that PM effects on visibility can vary widely and rapidly over the course of a day and such changes are almost instantaneously perceptible to human observers (Samet , 2010c, p. 19). The Policy Assessment noted that this view related specifically to a standard defined in terms of a directly measured PM light extinction indicator, in that CASAC also noted that a 1

- hour averaging time is well within the instrument respon se times of the various currently available and developing optical monitoring methods. However, CASAC also advised that if a PM 2.5 mass indicator were to be used, it would be appropriate to consider “somewhat longer averaging times

– 2 to 4 hours

– to
ass ure a more stable instrumental response” (Samet, 2010c, p. 19). In considering this advice, the Policy Assessment concluded that since a calculated PM 2.5 light extinction indicator relies in part on measured PM 2.5 mass, it would be appropriate to consider a multi

- hour averaging time on the order of a few hours (e.g. 4

- hours). A multi

- hour averaging time might reasonably characterize the visibility effects experienced by the segment of the population who have access to visibility conditions often or continuo usly throughout the day. For this segment of the population, it may be that their perception of visual air quality reflects some degree of offsetting an hour with poor visual air quality with one or more hours of clearer visual conditions. Further, the Pol icy Assessment recognized that a multi

- hour averaging time would have the effect of averaging away***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 422 of 790 Formatted: Left peak hourly visibility impairment, which can change significantly from one hour to the next (U.S. EPA, 2011a, p. 4

- 53; U.S. EPA, 2010b, Figure 3

- 12). In con sidering either 1

- hour or multi

- hour averaging times, the Policy Assessment recognized that no data are available with regard to how the duration and variation of time a person spends outdoors during the daytime impacts his or her judgment of the acceptabi lity of different degrees of visibility impairment. As a consequence, it is not clear to what degree, if at all, the protection levels found to be acceptable in the public preference studies would change for a multi

- hour averaging time as compared to a 1

- h our averaging time. Thus, the Policy Assessment concluded that it is appropriate to consider a 1

- hour or multi

- hour (e.g., 4

- hour) averaging time as the basis for a sub

- daily standard defined in terms of a calculated PM 2.5 light extinction indicator (U.S. EPA, 2011a, p. 4

- 53). In addition, as discussed above, some data quality uncertainties have been observed with regard to hourly data collected by FEMs. Specifically, as part of the review of data from all continuous FEM PM 2.5 instruments operating at state /local monitoring sites, the Policy Assessment noted that the occurrence of questionable outliers in 1

- hour data submitted to AQS from continuous FEM PM 2.5 instruments had been observed at some of these sites (Evangelista, 2011). Some of these outliers wer e questionable simply by virtue of their extreme magnitude, as high as 985 μg/m 3 , whereas other values were questionable because they were isolated to single hours with much lower values before and after, a pattern that is much less plausible than if the high concentrations were more sustained. 185 The Policy Assessment noted that any current data quality problems might

185 Similarly questionable hourly data were not observed in the 2005 to 2007 continuous PM 2.5 data used in the Visibility Assessment, all of which came from early

- gen eration***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 423 of 790 Formatted: Left be resolved in the normal course of monitoring program evolution as operators become more adept at instrument operation and maintenance and d ata validation or by improving the approval criteria and testing requirements for continuous instruments. Regardless, the Policy Assessment noted that multi

- hour averaging of FEM data could serve to reduce the effects of such outliers relative to the use o f a 1

- hour averaging time. The Policy Assessment noted that there are significant reasons to consider using PM 2.5 light extinction calculated on a 24

- hour basis to reduce the various data quality concerns described above with respect to relying on continu ous PM 2.5 monitoring data. However, the Policy Assessment recognized that 24 hours is far longer than the hourly or multi

- hour time periods that might reasonably characterize the visibility effects experienced by various segments of the population, includi ng both those who do and do not have access to visibility conditions often or continuously throughout the day. Thus, the Policy Assessment concluded that the appropriateness of considering a 24

- hour averaging time would depend upon the extent to which PM

- r elated light extinction calculated on a 24

- hour average basis would be a reasonable and appropriate surrogate for PM

- related light extinction calculated on a sub

- daily basis. To examine this relationship, the EPA conducted comparative analyses of 24

- hour and 4

- hour averaging times in conjunction with a calculated PM 2.5 indicator. For these analyses, 4

- hour average PM 2.5 light extinction was calculated based on using the Visibility Assessment approach. The 24

- hour average PM 2.5 light extinction was calculat ed using the original IMPROVE algorithm and long

- term relative humidity continuous instruments that had not been approved as FEMs. However, only 15 sites and instruments were involved in the Visibility Assessment analyses, versus about 180 currently operating FEM instruments submitting data to AQS. Therefore, there wer e more opportunities for very infrequent measurement errors to be observed in the larger FEM data set.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 424 of 790 Formatted: Left conditions to calculate PM 2.5 light extinction. Based on these analyses, 186 which are presented and discussed in Appendix G of the Policy Assessment, scatter plots comparing 24

- hour and 4

- hour calculated PM 2.5 light extinction were constructed for each of the 15 cities included in the Visibility Assessment and for all 15 cities pooled together (U.S. EPA, 2011a, Figures G

- 4 and G

- 5). Though there was some scatter around the regression line for each city because the calculated 4

- hour light extinction values included day

specific and hour

- specific influences that are not captured by the simpler 24

- hour approach, these analyses generally showed good correlation between 24

- hour and 4

- hour
avera ge PM 2.5 light extinction, as evidenced by reasonably high city

- specific and pooled R 2 values, generally in the range of over 0.6 to over 0.8. 187 This suggested that PM 2.5 light extinction calculated on a 24

- hour basis is a reasonable and appropriate surroga te to PM 2.5 light extinction calculated on a sub

- daily basis. Taking the above considerations and CASAC’s advice into account, the Policy Assessment concluded that it would be appropriate to consider a 24

- hour averaging time, in conjunction with a calcula ted PM 2.5 light extinction indicator and an appropriately specified standard level, as discussed below. By using site

- specific daily data on PM 2.5 composition and site

- specific long

- term relative humidity conditions, this 24

- hour average indicator would pr ovide more consistent protection from PM 2.5 - related visibility impairment than would a secondary PM 2.5 NAAQS based only on 24

- hour or annual average PM 2.5 mass. In particular, this approach would account for the systematic difference in humidity conditions between most eastern states and most western states.
186 These analyses are also based on the use of a 90 th percentile form, averaged over 3 years, as discussed below in section VI.D.3 and in section 4.3.3 of the Policy Assessment (U.S. EPA, 2011a). 187 The EPA staff noted that the R 2 value (0.44) for Houston was notably lower than for the other cities.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 425 of 790 Formatted: Left The Policy Assessment also concluded that it would also be appropriate to consider a multi

- hour, sub

- daily averaging time, for example a period of 4 hours, in conjunction with a calculated PM 2.5 light e xtinction indicator and with further consideration of the data quality issues discussed above. Such an averaging time, to the extent that data quality issues can be appropriately addressed, would be more directly related to the short

term nature of the per ception of visibility impairment, short

- term variability in PM

related visual air quality, and the short

- term nature (hourly to multiple hours) of relevant exposure periods for segments of the viewing public. Such an averaging time would still result in an indicator that is less sensitive than a 1

- hour averaging time to short

- term instrument variability with respect to PM 2.5 mass measurement. In conjunction with consideration of a multi

- hour, sub

- daily averaging time, the Policy Assessment concluded that co nsideration should be given to including daylight hours only and to applying a relative humidity screen of approximately 90 percent to remove hours in which fog or precipitation is much more likely to contribute to the observed visibility impairment (U.S. EPA, 2011a, p. 4

- 58). Recognizing that a 1

- hour averaging time would be even more sensitive to data quality issues, including short

- term variability in hourly data from currently available continuous monitoring methods, the Policy Assessment concluded that it would not be appropriate to consider a 1

- hour averaging time in conjunction with a calculated PM 2.5 light extinction indicator in this review (U.S. EPA, 2011a, p. 4

- 58). As noted above, in its review of the first draft Policy Assessment, CASAC conclud ed that PM effects on visibility can vary widely and rapidly over the course of a day and such changes are almost instantaneously perceptible to human observers (Samet, 2010c, p. 19). Based in part on this consideration, CASAC agreed that a 1

- hour averagin g***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 426 of 790 Formatted: Left time would be appropriate to consider in conjunction with a directly measured PM light extinction indicator, noting that a 1

- hour averaging time is well within the instrument response times of the various currently available and developing optical monito ring methods. At that time, CASAC also advised that if a PM 2.5 mass indicator were to be used, it would be appropriate to consider “somewhat longer averaging times

– 2

- to 4

- hours

– to assure a more stable instrumental response” (Samet, 2010c, p. 19). Thus , CASAC’s advice on averaging times that would be appropriate for consideration was predicated in part on the capabilities of monitoring methods that were available for the alternative indicators discussed in the draft Policy Assessment. CASAC’s views on a multi

- hour averaging time would also apply to the calculated PM 2.5 light extinction indicator since hourly PM 2.5 mass measurements are also required for this indicator when calculated on a sub

- daily basis. It is important to note that at the time it provi ded advice on suitable averaging times, CASAC did not have the benefit of EPA’s subsequent assessment of the data quality issues associated with the use of continuous FEMs as the basis for hourly PM 2.5 mass measurements. Furthermore, since CASAC only comme nted on the first and second drafts of the Policy Assessment, neither of which included discussion of a calculated PM 2.5 indicator based on a 24

- hour averaging time, CASAC did not have a basis to offer advice regarding a 24

- hour averaging time. In addition , the 24

- hour averaging time is not based on consideration of 24

- hours as a relevant exposure period, but rather as a surrogate for a sub

- daily period of 4 hours, which is consistent with CASAC’s advice concerning an averaging time associated with the use of a PM 2.5 mass indicator. Taking into account the information discussed above with regard to analyses and***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 427 of 790 Formatted: Left conclusions presented in the final Policy Assessment the Administrator recognize d that hourly or sub

- daily, multi

- hour averaging times, within daylig ht hours and excluding hours with relative humidity above approximately 90 percent, are more directly related than a 24

- hour averaging time to the short

- term nature of the perception of PM

- related visibility impairment and the relevant exposure periods for segments of the viewing public. On the other hand, she recognize d that data quality uncertainties have recently been associated with currently available instruments that would be used to provide the hourly PM 2.5 mass measurements that would be needed in conjunction with an averaging time shorter than 24

- hours. As a result, while the Administrator recognize d the desirability of a sub

- daily averaging time, she ha d strong reservations about proposing to set a standa

rd at this time in terms of a sub

- daily averaging time. In considering the information and analyses related to consideration of a 24

- hour averaging time, the Administrator recognized that the Policy Assessment concluded that PM 2.5 light extinction calcula ted on a 24

- hour averaging basis is a reasonable and appropriate surrogate for sub

- daily PM 2.5 light extinction calculated on a 4

- hour average basis. In light of this finding and the views of CASAC based on its reviews of the first and second drafts of the Policy Assessment, the Administrator proposed to set a distinct secondary standard with a 24

- hour averaging time in conjunction with a PM 2.5 visibility index. iv. Form As discussed in section VI.D.3 of the proposal, the “form” of a standard defines the air quality statistic that is to be compared to the level of the standard in determining whether the standard is achieved. The form of the current 24

- hour PM 2.5 NAAQS is such***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 428 of 790 Formatted: Left that the level of the standard is compared to the 3

- year average of the annual 98 th percentile value of the measured indicator. The purpose in averaging for three years is to provide stability from the occasional effects of inter

- annual meteorological variability that can result in unusually high pollution levels for a particular year. The use of a multi

year percentile form, among other things, makes the standard less subject to the possibility of transient violations caused by statistically unusual indicator values, thereby providing more stability to the air quality management proces s that may enhance the practical effectiveness of efforts to implement the NAAQS. Also, a percentile form can be used to take into account the number of times an exposure might occur as part of the judgment on protectiveness in setting a NAAQS. For all of these reasons, the Policy Assessment concluded it would be appropriate to consider defining the form of a distinct secondary standard in terms of a 3

- year average of a specified percentile air quality statistic (U.S. EPA, 2011a, p. 4

- 58). The urban visibil ity preference studies that provided results leading to the range of CPLs being considered in this review offer no information that addresses the frequency of time that visibility levels should be below those values. Given this lack of information, and rec ognizing that the nature of the public welfare effect is one of aesthetics and/or feelings of well

- being, the Policy Assessment concluded that it would not be appropriate to consider eliminating all exposures above the level of the standard and that allowi ng some number of hours/days with reduced visibility can reasonably be considered (U.S. EPA, 2011a, p. 4

- 59). In the Visibility Assessment, 90 th , 95 th , and 98 th percentile forms were assessed for alternative PM light extinction standards (U.S. EPA, 2010b, section 4.3.3). In considering these alternative percentiles, the Policy Assessment***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 429 of 790 Formatted: Left noted that the Regional Haze Program targets the 20 percent most impaired days for improvements in visual air quality in Federal Class I areas. If improvement in the 20 per cent most impaired days were similarly judged to be appropriate for protecting visual air quality in urban areas, a percentile well above the 80 th percentile would be appropriate to increase the likelihood that all days in this range would be improved by c ontrol strategies intended to attain the standard. A focus on improving the 20 percent most impaired days suggests that the 90 th percentile, which represents the median of the distribution of the 20 percent worst days, would be an appropriate form to consi der. Strategies that are implemented so that 90 percent of days have visual air quality that is at or below the level of the standard would reasonably be expected to lead to improvements in visual air quality for the 20 percent most impaired days. Higher p ercentile values within the range assessed could have the effect of limiting the occurrence of days with peak PM

- related light extinction in urban areas to a greater degree. In considering the limited information available from the public preference studie s, the Policy Assessment found no basis to conclude that it would be appropriate to consider limiting the occurrence of days with peak PM

- related light extinction in urban areas to a greater degree. Another aspect of the form discussed in the proposal for a sub

- daily averaging time was whether to include all daylight hours or only the maximum daily daylight hour(s). The maximum daily daylight 1

- hour or multi

- hour form would be most directly protective of the welfare of people who have limited, infrequent or intermittent exposure to visibility during the day (e.g., during commutes), but spend most of their time without an outdoor view. For such people a view of poor visibility during their morning commute***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 430 of 790 Formatted: Left may represent their perception of the day’s visibility conditions until the next time they venture outside during daylight, which may be hours later or perhaps the next day. Other people have exposure to visibility conditions throughout the day. For those people, it might be more appropriate to include every daylight hour in assessing compliance with a standard, since it is more likely that each daylight hour could affect their welfare. The Policy Assessment did not have information regarding the fraction of the public that has only one or a few opportunities to experience visibility during the day, nor did it have information on the role the duration of the observed visibility conditions has on wellbeing effects associated with those visibility conditions. However, it is logical to conclude that people with l imited opportunities to experience visibility conditions on a daily basis would experience the entire impact associated with visibility based on their short

- term exposure. The impact of visibility for those who have access to visibility conditions often or continuously during the day may be based on varying conditions throughout the day. In light of these considerations, the analyses conducted as part of the Visibility Assessment analyses included both the maximum daily hour and the all daylight hours form s. The Policy Assessment noted that there is a close correspondence between the level of protection afforded for all 15 urban areas by a maximum daily daylight 1

- hour approach using the 90 th percentile form and an all daylight hours approach combined with the 98 th percentile form (U.S. EPA, 2010b, section 4.1.4). This suggests suggest ed that reductions in visibility impairment required to meet either form of the standard would provide protection to both fractions of the public (i.e., those with limited oppor tunities and those with greater opportunities to view PM

- related visibility conditions). CASAC***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 431 of 790 Formatted: Left generally supported consideration of both types of forms without expressing a preference based on its review of information presented in the second draft Policy Assessment (Samet, 2010d, p. 11). In conjunction with a calculated PM 2.5 light extinction indicator and alternative 24

- hour or sub

- daily (e.g., 4

- hour) averaging times, based on the above considerations, and given the lack of information on and the high de gree of uncertainty over the impact on public welfare of the number of days with visibility impairment over a year, the Policy Assessment concluded that it would be appropriate to give primary consideration to a 90 th percentile form, averaged over three ye ars (U.S. EPA, 2011a, p. 4

- 60). Further, in the case of a multi

- hour, sub

- daily alternative standard, the Policy Assessment concluded that it would be appropriate to give primary consideration to a form based on the maximum daily multi

- hour period in conju nction with the 90 th percentile form (U.S. EPA, 2011a, p. 4

- 60). This sub

- daily form would be expected to provide appropriate protection for various segments of the population, including those with limited opportunities during a day and those with more ext ended opportunities over the daylight hours to experience PM

- related visual air quality. Though CASAC did not provide advice as to a specific form that would be appropriate, it took note of the alternative forms considered in that document and encouraged f

urther analyses in the final Policy Assessment that might help to clarify a basis for selecting from within the range of forms identified. In considering the available information and the conclusions in the final Policy Assessment in light of CASAC’s

comme nts, at the time of proposal the Administrator provisionally concluded that a 90 th percentile form, averaged over 3 years, is appropriate, and proposed such a form in***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 432 of 790 Formatted: Left conjunction with a PM 2.5 visibility index and a 24

- hour averaging time.

v. Level As discu ssed in section VI.D.4 of the proposal, in considering appropriate levels for a 24

- hour standard defined in terms of a PM 2.5 visibility index and an 90 th percentile form, averaged over 3 years, the Policy Assessment took into account the evidence

- and impa ct
- based considerations discussed above, with a focus on the results of public perception and attitude surveys related to the acceptability of various levels of visual air quality and on the important limitations in the design and scope of such available s tudies
. The Policy Assessment considered a variety of approaches for identifying appropriate levels for such a standard, including utilizing both adjusted and unadjusted CPLs derived from the visibility preference studies. The Policy Assessment interpreted the results from the visibility preferences studies conducted in four urban areas to define a range of low, middle, and high CPLs for a sub

- daily standard (e.g., 1

- to 4

- hour averaging time) of 20, 25, and 30 dv, which are approximately equival ent to PM 2.5 light extinction of values of 65, 110, and 190 Mm - 1

. The Policy Assessment noted that CASAC agreed that this was an appropriate range of levels to consider for such a standard The CASAC generally supported this approach, noting that the “ EPA st aff’s approach for translating and presenting the technical evidence and assessment results is logically conceived and clearly presented. The 20

- 30 deciview range of levels chosen by EPA staff as “Candidate Protection Levels” is adequately***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 433 of 790 Formatted: Left supported by the evidence presented” (Samet, 2010d, p. 11). 188 The Policy Assessment also recognized that to define a range of alternative levels that would be appropriate to consider for a 24

- hour calculated PM 2.5 light extinction standard, it would be appropriate to consi der whether some adjustment to these CPLs is warranted since these preference studies cannot be directly interpreted as applying to a 24

- hour exposure period (as noted above and in Policy Assessment section 4.3.1). Considerations related to such adjustment s are more specifically discussed below. In considering alternative levels for a sub

- daily standard based directly on the four preference study results, the Policy Assessment noted that the individual low and high CPLs are in fact generally reflective of t he results from the Denver and Washington, DC studies respectively, and the middle CPL is very near to the 50 th percentile criteria result from the Phoenix study, which was by far the best of the studies, providing somewhat more support for the middle CPL. In considering the results from the four visibility preference studies, the Policy Assessment recognized that currently available studies are limited in that they were conducted in only four areas, three in the U.S. and one in Canada. Further, the Policy Assessment recognized that available studies provide no information on how the duration and variation of time a person spends outdoors during the daytime may impact their judgment of the acceptability of different degrees of visibility impairment
. As such, there is a relatively high degree of uncertainty associated with using the results of these studies
188 In 2009 , the D.C. Circuit remanded the secondary PM 2.5 standards to the EPA in part because the Agency failed to identify a target level of protection, even though EPA staff and CASAC had identified a range of target levels of protection that were appropriate for consideration. The court determined that the Agency’s failure to identify a target level of protection as part of its final decision was contrary to the statute and therefore unlawful, and that it deprived EPA’s decision

- making of a reasoned basis. See 55 9F. 3d at 528

- 31; see also section VI.A.2 above and the Policy Assessment, section 4.1.2.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 434 of 790 Formatted: Left to inform consideration of a national standard for any specific averaging time. Nonetheless, the Policy Assessment concluded, as did CASAC, that these stud ies are appropriate to use for this purpose (U.S. EPA, 2011a, p. 4

- 61). Using approaches described in section VI.C.4 of the proposal, the Policy Assessment explored various approaches to adjusting the CPLs derived from the preference studies to inform alte rnative levels for a 24

- hour standard. These various approaches, based on analyses of 2007

– 2009 data from the 15 urban areas assessed in the Visibility Assessment, focused on estimating CPLs for a 24

- hour standard that would provide generally equivalent protection as that provided by a 4

- hour standard with CPLs of 20, 25, and 30 dv. In conducting these analyses, staff initially expected that the values of 24

- hour average PM 2.5 light extinction and daily maximum daylight 4

- hour average PM 2.5 light extincti on would differ on any given day, with the shorter term peak value generally being larger. This would mean that, in concept, the level of a 24

- hour standard should include a downward adjustment compared to the level of a 4

- hour standard to provide generall y equivalent protection. As discussed more fully in section G.5 of Appendix G and summarized below, this initial expectation was not found to be the case across the range of CPLs considered. In fact, as shown in Table Table s G

- 6 7 and G

- 8 of Appendix G , and in the corrected version of Table G

- 6 found in Frank et al. (2012b) , 189 in considering estimates aggregated or averaged over all 15 cities as well as the range of
189 Note that the city

- specific ranges shown in Table G

- 6, Appendix G of the Policy Assessment are incorrectly stated for Approaches C and E. Drawing from the more detai led and correct results for Approaches C and E presented in Tables G

- 7 and G

- 8, respectively, the city

- specific ranges in Table G

- 6 for Approach C should be 17

– 21 dv for the CPL of 20 dv; 21

– 25 dv for the CPL of 25 dv; and 24

– 30 dv for the CPL of 30 dv; the city

- specific ranges in Table G

- 6 for Approach E should be 17

– 21 dv for the CPL of 20 dv; 21

– 26 dv for the CPL of 25 dv; and 25

– 31 dv for the CPL of 30 dv. In the EPA’s reanalysis comparing 4

- vs. 24

- hour values, Frank et al. (2012b) recreate d Table G

- 6 using the correct values from Tables G

- 7 and G

- 8.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 435 of 790 Formatted: Left city

- specific estimates for the various approaches considered, these analyses indicated that the generally equivalent 24

- hour levels ranged from somewhat below the 4

- hour level to just above the 4

- hour level for each of the CPLs. 190 In all cases, the range of city

specific estimates of generally equivalent 24

- hour levels included the 4

- hour level fo r each of the CPLs of 20, 25, and 30 dv. As noted in the proposal, looking more broadly at these results could support consideration of using the same CPL for a 24

- hour standard as for a 4

- hour standard, recognizing that there is no one approach that can m ost closely identify a generally equivalent 24

- hour standard level in each urban area for each CPL. The use of such an unadjusted CPL for a 24

- hour standard would place more emphasis on the relatively high degree of spatial and temporal variability in rela tive humidity and fine particle composition observed in urban areas across the country, so as to reduce the potential of setting a 24

- hour standard level that would require more than the intended degree of protection in some areas. In considering the appro priate level of a secondary standard focused on protection from PM

- related urban visibility impairment based on either a 24

- hour or a multi

- hour, sub

- daily (e.g., 4

- hour) averaging time, the EPA has been mindful of the important limitations in the availabl e evidence from public preference studies. These uncertainties and limitations are due in part to the small number of stated preference studies available for this review; the relatively small number of study participants and the extent to which
190 As discussed in more detail in Appendix G of the Policy Assessment, some days have higher values for 24

- hour average light extinction than for daily maximum 4

- hour daylight light extinction, an d consequently an adjusted "equivalent" 24

- hour CPL can be greater than the original 4

- hour CPL. This can happen for two reasons. First, the use of monthly average historical RH data will lead to cases in which the f (RH) values used for the calculation of 24

- hour average light extinction are higher than all or some of the four hourly values of f

(RH) used to determine daily maximum 4

- hour daylight light extinction on the same day. Second, PM 2.5 concentrations may be greater during non

- daylight periods than d uring daylight hours.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 436 of 790 Formatted: Left the study p articipants may not be representative of the broader study area population in some of the studies; and the variations in the specific materials and methods used in each study such as scene characteristics, the range of VAQ levels presented to study partici pants, image presentation methods and specific wording used to frame the questions used in the group interviews. In addition the EPA has noted that the scenic vistas available on a daily basis in many urban areas across the country generally may not have t he inherent visual interest or the distance between viewer and object of greatest intrinsic value as in the Denver and Phoenix preference studies, and that there is the possibility that there could be regional differences in individual preferences for VAQ. It is also important to note that as in past reviews, the EPA is considering a national visibility standard in conjunction with the Regional Haze Program as a means of achieving appropriate levels of protection against PM

- related visibility impairment in urban, non

- urban, and Federal Class I areas across the country. The EPA recognizes that programs implemented to meet a national standard focused primarily on the visibility problems in urban areas can be expected to improve visual air quality in surroundin g non urban areas as well, as would programs now being developed to address the requirements of the Regional Haze Program established for protection of visual air quality in Federal Class I areas. The EPA also believes that the development of local program s, such as those in Denver and Phoenix, can continue to be an effective and appropriate approach to provide additional protection, beyond that afforded by a national standard, for unique scenic resources in and around certain urban areas that are particula rly highly valued by people living in those areas. The Policy Assessment concluded that it is appropriate to give primary***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 437 of 790 Formatted: Left consideration to alternative standard levels toward the upper end of the ranges identified above for 24

- hour and sub

- daily standards, respectively (U.S. EPA, 2011a, p. 4

- 63). Thus, the Policy Assessment concluded it is appropriate to consider the following alternative levels: a level of 28 dv or somewhat below, down to 25 dv, for a standard defined in terms of a calculated PM 2.5 light ex tinction indicator, a 90 th percentile form, and a 24

- hour averaging time; and a standard level of 30 dv or somewhat below, down to 25 dv, for a similar standard but with a 4

- hour averaging time (U.S. EPA, 2011a, p. 4

- 63). The Policy Assessment judged that such standards would provide appropriate protection against PM

- related visibility impairment primarily in urban areas. The Policy Assessment noted that CASAC generally supported consideration of the 20

– 30 dv range as CPLs and, more specifically, that sup port for consideration of the upper part of the range of the CPLs derived from the public preference studies was expressed by some CASAC Panel members during the public meeting on the second draft Policy Assessment. The Policy Assessment concluded that suc h a standard would be appropriate in conjunction with the Regional Haze Program to achieve appropriate levels of protection against PM

- related visibility impairment in areas across the country (U.S. EPA, 2011a, p. 4

- 63). Based on the considerations discuss ed above and in section VI.D.4 of the proposal, and taking into account the advice of CASAC, at the time of proposal the Administrator provisionally concluded that it would be appropriate to establish a target level of protection

– for a standard defined i n terms of a PM 2.5 visibility index; a 90 th percentile form averaged over 3 years; and a 24

- hour averaging time

– equivalent to the protection afforded by such a sub

- daily (i.e., 4

- hour) standard at a level of 30 dv, which is***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 438 of 790 Formatted: Left the upper end of the range of CPLs identified in the Policy Assessment and generally supported by CASAC. More specifically, the Administrator provisionally concluded that a 24

- hour level of either 30 dv or 28 dv could be construed as providing such a degree of protection, and that eith er level was supported by the available information and was generally consistent with the advice of CASAC. Thus, the EPA proposed two options for the level of a new 24

- hour standard (defined in terms of a PM 2.5 visibility index and a 90 th percentile form, averaged over 3 years) to provide appropriate protection from PM

related visibility impairment: either 30 dv or 28 dv. As noted in the proposal, the option of setting such a 24

- hour standard at a level of 30 dv would reflect recognition that there is consi derable spatial and temporal variability in the key factors that determine the value of the PM 2.5 visibility index in any given urban area, such that there is a relatively high degree of uncertainty as to the most appropriate approach to use in selecting a 24

- hour standard level that would be generally equivalent to a specific 4

- hour standard level. Selecting a 24

- hour standard level of 30 dv would reflect a judgment that such substantial degrees of variability and uncertainty should be reflected in a highe r standard level than would be appropriate if the underlying information were more consistent and certain. Alternatively, the option of setting such a 24

- hour standard at a level of 28 dv would reflect placing more weight on statistical analyses of aggrega ted data from across the study cities and not placing as much emphasis on the city

- to
- city variability as a basis for determining an appropriate degree of protection on a national scale. The information available for the Administrator to consider when sett ing the secondary PM standard raises a number of uncertainties. While CASAC supported moving forward with a new standard on the basis of the available information, CASAC***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 439 of 790 Formatted: Left also recognized these uncertainties, referencing the discussion of key uncertainties a nd areas for future research in the second draft of the Policy Assessment. In discussing areas of future research, CASAC stated that: “The range of 50% acceptability values discussed as possible standards are based on just four studies (Figure 4

- 2), which, given the large spread in values, provide only limited confidence that the benchmark candidate protection levels cover the appropriate range of preference values. Studies using a range of urban scenes (including, but not limited to, iconic scenes

– “value d scenic elements” such as those in the Washington, DC study), should also be considered” (Samet, 2010d, p. 12). The EPA solicited comment on how the Administrator should weigh those uncertainties as well as any additional comments and information to infor m her consideration of these uncertainties. In addition, the EPA solicited comment on a number of other issues related to the level of the standard, including: (1) Both of the proposed levels and the various approaches to identifying generally equivalent lev els upon which the alternative proposed levels are based. (2) A broader range of levels down to 25 dv in conjunction with a 24

- hour averaging time. (3) A range of alternative levels from 30 to 25 dv in conjunction with a sub

- daily (e.g., 4

- hour) averaging time. (4) T he strengths and limitations associated with the public preference studies and the use of these studies to inform the selection of a range of levels that could be used to provide an appropriate degree of public welfare protection when combined with the oth er elements of the standard (i.e. indicator, form and averaging time). (5) Specific aspects of the public preference studies, including the extent to which the 50 percent acceptability criterion is an appropriate basis for establishing target protection levels in the context of establishing a distinct secondary NAAQS to address PM

- related visibility impairment in urban areas; how the variability among preference studies in the extent to which study participants may be representative of the broader study area po pulation should be weighed in the context of considering these studies in reaching proposed conclusions on a***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 440 of 790 Formatted: Left distinct secondary NAAQS; and the extent to which the ranges of VAQ levels presented to participants in each of the studies may have influenced stu dy results and on how this aspect of the study designs should appropriately be weighed in the context of considering these studies in the context of this review. vi. Administrator’s Proposed Conclusions Regarding PM Standards to Protect Visibility At th e time of proposal, based on the considerations described above, the Administrator proposed to revise the suite of secondary PM standards by adding a distinct standard for PM 2.5 to address PM

- related visibility impairment, focused primarily on visibility i n urban areas. This proposed visibility standard was to be defined in terms of a PM 2.5 visibility index, which would use measured PM 2.5 mass, combined with PM 2.5 speciation data and relative humidity data, to calculate PM 2.5 light extinction, translated in to the deciview (dv) scale; a 24

- hour averaging time; a 90 th percentile form, averaged over 3 years; and a level of 28

- 30 dv. vii. Related Technical Analysis At the time of proposal, the EPA conducted a two

- pronged technical analysis of the relationships between the proposed PM 2.5 visibility index standard and the current 24

- hour PM 2.5 mass - based standard (Kelly, et al., 2012a). This analysis was designed to provide technical information to inform key issues related to implementing a distinct secondary st andard for visibility as proposed. Specifically, the EPA recognized that significant technical issues were likely to arise for new or modified emissions sources conducting air quality analyses for purposes of demonstrating that they would not cause or cont ribute to a violation of the visibility standard under the Prevention of Significant Deterioration (PSD) program. Such a demonstration for the proposed secondary PM 2.5 visibility index NAAQS standard could require each PSD applicant to predict, via air***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 441 of 790 Formatted: Left qual ity modeling, the increase in visibility impairment, in terms of the proposed PM 2.5 visibility index, that would result from the proposed source's emissions in conjunction with an assessment of existing air quality (visibility impairment) conditions in terms of the proposed PM 2.5 visibility index. The EPA noted that if this demonstration were to be attempted using the six

- step procedure that the EPA proposed to use for calculating PM 2.5 visibility index design values from monitored air concentrations of PM 2.5 components, significant technical issues with the modeling procedures could aris e. To address these technical issues, the EPA sought to explore whether sources that met the requirements pertaining to the 24

- hour mass

- based standard of 35 μg/m 3 would also meet the requirements pertaining to the proposed visibility index standard. As de scribed in Kelly et al. (2012a), the first prong of the analysis addressed aspects of a PSD significant impact analysis by evaluating whether an individual source’s impact resulting in a small increase in the ambient PM 2.5 concentration would produce a

com parably small increase in visibility impairment. This analysis included estimates of PM 2.5 speciation profiles based on direct PM 2.5 emission profiles for a broad range of source categories and for theoretical upper and lower bound scenarios. The second pr ong of the analysis addressed aspects of a PSD cumulative impact analysis by exploring the relationship between the three

- year design values for the existing 24

- hour PM 2.5 NAAQS standard and coincident design values for the proposed PM 2.5 visibility index N AAQS standard based on recent air quality data. This aspect of the analysis indicated that increases in 24

- hour PM 2.5 design values generally correspond to increases in visibility index design values, and vice

- versa. The analysis further explored the approp riateness of using a demonstration that a source does not cause or contribute to***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 442 of 790 Formatted: Left a violation of the 24

- hour PM 2.5 NAAQS standard as a surrogate for a demonstration that a source does not cause or contribute to a violation of the proposed secondary PM 2.5 vis ibility index NAAQS standard . This analysis is wa s based on 2008 to 2010 air quality data, and compares compare d the proposed level of 35 μg/m 3 for the 24

- hour PM 2.5 standard and for illustrative purposes an alternative standard level of 12 μg/m 3 for the

annu al PM 2.5 standard with the proposed levels of 28 or 30 dv for the secondary PM 2.5 visibility index standard in conjunction with a 24

- hour averaging time and a 90th percentile form. The results indicate indicate d that all (for the 30 dv level) or nearly all (for the 28 dv level) areas in attainment of the 24

- hour PM 2.5 standard would also be have been in attainment of the proposed secondary PM 2.5 visibility index standard. Based on this technical analysis, the EPA proposed that there is sufficient evidence that a demonstration that a source does not cause or contribute to a violation of the mass

- based 24

- hour PM 2.5 NAAQS standard serves as a suitable surrogate for demonstrating that a source does not cause or contrib ute to a violation of the proposed secondary 24

- hour PM 2.5 visibility index NAAQS standard under the PSD program. As such, the EPA proposed to conclude that many or all sources undergoing PSD review for PM 2.5 could rely upon their analysis for demonstrating that they do not cause or contribute to a violation of the mass

- based 24

- hour PM 2.5 NAAQS standard to also show that they do not cause or contribute to a violation of the proposed secondary PM 2.5 visibility index NAAQS standard , if a distinct visibility sta ndard were finalized. Although this proposed “surrogacy policy” was designed to address an implementation

- related issue, the second prong of the technical analysis addresses the broader technical question of the relationship between the existing 24

- hour P M 2.5***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 443 of 790 Formatted: Left NAAQS standard and the proposed PM 2.5 visibility index standard in terms of the degree of protection likely to be afforded by each standard. Specifically, the analysis indicated that depending on the level of the proposed PM 2.5 visibility index standar d, the existing 24

- hour PM 2.5 mass - based standard would be as protective or in some areas more protective of visibility than a distinct secondary standard set within the range of levels proposed. Commenters on the proposed PM 2.5 visibility index explored t he implications of this analysis at length, as discussed further below in section VI.C.1.f. For this reason, the analysis is described in some detail here. Kelly et al. (2012a) noted that the relationship between design values for the 24

- hour PM 2.5 NAAQS st andard and the proposed secondary visibility index standard is not obvious a priori because of differences in design value calculations for the standards. However, closer examination of this relationship indicated that increases or decreases in 24

- hour PM 2 .5 design values correspond, respectively, to increases or decreases in visibility index values. Specifically, based on measurements from 102 sites with complete data from 2008

- 2010, Kelly et al. (2012a) found linear correlations between the 24

- hour PM 2.5 design values and the visibility index design values with r 2 values ranging from 0.65 to 0.98 across these sites, with an average r 2 value of 0.75 across all U.S. sites. Moreover, the data indicated that no design value existed where the visibility index d esign value exceeded 30 dv, but the 24

- hour PM 2.5 NAAQS standard level of 35 μg/m 3 was attained. Visibility index design values for certain sites in the Industrial Midwest were shown to exceed 28 dv despite the fact that the 24

- hour PM 2.5 design values for these sites were below 35 μg/m 3 . This was attributed to the combination of high nitrate and sulfate fractions, substantial RH adjustment factors, and PM 2.5 distribution***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 444 of 790 Formatted: Left characteristics that led to relatively high visibility index design values for a given 24

- hour PM 2.5 design value for counties in the Industrial Midwest. 191 Kelly et al. (2012a) concluded that the “overall, design values based on 2008

- 2010 data suggest that counties that attain 24

- hour PM 2.5 NAAQS level of 35 μg/m 3 would att ain the proposed secondary PM 2.5 visibility index NAAQS level of 30 dv and generally attain the level of 28 dv” (pp. 17

- 18). In addition, the Kelly et al. analysis indicated that at sites that violated both the 24

- hour PM 2.5 level and the secondary proposed visibility index 30 dv level, the secondary standard proposed level of 30 dv would likely be attained if PM 2.5 concentrations were reduced such that the 24

- hour PM 2.5 level of 35 μg/m 3 was attained
. ( Kelly et al. , 2012a, p.15 )
. 192 A key implication of this analysis, therefore, was that within the range of levels proposed by the EPA for the a visibility index NAAQS standard (28

- 30 dv), the 24

- hour PM 2.5 standard of 35 μg/m 3 would be controlling in almost all (at 28 dv) or all (at 30 d v) instances. 2. Other (Non

- Visibility) PM

- related Welfare Effects In the 2006 review, the EPA concluded that there was insufficient information to consider a distinct secondary standard based on PM

- related impacts to ecosystems, materials damage and soil ing, and climatic and radiative processes (71 FR 61144, October 17, 2006). Specifically, there was a lack of evidence linking various non

visibility welfare effects to specific levels of ambient PM. In that review, to provide a
191 Kelly et al. (2012a) also noted that “Regional reductions in sulfate PM 2.5 due to emission controls planned as part of national rules as well as emission reductions associated with potential annual standard violations are expected t o improve visibility in this region” (p. 17). 192 Kelly et al. (2012a), p.15. The analysis also showed that attaining the 24

- hour PM 2.5 NAAQS standard level of 35 μg/m 3 would result in achieving a lower PM 2.5 visibility index level in certain areas of the coun try, largely western areas, than would be achieved in other areas of the country. This is due to differences in the composition of ambient PM 2.5 and the lower relative humidity in those areas.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 445 of 790 Formatted: Left level of protection for thes e welfare

- related effects, the secondary standards were set equal to the revised primary standards to directionally improve the level of protection afforded vegetation, ecosystems, and materials (71 FR 61210, October 17, 2006). This section briefly outline s key conclusions discussed more fully in section VI.E of the proposal regarding the non

- visibility welfare effects of PM. These conclusions relate to the climate, ecological (including effects on plants, soil and nutrient cycling, wildlife and water) and materials damage effects of PM. For all of these effects, the Policy Assessment concluded that there is insufficient information at this time to revise the current suite of secondary standards. It is important to note that the Policy Assessment explicitly excluded discussion of the effects associated with deposited particulate matter components of NO x and SO x and their transformation products which are addressed fully in the joint review of the secondary NO 2 and SO 2 NAAQS.

a. Evidence of Other Welfare Effe cts Related to PM With regard to the role of PM in climate, the proposal noted that there is considerable ongoing research focused on understanding aerosol contributions to changes in global mean temperature and precipitation patterns. The Integrated Scien ce Assessment concluded “that a causal relationship exists between PM and effects on climate, including both direct effects on radiative forcing and indirect effects that involve cloud feedbacks that influence precipitation formation and cloud lifetimes” ( U.S. EPA, 2009a, section 9.3.10). These effects are discussed in more detail in section VI.E.1 of the proposal, which provides information on the major aerosol components of interest for climate processes, including black carbon (BC), organic carbon (OC), sulfates, nitrates, and mineral dusts, and the nature, magnitude, and direction (e.g., cooling vs. warming) of***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 446 of 790 Formatted: Left various aerosol impacts on climate. 193 The Policy Assessment concluded that aerosols alter climate processes directly through radiative forcing and by indirect effects on cloud brightness, changes in precipitation, and possible changes in cloud lifetimes (U.S. EPA, 2011a, p. 5

- 10). Further, the Policy Assessment noted that the major aerosol components that contribute to climate processes (i.e. BC, OC , sulfate, nitrate and mineral dusts) vary in their reflectivity, forcing efficiencies and even in the direction of climate forcing, though there is an overall net climate cooling associated with aerosols in the global atmosphere (U.S. EPA, 2009a, section 9.2.10). The Policy Assessment concluded that the current mass
- based PM 2.5 and PM 10 secondary standards were not an appropriate or effective means of focusing protection against PM

- associated climate effects due to these differences in components (U.S. EPA , 2011a, p. 5

- 11). In addition, in light of the significant uncertainties in current scientific information and the lack of sufficient data, the Policy Assessment concluded it is not currently feasible to conduct a quantitative analysis for the purpose of informing revisions of the current secondary PM standards based on climate (U.S. EPA, 2011a, p. 5

- 11). Overall the Policy Assessment concluded that there is insufficient information at this time to base a national ambient standard on climate impacts associ ated with current ambient concentrations of PM or its constituents (U.S. EPA, 2011a, p. 5

- 11,

- 12). 194 With regard to ecological effects, the proposal noted that several ecosystem components (e.g., plants, soils and nutrient cycling, wildlife and water) are impacted by PM air pollution, which may alter the services provided by affected ecosystems.

193 Atmospheric PM is referred to as aerosols in the remainder of this section to be consistent with the Integrated Science Assessment. 194 This conclusion would apply for both the secondary (welfare

- based) and the primary (health

- based) standards.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 447 of 790 Formatted: Left Ecological effects include both direct effects due to deposition (e.g., wet, dry or occult) to vegetation surfaces and indirect effects occurring via deposition to ecosystem soils or surface waters where the deposited constituents of PM then interact with biological organisms. Some of the ecological effects considered in this review include direct effects to metabolic processes of plant foliage; contribution to tota l metal loading resulting in alteration of soil biogeochemistry and microbiology, and plant and animal growth and reproduction; and contribution to total organics loading resulting in bioaccumulation and biomagnification across trophic levels. Section VI.E .2 of the proposal summarizes key findings related to: (1) Impacts on plants and the ecosystem services they provide due to deposition of PM to vegetative surfaces, which alters the radiation received by the plant, and uptake of deposited PM components by plan ts from soil or foliage, which can lead to stress and decreased photosynthesis; (2) Impacts on ecosystem support services such as nutrient cycling, products such as crops and the regulation of flooding and water quality; (3) Impacts on wildlife, especially due to biomagnification of heavy metals (especially Hg) up the food chain and bioconcentration of POPs and PBDEs; and (4) Impacts of deposited PM, especially metals and organics, on the ecosystem services provided by water bodies, including primary production, provis ion of fresh water, regulation of climate and floods, recreational fishing and water purification. The proposal noted that the Integrated Science Assessment had concluded that ecological evidence is sufficient to conclude that a causal relationship is like ly to exist between deposition of PM and a variety of effects on individual organisms and ecosystems (U.S. EPA, 2009a, sections 2.5.3 and 9.4.7), and also noted that vegetation and other ecosystem components are affected more by particulate chemistry than size fraction. However, the proposal also pointed to the Integrated Science Assessment conclusion that it is generally difficult to characterize the nature and magnitude of effects***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 448 of 790 Formatted: Left and to quantify relationships between ambient concentrations of PM and ecos ystem response due to significant data gaps and uncertainties as well as considerable variability that exists in the components of PM and their various ecological effects. There are few studies that link ambient PM concentrations to observed effect. Most d irect ecosystem effects associated with particulate pollution occur in severely polluted areas near industrial point sources (quarries, cement kilns, metal smelting) (U.S. EPA, 2009a, sections 9.4.3 and 9.4.5.7). Based on the evidence available at this time, the proposal noted the following key conclusions in the Policy Assessment: (1) A number of significant environmental effects that either have already occurred or are currently occurring are linked to deposition of chemical constituents found in ambient P M. (2) Ecosystem services can be adversely impacted by PM in the environment, including supporting, provisioning, regulating and cultural services. (3) The lack of sufficient information to relate specific ambient concentrations of particulate metals and organics to a degree of impairment of a specific ecological endpoint hinders the identification of a range of appropriate indicators, levels, forms and averaging times of a distinct secondary standard to protect against associated effects. (4) Data from regionally

- base d ecological studies can be used to establish probable local, regional and/or global sources of deposited PM components and their concurrent effects on ecological receptors. The proposal noted that the Policy Assessment had concluded that the currently

ava ilable information is insufficient for purposes of assessing the adequacy of the protection for ecosystems afforded by the current suite of PM secondary standards or establishing a distinct national standard for ambient PM based on ecosystem effects of par ticulates not addressed in the NO x /SO x secondary review (e.g., metals, organics) (U.S. EPA, 2011a, p. 5

- 24). Furthermore, the Policy Assessment had concluded that in the***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 449 of 790 Formatted: Left absence of information providing a basis for specific standards in terms of particle

c omposition, the observations continue to support retaining an appropriate degree of control on both fine and coarse particles to help address effects to ecosystems and ecosystem components associated with PM (U.S. EPA, 2011a, p. 5

- 24). With regard to mater ials damage, the proposal discussed effects associated with deposition of PM, including both physical damage (materials damage effects) and impaired aesthetic qualities (soiling effects). As with the other categories of welfare effects discussed above, the Integrated Science Assessment concluded that evidence is sufficient to support a causal relationship between PM and effects on materials (U.S. EPA, 2009a, sections 2.5.4 and 9.5.4). The deposition of PM can physically affect materials, adding to the effec ts of natural weathering processes, by potentially promoting or accelerating the corrosion of metals, by degrading paints and by deteriorating building materials such as stone, concrete and marble (U.S. EPA, 2009a, section 9.5). In addition, the deposition of ambient PM can reduce the aesthetic appeal of buildings and objects through soiling. The Policy Assessment made the following observations: (1) Materials damage and soiling that occur through natural weathering processes are enhanced by exposure to atmosph eric pollutants, most notably sulfur dioxide and particulate sulfates. (2) While ambient particles play a role in the corrosion of metals and in the weathering of materials, no quantitative relationships between ambient particle concentrations and rates of da mage have been established. (3) While soiling associated with fine and course particles can result in increased cleaning frequency and repainting of surfaces, no quantitative relationships between particle characteristics and the frequency of cleaning or repai nting have been established. (4) Limited new data on the role of microbial colonizers in biodeterioration processes and contributions of black crust to soiling are not sufficient for quantitative analysis.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 450 of 790 Formatted: Left (5) While several studies in the PM Integrated Science Ass essment and NO x /SO x Integrated Science Assessment suggest that particles can promote corrosion of metals there remains insufficient evidence to relate corrosive effects to specific particulate levels or to establish a quantitative relationship between ambi ent PM and metal degradation. With respect to damage to calcareous stone, numerous studies suggest that wet or dry deposition of particles and dry deposition of gypsum particles can enhance natural weathering processes. The Policy Assessment concluded that none of the new evidence in this review called into question the adequacy of the current standards for protecting against material damage effects, that such effects could play no quantitative role in determining whether revisions to the secondary PM NAAQS are appropriate at this time, and that observations continue to support retaining an appropriate degree of control on both fine and coarse particles to help address materials damage and soiling associated with PM (U.S. EPA, 2011a, p. 5

- 29). b. CASAC Advi ce In advising the EPA regarding the non

- visibility welfare effects, CASAC stated that it “ concurs with the Policy Assessment’s conclusions that while these effects are important, and should be the focus of future research efforts, there is not currently a strong technical basis to support revisions of the current standards to protect against these other welfare effects” (Samet, 20 10c). More specifically, with regard to climate impacts, CASAC concluded that while there is insufficient information on which to base a national standard, the causal relationship is established and the risk of impacts is high, so further research on a reg ional basis is urgently needed (Samet, 2010c, p. 5). CASAC also noted that reducing certain aerosol components could lead to increased radiative forcing and regional climate warming while having a beneficial effect on PM

- related visibility. As a consequenc e, CASAC noted that a secondary standard directed toward reducing PM

- related visibility impairment has the potential to be accompanied by regional***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 451 of 790 Formatted: Left warming if light scattering aerosols are preferentially targeted. With regard to ecological effects, CASAC co ncluded that the published literature is insufficient to support a national standard for PM effects on ecosystem services (Samet, 2010c, p.23) . CASAC noted that the best

- established effects are related to particles containing nitrogen and sulfur, which are being considered in the EPA’s ongoing review of the secondary NAAQS for NO x /SO x . With regard to PM

- related effects on materials, CASAC concluded that the published literature, including literature published since the last review, is insufficient either to call into question the current level of the standard or to support any specific national standard for PM effects on materials (Samet, 2010c, p.23) . Nonetheless, with regard to both types of effects, CASAC noted the importance of maintaining an appropriate degree of control of both fine and coarse particles to address such effects, even in the current absence of sufficient information to develop a standard.

c. Summary of Proposed Decisions Regarding Other Welfare Effects Based on the above considerations and the advice of CASAC, at the time of proposal the Administrator provisionally concluded that it would not be appropriate to establish any distinct secondary PM standards to address other non

- visibility PM

- related welfare effects, including ecological ef fects, effects on materials, and climate impacts. Nonetheless, the Administrator concurred with the conclusions of the Policy Assessment and CASAC advice that it is important to maintain an appropriate degree of control of both fine and coarse particles to address such effects. Noting that there is an absence of information that would support any different standards, the Administrator proposed***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 452 of 790 Formatted: Left generally to retain the current suite of secondary PM standards 195 to address non

- visibility welfare effects. Specifi cally, the Administrator proposed to retain all aspects of the current secondary 24

- hour PM 2.5 and PM 10 standards. With regard to the secondary annual PM 2.5 standard, the Administrator proposed to retain the level of the current standard and to revise the form of the standard by removing the option for spatial averaging consistent with this change to the primary annual PM 2.5 standard
. C. Public Comments on Proposed Decisions regarding Secondary PM Standards The EPA received a large number of comments on its pr oposed decisions with regard to secondary PM standards, with the large majority of those comments focusing on the proposal to set a distinct standard to protect against visibility impairment, discussed below in section VI.C.1. Very few commenters addressed the proposal to retain the existing secondary standards for non

- visibility welfare effects, discussed below in section VI.C.2
. As discussed in section VI.D. below, the Administrator has decided to retain the current suite of secondary PM standards generally, while revising only the form of the secondary annual PM 2.5 standard to remove the option for spatial averaging consistent with this change to the primary annual PM 2.5 standard. The Administrator has also decided, contrary to what was proposed, n ot to establish a distinct secondary standard to address PM

- related visibility impairment. This section discusses EPA’s responses to the comments EPA received on its proposal, and the rationale behind the Administrator’s final decisions is discussed in sec tion VI.D. below. 1. Comments on Proposed Secondary Standard for Visibility Protection

a. Overview of Comments

195 As summarized in section VI.A and Table 1 above, the current suite of s econdary PM standards includes annual and 24

- hour PM 2.5 standards and a 24

- hour PM 10 standard.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 453 of 790 Formatted: Left Among those commenting on the proposal to set a distinct secondary PM 2.5 visibility index standard, a large majority of commenters, including more than 25 state and local agencies; regional organizations such as NACAA, NESCAUM, and WESTAR; and industry commenters, such as ACC, API, BP, EPRI, NCBA, NEDA

- CAP, NMA, NSSGA, and UARG, opposed setting a distinct secondary standard for visibility at thi s time. Many commenters in this group expressed the view that such a standard was not needed, primarily on the basis that adequate protection was provided by the existing 24

- hour secondary PM 2.5 standard. Some of these commenters also expressed legal conce rns with the nature of the proposed standard. Other commenters in this group supported a distinct secondary standard for visibility in concept, but expressed the view that it was premature to set such a standard pending collection of additional visibility preference study data and the resolution of a number of key technical issues. Support for setting such a distinct secondary standard for visibility at this time came from a second group of commenters, including the Department of the Interior (National Park Service), several states, the Mid

- Atlantic/Northeast Visibility Union (MANE

- VU), the National Tribal Air Association (NTAA), environmental organizations such as the Appalachian Mountain Club, National Parks Conservation Association, Earthjustice (AMC, et al.) and the League of Women Voters of Texas. These commenters argued that the existing secondary standards are not sufficiently protective of visual air quality, and that a distinct secondary standard similar to the proposed visibility index standard is b oth necessary and appropriate to ensure adequate protection of visibility. Commenters in both groups expressed concerns about various aspects of the proposed distinct secondary standard, including the indicator, averaging time, level, and***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 454 of 790 Formatted: Left form. In addition , a large number of commenters, including commenters from both groups, expressed concern and/or confusion over the relationship between the Regional Haze Program and the proposed distinct secondary standard for visibility, raising issues such as analytical differences in methods between the programs, monitoring issues, and other implementation challenges. A discussion of the significant comments outlined above, including EPA’s responses to the comments, is presented here, with more detailed discussion in th e Response to Comments document. Comments relating to the specific elements of the proposed standard

– indicator, averaging time, form and level

– are discussed in sections VI.C.1.b

- e, respectively. Comments related to the need for a distinct secondary stan dard at this time are discussed in section VI.C.f. Legal issues raised by commenters opposed to setting a secondary standard based on the proposed visibility index are discussed in section VI.C.g. Finally, comments related to the relationship between a dis tinct secondary standard and the Regional Haze Program are discussed in section VI.C.h. 196 While the EPA concludes in section VI.D below to retain the current suite of secondary PM 2.5 standards, the appropriateness of the protection that would be provided by the proposed PM 2.5 visibility index standard, and the relationship between this degree of protection and that provided by the current secondary 24

- hour secondary PM 2.5 standard, are key elements in the Administrator's decision, and are discussed below. b
. Indicator Numerous commenters, both those supporting a distinct secondary standard and

196 Comments pertaining to implementation issues, which the Administrator may not consider in making decisions about setting national ambient air quality standard s, are discussed in the Response to Comments document, as are comments regarding monitoring issues related to the proposed distinct visibility index standard.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 455 of 790 Formatted: Left those opposed to setting such a standard, expressed views on the suitability of utilizing a PM 2.5 calculated light extinction indicator for the standard as proposed. W hile these groups of commenters differed in terms of their views on the appropriateness of using calculated PM 2.5 light extinction as the basis for the indicator rather than relying on direct measurements of PM 2.5 light extinction, commenters from both gro ups expressed concern over specific elements of the proposed method of calculating PM 2.5 light extinction. In particular, commenters expressed differing views on which IMPROVE algorithm should be utilized; whether it is appropriate to exclude coarse partic les from the indicator; and whether the proposed protocols for incorporating data on relative humidity and PM 2.5 species are appropriate. 197 i. Comments on Calculated vs. Directly Measured Light Extinction The majority of commenters in both groups noted the uncertainties associated with relying on a calculated light extinction indicator and stated a preference for utilizing direct light extinction measurements. However, recognizing the limitations on applying direct measurements at present, commenters suppor ting the proposal to set a distinct standard argued that relying on “calculated light extinction is a reasonable first approach” (DOI, p. 2). These commenters pointed to the advice of CASAC, which had acknowledged that it was not possible for the EPA to de velop an FRM for direct measurement of light extinction within the time frame of this review and had concluded that relying on a calculated PM 2.5 light extinction indicator represented a reasonable approach that could be implemented sooner than a directly measured indicator. These commenters generally supported the proposal to adopt a calculated PM 2.5 light extinction
197 Some commenters expressed concern about the omission of other contributors to visibility impair ment from the visibility index, as discussed in the Response to Comments document.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 456 of 790 Formatted: Left indicator, at least as an interim approach. Commenters opposed to setting a distinct standard generally argued that it was inappropriate to r ely on a calculated light extinction indicator rather than direct measurements. Some of these commenters argued that the proposed calculated light extinction indictor is ill suited for a bright line standard because the method uses average humidity and a r econstructed visibility measurement calculated from PM 2.5 speciation filter analysis, rather than measuring what is actually observed by individuals. A number of commenters advocated postponing setting a distinct standard until an approach based on direct light extinction measurements can be adopted. Many of these commenters stated that relying on direct light extinction measurements would enable a standard to be based on a shorter averaging time, either 1

- hour or sub

- daily (4 to 6 hours), consistent with t he more instantaneous nature of perceptions of visual air quality and the advice of CASAC in this review. The EPA generally agrees with commenters that an indicator based on directly measured light extinction would provide the most direct link between PM i n the ambient air and PM

- related light extinction. However, as noted at the time of proposal and in accordance with the advice of CASAC, the EPA has concluded that this is not an appropriate option in this review because a suitable specification of current ly available equipment or performance

- based verification procedures could not be developed in the time frame of this review. Moreover, CASAC concluded that relying on a calculated PM 2.5 light extinction indicator based on PM 2.5 chemical speciation and relative humidity data represented a reasonable approach . The inputs that are necessary include measurements that are available through existing monitoring networks and approved***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 457 of 790 Formatted: Left protocols. Thus, the EPA remains confident that the a vailable evidence demonstrates that a strong correspondence exists between calculated PM 2.5 light extinction and PM

- related visibility impairment. Furthermore, CASAC agreed, noting that the proposed calculated PM 2.5 light extinction indicator based on the original IMPROVE algorithm “appears to be a reasonable approach for estimating hourly light extinction” (Samet, 2010d, p. 11) and “its reliance on procedures that have already been implemented in the CSN and routinely collected continuous PM 2.5 data sugges t that it could be implemented much sooner than a directly measured indicator” (Samet, 2010d, p. iii). Thus it would not be appropriate to postpone setting a distinct secondary standard until an approach based on direct light extinction measurements could be adopted. ii. Comments on Specific Aspects of Calculated Light Extinction Indicator Some commenters, even those supporting the adoption of a calculated light extinction indicator, also expressed concern over specific aspects of the proposed indicator. First, a number of commenters expressed concern over the proposal to use the original IMPROVE algorithm as the basis for the calculated light extinction indicator. These commenters noted that the original IMPROVE algorithm has been shown to have consisten t biases at both low and high levels of light extinction. In particular, these commenters expressed concern with the algorithm’s bias at higher levels of light extinction, which they pointed out were the conditions that might be encountered on hazier days in urban areas. Some commenters supported use of the new ( revised ) IMPROVE algorithm. These commenters noted that the revised equation has been through a peer review which confirmed that it is based on the best science and corrects the biases inherent in the***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 458 of 790 Formatted: Left original algorithm. Commenters also noted that this revised algorithm has been widely incorporated into Regional Haze plans, and urged the EPA to use this same equation in the visibility index for the sake of consistency: “EPA approved this approach fo r regional haze and does not dispute its greater accuracy. Therefore, a national secondary ambient air quality standard based on criteria that accurately reflect the latest scientific knowledge logically should not revert to the original IMPROVE algorithm” (Oklahoma DEQ, p. 2). Other commenters noted that both the original and the revised IMPROVE algorithms were designed in support of the Regional Haze Program which is focused on largely rural Class I areas, and that neither algorithm is necessarily suitabl e for urban areas. Noting that the EPA has not thoroughly evaluated the applicability of either IMPROVE algorithm in urban areas, these commenters urged additional research to evaluate the suitability of either algorithm (or an alternative approach) in urb an areas. 198 Second, a number of commenters argued that exclusion of coarse PM from the calculated light extinction indicator was inappropriate. These commenters noted that coarse particulate matter is an important contributor to visibility impairment in man y areas, particularly in the western U.S., and that the levels of “acceptable” visual air quality derived from the visibility preference studies reflected total light extinction due to the full mix of particles (including coarse PM) in ambient air. A few c ommenters noted
198 The new algorithm incorporat es terms to account for particles representing the different dry extinction and water uptake from two size modes of sulfate, nitrate and organic mass ; adjustments for the calculation of organic mass (OM) as 1.8*organic carbon (OC) to better represent aged aerosol found in remote areas; and a term for hygroscopic sea salt. While sulfate and nitrate contribute the same to visibility impairmen t as with the old formula, the effect of their relative concentrations is different due to the combination of the dry extinction coefficient and f(RH) functions for derived concentration of small and large particles. The new algorithm was evaluated at 21 r emote locations and it is generally used by RPOs and States for implementation of the Regional Haze Rule.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 459 of 790 Formatted: Left that due to the exclusion of coarse particles, a “deciview” calculated for purposes of the proposed PM 2.5 visibility index is inconsistent with the unit as conventionally defined under the Regional Haze Program. Other commenters, however, s upported the proposal to exclude coarse PM from the calculated light extinction indicator, noting the important role that PM 2.5 plays in urban visibility and arguing it would be more difficult to control the contribution of coarse particle sources such as wind

- blown dust to urban visibility impairment. Third, some commenters questioned why the EPA was proposing to rely on monthly average relative humidity (f(RH)) values when hourly humidity data are widely available, particularly in urban areas. One commen ter argued that the EPA’s proposed approach involves “guessing relative humidity” rather than relying on accurate, readily available measurements (Oklahoma DEQ, p. 1). The commenter stated that since relative humidity is highly variable and weather depende nt, the proposed approach “effectively undermines the capacity of the prescribed monitoring regime to identify periods when PM 2.5 adversely affects visibility.” Other commenters supported this view, noting that relative humidity can vary substantially even within a 24

- hour period, and that light extinction can be very sensitive to these changes. These commenters recommended that hourly or daily humidity measurements should be utilized in place of the proposed monthly average f(RH) values. Some commenters a lso recommended that the EPA should utilize a 90 percent relative humidity screen rather than 95 percent cap for purposes of eliminating periods in which visibility impairment is due to rain or fog. These commenters claimed that under a 95 percent cap, bot

h the average f(RH) values and the PM 2.5 visibility index values could***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 460 of 790 Formatted: Left be inflated in locations frequently affected by fog and/or precipitation. These commenters preferred the approach of excluding hours with relative humidity above 90 percent on the groun ds that this approach would eliminate foggy/rainy hours irrespective of the frequency of occurrence. The EPA does not agree with commenters who advocated using the revised IMPROVE algorithm. Both the original and the revised IMPROVE algorithms 199 have been evaluated by comparing the calculated estimates of light extinction with coincident optical measurements. The As discussed above in section VI.B.1.a.i, t he revised algorithm was developed to address observed biases in the predictions using the original alg orithm under very low and very high light extinction conditions
. 200 The new IMPROVE algorithm (Pitchford et al., 1997) incorporates additional terms to account for particles representing the different dry extinction and water uptake (f(RH)) from two size mod es of sulfate, nitrate and organic mass, as well as adding a term for hygroscopic sea salt. There are also adjustments for the calculation of OM as 1.8*OC compared to 1.4*OC in the original algorithm to better account for the more aged PM organic components found in remote areas , with further modifications and additions to better
199 In either version of the IMPROVE algorithm, the concentration of each of the major aerosol components is multiplied by a dry extinction efficiency value and, for the hygroscopic components (i.e., ammoniated sulfate and ammonium nitrate), also multiplied by an additional factor to account for the water growth to estimate these components’ contribution to light extinction. Both the dry extinction effi ciency and water growth terms have been developed by a combination of empirical assessment and theoretical calculation using typical particle size distributions associated with each of the major aerosol components. 200 The original algorithm is referred to a s the IMPROVE algorithm because it was developed specifically to use the aerosol monitoring data generated at network sites and with equipment specifically designed to support the IMPROVE program and was evaluated using IMPROVE optical measurements at the subset of sites that make those measurements (Malm et al., 1994). The biases in this algorithm were detected by comparing light extinction estimates generated from the original IMPROVE algorithm to direct optical measurements in a number of rural Class I a reas.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 461 of 790 Formatted: Left account for differences in particle composition and aging in remote areas
. 201 However, the EPA does not believe that these same modifications and additions would necessarily be appropriate for calculating light extinction in urban areas. Instead, the EPA considers the original algorithm to be suitable for purposes of calculating urban light

- extinction, although some adjustments may be appropriate for urban environments as wel l. The reasons why the original algorithm is suited to urban environments are discussed further below, along with adjustments that the EPA believes are likely appropriate based on the current (limited) state of knowledge
. First, the EPA considers that the multiplier of 1.8 used to convert OC to OM in the revised IMPROVE algorithm is too high for urban environments. The EPA is aware that there has been considerable debate within the research community about the appropriate multiplier to use to best represent urban environments. As discussed in Appendix F of the Policy Assessment (U.S. EPA, 2011a) , the EPA used the SANDWICH mass closure approach (Frank, 2006) in the Urban Focused Visibility Assessment (U.S. EPA, 2010b) for purposes of calculating maximum dayli ght hourly PM 2.5 light extinction and evaluated which multiplier would produce 24

- hour results most similar to the SANDWICH approach using 24

- hour PM 2.5 organic carbon derived from the new Chemical Speciation Network (CSN) carbon monitoring protocol establ ished in 2007. 202

201 Specifically, the revised IMPROVE algorithm incorporates additional terms to account for particles representing the different dry extinction and water uptake (f(RH)) from two size modes of sulfate, nitrate and organic mass, as well as adding a term for hygroscopic sea salt. There are also adjustments for the calculation of OM as 1.8*OC compared to 1.4*OC in the original algorithm to better account for the more aged PM organic components found in remote areas. 202 Starting in 2007, the CSN adopted the IMPROVE monitoring protocol for the measurement of organic and elemental carbon using the IMPROVE analytical method and an IMPROVE

- like sampler. The transition was completed in 2009. ( See***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 462 of 790 Formatted: Left Analyses presented in Appendix F of the Policy Assessment indicate that a multiplier of 1.6 is most appropriate for purposes of comparing the hourly PM 2.5 light extinction with calculated 24

- hour extinction (see Appendix F, section F.6 for a full explanation). The EPA also considers this higher multiplier to be a better approach for urban CSN monitoring sites where the new measurements of organic carbon tend to be lower than those produced by the older NIOSH

- type monitoring protocol (Malm, 2011). A multiplier of 1.6 is now used to calculate OM from OC measurements at CSN sites. At the time of proposal, the EPA proposed to use the original IMPROVE algorithm with its 1.4 multiplier for converting OC to OM, but requested comment on whether this value was appropriate. Comments received by the Agency generally indicate that t he OC

- to
- OM multiplier of 1.4 used in the original IMPROVE algorithm is too low for urban areas. Based on the analyses presented in Appendix F of the Policy Assessment, the EPA agrees with these commenters. However, the EPA also believes that it would be inappropriate to use a multiplier as high as 1.8 to convert OC to OM in urban areas. As noted by commenters, the organic mass contribution to visibility impairment can be large, and generally OM is significantly larger in urban areas compared to surrounding rural

areas. 203 Because a large portion of the organic component of urban PM results from nearby emissions sources, the total OM mass is generally closer to the measured organic carbon ( OC ) from which it is derived. This means it is appropriate to use a smaller multiplier to convert OC to OM in ur ban areas as compared to the value of 1.8 used in the revised algorithm, which is tailored to remote areas. The CASAC noted that urban OM

“ Modification of Carbon Procedures in the Speciation Network,” http://www.epa.gov/ttn/amtic/files/ambient/pm25/spec/faqcarbon.pdf
. ) 203 The difference between higher PM 2.5 mass in urban areas compared to surrounding regions, known as the urban excess, is largely attributed to organic mass (U.S. EPA Particle Pollution Report, 2004). , 2004b). Formatted: Widow/Orphan control***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 463 of 790 Formatted: Left includes fresh emissions and the EPA concluded in the Visibility Assessment that “the original version is considered m ore representative of urban situations when emissions are still fresh rather than aged as at remote IMPROVE sites” (U.S. EPA, 2010b, p. 3

- 19). Although the new revised algorithm represents the best science of estimating extinction in remote areas with its a ged aerosol, the commenters did not address how the EPA should modify the new revised algorithm to best represent the more complex and different urban aerosol, particularly for OM. However, recognizing In light of all of these considerations, in particular the analyses the EPA conducted for Appendix F of the Policy Assessment and the fact that the monitoring method for organic carbon has recently changed in the CSN network, the EPA agrees with commenters judges that a multiplier of 1. 4 is likely too low, and 6 for urban areas would be most appropriate for purposes of calculating PM 2.5 light extinction in urban areas. 204 In formulating this judgment, the EPA recognizes that a somewhat higher neither the original nor the revised IMPROVE algorithm has been tested f or suitability in urban areas and that additional research is necessary to reduce the uncertainties about the most appropriate value would be appropriate. Based on the analyses the EPA conducted for Appendix F of the Policy Assessment, a for the OC to OM mu ltiplier of 1.6 for urban areas is judged to in urban environments. With regard to other changes between the original and revised IMPROVE algorithms, the EPA also does not believe that it would be appropriate for data produced with the new CSN carbon monitoring protocol. 205 to include a term for hygroscopic sea salt for urban light

204 The implications of this shift to a 1.6 multiplier for OC in urban areas for decis ions about averaging time, level, and need for a distinct secondary standard are discussed further below in sections VI.C.1.c, VI.C.1.e, and VI.C.1.f, respectively. 205 The implications of this shift to a 1.6 multiplier for OC in urban areas for decisions about averaging time, level, and need for a distinct secondary standard are discussed further below in sections VI.C.1.c, VI.C.1.e, and VI.C.1.f, respectively.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 464 of 790 Formatted: Left extinction, or to differentiate between different size modes of sulfate, nitrate, and organic mass as empirically defined by the revised IMPROVE algorithm. Unlike in some remot e coastal locations, sea salt is not major contribut or to light extinction in urban areas
. Mor e over, urban sources of salt include sanding of roads during the winter and those re entrained particles are mostly in the coarse size range
. Like in remote areas, small and large size modes of sulfate, nitrate and organic mass would exist in the urban environment. However, the apportionment of the total fine particle concentration of each of the three P M 2.5 components into the concentrations of the small and large size fractions would likely need a different approach than that used for remote areas. This is because of the closer proximity of urban sources to their emissions
. This is a particular concern not o nly for organic mass, which as explained previously has a large contribution from nearby urban emission sources, but also for P M 2.5 nitrate whose concentrations are also higher in urban areas compared to the surrounding regions. Thus, a higher portion of t he total urban concentration may be in the small mode compared to remote areas and thus a different apportionment algorithm would be needed. Finally, the EPA does not consider it necessary to employ site

- specific Rayleigh light scattering terms in place of a universal Rayleigh light scattering value for purposes of calculating light extinction in urban areas for purposes of calculating the 90 th percentile values. The site

- specific Rayleigh value is most important to accurately estimate extinction on the bes t visibility days which is an essential metric for the regional haze program. For all of these reasons, the EPA considers the original IMPROVE algorithm Formatted: Font: StoneSerif, 9 pt, Not Italic***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 465 of 790 Formatted: Left better suited to the task of calculating urban light extinction than the revised IMPROVE algorithm. How ever, the EPA does consider it appropriate to make certain adjustments to the original algorithm for purposes of calculating urban light extinction. As discussed above, the EPA believes it is appropriate to use a 1.6 multiplier to convert OC to OM in urban areas . In addition, the EPA believes it is appropriate to exclude the term for coarse particles from the equation. The EPA does not agree with commenters who suggested that coarse particles should be included in the calculated light extinction indicator. As noted in the proposal, PM 2.5 is the component of PM responsible for most of the visibility impairment in most urb an areas. Currently available data suggest that PM 10

– 2.5 is a minor contributor to visibility impairment most of the time, although at some locations (U.S. EPA, 2010b, Figure 3

- 13 for Phoenix) PM 10

– 2.5 can be a major contributor to urban visibility effects . While it is reasonable to assume that other urban areas in the desert southwestern region of the country may have conditions similar to the conditions shown for Phoenix, in fact few urban areas conduct continuous PM 10

- 2.5 monitoring. This significantly i ncreases the difficulty of assessing the role of coarse particles in urban visibility impairment. For example, among the 15 urban areas assessed in this review, only four areas had collocated continuous PM 10 data allowing calculation of hourly PM 10

-
2.5 dat a for 2005 to 2007. In addition, PM 10

- 2.5 is generally less homogenous in urban areas than PM 2.5 : in that coarse particles particle concentrations exhibit greater temporal variability and a steeper gradient across urban areas than fine particles (U.S. EPA, 2009a, p. 3

- 72). This makes it more challenging to select sites that would adequately represent urban visibility conditions. Thus, while it would be possible to include a PM 10

– 2.5 light extinction term in a calculated light extinction indicator, as was don e in the Visibility***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 466 of 790 Formatted: Left Assessment, there is insufficient information available at this time to assess the impact and effectiveness of such a refinement in providing public welfare protection in areas across the country (U.S. EPA, 2011a, pp. 4

- 41 to 4

- 42). The refore, the EPA concludes that it is not appropriate to set a standard based on a calculated light extinction indicator that includes coarse particles at this time, and the calculated indicator should be based on PM 2.5 light extinction. With regard to the suggestion by some commenters that the calculated light extinction indicator should be calculated using hourly humidity data, the EPA disagrees that concurrent humidity measurements should be used. The use of longer

- term averages for each monitoring site a dequately captures the seasonal variability of relative humidity and its effects of visibility impairment, and this approach focuses more on the underlying aerosol contributions to visibility impairment and less on the day

- to
- day variations in humidity. Th is provides a more stable indicator for comparison to the NAAQS and one that is more directly related to the underlying emissions that contribute to visibility impairment. With regard to the comments advocating the use of a 90 percent humidity screen

as o pposed to a 95 percent humidity cap, the EPA believes that relying on monthly average relative humidity values based on 10 years of climatological data appropriately reduces the effect of fog and precipitation. Although the approach of using a 95 percent h umidity cap, as in the Regional Haze Program, includes some hours with relative humidity between 90

- 95 percent, the general approach of using a longer

- term average for each monitoring site effectively eliminates the effect of very high humidity conditions on visibility at those locations.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 467 of 790 Formatted: Left Therefore, taking all of the above considerations and CASAC advice into account, the EPA continues to conclude that a calculated PM 2.5 light extinction indicator, similar to that used in the Regional Haze Program (i.e., us ing an IMPROVE algorithm as translated into the deciview scale), would be the most appropriate indicator to replace the current PM 2.5 mass indicator for a distinct secondary standard. Moreover, the EPA continues to conclude that this calculated indicator s hould based on the original IMPROVE algorithm , adjusted to use a 1.6 OC multiplier and exclude the term for coarse particles, in conjunction with monthly average relative humidity data (i.e., f(RH) values) based on long

- term climatological means as used in the Regional Haze Program. A PM 2.5 visibility index defined in this way would appropriately reflect the relationship between ambient PM and PM

- related light extinction, based on the analyses discussed in the proposal and reflecting the aerosol and relativ e humidity contributions to visibility impairment by incorporation of factors based on measured PM 2.5 speciation concentrations and climatological average relative humidity data. In addition, this type of indicator would address, in part, the issues raised in the court’s remand of the 2006 PM 2.5 standards. Such a PM 2.5 visibility index would afford a relatively high degree of uniformity of visual air quality protection in areas across the country by virtue of directly incorporating the effects of difference s in PM 2.5 composition and relative humidity across the country.

c. Averaging time Few commenters specifically addressed the issue of averaging time. Those who did generally expressed the view that an hourly or sub

- daily averaging time would be the most appropriate approach, as supported by CASAC and the EPA’s own analyses in this***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 468 of 790 Formatted: Left review. These comments were generally consistent with the emphasis among all commenter groups commenters on the desirability of adopting a directly measured light extinction indi cator that could be measured on an hourly or sub

- daily time scale. Some commenters noted that a standard based on a 4

- 6 hour averaging time would better capture peak daily light extinction while allowing stable signal quality; others urged EPA to adopt a 1

- hour averaging time in conjunction with direct measurements. Commenters pointed to significant limitations associated with using a 24

- hour averaging time, including the uncertainties in translating hourly or sub

- daily visibility index values into 24

- hour equivalent values. Some commenters criticized the analysis presented in the Policy Assessment comparing the 24

- hour calculated light extinction values to the maximum daylight 4

- hour calculated light extinction values. These commenters stated that the scatt er plots and regressions presented in the Policy Assessment indicate there is considerable variation in the 24

- hour vs. 4

- hour relationship, and interpreted this to mean that 24

- hour light extinction values are a poor surrogate for 4

- hour values. For examp le, several industry commenters cited an analysis which noted that the correlation coefficient between the 24

- hour and 4

- hour values was as low as r 2 = 0.42 in Houston, and stated that the EPA was being overly “optimistic” in concluding that city

- specific and pooled r 2 values in the range of 0.6 to 0.8 showed good correlation (UARG, Attachment 2, p. 27). In addition, some commenters expressed concern o ver potential bias and greater uncertainty introduced by the inclusion of nighttime hours, noting that because relative humidity tends to be higher at night, inclusion of these hours could cause areas to “record NAAQS exceedances that have no corresponding visibility impairment value” (UARG, p. 36). Commenters also emphasized the poor fit of a 24

- hour averaging time with the near***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 469 of 790 Formatted: Left instantaneous judgments about visibility impairment reflected in the visibility preference studies. Commenters also noted that th ere is greater hourly variation in PM concentrations and resulting visibility conditions in urban areas than in Class I areas; thus, while the Regional Haze Program uses 24

- hour IMPROVE data, the commenters stated that a shorter averaging time is needed fo r an urban

- focused PM 2.5 visibility standard. Some commenters objected to a 24

- hour averaging time as unsupported by the record in this review: “Because the science the Administrator relies on for the other elements of the proposed visibility standard is t ied to short

- term exposures to visibility impairment, the EPA has no basis for promulgating a standard that uses a 24

- hour averaging time” (API, p. 43). These commenters claimed that while the EPA may not have the information or infrastructure in place to allow the Agency to set a standard based on a 1

- hour or other sub

- daily averaging time, this does not justify moving to a 24

- hour averaging time. Among commenters supporting the proposed distinct secondary standard for visibility, many commenters recogniz ed the limitations on monitoring methods and currently available data that led to the EPA’s proposal to adopt a standard based on a 24

- hour averaging time. Most of these commenters acknowledged that the lack of reliable hourly speciation data means that a 24

- hour averaging time is the only workable approach for a standard based on calculated light extinction. Commenters advocating a distinct secondary standard for visibility therefore generally supported the proposal to adopt a 24

- hour averaging time, at le ast as an interim approach until a directly measured light extinction indicator could be adopted in the future. This approach was also supported by a few industry commenters who noted that since a visibility index standard***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 470 of 790 Formatted: Left would be based on data from the I MPROVE and CSN monitors, which operate on a 24

- hour basis with 1

- in

- 3 (or 1

- in

- 6) day sampling, “it is imperative that EPA retain a 24

- hour averaging time if a secondary visibility standard is promulgated” (API, Attachment 2, p. 9). In response to comments supporting a 1

- hour or sub

- daily (4

- to 6

- hour) averaging time in conjunction with a direct light extinction measurements, the EPA notes that, as discussed above in the response to comments on indicator, the Agency has concluded that a directly measured light extinction indicator is not an appropriate option in this review, independent of the decision on averaging time. Having reached the conclusion that a calculated PM 2.5 light extinction indicator would be most appropriate, the EPA has next considered w hat averaging time would be most desirable for such an indicator. As noted in the proposal, the EPA has recognized that hourly or sub

- daily (4

- to 6

- hour) averaging times, within daylight hours and excluding hours with high relative humidity, are more dire ctly related than a 24

- hour averaging time to the short

- term nature of the perception of PM

- related visibility impairment and the relevant exposure periods for segments of the viewing public. Thus, the Agency agrees with commenters’ general point that, as a starting premise, a sub

- daily averaging time would generally be preferable. However, as noted at the time of proposal and discussed above in section VI.B.1.c, important data quality uncertainties have recently been identified in association with current ly available instruments that would be used to provide the hourly PM 2.5 mass measurements that would be needed in conjunction with an averaging time shorter than 24 hours. As a result, at this time the Agency has strong technical reservations about a***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 471 of 790 Formatted: Left

secon dary standard that would be defined in terms of a sub

- daily averaging time. The data quality issues which have been identified, including short

- term variability in hourly data from currently available continuous monitoring methods, effectively preclude ado ption of a 1

- hour averaging time in this review, given the sensitivity of a 1

- hour averaging time to these data quality limitations. Even with regard to multi

- hour averaging times, the EPA continues to conclude that the data quality concerns preclude adopt ion of a sub

- daily averaging time. Moreover, analyses conducted for the Policy Assessment indicate that PM 2.5 light extinction calculated on a 24

- hour average basis would be a reasonable and appropriate surrogate for PM 2.5 light extinction calculated on a 4

- hour basis. The scatter plots comparing 24

- hour and 4

- hour calculated PM 2.5 light extinction in the Policy Assessment (U.S. EPA, 2011a, Figures G

- 4 and G

- 5) do show some scatter around the regression line for each city. This was to be expected, since the calculated 4

- hour light extinction includes day

- specific and hour

- specific influences that are not captured by the simpler 24

- hour approach. Overall, however, in the EPA’s view, both the city

- specific and pooled 15

- city 24

- hour vs. 4

- hour comparisons show strong correlation between the two averaging times. Moreover, the 90th percentile design values calculated for 4

- hour vs. 24

- hour light extinction are much more closely correlated than are the values for individual days in particular urban areas calculate d using these two approaches. Thus, while the EPA agrees with commenters who pointed out the relatively low correlation between 4

- and 24

- hour values in cities such as Houston, the Agency points out that the correlations of 90 th percentile values are much higher, particularly when one considers the average values across urban areas. In general, the 90th percentile values line up better***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 472 of 790 Formatted: Left and demonstrate closer to a one

- to
- one relationship. The EPA has conducted a reanalysis (Frank et al., 2012b) of the relat ionships between estimated 24

- hour and 4

- hour visibility impairment based on the variety of metrics discussed in Appendix G of the Policy Assessment that further supports this finding. The reanalysis more appropriately considered the uncertainty of the cal culated 4

- hour values. It also considered the effect of changing the OC to OM multiplier used in urban areas with the new CSN monitoring protocol from 1.4 to 1.6. The revised analysis shows that , for all cases considered, the 24

- hour values are generally c loser to the 4

- hour values than originally estimated. Since conclusions in the proposal about the relationship between 4

- hour and 24

- hour values were drawn not just on the basis of the city

- specific results but also on the more robust 90 th percentile pool ed values, the EPA disagrees with commenters who state that the Agency was overly optimistic in considering 24

- hour values an appropriate surrogate for 4

- hour values. Also, it is appropriate to focus on the 90 th percentile design value comparison since the design values would determine attainment status and the degree of improvement in air quality that could be expected in areas instituting controls to meet the NAAQS. Therefore the EPA does not agree with commenters who state that a 24

- hour averaging time c annot serve as an appropriate surrogate for sub

- daily periods of visibility impairment. On the contrary, the EPA continues to conclude, on the basis of this analysis, that PM 2.5 light extinction calculated on a 24

- hour basis is a reasonable and appropriate surrogate for sub

- daily PM 2.5 light extinction calculated on a 4

- hour basis. The EPA recognizes that the effect of adopting a 24

- hour averaging time may be to smooth out some of the hour

- by

- hour variability in visibility index values. (Indeed, this***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 473 of 790 Formatted: Left is tru e if we compare a 4

- hour averaging time to a 1

- hour averaging time as well.) Hour

specific influences which would be evident if an hourly or sub

- daily averaging time were to be used will be masked to some extent when those hours are averaged together with other hours. This means, in part, that a 24

- hour averaging time may effectively reduce peak values by means of averaging them together with other hours, which may have lower values. However, given the well documented variability in hourly visibility condit ions, especially in urban areas, as noted by commenters, it is reasonable to assume that in some cases peak hours may be significantly influenced by atypical conditions, making it appropriate to adopt an averaging time that is sufficiently long to ensure t hat hour

- specific influences are balanced against more typical conditions. Perhaps even more important is the concern that many peak hourly measurements may be significantly influenced by atypical instrument performance; this reinforces the conclusion that it is appropriate to adopt a longer averaging time, to ensure that hour

- specific uncertainties are balanced against more robust measurements. Thus, in agreement with commenters who supported a daily averaging time, the EPA concludes that a 24

- hour averagi ng time would be appropriate for a distinct secondary standard based on a calculated PM 2.5 light extinction indicator. d. Form The EPA received very few comments with regard to the proposal to adopt a 90 th percentile form, averaged over 3

- years, in conjunction with a PM 2.5 visibility index and a 24

- hour averaging time. One commenter stated that it was inappropriate to use a 90 th percentile form, noting that this would result in the exclusion of a minimum of 36 days of data annually. The commenter expressed particular concern that this proposed approach,***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 474 of 790 Formatted: Left in combination with a 24

- hour standard based on an unadjusted CPL, would not capture the worst visibility impairment and that this would undermine “the inten t of setting a meaningful secondary visibility standard” (AMC, et al., p. 2). Another commenter argued that the EPA had provided no scientific basis for why the 90 th percentile form was suitable, and claimed that the Agency was making “a somewhat arbitrary judgment that people’s welfare would be affected only if adverse urban visibility were to occur more than 10 percent of the time” (API, Attachment 2, p. 4). On other hand, a few commenters who appeared to generally support the proposal to use a 90 th perc entile form advocated averaging the 90 th percentile values over longer time periods, arguing that averaging over only 3 years would not provide a stable assessment of visual air quality in the West because this time period is insufficient to properly accou nt for western drought and fire cycles. These commenters pointed to the approach in the Regional Haze Program of averaging visibility impairment over 5 years, and noted that even within this longer time period data can be significantly influenced by high e missions during significant fire years. The EPA disagrees with all of these comments, noting first that a multi

- year percentile form offers greater stability to the air quality management process by reducing the possibility that statistically unusual indic ator values will lead to transient violations of the standard. Furthermore, this approach is consistent with the approach taken in other NAAQS, including the current 24

- hour PM 2.5 NAAQS, which has a 98 th percentile form averaged over 3 years. The EPA disagr ees with all of these comments. With regard to the comment opposing the 90 th percentile form as inappropriately excluding the worst visibility days, the EPA notes that there is a significant lack of information on, and a high***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 4 75 of 790 Formatted: Left degree of uncertainty regardin g, the impact on public welfare of the number of days with visibility impairment over the course of a year. For example, the visibility preference studies used to derive the range of CPLs considered in this review offered no information regarding the frequ ency of time that visibility levels should be below those values. Based on this limitation, the EPA concluded in the Policy Assessment that it would not be appropriate to consider eliminating all exposures above the level of the standard and that it was re asonable to consider allowing some number of days with reduced visibility. Recognizing that the Regional Haze Program focuses attention on the 20 percent worst visibility days (i.e., those at or above the 80 th percentile of visibility impairment), the EPA continues to believe, as noted in the proposal, that a percentile well above the 80 th percentile would be appropriate to increase the likelihood that all days in this range would be improved by control strategies intended to help areas attain the standard. Focusing on the 90 th percentile, which represents the median of the distribution of the 20 percent worst visibility days, could be reasonably expected to lead to improvements in visual air quality on the 20 percent most impaired days. Thus, the EPA has ma de a reasoned judgment based on a full consideration of the upper end of the distribution of visibility impairment conditions and continues to conclude that it is appropriate to focus on the 90 th percentile of visibility impairment values. With regard to c omments requesting the EPA adopt a longer multi

- year averaging period for the 90 th percentile values, the EPA disagrees that it would be appropriate to average the 90 th percentile values over periods longer than 3 years. The EPA recognizes that a multi

- yea r percentile form offers greater stability to the air quality management process by reducing the possibility that statistically unusual indicator values will lead to***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 476 of 790 Formatted: Left transient violations of the standard. Utilizing a 3

- year average form provides stability f rom the occasional effects of inter

- annual meteorological variability that can result in unusually high pollution levels for a particular year. The Agency has adopted this approach in other NAAQS, including the current secondary 24

- hour PM 2.5 NAAQS, which has a 98 th percentile form averaged over 3 years
. However, adopting a longer multi

- year averaging period longer than 3 years would increase even more the number of days with visibility impairment above the target level of protection and would therefore reduce the protectiveness of a visibility the standard. Based on this the EPA does not believe it would be appropriate to average 90 th percentile values over a period as long as five years. Therefore, the EPA continues to conclude that a 90 th percentile form, averaged over 3 years, would be appropriate, in conjunction with a calculated PM 2.5 visibility index light extinction indicator and a 24

- hour averagin g time.

e. Level With regard to level, commenters focused on two main themes. First, a large number of commenters addressed the information available from the public preference studies with regard to the acceptability of various levels of visual air qual ity. These comments, which are discussed in subsection VI.C.1.e.i below, address the EPA’s use of visibility preference studies as the basis for the selection of a range of appropriate levels for the Administrator to consider. Many commenters challenged th e use of these studies as the basis for setting a distinct secondary standard, arguing that limitations in these studies rendered them an unsuitable and insufficient basis on which to establish such a standard. Second, commenters expressed different views as to what level(s) of a distinct secondary standard would be appropriate, if the EPA were to set such a standard. These***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 477 of 790 Formatted: Left comments reflected consideration of the results of the public preference studies as well as analyses conducted in the Visibility Assess ment and the Policy Assessment, as discussed in the proposal. Comments addressing the appropriateness of specific levels are discussed in subsection VI.C.1.e.ii below. i. Comments on Visibility Preference Studies A majority of commenters expressed the view that the existing preference studies provide an insufficient basis for selection by the Administrator of an appropriate level of public welfare visibility protection for a national standard. These commenters high lighted a number of limitations and uncertainties (enumerated below) and uncertainties associated with these studies as support for this view. In contrast, other commenters felt that despite certain limitations, these studies do provide a sufficient basis on which the Administrator can select an appropriate level of a standard to provide national public welfare visibility protection. The remainder of this section organizes and discusses these comments under four broad topic areas, including: (a) limitations and uncertainties associated with the visibility preference studies; (b) preference study methods and design; (c) use of preference study results for determining adversity; (d) the appropriateness of using regionally varying preference study results to se lect a single level for a national standard. (a) Preference Study Limitations and Uncertainties A large and diverse number of limitations and uncertainties associated with the visibility preference studies have been identified and discussed in the public comm ents. Many of these same limitations and uncertainties were also identified and discussed by the EPA in the various documents developed throughout this review such as the Integrated Science Assessment, Visibility Assessment, and Policy Assessment, as well as***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 478 of 790 Formatted: Left in the proposed rule (see section VI.b.2 at 77 FR 38975 and also at 38990).
. The most important and fundamental limitations and uncertainties will be discussed here in the preamble, while more specific, unique or detailed comments will be addressed in t he Response to Comments document. The primary or most frequent limitation (s) cited by many commenters relate relate s to the small number of preference studies that are available in this review. In particular, some commenters note that these preference stud ies cover just four locations, only three of which occur in the U.S., that the two studies conducted in Washington, DC were pilot studies, not full preference studies, and/or that three of the preference studies were conducted in the West, while only one was conducted in the East, providing only limited geographic cove rage. Typically, these same commenters also pointed out that taken together, these limited studies only included a total of 852 participants, which they claimed was too small a sample size and unrepresentative nationally. These commenters thus concluded th at there is insufficient information, both geographically and demographically, upon which to select a national level of a visibility index for purposes of visibility protection. In contrast, several commenters stated support for using the preference studi es, concluding they provide an adequate basis, in spite of their limited nature. In particular, AMC et al. state: We believe that these studies provide sufficient results to inform setting a national visibility standard. While the number of studies is smal l, they do incorporate spatial variation and, in the case of Denver and Phoenix, varied populations.... EPA should have confidence, rather than uncertainty, in the fact that these studies used different methods and respondents and yield a range of 20

– 24 dv , with one outlier of 29. (AMC, et al., pp. 6

- 7) In response Regarding the first group of commenters , the EPA notes that it is well***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 479 of 790 Formatted: Left aware of the limited nature of the information, which it has described in great detail in the Integrated Science Assessment, Visibility Assessment, and Policy Assessment, as well as in section VI.B.2 of the proposed rule (77 FR 38975 3897 3 ). The EPA further notes, however, that limited information does not preclude the Administrator from making judgments based on the best availa ble science, taking into account the existing uncertainties and limitations associated with that available science. Thus, in reaching judgments based on the science, the Administrator appropriately weighs the associated uncertainties. In this review of the PM standards, the EPA notes that the CASAC The CASAC supported this view and concluded that the available information provided a sufficient basis on which the Administrator could form a judgment about requisite PM

related public welfare visibility protecti on . Specifically, CASAC stated “[t]he 20

- 30 deciview range of levels chosen by EPA staff as ‘Candidate Protection Levels’ is adequately supported by the evidence presented ” (Samet, 2 010b, p. iii). As discussed below, in determining an appropriate degree of protection for visibility, in the proposed rule (77 FR 38990), the Administrator has recognized and explicitly taken took into account the uncertainties and limitations in the science in determining an appropriate degree of protection when she proposed a le vel at the upper end of the recommended range. As discussed below, the Administrator continues to be mindful of these uncertainties and limitations in reaching her final determination regarding what constitutes an appropriate degree of protection with resp ect to PM

- related visibility impairment
. With respect to the comments of AMC et al., the EPA agrees that these studies provide a sufficient basis to inform the Administrator’s judgments regarding an***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 480 of 790 Formatted: Left appropriate level of protection from PM

- related visibili ty impairment, but she recognizes that these studies, which are the only studies before her, are a limited source of information . However, the EPA does not agree that the Washington, DC , results represent an outlier , and thus the EPA believes these results are appropriately included in the range identified for the Administrator to consider
. Some commenters made the point that the EPA relied on much of this same evidence to reach the conclusion in 2006 that the information was too limited to allow selection of a national standard. For example, API stated: [T]he bulk of the VAQ preference studies were available during the previous PM NAAQS review and were considered by the Agency in its establishment of the 2006 PM secondary NAAQS.... The Proposed Rul e does not mention this fact and does not explain why many of these same studies now compel EPA to propose this new secondary NAAQS....The Proposed Rule notes in passing that, since the last review of the PM NAAQS, ‘limited information that has become availa ble regarding the characterization of public preferences in urban areas has provided some new perspectives on the usefulness of this information in informing the selection of target levels of urban visibility protection.’ 77 Fed. Reg. at 38969/2. It is a s erious oversight that the Proposed Rule makes no attempt to explain what that information is or how it affects the interpretation of the VAQ preference studies. This ‘limited information’ is an apparent reference to information provided by Dr. Anne Smith. (API, p. 37) The EPA disagrees with these commenters. First, the EPA disagrees that it failed to distinguish between studies that were available in the previous review and the current review. The discussion in section IV VI .A.1 of the proposal specifically identifies the studies from Denver, Phoenix and British Columbia (77 FR 38967/2) as being considered in the last review. The EPA further disagrees with the implication that it is being circumspect about identifying the “limited information that has become available regarding the characterization of public preferences in urban areas.” Beginning in section IV VI .A.3 of the proposed rule (77 FR 38969), the EPA was clear about what Formatted: Font: 10 pt***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 481 of 790 Formatted: Left information, both preexisting and new, it relied upon in this review to inform its views and provide the basis for its proposal. In section VI.B.2, the EPA elaborates on the specific information, tools, methods and data which are considered in relation to the public preference studies, including the new information available since t he last review. As noted above and in the proposal, in addition to the substantial PM urban air quality information and analyses new to this review, there are three other noteworthy sources of information that have specifically “provided some new perspect ives on the usefulness of” the preference studies “in informing the selection of target levels of urban visibility protection .” ” (77 FR 38969). They include: (1) results from additional urban visibility preference study experiments conducted for Washington , DC by Smith and Howell (2009) which added to the preference data for that location , provided proof that the 2001 study could be replicated, and shed light on the role of location in preference responses 206 ; (2) an extensive a review and reanalysis (Stratus Consulting, 2009) of the urban visibility public preference studies from the four urban areas, including the newly available Smith and Howell (2009) experiments which examined the similarities and differences between the studies and evaluated the potential significance of those differences on the study results 207 ; and (3) additional analyses conducted in response to questions raised by the CASAC, , including most importantly a logit analysis presented in the (Deck and Lawson, 2010, as discussed in Chapter 2 an d Appendix J of the Visibility Assessment (see Appendix J and discussion in Chapter 2) ) , which was requested and

206 Smith, AE; Howell S (2009). An assessment of the robustness of visual air quality preference study results. CRA International. Washington, DC. http://yosemite.epa.gov/sab/sabproduct.nsf/B55911DF9796E5E385257592006FB737/$F ile/CRA+VAQ+Pref+Robustness+Study+3+30+09 +final.pdf. 207 Stratus Consulting, 2009. Review of Urban Visibility Public Preference Studies: Final Report. EPA

- HQ

- OAR

- 2007

- 0492

- 0042.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 482 of 790 Formatted: Left reviewed by CASAC, which showed that each city’s responses represented unique and statistically different curves. 208 Taken together, these sourc es contributed to an increase in the EPA’s current knowledge and understanding of the robustness of each survey study study ’s results, the appropriateness of comparing each study’s results to the others, and the key uncertainties relevant to data interpretation. In addition, in the last review the decision to not adopt a distinct secondary standard was remanded as contrary to la w and failing to provide a reasoned explanation for the decision. As such it is not appropriate for purposes of comparison with the Administrator's judgment and reasoning in this review. (b) Preference Study Methods and Design In addition to the limitations and uncertainties noted above, many comments also asserted the methodologies used in the preference studies are fundamentally flawed. Many commenters cited some of the same issues that have already been identified by the EPA as sources of uncertainty and p otential factors in producing the statistically different study results (see section VI.B.1.b above). As noted above, the EPA is well aware of the issues raised regarding the adequacy of the preference studies to serve as a basis for a secondary NAAQS (see 77 FR 38975) and solicited comment on how these uncertainties should be considered (see 77 FR 38990). Most of these same commenters also pointed to an assessment of the preference studies methodology provided by Smith and Howell (2009) and others as the b asis for their views, as indicated by the following comments: Smith and Howell (2009) show that VAQ preference study outcomes are malleable and depend entirely on the design of the study. Accordingly, such studies do not identify any meaningful threshold o f acceptable visibility conditions. Despite Smith and Howell’s conclusions, EPA continues to assert that the VAQ preference studies can be used to identify minimally acceptable visibility conditions even though the Agency has never provided any valid
208 Deck L., Lawson M. 2010. Statistical Analysis of Existing Urban Visibility Preference Studies. EPA

- HQ

- OAR

- 2007

- 0492

- 0089.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 483 of 790 Formatted: Left scien tific basis for discounting the Smith and Howell (2009) results. (API, p. 38) Well

- controlled preference studies discussed by Anne Smith of Charles River Associates at the March 2010 CASAC meeting demonstrated that the judgment of panel members was affect ed by the order in which photographs were presented and tendency to identify the middle of the range of visibility degredation as a threshold of acceptability. This points to a potential flaw in these studies and that artifacts caused by these tendencies m ay have influenced study results. Dismissing these inherent flaws in the existing preference studies and then using these studies to set a secondary NAAQS is arbitrary and capricious. (API, Attachment 2, p. 12) EPA also fails to acknowledge that the only study conducted since the last review rebuts the validity of the VAQ preference studies previously conducted. (UARG, Attachment 2, p. 28) As is explained in a more detailed discussion in the Response to Comments document, the EPA disagrees that the analysis study conducted by Smith and Howell (2009) supports the conclusion that the preference study methodologies were fundamentally flawed
. ; however, the EPA notes that their experiments do identify areas where additional research would be useful to furt her inform our limited understanding of public preferences in urban areas
. Th e EPA views the Smith and Howell experiments as increasing the EPA’s knowledge and understanding of the findings of the 2001 Washington, DC focus group pilot study (Abt, 2001) in several important ways
. , although this information still remains limited overall
. Specifically, the Smith and Howell results suggest: 1) the 2001 s results, while based on a small sample size of 9, may be were consistent with results from a fair representat ion for the preferences for larger sample of the general Washington, DC population; 2) an individual’s preferences for visibility in one location may not depend on whether they live in that location; and 3) presentation method (i.e., changing from slide pro jection to computer monitor) does did not appear to affect the reported preferences. The EPA provides detailed responses to specific***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 484 of 790 Formatted: Left comments on the design of the Smith and Howell experiments in the Response to Comments document. (c) Preference Study Results a nd Adversity A number of comments were received regarding the EPA’s use of preference study results to make the determination that adverse PM 2.5 - related visibility effects on the public welfare are occurring. In this context, several commenters questioned whether the EPA had made the case that unacceptable levels of visual air quality based on preference study results alone can be equated with an adverse public welfare effect. These commenters suggested that unless preference study information is linked to personal comfort and well

- being or other associated welfare effects, it cannot form the basis of a determination of adversity. For example, Kennecott Utah Copper LLC stated that: Thus, EPA seemingly was building the foundation for a determination of what constitutes an adverse effect on visibility in the context of public welfare. However ... EPA subsequently veered toward an oversimplified focus on public acceptance of visibility conditions.... EPA’s discussion of visibility in the Policy Assessment and its p roposed rule in the Federal Register focuses entirely on “acceptable” and “unacceptable” visual air quality and make no mention of an “adverse effect” in the context of visibility. EPA’s reliance on only 3 urban PS preference studies represents a paucity of data and a wholesale abandonment of any effort to seek a scientifically measurable adverse effect. (Kennecott Utah Copper LLC, p. 26) In response, the EPA first notes that the definition of effects on welfare included in section 302(h) of the CAA identifi es both visibility and the broader category of effects on personal comfort and well

- being as effects on welfare. In setting a secondary standard to address visibility impairment, the EPA considers the effect on the public from impairment of visibility as a separate and distinct welfare effect in its own right. The EPA is not required to translate this into terms of personal comfort and well

- being, as visibility impairment is designated explicitly by Congress as an effect on welfare. While there may***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 485 of 790 Formatted: Left be a lar ge degree of overlap among these different welfare effects, the EPA properly focuses on evaluating all of the information before the Agency on the effect visibility impairment has on the public, whether or not this impairment would also be categorized as h aving an adverse effect on personal comfort and well

- being. It is in the context of all of this information that the EPA makes the judgment as to the appropriate degree of protection from known and anticipated adverse effects on the public from visibility impairment. The EPA recognizes that there is uncertainty about the degree of adversity to the public welfare associated with PM

- related visibility impairment. However a secondary standard is designed to provide protection from "known or anticipated" advers e effects, and a bright line determination of adversity is not required in judging the requisite degree of protection under section 109(b)(2). Furthermore, the EPA disagrees that it has abandoned its consideration of visibility

- related impacts on the welfar e effect of personal comfort and well

- being, as is made clear in the following quote: Research has demonstrated that people are emotionally affected by low visual air quality, that perception of pollution is correlated with stress, annoyance, and symptoms of depression, and that visual air quality is deeply intertwined with a ‘‘sense of place,’’ affecting people’s sense of the desirability of a neighborhood (U.S. EPA, 2009a, section 9.2.4). Though it is not known to what extent these emotional effects are l

inked to different periods of exposure to poor visual air quality, providing additional protection against short - term exposures to levels of visual air quality considered unacceptable by subjects in the context of the preference studies would be expected t o provide some degree of protection against the risk of loss in the public’s ‘‘sense of well - being.’’ (77 FR 38973/1, emphasis added) The approach taken to address such qualitative, but policy

- relevant, information in this review is the same as in other N AAQS reviews. The review is initiated with a comprehensive assessment of all possible public health and welfare effects associated with PM in the Integrated Science Assessment. Then policy

- relevant effects for which***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 486 of 790 Formatted: Left there is sufficient quantitative informa tion to allow a determination of the change in risks associated with incremental changes in air quality are assessed (in this review, in the Visibility Assessment) and used to provide a quantitative basis to inform the selection of an appropriate range of levels for further consideration in the Policy Assessment. In the Policy Assessment, the EPA considers all important policy

- relevant evidence and information, both quantitative and qualitative, in making recommendations regarding the range of policy option s appropriate for the Administrator to consider. It is in the context of all of this information that the Administrator makes her final judgment as to the appropriate degree of protection from known and anticipated adverse effects on the public from visibi lity impairment. The EPA recognizes that there is uncertainty about the degree of adversity to the public welfare associated with impairment of VAQ. However a secondary standard is designed to provide protection from "known or anticipated" adverse effects, and a bright line determination of adversity is not required in judging the requisite degree of protection under section 109(b)(2). Another issue raised in the comments regarding adversity is the EPA’s decision to use the 50 percent acceptability criterio n from the public preference studies in determining candidate protection levels of visibility impairment . In particular, some of these commenters questioned the appropriateness of using the preference study 50 percent acceptability criteria results as a ba sis for the selection of a national level of visibility protection. For example, AMC et al. recommended “a 75% acceptability criterion as a target that is in line with protecting the broader public from the negative effects of visibility impairment” (AMC, et al., p. 9). In the Visibility Assessment, the EPA noted that the use of the 50 percent***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 487 of 790 Formatted: Left acceptance level for urban visibility was first presented in Ely et al. (1991) (U.S. EPA, 2010b, p. 2

- 5). Ely discussed the use of the 50 percent acceptability criter ion as a reasonable basis for setting an urban visibility standard. The standard was determined based on a 50% acceptability criterion, that is, the standard was set at the level of extinction that would divide the slides into two groups: those judged acce ptable and those judged unacceptable by a majority of the people in the study. The criterion is politically reasonable because it defines the point where a majority of the study participants begin to judge slides as representing unacceptable visibility. It is also consistent with psychological scaling theory 209 which indicates that a “true score” exceeds a standard when more than 50% of the “observed scores” exceed that standard. (Ely et al., 1991, p. 11) As Ely described, the 50 percent acceptability criterion and the preference study conducted by Ely were used as the basis for setting the level of the Denver Visibility Standard in 1990. The Th at same criterion was used judged appropriate and selected for

us e in the Phoenix preference study (BBC research, 2003) and was also used as the basis for setting the level of the Phoenix Visibility Standard in 2003. Most recently, the 50 percent acceptability criterion has been recommended by the British Columbia Visib ility Coordinating Committee as the basis for the visibility standard currently under consideration by British Columbia, Canada. Thus Furthermore, CASAC supported this approach, while recognizing the uncertainty associated with this issue. Specifically, CAS AC agreed that “the 50 th percentile for the acceptability criteria is logical, given the noted similarities in methodologies employed in the 4 study areas. ... In terms of choosing a specific percentile from the preference studies, we note that there may not be a “preferred” one, but in assessing preference studies to propose a PM secondary NAAQS, the 50 th percentile is sufficient, as it is the basis for existing visibility indexes used in the Denver/Colorado Front Range and Phoenix metropolitan areas” (Samet , 2009c, pp. 8

- 9).

209 J.C. Nunnally, Psychometric Theory , 2nd ed., MacGraw

- Hill, New York, 1978.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 488 of 790 Formatted: Left Therefore , after considering the information that served as the original basis for its selection as described in Ely et al., 1991, and given its acceptance and use in existing visibility programs and the absence of information to support a different acceptability criterion , the EPA continues to conclude , consistent with the advice of CASAC, that it is reasonable to use the 50 percent acceptability criterion in determining target levels of protection from visibility impairment. (d) Appropriat eness of using regionally varying preference study results to select a single level for a national standard. A number of commenters raised concerns regarding the bases for and implications of the differences observed in the preference study results, concl uding that these results were due to regionally varying factors and thus could not be used to set a national standard. In particular For example , some commenters asserted that because the confidence intervals around the four 50 percent acceptability levels do not overlap at all, and because there are variations in preference study designs and inherent differences of in the visual setting among cities and panels, the four preference curves and their associated 50 percent dv values are city

- specific and statist ically different. The commenters asserted conclud ed , therefore, that it was inappropriate to aggregate the 50 th percentile dv values from multiple studies and concluded that they should instead be evaluated individually. Other commenters expressed the rela ted view that the preference study results cannot be used to set a national standard for visibility impairment because the results show that visibility preferences vary regionally. For example, API stated that: The ‘one

- size

- fits

- all’ approach...is not viab le because it does not account for regional and city

- specific factors that have been made evident in the disparity of preference study data.... It is well known, for example, that the level of light extinction to which people in different areas of the countr y are accustomed, as***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 489 of 790 Formatted: Left well as the urban setting, are the primary factors that affect a person’s visual perception of an urban vista. Thus, the degree to which extinction threshold can be related to human welfare is inevitably regionally

- dependent. (API, Att achment 2, p. 4) Some of these commenters argued that because acceptable visual air quality is regionally dependent, it would be more appropriate to develop distinct visibility standards at the state or local level. Others pointed out that areas lacking which lack “important visibility vistas” might not need standards at all, since flat areas without significant terrain have a limited maximum visual range (NEDA/CAP, p. 3). Other commenters stated that due to regionally varying factors, such as relative hu midity, it is not possible to select a single level for a national standard to protect visibility across the United States
. In particular, these commenters pointed to differences between Eastern and Western areas, arguing that a single national standard could not offer the appropriate degree of protection in locations with distinct characteristics. For example: [T]he proposed method falls short because it is not temporally or geographically representative enough to have any meaning.... The uncertainty evide nced in these studies and the non

- uniformity between the western and eastern vistas makes it impossible at this time to set an acceptable light extinction value that would appropriately address visibility concerns in non

- Class I areas. (New York DOH/DEC, p p. 5

- 6) The EPA agrees that the preference curves and the 50 percent dv levels are separate and distinct data points representing four different VAQ preference curves for four unique urban scenes. However, the EPA does not agree that the study results

nece ssarily support a conclusion that preferences are regionally dependent, nor does the EPA consider the fact that the four curves are distinct as a weakness of the approach or a reason that the results cannot be compared. In addition, the EPA does not agree that the study results necessarily support a conclusion that preferences are regionally dependent
.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 490 of 790 Formatted: Left In particular, the EPA notes that the results of Smith and Howell (2009) which show that participants in Houston and Washington, DC did not have significantl y different views on acceptable air quality in Washington, DC, provide limited support for the conclusion that people’s preferences differ less because of where they live and more because of the scene they are viewing. Indeed, these preference study result s seem to substantiate what is already known, On the other hand, the existing literature indicates that people’s preferences for VAQ depend in large part on the characteristics and sensitivity of the scene being viewed. It is to be expected that people lo oking at different scenes would have different preferences, measured using the 50% acceptability criterion, depending on how changes in VAQ impact the various scenes. Therefore, it might also be the case that if the same scene was shown to participants in different regions of the country, a single preference curve could be drawn. The preference study results showing that people find less air quality degredation acceptable for sensitive scenes than for less sensitive scenes could be interpreted as validating the appropriateness of the approach for eliciting public preferences. It is the EPA’s view that the differences in the preference study results appropriately reflect the different sensitivities to visibility impairment among the four urban scenes and thus provide useful information about how people’s preferences for visual air quality would change when viewing urban scenes of differing sensitivities. The EPA understands there is a wide variety or range of urban scenes within the United States. These sens itive urban scenes include those with natural vistas such as the Colorado Rocky Mountains as well as those with iconic man

- made urban structures like the Washington Monument. The EPA believes that the scenes presented in the four urban***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 491 of 790 Formatted: Left areas include import ant types of sensitive valued urban scenes and therefore, when considered together, can inform the selection of a level of acceptable urban VAQ at the national scale, taking into account the variation across the country evidenced in the studies. This is di scussed further in the next section, below. The EPA agrees does agree with commenters that there are factors that vary regionally varying factors that are important to take into account when setting a national standard for visibility protection. Section VI. A above regarding the history of the secondary PM NAAQS review discusses the evolution of the EPA’s understanding regarding the regional differences in PM concentrations, relative humidity and other factors. As a result, the current review has gone to grea t lengths to address these factors, leading to the EPA’s proposal to use the IMPROVE algorithm to calculate light extinction in order to take into account the varying effects of relative humidity and speciated PM. While this approach does not result in a u niform level of ambient PM 2.5 , it does ensure a nationally uniform level of visibility protection. The EPA refers the reader to other sections of the final rule, including sections VI.B.1.a, VI.B.1.c, VI.C.1.b and VI.C.1.f, and the Response to Comments doc ument for a more detailed response as to how it is taking these variables into account. ii. Specific Comments on Level The EPA received relatively few comments endorsing a specific level for a distinct secondary standard for visibility. In general, commen ters who opposed setting a distinct secondary standard at this time did not address the question of what level would be appropriate if the EPA were to set a distinct secondary standard for visibility; similarly, commenters who supported adopting a distinct secondary standard at this time***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 492 of 790 Formatted: Left generally did not recommend a specific level. However, a few commenters did provide comments in support of a specific level or range of levels, with some commenters advocating standards at the upper end of the range of prop osed levels (i.e., 30 dv), while others supported levels below the lower end of the proposed range (i.e., below 28 dv). As discussed above, a large number of commenters argued that the currently available data are insufficient to determine what constitute s a standard that would be neither more nor less protective than necessary and that no standard should be set at this time. These commenters pointed to the limitations and uncertainties in the preference studies discussed above as the basis for this claim. These commenters pointed to significant variation in the results of the preference studies in support of their arguments that the studies should not be used to derive a level for a distinct secondary standard for visibility. For example, one consultant ci ted by several industry commenters argued that the proposed level of 28 or 30 dv did not reflect the substantial difference in visibility preferences between the East and the West reflected in the preference studies (UARG, Attachment 2, p. 11), and that it did not reflect the full range of preferences (i.e., potential 50 percent acceptability levels) likely to exist nationwide (UARG, Attachment 2, p. 19). This commenter further objected to the EPA’s proposal for a level of 28 or 30 dv on the grounds that th e EPA had inaccurately adjusted 4

- hour values into 24

- hour values. Based on his analysis, the consultant concluded that “a range of adjusted values from 28 to 32 dv is needed” to account for the majority of the spread between the 4

- hour vs. 24

- hour equival ent values at the upper end of the distribution of values. A number of commenters questioned whether the proposed range of levels was appropriate. One industry commenter claimed that the EPA had not explicitly justified***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 493 of 790 Formatted: Left why a standard within the proposed range was requisite, stating that “EPA makes no attempt to explain how the proposed level of the standard is neither lower nor higher than necessary to protect public welfare” (NSSGA, p. 15). Arizona DEQ noted that since the proposed calculated light extin ction indicator excluded coarse particles and Rayleigh scattering, the proposed levels of 28 or 30 dv were inconsistent with the visibility preference studies, which considered total light extinction. Noting these perceived problems with the proposed range of levels, a few commenters noted that if the EPA were to set a distinct secondary standard, the level should be set no lower than 30 dv, “to account for inconsistent value judgments, a great deal of spatial and temporal variability, and a very high level of uncertainty” (Texas CEQ, p. 7). In contrast, some commenters supporting the EPA’s proposal for a distinct secondary standard for visibility stated that the proposed range of levels from 28

- 30 dv was insufficiently protective based on a 24

- hour averagi ng time, and recommended a lower level for the visibility index standard. These commenters expressed the view that the proposed levels of 28 or 30 dv represented neither adequate surrogates for equivalent 4

- hour values, as the EPA claimed, nor sufficiently protective levels based on recent air quality data. Several commenters stated that the EPA’s own analyses suggested that a standard set at a level of 28 or 30 dv was insufficiently protective based on a 24

- hour averaging time. One commenter emphasized tha t the Policy Assessment had indicated a level between 25

- 28 dv was appropriate for a standard calculated on a 24

- hour average, and encouraged the EPA to adopt a standard level of 25 dv. Several environmental groups provided comments stating that a 24

- hour average would underestimate a 4

- hour value by 13

- 42 percent and certain areas of the country

— particularly the Northeast

—***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 494 of 790 Formatted: Left would be affected disproportionately. These commenters suggested that a 24

- hour PM 2.5 visibility index standard should be set at a level of 18.6

- 20 dv. The Department of the Interior pointed to recent air quality data indicating that visibility on the 20% worst days in several large metropolitan areas, including Birmingham, Fresno, New York City, Phoenix, and Washington, DC was below 29 dv . While noting that these calculations were based on IMPROVE calculations which include contributions from coarse PM mass, DOI expressed the view that the proposed level of 28 to 30 dv would not provide adequate visibility protection compared to the curren t 24

- hour PM 2.5 standard of 35 μg/m 3 and recommended that the standard be set at a level of 25 dv consistent with the results of the Phoenix visibility preference study. In contrast, the states of Arizona and Colorado submitted comments arguing that the v isibility preference studies conducted in Phoenix and Denver, respectively, were designed to address a specific local problem and that the results of these studies were not an appropriate basis for selecting the level of a national standard. For example, A rizona DEQ noted: The cited studies were conducted considering total light extinction; including extinction resulting from particulate matter and Rayleigh scattering. Visibility impairment due to coarse particulate matter can be an important contributor i n Arizona, specifically in the Phoenix area where ongoing measurements have been made. Therefore, ADEQ believes that the proposed levels of the secondary visibility standard are inconsistent with applicable urban studies. (Arizona DEQ, p. 2) Similarly, the Colorado Department of Public Health and the Environment noted that the Denver visibility standard was designed to address “brown clouds”, i.e., strong inversions that occur in the Denver metropolitan area, and that this standard “is based on a specific

v iew of Denver” associated with particular sight paths and direct measurement methods. The commenter stated that this standard “is applicable only to this location,” and that***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 495 of 790 Formatted: Left these limitations make it potentially unsuitable for application as “a national se condary standard, particularly a proposed standard that does not use a direct measurement method” (Colorado DPHE, p. 2). While acknowledging the uncertainties and limitations associated with the visibility preference studies as discussed above, the EPA co ntinues to conclude, as did CASAC, that the preference studies are appropriate to use as the basis for selecting a target level of protection from visibility impairment. However, the EPA agrees with commenters who emphasize the high degree of variability i n visibility conditions and the potential variability in visibility preferences across different parts of the country. In light of the associated uncertainty, as noted in the proposal, the Administrator judged it appropriate to establish a target level of protection equivalent to the upper end of the range of Candidate Protection Levels (CPLs) identified in the Policy Assessment and generally supported by CASAC. Thus, the EPA proposed to set a 24

- hour visibility index standard that would provide protection equivalent to the protection afforded by a 4

- hour standard set at a level of 30 dv. In light of the comments received on the proposal, in particular comments emphasizing the uncertainty and variability in the results of the public preference studies, the E PA continues to conclude that this approach is warranted, and that it is appropriate to set a target level of protection equivalent to the protection that would be afforded by a 4

- hour, 30 dv visibility index standard. Moreover, t he EPA disagrees with comm enters who argued that the EPA’s approach for translating 4

- hour CPLs into equivalent 24

- hour values was inappropriate. In adjusting 4

- hour values for purposes of defining an appropriate level for a 24

- hour standard, the EPA noted at the time of proposal that there were multiple approaches for***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 496 of 790 Formatted: Left estimating generally equivalent levels on a city

- specific or national basis , and that both of . While expressing the view that it was appropriate to consider the two preferred approaches identified with the highest r 2 values (Approaches A and B in Appendix G of the Policy Assessment ), 210 which used regressions of 90 th percentile light extinction values, the EPA determined it would also be appropriate to consider the city

- specific estimates resulting from Approaches C and E which showed greater variability than the aggregated estimates. Approaches C and E generated a range of city

- specific estimates of generally equivalent 24

- hour levels that encompassed the range of levels considered appropriate for 4

- hour CPLs, including the CPL of 30 dv at the upper end of that range. This led to the conclusion that it would be appropriate to use This information provided support for using the same CPL for a 24

- hour standard as for a 4

- hour standard, since no single approach could genera te an equivalent 24

- hour standard level in each urban area for each CPL. The EPA continues to conclude, as it did at the time of proposal, that using an unadjusted 4

- hour CPL for purposes of establishing a target level of protection for a 24

- hour standard
. The EPA disagrees is appropriate because this approach places more emphasis on the relatively high degree of spatial and temporal variability in relative humidity and fine particle composition observed in urban areas across the country, consistent with co mmenters who argued that the EPA’s approach for translating 4

- hour CPLs into equivalent 24

- hour values was inappropriate. reanalysis discussed below
. The EPA has conducted a reanalysis (Frank et al., 2012b) of the relationships

210 In particular, EPA staff expressed a preference for Approach B in the Policy Assessment. However, in light of the additional information provided by the other approaches explored in Appendix G of the Policy Assessment and the reanalysis in Frank, et al. (2012b), the EPA judges it more appropriate to consider the range of values resulting from all five analytical approaches for purposes of informing decisions about the equi valent level of a 24

- hour standard.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 497 of 790 Formatted: Left between estimated 24

- hour a nd 4

- hour visibility impairment based on the variety of metrics discussed in Appendix G of the Policy Assessment. The reanalysis has more appropriately considered the uncertainty of the calculated 4

- hour values. The revised analysis shows that , for all cas es considered, the 24

- hour equivalent level is

even generally closer to the 4

- hour values value at the upper end of the range of CPLs than originally estimated , demonstrating as can be seen in the results for Approaches B, C, and D. 211 For example, the reanaly sis indicates that Approach B yields an adjusted 24

- hour CPL of 29 dv 212 as generally being equivalent to a 4

- hour CPL of 30 dv, while Approach C yields a 24

- hour equivalent CPL of 29 dv averaged across cities and a range of city

- specific values from 25

- 36 d v. 213 , 214 Not only are the 90 th percentile and pooled average values closer to the 4

- hour CPL of 30 dv, the range of city

- specific results shows a wider spread that clearly encompasses the unadjusted 4

- hour value of 30 dv near the midpoint of the city

- specific range. This provides suppo rt for concluding that the EPA’s approach to translating of 4

- hour CPLs into equivalent 24

- hour values was appropriate , and that it is appropriate to use unadjusted 4

- hour values for purposes of selecting a level

211 Approach E as presented in the Policy Assessment is based on the median values for each city; these results are not affected by the regression analyses. Therefore, Approach E was not included in the reanalysis, and the results remain unchanged from those reported in the corrected Table G

- 6 as reported in Frank, et al., 2012b. 212 In Appendix G of the Policy Assessment, a 24

- hour adjusted CPL of 28 dv was estimated to be equivalent to a 4

- hour value of 30 dv under Approach B (annual 90 th percentile values reg ression)
. 213 In Appendix G of the Policy Assessment, under Approach C (all

- days city

- specific regression) , a 24

- hour adjusted CPL of 27 dv was estimated to be equivalent to a 4

- hour CPL of 30 dv when averaged across cities, while city

- specific values were e stimated to range from 24

- 30 dv. 214 In the reanalysis, Approach D (all days pooled regression) generated results of 28 dv for the 24

- hour CPL equivalent to a 4

- hour value of 30 dv as compared to a value of 27 dv in the original analysis described in Appendi x G.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 498 of 790 Formatted: Left for a standard based on a 24

- hour averaging time
. 215 Moreover, the EPA disagrees with commenters who argue that the currently available evidence is sufficient to justify establishing a target level of protection at 25 dv or below. The EPA recognizes that 25 dv represents the middle of the range of 50 percent acceptability levels from the 4 cities studied, and represents the 50 percent acceptability level from the Phoenix study, which the Agency has acknowledged as the best of the four studies in terms of having the least noise in the preference study results and the most representative selection of participants
.. . The EPA also notes the caveats discussed in the proposal regarding whether it would be appropriate to interpret results from the western studies as generally representative of a broader range of scenic vistas in urban areas across the country. The Policy Assessment noted significant differences in the characteristics of the urban scenes used in each study, with western urban visibility preference study scenes including mountains in the backgro und and objects at greater distances, while scenes in the eastern study did not. Since objects at a greater distance have a greater sensitivity to perceived visibility changes as light extinction changes compared to otherwise similar scenes with objects at a shorter range, this likely explains

215 The analysis in Appendix G of the Policy Assessment used the 4

- hour light extinction value treated as the independent (x

- axis) variable in an ordinary least squares regression. This The EPA now concludes that this regression approach was inappropriat e not the most appropriate approach because that variable has error and in fact may be more uncertain than the calculated 24

- hour extinction values. The Frank et al. (2012b) reanalysis uses an orthogonal regression instead of ordinary least squares regressi on and results in slopes closer to the 1:1 line for all the results, particularly for Dallas, TX. Furthermore, consistent with the EPA’s conclusion that a higher multiplier for converting OC to OM would be appropriate (see section VI.C.1.b.ii above), the r eanalysis substitutes a 1.6 multiplier for converting OC to OM in the calculation of 24

- hour values instead of the value of 1.4 that was used in calculating 24

- hour values for Appendix G. The higher multiplier is more consistent with the SANDWICH approach used to calculate the 4

- hour values found in Appendix G. See Frank et al. ( 2012 2012b ) for a more detailed explanation.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 499 of 790 Formatted: Left part of the difference between the results of the eastern study and results of the western studies. In the proposal, the EPA noted that the scenic vistas available on a daily basis in many urban areas across the count ry generally do not have the inherent visual interest or the distance between viewer and object of greatest intrinsic value as in the Denver and Phoenix preference studies. Also, the Agency takes note of the caution expressed by Colorado and Arizona about using the results of the Denver and Phoenix preference studies, which were aimed at addressing specific local visibility problems, to inform the choice of level for a national standard. Therefore, the Agency considers it reasonable to conclude, especially in light of the significant uncertainties, that it is appropriate to place less weight on the western preference results and that the high CPL value (30 dv) that is based on the eastern preference results is likely to be more representative of urban areas that do not have associated mountains or other valued objects visible in the distant background. These areas would include the middle of the country and many areas in the eastern U.S., as well as some western areas. As a result, the EPA concludes that it i s more appropriate to establish a target level of protection at the upper end of the range of 24

- hour CPLs considered, recognizing that no one level will be "correct" for every urban area in the country. In considering the upper end of this range, the EPA must identify a target level of protection that is considered requisite to protect public welfare from a national perspective, recognizing that the same target level would apply in all locations. Making this judgment requires a balancing of the risks to th e public welfare and the substantial uncertainties surrounding appropriate levels of visibility protection. As acknowledged in the proposal, the EPA recognizes that setting a target level of protection for a 24

- hour***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 500 of 790 Formatted: Left standard at 30 dv would reflect a judgme nt that the current substantial degrees of variability and uncertainty inherent in the public preference studies should be reflected in a higher target protection level than would be appropriate if the underlying information were more consistent and certai n. Also, a 24

- hour visibility index at a level of 30 dv would reflect recognition that there is considerable spatial and temporal variability in the key factors that determine the value of the PM 2.5 visibility index in any given urban area, such that there is a relatively high degree of uncertainty as to the most appropriate approach to use in selecting a 24

- hour standard level that would be generally equivalent to a specific 4

- hour standard level. In light of these uncertainties, the EPA continues to belie ve that it is appropriate to establish a target level of protection for visual air quality of 30 dv, averaged over 24

- hours, with a form as discussed above. In reaching this conclusion, the EPA notes that any national ambient air quality standard for visi bility would be designed to work in conjunction with the Regional Haze Program as a means of achieving appropriate levels of protection against PM

- related visibility impairment in all areas of the country, including urban, non

- urban, and Federal Class I ar eas. While the Regional Haze Program is focused on improving visibility in Federal Class I areas and a secondary visibility index NAAQS would focus on protecting visual air quality principally in urban areas, both programs could be expected to provide bene fits in surrounding areas. In addition, the development of local programs, such as those in Denver and Phoenix, can continue to be an effective and appropriate approach to provide additional protection, beyond that afforded by a national standard, for uniq ue scenic resources in and around certain urban areas that are particularly highly valued by people living in those areas. With regard to comments from the Department of Interior***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 501 of 790 Formatted: Left noting that many large metropolitan areas have 24

- hour IMPROVE values below 3 0 dv on the worst 20 percent of days already, the EPA notes that the purpose of establishing NAAQS is to ensure adequate protection of public welfare everywhere, not to mandate continuous improvements in areas that may already be relatively clean. In fact, the evidence from the IMPROVE program that many urban areas have total 24

- hour PM

related light extinction below 29 dv on the 20 percent worst visibility days suggests that many areas have relatively good visual air quality already. f. Need for a Distinct Secondary Standard to Protect Visibility Numerous commenters questioned whether a distinct secondary standard for visibility is necessary in light of the analysis described in section VI.B.1.c.vii above (Kelly et al., 2012a) which indicated that a 24

- hour mass - based PM 2.5 standard of 35 μg/m 3 would protect against visibility impacts exceeding the range of levels considered in the proposal (28

- 30 dv). While this analysis was conducted in support of proposed implementation requirements for a distinct seconda ry standard (specifically, the modeling demonstrations that would be required under the PSD program), the second prong of the analysis showed that within the range of levels proposed by the EPA for the visibility index NAAQS (28

- 30 dv), the 24

- hour PM 2.5 s tandard of 35 μg/m 3 would generally be controlling. Kelly et al. (2012a) concluded that the “overall, design values based on 2008

- 2010 data suggest that counties that attain 24

- hour PM 2.5 NAAQS level of 35 μg/m 3 would attain the proposed secondary PM 2.5 vi sibility index NAAQS level of 30 dv and generally attain the level of 28 dv” (pp. 17

- 18). Citing this conclusion, many state and local agencies and industry commenters argued that a visibility index standard in the range proposed (28

- 30 dv) would provide no***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 502 of 790 Formatted: Left additional protection beyond that afforded by the existing secondary 24

- hour PM 2.5 NAAQS, and therefore no distinct visibility standard was necessary. These commenters advocated retaining the current 24

- hour PM 2.5 mass - based standard to protect against visibility effects. “Since the 24

- hour PM 2.5 standard already protects the welfare the 24

- hour PM 2.5 visibility standard is designed to protect, the new standard is duplicative and unnecessary” (South Dakota DENR, p. 2). Furthermore, a number of state commenters objected to the additional resource burden associated with implementing a standard which had, in their view, no practical effect: “If the 24

- hour PM 2.5 mass standard has the same effect as the visibility standard, crafting complex regulations to implement another standard seems redundant” (South Carolina DHEC, p. 3). Other states agreed: “A PM 2.5 - related Visibility Index appears redundant since the benefits achieved from the current primary and secondary annual and 24

- hour PM 2.5 standards already provide reductions that would improve visibility. Establishing a new PM 2.5 secondary standard for visib ility would be an additional complication and burden to the states that is not warranted” (Indiana DEM, p. 5). In addition, several commenters submitted additional analyses supporting their position that a 35 μg/m 3 24

- hour PM 2.5 standard would provide at least equivalent protection to a distinct 24

- hour visibility standard within the range of levels proposed (API, Attachment 2, p. 8 and Attachment 3, p. 1). In responding to these comments stating that a distinct visibility stand ard is not needed, the EPA notes as an initial matter that the Administrator provisionally concluded at the time of proposal that the current PM standards were not sufficiently protective of visual air quality, and that consideration should be given to an alternative secondary***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 503 of 790 Formatted: Left standard that would provide additional protection against PM

- related visibility impairment, especially in urban areas. This provisional conclusion was based on the results of public preference surveys on the acceptability of varying d egrees of visibility impairment in urban areas, analyses of the number of days on which peak 1

- hour or 4

- hour light extinction values were estimated to exceed a range of CPLs under conditions simulated to just meet the current standards, and the advice of CASAC. The Administrator also noted that the current indicator of PM 2.5 mass, in conjunction with the current 24

- hour and annual averaging times, was not well suited for purposes of protecting visibility, since it does not incorporate species composition o r relative humidity, both of which play a central role in determining the impact of ambient PM on visibility. Taking into account the advice of CASAC and the court’s remand of the current secondary PM 2.5 standards, the Administrator provisionally concluded that the current secondary standards were neither sufficiently protective nor suitably structured to provide an appropriate degree of public welfare protection from PM

- related visibility impairment. As a result, the EPA proposed a new, distinct secondary standard that was designed to address these deficiencies. The EPA notes that in critiquing the proposed secondary standard, commenters generally did not advocate that the form of the existing mass

- based PM 2.5 standards
were was better suited scientifically to the task of protecting from against visibility impairment. Rather, the commenters’ position that a distinct secondary standard was not needed for purposes of protecting visibility was based almost entirely on the relative degree of protection likely to b e afforded by the existing standards (in particular, the existing 24

- hour PM 2.5 standard) as compared to the proposed visibility index, along with***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 504 of 790 Formatted: Left the relatively large uncertainties associated with the latter. Thus, for all the reasons discussed in the pro posal with regard to the scientific appropriateness of an indicator that takes into account both species composition and relative humidity, the EPA continues to conclude that the proposed standard based on a visibility index would be appropriate scientific ally to provide targeted protection of visibility, since it would provide a measure of PM

- related light extinction that directly takes into account the factors (i.e., species composition and relative humidity) that influence the relationship between PM 2.5 in the ambient air and PM

- related visibility impairment. Furthermore, the EPA disagrees with commenters who stated that implementation concerns, in particular the additional resource burden associated with implementing a distinct secondary standard, shoul d alter the Agency’s decision making with regard to a standard to protect visibility. The EPA may not take the costs of implementation into account in setting or revising the NAAQS. However, in light of the results of the Kelly et al. (2012a) analysis and the views expressed by commenters on the implications of this analysis for conclusions regarding the adequacy of the current secondary 24

- hour PM 2.5 standard, the EPA has reconsidered some of the conclusions drawn at the time of proposal, in particular wi th regard to the degree of protection that would be provided by the current secondary standard. Based on a review of comments related to indicator, averaging time, form and level, the Agency has concluded that (as described in sections VI.C.1b

- e above) a s tandard defined in terms of a PM 2.5 visibility index (based on speciated PM 2.5 mass concentrations and relative humidity data to calculate PM 2.5 light extinction), a 24

- hour averaging time, and a 90 th percentile form, averaged over 3 years, and a level of 30 dv, would provide sufficient but***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 505 of 790 Formatted: Left not more than necessary protection of the public welfare with regard to visual air quality. Having identified this target level of protection, the EPA is now in a position to compare it specifically to the existing secon dary 24

- hour PM 2.5 standard of 35 μg/m 3 for purposes of determining whether it would provide more, the same, or less protection from visibility impairment. The EPA must consider both whether the existing secondary 24

- hour PM 2.5 standard of 35 μg/m 3 is suff icient (i.e. not under

- protective) and whether it is more stringent than necessary (i.e. over

- protective). With regard to the degree to which the existing secondary 24

- hour PM 2.5 standard provides sufficient but not more than necessary protection for visibility, the EPA first notes that the kind of area

- specific analysis conducted in Kelly et al. (2012a) is essential for addressing the court remand of the 2006 secondary standards. In the case of the 2006 secondary standards , the EPA had argued that the 35 μg/m 3 24

- hour PM 2.5 standard was requisite because one part of the proposed range for a distinct secondary standard the Agency had considered would affect the attainment status of a somewhat fewer counties than the 35 μg/m 3 24

- hour PM 2.5 standard. The court rejected this kind of rough balancing, finding that the EPA’s equivalency analysis based on percentages of counties demonstrated nothing about the relative protection offered by the different standards. Based on this, an area

- by

- area evaluation of the relative degree of protection offered by different standards should be conducted to the extent air quality data is available. Kelly et al. (2012a) performed such an evaluation. Bas ed on 2008

- 2010 data, there are no areas that would have exceeded a 30 dv, 24

- hour visibility index standard that would not also have exceeded a 24

- hour PM 2.5 standard of 35 μg/m 3

. 216 Stated

216 The Kelly at al. (2012a) analysis used a 1.4 multiplier to convert OC to OM at those monitors not using the new CSN monitoring protocol.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 506 of 790 Formatted: Left another way, all areas that met the 24

- hour PM 2.5 standard of 35 μg /m 3 would have had visual air quality at least as good as 30 dv (24

- hour average, based on 90 th percentile form averaged over 3 years). The Kelly (2012a) analysis also showed that for some areas, particularly in the West, areas that would have met a 24

- hou r PM 2.5 standard of 35 μg/m 3 would have had visual air quality better than 30 dv for the PM 2.5 visibility index standard , and that at sites that violated both the 24

- hour level and the secondary visibility index 30 dv level, the secondary standard visibilit y index level of 30 dv would likely be attained if PM 2.5 concentrations were reduced such that the 24

- hour PM 2.5 level of 35 μg/m 3 was attained. The EPA has conducted a reanalysis (Kelly et al., 2012b) to update the area

- by

area analysis in the original Kelly et al. (2012a) analysis in t hree respects. First First, noting that the original Kelly at al. (2012a) analysis used a 1.4 multiplier to convert OC to OM at those monitors not using the new CSN monitoring protocol , the EPA recalculated the visibility i ndex design values for 2008

- 2010 using a higher multiplier for converting OC to OM at monitors not already using the new CSN monitoring protocol SANDWICH approach, consistent with the Agency’s view that it is more appropriate to use a multiplier of 1.6 at such monitors as compared to 1.4, as described in section VI.C.1.a.ii, above. 217 The recomputed visibility design index values for 2008

- 2010 show the same overall relationship to 24

- hour PM 2.5 design values as presented in Kelly et al., 2012a. Second, the E PA repeated the calculations comparing visibility index design index values with 24

- hour PM 2.5 design values using 2009

- 2011 data, the most recent

217 Some of the OC measurements were produced with CSN’s newer monitoring protocol and did not require a change in the computed OM.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 507 of 790 Formatted: Left three years of air quality information currently available. 218 Third, the EPA modified the

area - by

- area evaluation to ensure consistency with the data completeness criteria of 40 CFR p art 50, Appendix N , including the removal of data approved by EPA as exceptional events , for the current 24

– hour PM 2.5 NAAQS standard and the propo sed visibility index NAAQS standard
. The results of this re analysis, as presented in Kelly et al. (2012b), show a similar pattern to that described in the original Kelly memo. Specifically, the analysis indicates that there are were no areas with visibility impairment above 30 dv that do d id not also exceed the 24

- hour PM 2.5 standard of 35 μg/m 3 . The updated memo concludes that the results for 2009

- 2011 corroborate the findings for 2008

- 2010. Based on these analyses (Kelly et al., 2012a; 2012b), the EPA concludes with a high degree of confidence that having air quality that meets the 24

- hour PM 2.5 standard of 35 μg/m 3 would be sufficient to ensure areas would not exceed 30 dv. The EPA notes that this conclusion from Kelly et al. (2012a) is supported by tw o analyses submitted by industry commenters (API, Attachments 2 and 3). At the time of proposal, the EPA had reached a different conclusion, specifically that the 35 μg/m 3 24

- hour PM 2.5 standard was not sufficiently protective. This conclusion was based, in part, on the analyses conducted for the Visibility Assessment and Policy Assessment regarding 1

- to 4

- hour peak light extinction values based on 2007

- 2009 data. For the reasons outlined above in sections VI.B.1.c and VI.C.1.c, the EPA originally focused on hourly or sub

- daily timeframes for evaluating visibility conditions. However, data quality concerns effectively precluded adoption of a 1

- hour or sub

- daily averaging time in this review, and ultimately the EPA has concluded that a 24

- hour averaging tim e 218 The 2011 air quality data were not yet available at the time of proposal.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 508 of 790 Formatted: Left can serve as an appropriate surrogate. In reaching this conclusion, the EPA has recognized that adopting a 24

- hour averaging time will likely smooth out some of the hour

- by

- hour variability in visibility index values, and will effectively reduce peak val ues by averaging them together with other hours. In concluding it is appropriate to adopt a 24

- hour averaging time, which limits the impact of hour

- specific influences, the Agency is now placing less weight on the results of the 1

- hour and 4

- hour analyses presented in the Visibility Assessment and the Policy Assessment which focused on identifying the percent of days with peak hourly light extinction above various CPLs. In light of the Agency’s conclusion that a 24

- hour averaging time would be appropriate, the Agency has determined to place more weight on analyses of visibility conditions over a 24

- hour time period, especially the results in Kelly et al. (2012a and 2012b). In addition, the EPA notes that the Kelly et al. analyses reflects updated air quality information from more recent years of data (2008

- 2010 for Kelly et al., 2012a; 2009

- 2011 for Kelly et al. 2012b) as compared to the air quality information used in the Visibility Assessment and Policy Assessment
. In light of all of these considerations, including the results of the Kelly et al. (2012a; 2012b) analyses, and the supporting comments provided by a broad range of public commenters, the EPA is persuaded now concludes that the 24

- hour PM 2.5 standard of 35 μg/m 3 provides sufficient protection in a ll areas against the effects of visibility impairment. The EPA concludes that the existing 24

- hour PM 2.5 standard provides would provide at least the target level of protection for visual air quality defined by a visibility index set at 30 dv, as described above, which the EPA judges appropriate. However, the EPA also recognizes that it is important to evaluate whether such a***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 509 of 790 Formatted: Left standard would be over

- protective (i.e. more stringent than necessary to protect public welfare). The analyses presented in Kelly et a l. (2012a; 2012b) indicates that the 24

- hour PM 2.5 standard of 35 μg/m 3 would achieve more than the target level of protection of visual air quality (30 dv) in some areas. That is, when meeting a mass

- based standard of 35 μg/m 3 , some areas would have levels of PM

- related visibility impairment far below 30 dv. Thus, when considered by itself and without consideration of the secondary standards adopted for purposes of non

- visibility welfare effects, the 24

- hour PM 2.5 standard of 35 μg/m 3 would be over

- pr otective of visibility in some areas. However, it is important to note that as long as the current secondary 24

- hour PM 2.5 standard of 35 μg/m 3 remains in effect, this overprotection for visibility would occur, regardless of whether a distinct secondary st andard based on a visibility index set at 30 dv were adopted. These issues are discussed more fully in section VI.D, which outlines the Administrator’s final conclusions on the secondary PM standards, below. g. Legal Issues Some commenters opposed the pr oposal to establish a distinct secondary standard that would be defined in terms of a PM 2.5 visibility index. The proposed standard would use measured PM 2.5 mass concentration, in combination with speciated PM 2.5 mass concentration and relative humidity da ta, to calculate PM 2.5 light extinction, translated to the deciview (dv) scale. The standard would also be defined in terms of a specified averaging time and form, and a level for the PM 2.5 visibility index set at one of two options

— either 30 dv or 28 dv. The commenters argued that the entire approach proposed by the EPA is inconsistent with the requirements of CAA section 109(b). They pointed to a number of different aspects of the proposal which in their view made it***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 510 of 790 Formatted: Left incompatible with the CAA. For example , the Utility Air Resources Group (UARG) stated: In the past, EPA has always used a measure of PM mass as the indicator for both primary and secondary PM NAAQS. Such a standard is, as a general matter, consistent with the directive in the CAA that the NAAQ S “specify a level of air quality” and targets for control the listed criteria air pollutant. CAA § 109(b)(2). The standard contained in EPA’s proposed rule does neither of these things. Instead, it would (1) regulate relative humidity, which is not a crit eria pollutant; (2) fail to “specify a level of air quality” as required by section 109(b)(2) of the CAA; and (3) result in a standard necessitating nationally variable PM concentrations instead of a standard establishing a nationally uniform, minimally ac ceptable PM concentration. (UARG, p. 22

- 23) Other commenters raised similar or related issues, arguing that the EPA improperly set a visibility standard, and not a PM 2.5 standard, and that NAAQS can only be set in terms of a level or concentration of the air pollutant. Commenters also argued that an endangerment finding and air quality criteria would be needed before the EPA could set a standard based on PM components. Each of these comments is discussed below. As an initial matter, the commenters argued t hat the proposed standard is unlawful because it is “not a PM 2.5 standard at all, but rather a visibility standard, and visibility is neither an air pollutant nor a criteria pollutant for which a NAAQS may be promulgated” (NMA/NCBA, p. 21). According to th ese commenters, the CAA requires that NAAQS be established as limits on the concentration of an air pollutant in ambient air, not limits on the “identifiable effects” caused by that air pollutant. These commenters claimed that reduced visibility due to lig ht extinction is not an air pollutant but instead is an effect, noting that “the Act’s definition of ‘air pollutant’ speaks in terms of specific substances or matter in the ambient air” (NSSGA, p. 8). The commenters pointed to the use of the term “air poll utant” in sections 109(a)(1)(A) and (b)(2) as support for their***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 511 of 790 Formatted: Left argument, as these provisions refer to setting standards for the “air pollutant” to address the effects associated with the presence of the air pollutant in the ambient air. They likewise poin ted to section 108(a)(2)’s reference to the presence of the air pollutant in the ambient air. Since reduced visibility is not an air pollutant, they argue the EPA cannot set a NAAQS that is a standard for visibility. They argue that the proposed secondary standard it is not a PM 2.5 standard as it does not limit the concentration of PM 2.5 or any other fraction of particulate matter in the ambient air and therefore is not an “ambient air quality standard” for any pollutant. One commenter argued that the EPA i s required to “specify a level of air quality” under section 109(b)(2), which Congress intended as an acceptable concentration level of the air pollutant in the ambient air, noting that specification of acceptable visibility conditions is not the same as a n acceptable air pollution concentration level. Citing American Farm Bureau v. EPA , 559 F.3d at 516, one commenter claimed that the court had affirmed that “the NAAQS

— whether primary or secondary

— is a mass

- based standard” (Nevada DEP, p. 5). Commenters als o refer to the legislative history of the 1970 amendments, referring to NAAQS as setting the “ maximum permissible ambient air level” for an air pollutant. T he commenters argue that the proposed standard is improper because it does not limit the concentrati on of PM 2.5 or any fraction of PM in ambient air, but improperly sets a limit on visibility effects. With regard to humidity, these commenters argued that the proposed standard improperly regulates relative humidity because it is included in the calculat ion to determine the value of the visibility index. According to these commenters, the CAA allows the EPA to control criteria air pollutants through the NAAQS program, but not***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 512 of 790 Formatted: Left other various substances. The commenters stated that the EPA recognized this in the last review, treating humidity as a confounding factor and considering addressing it by measuring PM 2.5 mass - based concentration over the midday hours, when humidity would have the least effect. This would target the effects caused by PM, and not by hu midity. Referring to American Farm Bureau v. EPA , 559 F.3d 512, 528 (D.C. Cir. 2009) and 77 Fed. Reg. at 38979 n.153. UARG contested the proposed calculated visibility index as it does not approach relative humidity as a confounding factor but instead “emb races it and treats it as if it were a PM effect” (UARG p. 24). The commenters also stated that the use of a calculated visibility index, and the failure to exclude the effects of humidity, would result in acceptable PM concentrations that vary across the nation. These commenters claimed that such a standard is inconsistent with the requirements of the CAA because the proposed approach fails to establish a nationally uniform PM concentration standard. For example, API argued that the proposed visibility in dex approach is “essentially specifying levels

— not a level

— of air quality” (API, p. 29). UARG agreed, and stated that the Act “requires that criteria pollutant concentrations throughout the nation reach, at the least, a single , specified ambient concentrat ion level” (UARG, p. 25, emphasis in original). The commenters argue that a PM 2.5 visibility index standard cannot provide equal protection nationwide due to geographic variation in key factors such as relative humidity that affect level of particles allow ed in different areas. The commenters noted that establishing a single national level for the PM 2.5 visibility index would necessarily result in unequal acceptable PM 2.5 levels in different areas of the country, with lowest allowable PM 2.5 levels in urban areas in the Southeast and highest allowable levels in the arid West. UARG recognized***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 513 of 790 Formatted: Left that under section 108 the air quality criteria are to “address those variable factors (including atmospheric conditions) which of themselves or in combination with other factors may alter the effects on public health or welfare of such air pollutant,” but stated that while section 108 “allows” this, it has no bearing on this issue. Instead, the commenter stated that the EPA may take such information into account in settin g a permissible concentration of the pollutant that is uniform and national (UARG, p. 25). In addition, some commenters opposed to the proposed distinct secondary standard argued that in order to base a standard on measured levels of several speciated sub stances, the EPA must first make an endangerment finding and issue air quality criteria for each of the speciated substances included in the calculation of PM 2.5 light extinction. According to these commenters, “EPA cannot use NAAQS to indirectly regulate multiple substances which are not criteria pollutants under the guise of establishing a visibility standard” (NMA/NCBA, p. 21). Noting that air quality criteria for particulate matter were issued in 1969, NMA/NCBA argued that the 1969 Criteria Document “di d not establish air quality criteria for individual constituents that occur in particle form, instead it established criteria for particulate matter as a whole” (p. 27). In light of the fact that criteria have never been issued for “individual speciated co mponents of particulate matter,” these commenters argued, “if EPA wishes to promulgate a rule such as its secondary visibility NAAQS, it first must make a finding that the speciated components listed in Appendix N endanger public health or welfare and then issue an air quality criteria document for those components” (NMA/NCBA, p. 29). According to these commenters, the approach the EPA adopted in promulgating a NAAQS for lead supports this view:***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 514 of 790 Formatted: Left When EPA promulgated a NAAQS for lead, an individual substance in particle form, it did not assert that an endangerment finding or criteria document for lead was unnecessary because lead was already covered by the PM Criteria Document. Instead, EPA complie d with the Section 108 and 109 NAAQS prerequisites for lead, just as it must do for Appendix N substances if it intends to promulgate a NAAQS for those substances. ... [In 1976], EPA listed lead as an air pollutant that adversely affected public health or we lfare, issued an air quality criteria document for lead, and promulgated a NAAQS for lead. 43 Fed. Reg. 46246 (Oct. 5, 1976). (NMA/NCBA, p. 29) Finally, UARG argued that the EPA has in the past recognized that the secondary NAAQS is an inappropriate vehicl e for regulating PM

- related visibility, referring to 62 Fed. Reg. at 38680, including fn 49. UARG claimed the same situation continues, and the EPA has not provided a valid basis for changing this conclusion. The EPA disagrees with the points raised by th ese commenters. While the EPA is not adopting the proposed secondary standard, as explained below, this decision is not based on concern over the EPA’s authority to adopt a secondary standard such as the one proposed. The proposed distinct secondary stand ard is a standard for PM 2.5 , and is not a “visibility standard.” The proposed secondary standard is based on the mass concentration of PM 2.5 in the ambient air. The standard is defined in terms of calculated PM 2.5 light extinction which is based on the mea surement of the mass concentration of ambient PM 2.5 over a 24

- hour period. The measured mass concentration is adjusted based on information on the speciated mass components of the PM 2.5 and the relative humidity, resulting in a calculated visibility index. The level of the visibility index, combined with the form of the standard and averaging time, identifies whether a level of ambient mass concentration of PM 2.5 achieves the standard or not. Given any specific mass concentration of ambient PM 2.5 , combined with information on speciation and relative humidity, it can be determined whether the specific mass concentration of ambient PM 2.5***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 515 of 790 Formatted: Left achieved the NAAQS. Hence, the proposed secondary NAA QS specifies acceptable levels of ambient mass concentration of PM 2.5 . The combination of indicator, averaging time, form, and level of the proposed NAAQS is designed to provide the appropriate degree of protection from visibility impairment caused by ambi ent levels of PM 2.5 . It does this by calculating the light extinction associated with ambient concentrations of PM 2.5 and specifying the level of acceptable PM 2.5 mass concentration in terms of this calculation. However this does not change the fact that t

he standard is for the air pollutant PM 2.5 , and defines acceptable ambient levels of this air pollutant. It does not transform the standard into a “visibility standard” and not a standard for PM 2.5 . While the commenters had additional concerns over the use of relative humidity in the calculation, and the variation around the country of acceptable mass concentrations, those issues are separate and do not change the fact that the proposed standard defined in terms of calculated PM 2.5 light extinction is based on measurement of PM 2.5 concentration in the ambient air, and is a NAAQS for PM 2.5 . With regard to the contention that section 109(b) limits the EPA to setting a standard that is based on the concentration of the pollutant in the ambient air, we note tha t the term “concentration” typically means some measure of relative content. For example, this would include relative measures such as mass per unit of volume or parts per million. The EPA has often used such metrics to define the NAAQS, largely because th e scientific evidence of health or welfare effects supporting the NAAQS typically use such metrics in air pollution studies. For example, the current secondary standards for PM are defined in terms of the concentration of PM 2.5 and PM 10 in the ambient air, measured as the dried mass of the particulate matter per unit of air. However section***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 516 of 790 Formatted: Left 109(b) does not require that a NAAQS be defined this way. Sections 109(a) and (b) both use the general term “air quality” when discussing the EPA’s obligation to set NA AQS. The NAAQS are clearly national ambient “air quality” standards under section 109(b), which specifies that the primary NAAQS “shall be ambient air quality standards” and the secondary NAAQS “shall specify a level of air quality.” Both the primary and s econdary NAAQS are to be based on the “air quality criteria,” which are to accurately reflect the latest scientific knowledge on the effects on public health and welfare associated with “the presence of such air pollutant in the ambient air, in varying qua ntities.” Section 109(b), 108(a)(2). Congress spoke in broad terms, tasking the EPA with assessing the latest scientific knowledge about the public health and welfare associated with the presence of the pollutant in the air, without limiting this to consid eration of only those effects associated with one or more measures of concentration of the air pollutant. Congress referred to any and all effects associated with the presence of the pollutant in the ambient air, not just the effects associated with the co ncentration of the pollutant in the ambient air. Based on this knowledge, the EPA is required to set standards for the quality of the air that will provide the appropriate degree of protection from these health and welfare effects, without limitation on ho w to measure or define air quality. While concentration in the air has typically been an appropriate way to set a standard to achieve these requirements, the more general terms used in section 108(a) and 109(b) do not limit the EPA to using concentration a s the only way to measure air quality for purposes of setting a NAAQS. The EPA is charged with setting air quality standards, and has the discretion under section 109(b) to choose the metric for defining air quality that is appropriate to address the healt h or welfare effect at issue.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 517 of 79 0 Formatted: Left Congress did refer to “concentration” in certain situations. In section 109(c) Congress required the EPA to set a primary NAAQS for NO 2 concentration over 3 hours. This addressed Congress’ concern over whether the then current NO 2 standard, which used concentration as a metric, provided adequate protection. Congress also called on CASAC to advise the Administrator on the relative contribution to “air pollution concentrations” of natural and anthropogenic sources, under section 109(d)(2)(C)(iii). This information is in addition to the advice CASAC is required to provide concerning appropriate revisions to the “air quality criteria” and to the NAAQS under section 109(d)(2)(B). 219 While these provisions refer to ambient concentration s of pollutants, this reflects the EPA’s standard practice to date in setting NAAQS, and none of them change or limit the range of discretion provided under section 109(b) in setting NAAQS. They do not change the fact that the EPA is to set “air quality” s tandards, and is not limited to “air concentration” standards. The reference in the legislative history to a maximum permissible ambient air level for the pollutant also does not limit the EPA to a level of air pollutant concentration, as compared to a dif ferent metric for specifying the level of air quality, if that is judged to be appropriate. The text of sections 108 and 109 does not support the limited interpretation commenters suggest. Instead these provisions provide the EPA with significant discreti on in determining the metric for air quality that is appropriate to achieve the required degree of protection of public welfare. The commenters’ interpretation would improperly limit
219 In a pro vision that is not part of the CAA, in 1990 Congress required EPA to request a report from the National Academy of Sciences on the role of secondary national ambient air quality standards, including information on the “effects on welfare and the environmen t which are caused by ambient concentrations of pollutants” listed under section 108, and the “ambient concentrations of each such pollutant which would be adequate to protect welfare and the environment from such effects.” Section 817(a) of the CAA Amendm ents of 1990, P.L. 101

- 549.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 518 of 790 Formatted: Left this discretion, interfering with achieving the goals of section 109(b). For example, in this review the EPA considered whether it would be appropriate to base a secondary NAAQS on direct measurement of the light extinction caused by PM 2.5 . See 77 FR 38890, 38980

- 1 (June 29, 2012). There are several instrumental methods that di rectly measure PM 2.5 light extinction

– the amount of light extinction caused by the presence of PM 2.5 in the ambient air. This is not a measure of the concentration of PM 2.5 in the air, but a measure of the light extinction caused by PM 2.5 . This is clearl y an effect associated with the presence of PM 2.5 in the ambient air, and this atmospheric property is directly related to visibility effects. Unlike PM 2.5 mass concentration, there is a close scientific relationship between directly measured PM 2.5 light e xtinction and visibility effects. It would appear straightforward to say that PM 2.5 light extinction is a quality of the ambient air, and a secondary NAAQS that specified an acceptable level of PM 2.5 based on directly measured PM 2.5 light extinction would be an “ambient air quality standard” for the air pollutant that specifies a “level of air quality” designed to provide protection against visibility impairment. Unlike directly measured PM 2.5 light extinction, the mass concentration of PM 2.5 does not have the same direct relationship to light extinction, and specifying an acceptable level of mass concentration of PM 2.5 would be a more indirect and less effective way to provide protection from visibility impairment caused by the presence of PM 2.5 in the ambi ent air. Under the commenters’ interpretation, the EPA would be precluded from specifying a level of air quality in terms of directly measured PM 2.5 light extinction, the more scientifically appropriate and direct measure of the effect PM 2.5 has on visibil ity. Instead the EPA would be limited to the more indirect***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 519 of 790 Formatted: Left and less effective specification of a level of concentration of PM 2.5 . The commenters also objected to the inclusion of relative humidity as an adjustment factor in the calculation of PM 2.5 light e xtinction. Contrary to the claims of these commenters, the use of calculated PM 2.5 light extinction does not regulate relative humidity. The proposed secondary standard would define acceptable levels of ambient PM 2.5 , not acceptable levels of relative humi dity. In addition, section 108 explicitly requires that the air quality criteria include information on the atmospheric conditions that can alter the effects of the air pollutant on public health or welfare, and relative humidity certainly has this kind of impact. Section 109(b) requires that the standard be based on the air quality criteria, indicating that this information can and should be taken into account in setting the standard. Including relative humidity as an adjustment factor in the calculation o f PM 2.5 light extinction is a reasonable and straightforward way to use the scientific information in the air quality criteria in establishing a standard to provide protection from visibility impairment. 220 Some commenters pointed to the EPA’s position in the last review, stating that the EPA properly treated relative humidity as a confounding factor, and in this review improperly moves away from that position. See 77 FR at 38979, 71 FR 61144, 61205 (October 17, 2006). In the last review the EPA considered a distinct PM 2.5 mass - based secondary standard. In that context, limiting the measurement of PM 2.5 mass concentration to the mid

- day hours when relative humidity had the least impact would promote the correlation between measured PM 2.5 mass concentration a nd light extinction, which would promote achievement of a relatively consistent degree of visibility

220 UARG recognizes these provisions, but argues, as above, that this is limited by the requirement that the EPA set a NAAQS based solely on ambient concentration.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 520 of 790 Formatted: Left protection across the country. However in this rulemaking the proposed calculated PM 2.5 light extinction standard achieves a consistent degree of visibilit y protection by directly accounting for humidity, in a scientifically defensible manner. The goal has not changed

– achieving the desired degree of protection across the country. What has changed is that calculated PM 2.5 light extinction is a more direct a nd scientifically appropriate way to achieve that result. Finally, it should be made clear that water is not a separate compound from PM 2.5 that confounds the impact PM 2.5 has on light extinction. As described in the Integrated Science Assessment, “P M is t he generic term for a broad class of chemically and physically diverse substances that exist as discrete particles (liquid droplets or solids) over a wide range of sizes” (U.S. EPA, 2009a, p. 1

- 4). “ Particles composed of water soluble inorganic salts (i.e. , ammoniated sulfate, ammonium nitrate, sodium chloride, etc.) are hygroscopic in that they absorb water as a function of relative humidity to form a liquid solution droplet. Aside from the chemical consequences of this water growth, the droplets become la

rger when relative humidity increases, resulting in increased light scattering. Hence, the same PM dry concentration produces more haze” ( U.S. EPA, 2009a, p. 9

- 6). Thus water is not a compound that is separate and apart from the particle that acts as an ex traneous confounding factor. 221 The effect of relative humidity occurs after the water becomes part of the particle. Certain water soluble salts absorb water and the resulting particle is larger in size and scatters more light, increasing the visibility impa ct of the particle. But the particle is still a PM 2.5 particle. The fact that the PM
221 According to the Integrated Science Assessment, “ Confounding is ‘...a confusion of effects. Specifically, the apparent effect of the exposure of interest is distorted because the effect of an extraneous factor is mistaken for or mixed with the actual exposure effect (which may be null)’ (Rothman and Greenland, 1998, 086 599)” (U.S. EPA, 2009a, p. 1

- 16).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 521 of 790 Formatted: Left NAAQS traditionally uses a measurement of the dried mass of the particles as the metric for the standard does not change the fact that the particles in the air include liq uid droplets and particles that have increased in size because of absorption of water. These ambient PM 2.5 particles are what is in the air and impacting visibility, not just the dried mass of PM 2.5 that is measured in the laboratory and is currently used as the indicator for the PM NAAQS. Thus the commenters improperly claimed that the proposed secondary standard regulates water or relative humidity, and not PM 2.5 , when in fact the proposed secondary standard accounts in a scientific manner for the fact th at some PM 2.5 particles are larger in size and have a greater impact on light extinction when the relative humidity increases. The commenters also raised concerns that a standard based on calculated PM 2.5 light extinction, compared to a standard based on just PM 2.5 mass concentration, improperly results in variable levels of acceptable PM 2.5 mass concentrations across the country. This stems from the adjustments in the calculation for speciated components of PM 2.5 and relative humidity. According to commen ters, this is improper as section 109(b) requires that the NAAQS set a single, specified ambient concentration that is nationally uniform across the country. As discussed above, the text of section 109(b) does not specify this limitation of a single nation al acceptable concentration. Instead the secondary NAAQS is to specify a level of air quality that achieves the appropriate degree of protection. The proposed secondary standard would do just that

– specify a level of air quality, defined in terms of calcu lated PM 2.5 light extinction, that would achieve the desired degree of protection. The fact that this results in varying allowable levels of PM 2.5 mass concentrations is not***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 522 of 790 Formatted: Left inconsistent with the Act. The D.C. Circuit recently approved such a result. In th e last review of the PM 10 primary NAAQS, the court approved the EPA’s choice of an indicator that was designed to allow varying levels of acceptable coarse PM. The court stated that: The industry petitioners next argue that the 150 μg/m 3 standard for PM 10 will result in arbitrarily varying levels of coarse PM, and that the agency should instead have used a PM 10

- 2.5 indicator. The EPA does not dispute that using the PM 10 indicator will result in coarse PM levels that vary within the limit of 150 μg/m 3 . As th e EPA explains: "Because the PM 10 indicator includes both coarse PM (PM 10

- 2.5 ) and fine PM (PM 2.5 ), the concentration of PM 10

- 2.5 allowed by a PM 10 standard set at a single level declines as the concentration of PM 2.5 increases. Thus, the level of coarse p articles allowed varies depending on the level of fine particles present." Id. at 61,195
. Although the EPA acknowledges that a PM 10 indicator will result in varying coarse PM levels, it does not agree that the variance will be arbitrary. The EPA agrees with the industry petitioners that protection from coarse particles should be targeted at urban areas, where coarse particles have bee n shown to pose the greatest danger. Id. at 61,194 . But the agency argues that targeting of urban areas is effectively accomplished by using an indicator that permits the varying levels that the industry petitioners challenge. ... Id. at 61,195

- 96 (citations omitted). In other words: "The varying levels of coarse particles allowed by a PM 10 indicator will therefore target protection in urban and industrial areas where the evidence of adverse health effects associated with exposure to coarse particles is stron gest." Id
. The EPA also offers a further rationale for tying the stringency of coarse PM regulation to increases in the level of PM 2.5 . ... EPA argues that it is "logical to allow lower levels of coarse particles when fine particle concentrations are high. . . . [I]nclusion of PM 2.5 in the PM 10 indicator for purposes of coarse particle protection would appropriately reflect the contribution that contaminants emitted in fine particle form can make to the overall health risk posed by coarse particles." Id
. In sum, we find that the EPA has provided a reasonable explanation for its decision[ ] ... to utilize a standard that allows targeted variance in coarse PM levels in an inverse relationship to the amount of fine PM in the air. American Farm Bureau v. EPA , 559 F .3d 512, 534

- 5 (D.C. Cir. 2009). A similar result applies here. Under the proposed secondary standard there would be a single level of air quality specified for the NAAQS. The standard would apply across***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 523 of 790 Formatted: Left the nation; it would not be a regional standard. Th e proposed standard would be the same standard everywhere

— the acceptable level of mass concentration of PM 2.5 would be defined the same way across the nation, using the same method of calculating the allowable concentration of PM 2.5 . The same degree of pro tection from visibility impairment would apply across the country. While the allowable amount of PM 2.5 could vary, this would be a reasoned way to achieve the desired degree of protection from visibility impairment. The requirements of section 109(b) would be satisfied. Commenters also objected that the EPA could not set a NAAQS for the separate components of PM 2.5 without listing the components of PM 2.5 under section 108, based on an endangerment finding, and issuing air quality criteria for these componen ts. They argued that the issuance of air quality criteria for particulate matter starting in 1969 did not provide a lawful basis for a proposed secondary standard that is based on components of PM, as the 1969 air quality was for particulate matter “as a w hole,” defining PM as particles smaller than 500 micrometers (NMA/NCBA, p. 27). However, as discussed above, the proposed standard sets the allowable limit on ambient concentrations of PM 2.5 . Information on both the speciated components of PM 2.5 and the re lative humidity affect how much light extinction is associated with any specific level of PM 2.5 , but the standard is for PM 2.5 . The D.C. Circuit has made it clear that PM 2.5 , just like PM 10 and TSP before that, is an appropriate subset of PM for the EPA to focus on in setting the NAAQS based on the scientific evidence before the EPA. This focus of the NAAQS does not make the subset a new pollutant that requires listing and new air quality criteria under section 108 before setting a NAAQS. American Trucking Association et al. v. EPA , 175 F.3d 1027, 1055 (D.C. Cir. 1999). Commenters’ interpretation would apply to PM 2.5 as well as to***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 524 of 790 Formatted: Left components of PM 2.5 , and is inconsistent with the ATA decision. In addition, it is clear that the current air quality criteria do address the scientific basis for calculating PM 2.5 light extinction as the EPA proposed (U.S. EPA, 2009a, pp. 9

- 5 to 9

- 8). Finally, at least one commenter argued that the EPA has concluded in prior reviews that the secondary NAAQS program is an inappropr iate vehicle for regulating PM related visibility impairment (UARG, p. 26). UARG mischaracterized the EPA’s past decision

- making. In past reviews the EPA has been clear that the EPA should take into account the existence of the visibility program under sec tion 169A, the regional haze program, when considering a secondary NAAQS and should not treat the secondary NAAQS as the sole mechanism to address visibility impairment across the country. That is the approach the EPA has taken in this and prior reviews. S ee 77 FR at 38990. h. Relationship with Regional Haze Program A large number of commenters expressed confusion and concern over differences between the proposed visibility index standard and the Regional Haze Program. This included commenters who supported setting a distinct secondary standard to protect visibility a s well as those opposed to setting such a standard. A number of these commenters noted that visibility impairment would be assessed differently under the two approaches due to differences in the way light extinction is calculated, including different IMPRO VE equations and differences in the inclusion and weighting of specific species and components. The commenters argued it would be inappropriate to have two different regimes for managing visibility impairment in the exact same location. These commenters cl aimed that since data from the IMPROVE monitoring network would inform nonattainment designations, as well as an area’s obligations under the Regional***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 525 of 790 Formatted: Left Haze Program, there could be considerable confusion over how to draw nonattainment boundaries and what re quirements would affect large sources in rural areas. These commenters also noted the resource burden associated with maintaining two different programs aimed at protecting visibility in the same geographic area. Some commenters argued that a visibility NA AQS should not apply to rural areas. The Department of the Interior requested that the EPA clearly define the geographic area to which the visibility index standard would be applicable, and suggested that Class I and Class II areas should generally be excl uded from the standard. As discussed above, commenters questioned the need for a distinct visibility standard, arguing that the existing primary PM standards combined with the Regional Haze Program ensured adequate protection of visibility, even in urban a

reas. In response to these comments relating to the overlap between the Regional Haze program and a distinct secondary standard designed to protect visibility principally in urban areas, the EPA notes that the objectives of each program are distinct. While the Regional Haze program is designed to eliminate man

- made impairment of visibility in Federal Class I areas over the course of several decades, a distinct secondary standard for PM

- related visibility impairment would be focused on providing a nationally applicable level of protection for all areas, particularly urban areas which do not receive targeted protection under the Regional Haze Program. Moreover, the metric used to assess visibility impairment differs between the two programs precisely because e ach program is aimed at a different aspect of the problem. Recognizing the importance of fresh emissions for urban visibility, the Visibility Assessment focused on visibility impairment as measured by the original IMPROVE equation because “the original ver sion is***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 526 of 790 Formatted: Left considered more representative of urban situations when emissions are still fresh rather than aged as at remote IMPROVE sites” (U.S. EPA, 2010b, p. 3

- 19). The Regional Haze Program, on the other hand, has shifted to a revised IMPROVE algorithm more suited to remote locations. While this difference is discussed in more detail in section VI.C.1.b above, the result is that each program would appropriately measure those aspects of visibility impairment most closely related to the problem the program is trying to prevent. Since the same data can be used to calculate both visibility impairment under the Regional Haze approach and the proposed visibility index, the additional calculation burden for state and local agencies would be light. Also, to the exten t that there is any difference in terms of the emissions control obligations the two different programs would impose upon state and local areas, this is likely appropriate given the extent and nature of visibility impairment in those areas. The EPA notes t hat in general, there is likely to be substantial overlap in the control strategies a state or local area would pursue under either program. Thus, the EPA disagrees with commenters who stated that a distinct visibility standard as proposed would inherently conflict with the Regional Haze Program or that it would be appropriate to draw geographical distinctions that would explicitly exclude some areas (e.g., Class I areas) from the NAAQS. The EPA notes that the CAA requires that NAAQS be national in scope, a nd that the specific requirements laid out in the proposal for the distinct secondary standard would ensure that the protection it afforded would be appropriately targeted toward urban areas so that it could work in conjunction with

— not be in conflict with

— the Regional Haze Program under sections 169A and 169B of the CAA. 2. Comments on the Proposed Decision Regarding Non

- Visibility Welfare Effects***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 527 of 790 Formatted: Left Relatively few commenters addressed the proposal to retain the existing suite of secondary PM standards to add ress non - visibility welfare effects. A couple of states, including Mississippi and South Dakota, offered brief endorsements of the proposal , but the vast majority of commenters, even those who offered extensive comments on the proposed visibility index, di d not comment on the proposal to retain the existing secondary standards.
. A few other commenters offered more extensive comments on the proposal to retain the existing secondary standards, and these commenters opposed this aspect of the proposal for one o f two reasons. First, some commenters opposed the proposal to retain the current secondary annual PM 2.5 standard of 15 μg/m 3 in light of the proposal to revise the level of the primary annual PM 2.5 standard to a level between 12

- 13 μg/m 3 . Expressing concern over the implications of this decision for the air quality planning obligations of states, these commenters argued that the EPA should revise the secondary PM 2.5 standards to be equivalent in all respects to the primary PM 2.5 standards. For example , the American Association of State Highway and Transportation Officials (AASHTO) supported “retaining secondary standards that are consistent with the primary standards in order to reduce the complexity of the transportation and air quality planning proce sses, as well as the transportation conformity process” (AASHTO, p. 3). Thus, if the EPA were to adopt a lower level for the primary annual PM 2.5 standard, the commenters recommended that the EPA adopt this same lower level for the primary secondary PM 2.5 standard as well. In response to these comments, the EPA notes that the Agency lacks an appropriate scientific basis for revising the level of the secondary annual PM 2.5 standard. As noted above in section VI.B.2, there is an absence of information that w ould support***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 528 of 790 Formatted: Left any different secondary standards for PM. Comments related to the implementation challenges associated with distinct primary and secondary standards are not relevant to the Administrator’s final decisions regarding what standards are requisite to protect the public welfare. Therefore, the EPA continues to conclude that it would be appropriate to retain the current suite of secondary PM standards 222 to address non

- visibility welfare effects , while revising only the form of the secondary annual PM 2 .5 standard to remove the option for spatial averaging consistent with this change to the primary annual PM 2.5 standard , as proposed. Other commenters focused on the impacts of particulate matter on climate. One commenter cited a number of recent studies t hat considered mobile source black carbon emissions and associated climate impacts, and urged the EPA to protect the public welfare by setting “higher standards for gasoline quality” (Urban Air Initiative, p. 4). This commenter did not, however, advocate s pecific secondary NAAQS to address climate impacts of PM. More extensive comments on this same subject were provided by the Center for Biological Diversity (CBD), which urged the EPA to “set a separate limit for black carbon within the overall PM 2.5 standa rd” to ensure that public welfare is fully protected “from the serious climate impacts of black carbon” (CBD, p. 2). This commenter argued that “[p]recaution is required for secondary NAAQS,” citing American Trucking Associations, Inc. v. EPA , 283 F.3d 355 , 369 (D.C. Cir. 2002): [N]othing in the Clean Air Act requires EPA to wait until it has perfect information before adopting a protective secondary NAAQS. Rather, the Act mandates promulgation of secondary standards requisite to protect public welfare from any “ anticipated adverse effects associated with” regulated pollutants, 42 U.S.C. § 7409(b)(2) (emphasis added), suggesting that EPA must act as soon as it has enough information (even if crude) to “anticipate[]” such effects[.]
222 As summarized in section VI.A and Table 1 above, the current suite of secondary PM standards includes annual and 24

- hour PM 2.5 standards and a 24

- hour PM 10 standard.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 529 of 790 Formatted: Left The commenter stressed the growing scientific evidence regarding the impacts of black carbon on climate, and argued that the EPA’s proposal ignores important research studies published within the last five years which provide improved estimates of the radiative forcing associated w ith black carbon, and the effects of black carbon on snow and ice, the Arctic climate, water availability and climate “tipping points.” The commenter also noted that reductions in cooling aerosol species, particularly sulfate, due to pollution control prog rams are leading to an “unmasking” of the true extent of warming due to the accumulation of greenhouse gases in the atmosphere. The commenter argued that this unmasking effect can be offset by ensuring “that sufficient black carbon reductions accompany red uctions in overall aerosol pollution” (CBD, p. 10). The commenter also argued that the EPA did not consider the negative impacts of climate change on public health adequately in the proposal. The commenter stated that the EPA had an obligation to address t he impacts of black carbon in the PM NAAQS, despite the remaining uncertainties. The commenter pointed to the U.S. EPA’s report to Congress on Black Carbon (U.S. EPA, 2012c), stating that the “report shows that EPA is aware of the climate science and public health information that point to the importance of addressing black carbon pollution. EPA must use this informat ion in its relevant decisionmaking” (CBD, p. 13). The commenter also noted that the United States U
. S
. participates in a number of international forums that have recognized the need to take action on black carbon, and argued that the U.S. has “an obligation under the Gothenburg Protocol to address black carbon pollution.” The commenter challenged the uncertainties cited by EPA with regard to the climate impacts of aerosols generally, arguing that they “do not apply to the regulation of black carbon”***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 530 of 790 Formatted: Left (CBD, p. 14). Specifically, the commenter stated that “there are significant anthropogenic sources of black carbon that contribute a large proportion of total black carbon emissions”; that “there is enough information related to black carbon’s impact to know that global temperatures will rise due to black carbon emissions”; that spatial and temporal heterogeneity in black carbon emissions do not matter for estimating likely climate effects; that “[b]lack carbon’s negative climate impacts do not depend upon details of cloud interactions with aerosols”; and that the EPA does not need to be able to quantify the health or climate benefits precisely to know that it is appropriate to control black carbon as a specific component of PM under the CAA (CBD, pp. 14

- 15). As a result, the commenter concluded that the current size

- based PM mass standard “is insufficient to fully protect health and welfare,” and that the EPA was obligated to establish a specific limit on black carbon as a component of PM. The commenter argued that “Black carbon must be regulated separately and in addition to PM 2.5 because absent separate standards sulfates and nitrates may be more likely to be mitigated than the black carbon component of PM” (CBD, p. 17). To support this point, the commenter cited the conclusion in the Policy Assessment that: The current standards that are defined in terms of aggregate size mass cannot be expected to appropriately target controls on components of fine and coarse particles that are related to climate forcing effects. Thus, the current mass

- based PM 2.5 and PM 10 secondary standards are not an appropriate or effective means of focusing protection against PM

- associated climate effects due to these differences in components. (U.S. EPA, 2011a, p. 5

- 11) The commenter also n oted that existing regulations on diesel engines, which are the largest source of black carbon in the United States, do not affect existing engines and vehicles, and stated that “The NAAQS program is one of the few opportunities to reduce Formatted: Indent: First line: 0.5"***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 531 of 790 Formatted: Left black carbon from existing engines, industrial and biofuel sources within the United States and rapidly reduce emissions from this pollutant” (CBD, p. 18). The EPA agrees with the commenters’ assertion that the scientific information about the impacts of aerosol species on climate is developing rapidly, and that understanding of the magnitude of aerosol effects on climate and the contribution of individual aerosol components to those effects has improved substantially over the past decade. The EPA also agrees that certain s pecies, in particular black carbon, play a significant role in multiple aspects of climate. The Policy Assessment recognized that “Aerosols can impact glaciers, snowpack, regional water supplies, precipitation and climate patterns,” and may contribute to t he melting of ice and snow, a decrease in surface albedo, and climate impacts in the Arctic and other locations (U.S. EPA, 2011a, p. 5

- 9). The contribution of black carbon to these effects is discussed in detail in the EPA’s recent Report to Congress on Bl ack Carbon (U.S. EPA, 2012c). In particular, black carbon plays an important role in heating the lower atmosphere by absorbing incoming solar radiation and outgoing terrestrial radiation, i.e. via “direct” radiative forcing. However, the EPA disagrees that there is sufficient information available at this time to establish a NAAQS to protect against the climate impacts associated with current ambient concentrations of black carbon or other PM constituents. While the Integrated Science Assessment concluded t hat “a causal relationship exists between PM and effects on climate, including both direct effects on radiative forcing and indirect effects that involve cloud feedbacks that influence precipitation formation and cloud lifetime” (U.S. EPA, 2009a, section 9 .3.10), it also identified substantial remaining uncertainties with***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 532 of 790 Formatted: Left regard to the contribution of individual aerosol species to these climate effects. The contribution of individual aerosol components to total aerosol direct radiative forcing is

more uncer tain than the global average (U.S. EPA, 2009a, section 9.3.6.6), and the indirect effects of aerosols and aerosol components remain highly uncertain, in particular with regard to their complex interactions with clouds. With regard to black carbon, for exam ple, the EPA disagrees with CBD’s claims that “black carbon’s negative climate impacts do not depend upon details of cloud interactions with aerosols” and that the uncertainties associated with climate impacts of aerosols generally do not apply to black ca rbon. In fact, the EPA has pointed to cloud interactions as the area of greatest uncertainty with regard to black carbon: recognizing that black carbon affects cloud reflectivity (albedo), lifetime, and stability as well as precipitation, the Report to Con gress on Black Carbon noted that “few quantitative estimates of these effects are available, and significant uncertainty remains. Due to all of the remaining gaps in scientific knowledge, it is difficult to place quantitative bounds on the forcing attribut able to [black carbon] impacts on clouds at present” (U.S. EPA, 2012c, p. 4). The Report acknowledged that “most estimates of the forcing from aerosol indirect effects are based on all aerosol species (e.g. total PM) and are not estimated for individual sp ecies (e.g, BC alone)” (U.S. EPA, 2012c, p. 40). The Report concluded that it remains unclear the extent to which black carbon contributes to the overall aerosol indirect effect, and did not assign any central estimate or even a range of possible values to the role of black carbon in the overall aerosol indirect effect. With regard to black carbon’s net contribution to climate, therefore, the Report concluded: The direct and snow/ice albedo effects of BC are widely understood to lead to climate warming. How ever, the globally averaged net climate effect of BC also***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 533 of 790 Formatted: Left includes the effects associated with cloud interactions, which are not well quantified and may cause either warming or cooling. Therefore, though most estimates indicate that BC has a net warming in fluence, a net cooling effect cannot be ruled out. It is also important to note that the net radiative effect of all aerosols combined (including sulfates, nitrates, BC and OC) is widely understood to be negative (cooling) on a global average basis. (U.S. EPA, 2012c, p. 3) Given the remaining uncertainties about the impact of aerosols on climate, there is even greater uncertainty with regard to how aerosol

- induced climate change will affect public health. At this time, it is not possible to estimate the ext ent to which aerosols in general, let alone particular aerosol components, contribute to the occurrence or exacerbation of adverse health outcomes due to climate change. The EPA therefore disagrees with CBD’s claim that the EPA should pursue black carbon r eductions for purposes of reducing the impacts of climate change on public health. The Report to Congress on Black Carbon also stressed the importance of considering co

- emitted PM species, such as SO 2 and NO x , in evaluating the benefits of black carbon mit igation options. Noting that many of these co

- emitted particles and gases have a cooling influence on climate, the Report noted the difficulty of estimating the net effect of various mitigation measures on net radiative forcing or other climate variables. The EPA concluded that the location and timing of emissions reductions would be critically important for achieving climate benefits, and that “more research is needed on the benefits of individual control measures in specific locations to support policy de cisions made at the national level” (U.S. EPA, 2012c, p. 140). Thus, the EPA disagrees with CBD’s claim that spatial and temporal heterogeneity in black carbon emissions do not matter for estimating likely climate effects, and continues to believe that bei ng able to quantify the climate impacts of various aerosol species, alone and in combination, is***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 534 of 790 Formatted: Left essential for informing any possible revisions to the current secondary PM standards based on climate. Furthermore, while the EPA agrees with the commenter that a large percentage of black carbon emissions come from anthropogenic sources, including diesel engines and vehicles, the EPA notes that existing regulations on mobile diesel engines are already redu cing these emissions substantially. Between 1990 and 2005, new engine requirements resulted in a 32 percent reduction in black carbon emissions from mobile sources, and a further 86 percent reduction from 2005 levels is projected to occur by 2030 as vehicl es and engines meeting existing regulations are phased into the fleet (U.S. EPA, 2012c, p. 175). Long

- term historic data indicate that there has been a dramatic overall decline in black carbon emissions over the past century, due to changes in fuel use, mo re efficient combustion practices, and implementation of PM controls. Therefore, the EPA disagrees with CBD’s claim that a distinct black carbon NAAQS is necessary to achieve reductions in black carbon emissions. Clearly, U.S. emissions of black carbon are already declining substantially, suggesting that the existing mass

- based PM standards, though not targeting black carbon specifically, have been effective in achieving black carbon emissions reductions in practice. As acknowledged in the Report to Congres s on Black Carbon , “While [black carbon] is not the direct target of existing programs, it has been reduced through controls aimed at reducing ambient PM 2.5 concentrations and/or direct particle emissions” (U.S. EPA, 2012c, p. 161). The EPA has acknowledge d the need to encourage PM mitigation strategies that focus on reducing directly emitted PM 2.5 for purposes of reducing black carbon, and this is reflected in U.S. commitments under the Gothenburg Protocol: the new provisions in the Protocol pertaining to PM encourage***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 535 of 790 Formatted: Left parties to develop national inventories and projections for black carbon, and to “give priority” to black carbon when implementing measures to control PM. However, the EPA notes that the U.S. has not yet ratified the PM amendments to the Gothe nburg Protocol, and furthermore, these amendments do not require action specifically to reduce black carbon, but rather encourage countries to take such actions voluntarily within the context of their broader PM reduction strategies. Thus the EPA disagrees with the commenter that the U.S. has an “obligation” to reduce black carbon under the Gothenburg Protocol, or that it has “agree[d] to choose mitigation options for particulate matter that focus on black carbon reductions” under the Protocol (CBD, p. 13). In sum, the EPA notes the substantial remaining the uncertainties and gaps with regard to the climate impacts of PM components, including black carbon. These include the uncertainties associated with the spatial and temporal heterogeneity of PM components that contribute to climate forcing; the uncertainties associated with measurement of aerosol components; the inadequate consideration of aerosol impacts in climate modeling; and the currently insufficient data on local and regional microclimate variations and the heterogeneity of cloud formations. As a result, the EPA continues to conclude that it is not currently feasible to conduct a quantitative analysis for the purpose of informing revisions of the current secondary PM standards based on climate, and t hat there is insufficient information at this time to base a national ambient standard on climate impacts associated with current ambient concentrations of PM or any of its constituents. 223 D. Conclusions on Secondary PM Standards

223 This conclusion applies for both the secondary (welfare

- based) and the primary (health

- based) standards.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 536 of 790 Formatted: Left This section describes the Administrator’s conclusions regarding the secondary PM standards and the rationale leading to the Administrator’s final decision to retain the current suite of secondary PM standards , including an annual PM 2.5 standard of 15 μg/m 3 a 24

- hour PM 2.5 standard of 35 μg/m 3 , and a 24

- hour PM 10 standard of 150 μg/m 3 , to address PM

- related welfare effects, including visibility impairment as well as other PM

related welfare effects, including ecological effects, effects on materials, and climate impacts. Specifically , this section explains the Administrator’s decision, consistent with the proposal, to retain the current suite of secondary PM standards generally, while revising only the form of the secondary annual PM 2.5 standard to remove the option for spatial averag ing consistent with this change to the primary annual PM 2.5 standard. It also explains the Administrator’s decision, contrary to what was proposed, not to establish a distinct standard to address PM

- related visibility impairment. In reaching conclusions r egarding the need to revise the secondary PM standards for both visibility and non

- visibility welfare effects, the Administrator has taken into account several key factors, including: (1) The latest scientific information on both visibility and non

- visibil ity welfare effects associated with PM, as previously described; 2) the advice of CASAC; and 3) the comments received during the public comment period, as discussed above. Based on this information, the Administrator has reached final conclusions about the secondary PM standards and made final decisions about those standards, as outlined below. Because the Administrator’s final conclusions with regard to the need to establish a distinct secondary standard to protect against visibility impairment reflect, in part, her conclusions on the secondary standard PM standard s for

non - visibility welfare effects, section VI.D.1 first outlines her conclusions regarding the***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 537 of 790 Formatted: Left secondary PM standards to address non

- visibility welfare effects. This is followed by section VI.D. 2 which outlines her conclusions regarding a secondary PM standard to protect address PM

- related visibility impairment . Finally, section VI.D.3 summarizes the Administrator’s final decisions with regard to the secondary PM standards for both visibility and non - visibility welfare effects. 1. Conclusions Regarding Secondary PM Standards to Address Non

- Visibility Welfare Effects With regard to the secondary PM standards to address non

- visibility welfare effects, the Administrator concludes that it is generally app ropriate to retain the existing secondary standards and that it is not appropriate to establish any distinct secondary PM standards to address non

- visibility PM

- related welfare effects. This conclusion is based on the considerations discussed above in sect ion VI.B.2, including the latest scientific information and the advice of CASAC, and the public comments received on the proposal, as discussed above in section VI.C.2. The Administrator concurs with the advice of CASAC and the conclusions expressed at the time of proposal that it is important to maintain an appropriate degree of control of both fine and coarse particles to address non

- visibility welfare effects, including ecological effects, effects on materials, and climate impacts. In the absence of info rmation that would support any different standards the Administrator concludes that it is appropriate to retain the existing suite of secondary standards to address non

- visibility welfare effects, as proposed. More specifically, the Administrator concludes it is appropriate to retain all aspects of the current 24

- hour PM 2.5 and PM 10 standards. With regard to the secondary annual PM 2.5 standard, the Administrator concludes that it is appropriate to retain a level of 15.0 μg/m 3***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 538 of 790 Formatted: Left for this standard while revising only the form of the secondary annual PM 2.5 standard to remove the option for spatial averaging consistent with this change to the primary annual PM 2.5 standard. In reaching this conclusion, the Administrator notes that no areas in the country are currently using the option for spatial averaging to demonstrate attainment with the secondary annual PM 2.5 standard. 2. Conclusions Regarding Secondary PM Standards for Visibility Protection Having reached the conclusion that it is generally appropriate to retain the existing secondary standards to protect against non

- visibility welfare effects, the Administrator next considered the target level of protection that would be requisite to protect public welfare with regard to visual air quality. The Administrator then determined whether to adopt a distinct secondary standard to achieve this target level of protection. In making this decision, the Administrator compared the degree of protection for visibility that would be provided by suc h a distinct secondary standard to the degree of protection provided by the existing secondary standards, focusing specifically on the secondary 24

- hour PM 2.5 standard of 35 μg/m 3

. 224 Based on the considerations discussed above in section VI.B and VI.C, the Administrator first concludes that a target level of protection for a secondary standard is most appropriately defined in terms of a PM 2.5 visibility index as proposed, since it would provide a measure of PM

- related light extinction that directly takes int o account the factors (i.e., species composition and relative humidity) that influence the relationship between PM 2.5 in the ambient air and PM

- related visibility impairment. Such a PM 2.5

224 This focus on the 24

- hour PM 2.5 standard reflects the Administrator’s judgments that PM

- related visibility impairment is principally related to fin e particle concentrations and that perception of visibility impairment is most directly related to short

- term levels of visual air quality.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 539 of 790 Formatted: Left visibility index standard would afford a relatively high degree of u niformity of visual air quality protection in areas across the country by virtue of directly incorporating the effects of differences in PM 2.5 composition and relative humidity across the country. In defining a target level of protection based on a PM 2.5 visibility index, the Administrator has considered specific aspects of such an index, including the appropriate indicator, averaging time, level, and form. First, with regard to indicator, the Administrator notes the conclusion of CASAC that relying on a c alculated PM 2.5 light extinction indicator based on PM 2.5 chemical speciation and relative humidity data represented a reasonable approach . Based on the analyses conducted in support of this rulemaking, as described above, as well as the advice of CASAC, t he Administrator concludes that a calculated PM 2.5 light extinction indicator that utilizes the original IMPROVE algorithm , adjusted to use a 1.6 OC multiplier and exclude the term for coarse particles, in conjunction with monthly average relative humidity data (i.e., f(RH) values) based on long

- term climatological means would be the most appropriate indicator for a PM 2.5 visibility index standard. With regard to averaging time, the Administrator notes that both CASAC and EPA staff have concluded that hour ly or sub

- daily (4

- to 6

- hour) averaging times, within daylight hours and excluding hours with high relative humidity, are more directly related than a 24

- hour averaging time to the short

- term nature of the perception of PM

- related visibility impairment an d the relevant exposure periods for segments of the viewing public. However, in light of the important data quality uncertainties that have recently been identified in association with currently available instruments that would be used to provide the hourl y PM 2.5 mass measurements that would be needed in conjunction with***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 540 of 790 Formatted: Left an averaging time shorter than 24 hours, the Administrator concludes it would not be appropriate at this time to set a standard based on a sub

- daily averaging time. Moreover, the Administra tor notes that analyses conducted by the EPA during this review clearly indicate that PM 2.5 light extinction calculated on a 24

- hour average basis would be a reasonable and appropriate surrogate for PM 2.5 light extinction calculated on a 4

- hour basis. Thus , the Administrator concludes that a 24

- hour averaging time would be appropriate for a PM 2.5 visibility index. The Administrator recognizes that a 24

- hour averaging time would effectively reduce the influence of peak hours of visibility impairment on visib ility index values, but concludes that in light of the concern that peak hourly measurements may be significantly influenced by atypical conditions and/or atypical instrument performance, it is appropriate to adopt a longer averaging time to ensure that ho ur - specific influences and uncertainties are balanced against more robust measurements. With regard to form, the Administrator notes that consistent with the approach taken in other NAAQS, including the current 24

- hour PM 2.5 NAAQS, a multi

- year percentile form offers greater stability to the air quality management process by reducing the possibility that statistically unusual indicator values will lead to transient violations of the standard. Utilizing a three

- year average form provides stability from the occasional effects of inter

- annual meteorological variability that can result in unusually high pollution levels for a particular year. Moreover, considering the lack of information on and the high degree of uncertainty regarding the impact on public welfa re of the number of days with visibility impairment over the course of a year, the Administrator considers it reasonable to focus on the 90 th percentile, which represents the median of the***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 541 of 790 Formatted: Left distribution of the 20 percent worst visibility days, a key focus o f the Regional Haze program. The Administrator concludes that ensuring that 90 percent of days have visual air quality that is at or below the target level of protection could be reasonably expected to lead to improvements in visual air quality on the 20 p ercent most impaired days, and that the limited information available in this review provides no basis for adopting a different form which would limit the occurrence of days with peak PM

- related light extinction in urban areas to a greater degree. Therefor e, the Administrator concludes that a 90 th percentile form, averaged over 3 years, is appropriate, for purposes of establishing a target level of protection in terms of a 24

- hour PM 2.5 visibility index. With regard to level, the Administrator concludes tha t in light of the uncertainty associated with the high degree of variability in visibility conditions and the potential variability in visibility preferences across different parts of the country, it is appropriate to establish a target level of protection based on the upper end of the range of Candidate Protection Levels (CPLs) identified in the Policy Assessment (i.e., 20

- 30 dv) and generally supported by CASAC. Thus, the Administrator concludes that it would be appropriate to set a target level of protec tion in terms of a PM 2.5 visibility index with a 24

- hour averaging time that would provide protection equivalent to the protection afforded by a 4

- hour PM 2.5 visibility index with a level of 30 dv. Furthermore, the Administrator notes that for purposes of estimating the approaches used to estimat e generally equivalent levels for a 24

- hour PM 2.5 visibility index , both of the EPA’s two preferred approaches generated 90 th percentile 24

- hour values similar to the 4

- hour values and a range of city

- specific estim ates of generally equivalent 24

- hour levels that encompassed the range of levels considered appropriate for 4

- hour CPLs, including the***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 542 of 790 Formatted: Left CPL of 30 dv at the upper end of that range. The Administrator thus concludes that it would be appropriate to use an unad justed 4

- hour CPL for purposes of establishing a target level of protection in terms of a 24

- hour PM 2.5 visibility index. In considering the alternative levels proposed for a 24

- hour standard, either 28 dv or 30 dv, the Administrator concludes that the cu rrent substantial degrees of variability and uncertainty inherent in the public preference studies should be reflected in a higher target protection level than would be appropriate if the underlying information were more consistent and certain. In addition , she concludes that, in light of the significant uncertainties, it is appropriate to place less weight on the results of western visibility preference studies and that the CPL value (30 dv) that is based on the eastern preference study results is likely t o be more representative of urban areas that do not have associated mountains or other valued objects visible in the distant background For all of these reasons, the Administrator concludes that it is appropriate to set a target level of protection in term s of a 24

- hour PM 2.5 visibility index at 30 dv. In summary, in light of all the information available in this review, the Administrator concludes that the protection provided by a standard defined in terms of a PM 2.5 visibility index (based on speciated P M 2.5 mass concentrations and relative humidity data to calculate PM 2.5 light extinction), a 24

- hour averaging time, and a 90 th percentile form, averaged over 3 years, set at a level of 30 dv, would be requisite to protect public welfare with regard to visu al air quality. In reaching this conclusion, the Administrator notes that any national ambient air quality standard for to address PM

- related visibility impairment would be designed to work in conjunction with the Regional Haze Program as a means of achiev ing***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 543 of 790 Formatted: Left appropriate levels of protection against PM

- related visibility impairment in all areas of the country, including urban, non

- urban, and Federal Class I areas. While the Regional Haze Program is focused on improving visibility in Federal Class I areas an d a secondary NAAQS to address PM

- related visibility NAAQS impairment would focus on protecting visual air quality principally in urban areas, both programs could be expected to provide benefits in surrounding areas. In addition, the development of local pr ograms, such as those in Denver and Phoenix, could continue to be an effective and appropriate approach to provide additional protection, beyond that afforded by a national standard, for unique scenic resources in and around certain urban areas that are pa rticularly highly valued by people living in those areas. Having concluded that the protection provided by a standard defined in terms of a PM 2.5 visibility index, with a 24

- hour averaging time, and a 90 th percentile form, averaged over 3 years, set at a l evel of 30 dv, would be requisite to protect public welfare with regard to visual air quality, the Administrator next has to determine whether to adopt such a visibility index as a distinct secondary standard. This determination requires considering such a secondary standard not in isolation but in the context of the full suite of secondary standards. As discussed above, the Administrator has determined to retain the current suite of secondary PM standards to address non

- visibility welfare effects (except f or the form of the annual standard). A distinct secondary standard to address visibility impairment is properly considered in a context where there is also a 24

- hour PM 2.5 standard of 35 μg/m 3

. In this context, the Administrator has considered the degree of protection from visibility impairment afforded by the existing secondary PM 2.5 standards. The***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 544 of 790 Formatted: Left Administrator has considered both whether the existing 24

- hour PM 2.5 standard of 35 μg/m 3 is sufficient (i.e. not under

- protective) and whether it is not more stringent than necessary (i.e. not over

- protective). As discussed above in section VI.C.1. f , the results of the Kelly et al. (2012 a; 2012b ) analys es indicate that based on 2008

- 2010 and 2009

- 2011 data, all areas meeting the 24

- hour PM 2.5 standard of 35 μg/m 3 had visual air quality at least as good as 30 dv (24

- hour average, based on 90 th percentile form averaged over 3 years). This means that it is highly likely that the secondary 24

- hou r PM 2.5 standard of 35 μg/m 3 would be controlling relative to a 24

- hour standard based on a PM 2.5 visibility index set at a level of 30 dv, and highly unlikely that areas would exceed the target level of protection for visibility of 30 dv without also exce eding the existing secondary 24

- hour standard. On the basis of this evidence, and the supporting public comments, the Administrator judges that the 24

- hour PM 2.5 standard of 35 μg/m 3 provides sufficient protection in all areas against the effects of visibi lity impairment

— i.e., that the existing 24

- hour PM 2.5 standard would provide at least the target level of protection for visual air quality of 30 dv which the Administrator judges appropriate. The Administrator also recognizes that the analyses presented i n Kelly et al. (2012a; 2012b) indicate that the 24

- hour PM 2.5 standard of 35 μg/m 3 also would likely achieve more than the target level of protection of visual air quality (30 dv) in some areas. That is, when meeting a mass

- based standard of 35 μg/m 3 , some areas would have levels of PM

- related visibility impairment below 30 dv. Thus, the 24

- hour PM 2.5 standard of 35 μg/m 3 would be over

- protective in some areas (i.e. more stringent than necessary) relative to the target level of protection for visibility. Th is is not surprising, as the current***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 545 of 790 Formatted: Left

mass - based standard does not account for variation in particle species and relative humidity. The 24

- hour PM 2.5 standard of 35 μg/m 3 would provide more than the necessary protection in the areas where this would be expe cted, for example western areas with lower relative humidity. In light of the Administrator’s conclusion that it is appropriate to retain the current secondary 24

- hour PM 2.5 standard of 35 μg/m 3 for non

- visibility welfare effects, the Administrator notes that this standard will remain in place regardless of whether she elects to set a distinct secondary standard in terms of a PM 2.5 visibility index. The issue is not whether to adopt a PM 2.5 visib ility index standard when viewed in isolation, but whether such a distinct secondary standard should be adopted in addition to the current secondary 24

- hour PM 2.5 standard of 35 μg/m 3 . The EPA notes that adoption of such a distinct secondary standard is no t needed to provide sufficient protection from visibility impairment with respect to the target level of protection determined above. In addition, adoption of such a distinct secondary standard would not change the fact that the current secondary 24

- hour P M 2.5 standard of 35 μg/m 3 would result in over

- protection from visibility impairment in certain areas of the country. Such over

- protection will occur whether or not such a distinct secondary standard is adopted. In effect, adopting such a distinct secondar y standard would have no impact on the degree of protection provided from visibility impairment. Since sufficient protection from visibility impairment would be provided for all areas of the country without adoption of a distinct secondary standard, and ad option of a distinct secondary standard will not change the degree of over

protection provided for some areas of the country, the Administrator judges that adoption of such a distinct secondary standard is not needed to provide requisite protection for***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 546 of 790 Formatted: Left bot h visibility and non

- visibility related welfare effects. It is important to note that this conclusion is based on the specific target level of protection determined above, and the specific set of current secondary standards. The Administrator’s conclusion with regard to the sufficiency of the protection provided by the current suite of secondary standards is based on comparing the a 30 dv target level of protection for a PM 2.5 visibility index standard against the degree of protection provided by the curre nt secondary 24

- hour PM 2.5 standard of 35 μg/m 3 . It is the combination of the specific target level of protection and the current suite of secondary standards that is the basis for the decision not to adopt a distinct secondary standard in terms of a PM 2.5 visibility index at this time. The EPA recognizes that, as in the last review, the final decision is to not adopt a distinct secondary standard to address visibility impairment. While the D.C. Circuit remanded the decision on a secondary standard in the last review, the EPA’s decision in this review fully comports with has addressed the issues raised in the court’s remand. Here the EPA has clearly identified the target degree of protection (defined in terms of a PM 2.5 visibility index at a level of 30 dv b ased on a 24

- hour averaging time, and a 90 th percentile form, averaged over 3 years) that would be requisite to protect public welfare with regard to visual air quality. The EPA has carefully compared this degree of protection with that provided by the cur rent secondary 24

- hour PM 2.5 secondary standard of 35 μg/m 3 , based on an area - specific analysis of recent air quality data and concluded that the degree of protection from visibility impairment provided by the current secondary standard is sufficient to pr otect public welfare consistent with section 109(b)(2). This provides a clear basis for judging that the current secondary 24

- hour***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 547 of 790 Formatted: Left
PM 2.5 secondary standard of 35 μg/m 3 would provide sufficient protection. The analysis also shows that the current 24

- hour se condary 24

- hour PM 2.5 standard would provide more protection than is needed in some areas, largely because it does not take into account variable factors such as relative humidity. However, the EPA has recognized that adoption of a distinct secondary stand ard to address visibility, in addition to retaining the current secondary standard, would not change this result. The EPA has therefore concluded that adoption of such a distinct secondary standard, in addition to the current suite of secondary PM standard s, is not needed to provide requisite protection for both visibility and non

- visibility related welfare effects. Thus the EPA’s decision has carefully considered and accounted for the views of the court in the remand of the 2006 NAAQS. E. Administrator’s Final Decisions on Secondary PM Standards To address PM

- related welfare effects, including ecological effects, effects on materials, climate impacts, and visibility impairment, the Administrator is retaining the current suite of secondary PM standards, exc ept for a change to the form of the annual standard. Specifically, the EPA is retaining the current secondary 24

- hour PM 2.5 and PM 10 standard to address PM

- related non

- visibility welfare effects including ecological effects, effects on materials, and clima te impacts , the EPA is retaining the current secondary 24

- hour PM 2.5 and PM 10 standard and is revising only the form of the secondary annual PM 2.5 standard to remove the option for spatial averaging consistent with this change to the primary annual PM 2.5 s tandard. With respect to PM

- related visibility impairment, the Administrator has identified a target degree of protection, defined in terms of a PM 2.5 visibility index (based on speciated PM 2.5 mass concentrations and relative humidity data to calculate PM 2.5 light extinction), a 24

- hour***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 548 of 790 Formatted: Left averaging time, and a 90 th percentile form, averaged over 3 years, and a level of 30 deciviews (dv), which she judges to be requisite to protect public welfare with regard to visual air quality. The EPA’s analysis of monito ring data provides the basis for concluding that the current secondary 24

- hour PM 2.5 standard would provide sufficient protection, and in some areas greater protection, relative to this target protection level. Adding a distinct secondary standard to addre ss PM

- related visibility impairment would not affect this protection. Since sufficient protection from visibility impairment will be provided for all areas of the country without adoption of a distinct secondary standard, and adoption of a distinct seconda ry standard will not change the degree of over

protection of visual air quality provided for some areas of the country by the secondary 24

- hour PM 2.5 standard, the Administrator judges that adoption of a distinct secondary standard, in addition to the curr ent suite of secondary standards, is not needed to provide requisite protection for both visibility and non

- visibility related welfare effects. VII. Interpretation of the NAAQS for PM This section discusses the EPA Administrator’s final decisions on the revisions proposed to the data handling procedures for the primary and secondary PM 2.5 standards. Appendix N to 40 CFR part 50 describes the computations necessary for determining when the PM 2.5 standards are met and also addresses which measurement data a re appropriate for comparison to the standards ; as well , it specifies associated data reporting protocols, data completeness criteria, and rounding conventions. The EPA is modifying appendix N to conform to the revised PM 2.5 standards; most notably, the EP A is simplifying the annual standard form and associated amending the appendix N procedures by removing the option for spatial averaging. Spatial averaging had been a component of the annual standard form since the original PM 2.5 NAAQS promulgation of 1997. In***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 549 of 790 Formatted: Left addition to making changes to appendix N that correspond to the change changes in the annual standard form and the revised primary annual standard level, the EPA is also finalizing additional proposed revisions to the appendix in order to codify existin g practices currently included in guidance documents or implemented as the EPA standard operating procedures ; better align appendix N language and requirements with changes in PM 2.5 ambient monitoring and reporting requirements ; provide greater clarity and transparency in the provisions; and enhance consistency with data handling protocols utilized for other pollutants. A. Revised Amendments to Appendix N: Interpretation of the NAAQS for PM 2.5 As discussed in sections III and VI above, the EPA Administrator h as decided to: (1) revise the form and level of the primary annual PM 2.5 standard, and retain the current primary 24

- hour PM 2.5 standard (section III.F) and (2) retain the current secondary 24

- - hour PM 2.5 standard, and revise the form and retain the level of the secondary annual PM 2.5 standard (for visibility and non

- visibility

- related welfare protection) (section VI.E). Appendix N is being revised to conform to those changes to the standards. In the prop osal, the EPA recommended to add additional data handling procedures to appendix N for the proposed distinct secondary standard to address PM 2.5 - related visibility impairment. However, as discussed in section VI. D.3 E , the Administrator has decided not to establish the proposed distinct secondary standard to address visibility impairment, and therefore, the associated proposed data handling procedures related to that proposed standard are not included in the final revised appendix N. In addition to the cha

nges to appendix N necessitated by the annual NAAQS form and level revisions (discussed in depth in sections III and VI above), t he EPA is also***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 550 of 790 Formatted: Left finalizing additional revisions to appendix N in order to: (1) better align appendix N language and requirements with proposed changes in the PM 2.5 ambient monitoring and reporting requirements as discussed in section VIII below; (2) enhance consistency with recently codified changes in data handling procedures for other criteria pollutants; (3) codify existing prac tices currently included in guidance documents or implemented as the EPA standard operating procedures; and (4) provide enhanced clarity and consistency in the articulation and application of appendix N provisions. Key elements of the finalized revisions t o appendix N are summarized in sections VI VII .A.1 through VI VII .A. 5 4 below , where the first four o f these preamble sections which correspond to the similarly numbered section sections in appendix N with the exception of section 5 . The proposed potential ne w fifth section of appendix N dealt with the proposed distinct PM 2.5 - related visibility secondary standard that was not finalized by the Administrator and thus the proposed appendix N section 5 was is not included in the final appendix N. Furthermore, prop osed changes to sections 1 through 4 of appendix N that also dealt with the proposed secondary visibility index standard (e.g., term definitions, rounding conventions, etc.)

were are also omitted from the final revised appendix. 1. General As proposed, the EPA is finalizing modifications to section 1.0 of appendix N to provide additional clarity regarding the scope and interpretation of the PM 2.5 NAAQS. This appendix section now references the finalized revisions of the primary annual PM 2.5 standard ( 40 CFR 50.18) and the retained secondary PM 2.5 NAAQS. With regard to the appendix N term definitions which are delineated in this initial section, the EPA has added, modified, and eliminated term definitions, as appropriate, in accordance with the***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 551 of 790 Formatted: Left proposed final data handling rule revisions such as the modification of terms that referenced spatial averaging. Additional term definitions were also added to reference otherwise unchanged appendix N content in an effort to streamline the appendix text, enhance clarity and thus improve readability and understanding. In particular, the definition of data substitution tests was shortened, and a definition for “test design value" (TDV) was added for completeness and for further clarity. This term was previously part of the data substitution definition and now it is more explicitly defined. The EPA notes that there were no substantive public comments received with regards regard to this section. 2. Monitoring Considerations ; Spatial Averaging. As proposed, t

he EPA has finalized revisions to section 2.0 of appendix N consistent with the concurrent modification of the form of the primary annual PM 2.5 standard that removes the option for spatial averaging. As described in more detail in section III.E.3.a above, the EPA dec ided to remove this option as part of the form of the primary annual PM 2.5 standard in light of analysis that indicates that the existing constraints on spatial averaging, as modified in 2006, may be inadequate to avoid substantially greater exposures in s ome areas, potentially resulting in disproportionate impacts on susceptible populations (Schmidt 2011 2011a , Analysis A). With respect to the form of the secondary annual PM 2.5 standard, as discussed in section V VI .E .5 above, the EPA has decided to retain the current secondary annual PM 2.5 standard to provide protection for welfare effects. However, as proposed, since In the proposal, the EPA believes believed it would be reasonable and appropriate to align the data handling procedures for the primary and s econdary annual PM 2.5 standards , the EPA***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 552 of 790 Formatted: Left has remove d and remove the option for spatial averaging for the secondary annual PM 2.5 standard to be consistent with the revised change in the form of the primary annual PM 2.5 standard
. (FR 77 39000, June 29, 2012 )
. The EPA notes note d that no areas in the country are currently using the option for spatial averag ing to demonstrate attainment with the secondary annual PM 2.5 standard. There were no comments on the proposed change and the EPA has therefore concluded it appropriate to remove the option for spatial averaging for the secondary annual PM 2.5 standard from Appendix N. Consistent with the revised form of the primary and secondary annual PM 2.5 standards, the levels of both standards will be compared to measurements from each appropriate (i.e., “eligible”) monitoring site in an area, as specified in 40 CFR 58.30, with no allowance for spatial averaging. Thus, for an area with multiple eligible m onitoring sites, the site with the highest design value would determine the attainment status for that area. As a result of the decision to eliminate the spatial averaging option for both the primary and secondary annual standards, the EPA omitted all ref erences to the spatial averaging option in the finalized version of appendix N. See section II III .E.3.a above for a discussion of EPA’s response to received public comment on the issue of removal of the spatial averaging option. 3. Requirements for Data Use and Reporting for Comparisons with the NAAQS for PM 2.5 In the proposal, the EPA suggested changes to section 3.0 of appendix N to correspond to the proposed new secondary standard to address PM

- related visibility impairment. Since the EPA is not final izing the proposed distinct secondary standard to address visibility impairment, none of these are proposed changes are necessary and are not being made. The EPA is , however , finalizing proposed changes to improve***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 553 of 790 Formatted: Left consistency with procedures used for other NAAQS as well as to improve consistency with current standard operating procedures. Specifically, the EPA proposed revisions to this section regarding: (1) clarification of monitoring data appropriate to compare to the PM 2.5 NAAQS; (2) clarification of pr ocedures for combining monitoring data from collocated instruments into a single “combined site” record; and (3) codification of the current standard operating procedure whereby the EPA uses data for which the certification deadline has passed but the moni toring agency has not requested certifi cation of the data to determine compliance with the PM 2.5 NAAQS provided the data are complete and accurate (thus making appendix N consistent with data handling appendices for other criteria pollutants). In the final revision to appendix N, the EPA is incorporating all the above noted proposed modifications to section 3 of appendix N. Additional details describ ing the incorporated modifications are provided below. With regards regard to clarification of which monitoring data are appropriate for comparison to the PM 2.5 NAAQS, the proposal acknowledged important data quality concerns associated with the PM 2.5 measu rements collected by continuous PM 2.5 FEMs and referenced a subsequent preamble proposal section that discussed the issue in more depth and put forward a solution to mitigate the data quality concerns. The revised monitoring rule, promulgated today in conj unction with the PM NAAQS revision, includes, as proposed, language allowing monitoring agencies to identify PM 2.5 FEMs that are not providing data of sufficient comparability to the FRM and, with EPA approval, to allow such data to be deemed ineligible fo r comparisons with the PM 2.5 NAAQS 225 ; see detailed discussion of this decision in section VIII.A.1 below. Rule

225 The EPA also allows use of alternative methods where explicitly stated in the monitoring methodology requirements (appendix C of 40 CFR part 58), such as PM 2.5 Formatted: Font: 10 pt

Formatted: Font: 10 pt***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 554 of 790 Formatted: Left language for the definition of “suitable monitors” in section 3 1.0 of the finalized revised appendix N accommodates and references the this monitoring rule revision codified in 40 CFR 58.1 1
. With respect to the procedures for combining monitored data from collocated instruments into a single “combined site” data record, the EPA had proposed to revise the current methodology in situation s whe re an FRM monitor operating on a non

- daily schedule is collocated with a continuous FEM monitor (that has acceptable comparability with an FRM)
. As noted in the proposal, the EPA was not advocating a change to the actual procedures for constructing a combi ned site record but rather a modification to the subsequent evaluation of whether the specific measurements were considered “creditable” or “extra” samples 226

. . 227 The language clarification proposed has already Approved Regional Methods (ARMs) which can be used to determine compliance with the NAAQS. Monitoring agencies identifying ARMs that are not providing data of sufficient quality will also be allowed to exclude these data in making comparisons to the PM 2.5 NAAQS. Currently, there are no designated ARMs for PM 2.5 . 226 Data for a combined site record originates by default from the designated “primary” monitor at the site location and is then augmented with data from collocated FRM or FEM monitors whenever valid data are not generated by the primary monitor. Samples in the combined site record are deemed “creditable” or “extra” according to the required sampling frequency for a specific monitoring site (i.e., “site

- le vel sampling frequency”) which, by default, is defined to be the same as the sampling frequency required of the primary monitor. Samples in the combined site data record that correspond to scheduled days according to the site

- level sampling frequency are d eemed “creditable” and, thus, are considered for determining whether or not a specific monitoring site meets data completeness requirements. These samples also determine which daily value in the ranked list of daily values for a year represents the annual 98 th percentile concentration. Samples that are not deemed “creditable” are classified as “extra” samples. These samples do not count towards data completeness requirements and do not affect which daily values represent the annual 98 th percentile concentra tion; “extra” samples, however, are candidates for selection as the 98 th percentile. 227 Data for a combined site record originates by default from the designated “primary” monitor at the site location and is then augmented with data from collocated FRM or FEM monitors whenever valid data are not generated by the primary monitor. Samples in t he combined site record are deemed “creditable” or “extra” according to the required sampling frequency for a specific monitoring site (i.e., “site

- level sampling frequency”)***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 555 of 790 Formatted: Left been implemented as is currently standard opera ting procedure in Agency design value computations so the language modification in appendix N merely codified proposed to modify actual practices 228

. . 229 The revised appendix N finalized in today’s action

which, by default, is defined to be the same as the sampling frequency required o f the primary monitor. Samples in the combined site data record that correspond to scheduled days according to the site

- level sampling frequency are deemed “creditable” and, thus, are considered for determining whether or not a specific monitoring site mee ts data completeness requirements. These samples also determine which daily value in the ranked list of daily values for a year represents the annual 98 th percentile concentration. Samples that are not deemed “creditable” are classified as “extra” samples. These samples do not count towards data completeness requirements and do not affect which daily values represent the annual 98 th percentile concentration; “extra” samples, however, are candidates for selection as the 98 th percentile. 228 Before the introduction of continuous FEMs, when two or more samplers were collocated at the same site, monitoring agencies typically identified the sampler that operated on the more frequent sampling schedule as the “primary” monitor for developing a sin gle site record. However, due to concerns regarding the comparability of FEMs to FRMs operated in some monitoring agency networks, and as briefly discussed above and in more detail in section VII.A.1 below, many monitoring agencies have kept the FRM as the “primary” monitor and delegated the continuous FEM (which samples more frequently, except in cases where the FRM operates on an “every day” schedule) to be the “supplemental” (non

- primary) collocated monitor. In such cases, FEM measurements reported on th e FRM “off” days were technically considered “extra.” In light of this practice, the EPA modified standing operating procedures whereby supplemental collocated FEM samples reported on the FRM “off” days would be considered “scheduled" and “creditable.” Thu s, collocated FEM samples would count towards data capture rates (actually, increasing both the numerator and the denominator in the capture rate equation), and also would count towards identifying annual 98 th percentile concentrations. Further, if data fr om a supplemental collocated FEM are missing on an FRM “off” day (and no unscheduled FRM data are reported that day), the EPA proposed not to identify these as “scheduled” days consistent with current practice, and thus, reported data generated from the su pplemental collocated continuous FEMs can only help increase data capture rates (77 FR 39001)
.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 556 of 790 Formatted: Left incorporates the modification as proposed. The EPA notes that there were no substantive public comments received regarding this change. 4. Comparisons with the PM 2.5 NAAQS Section 4.0 of appendix N specifies the procedures for comparing monitored data to the PM 2.5 standards. The EPA propose d revisions to section 4.0 of appendix N to: (1) provide consistency with the proposed primary and secondary annual PM 2.5 standards; (2) expand the data completeness assessments to be consistent with current guidance and standard operating procedures; and ( 3) simplify the procedure for calculating annual 98 th percentile concentrations when using an approved seasonal sampling schedule
. Consistent with the proposed decisions to revise the level of the primary annual PM 2.5 standard (section III. F E.4.b.iii ) and to retain the current level of the secondary annual PM 2.5 standard (section VI. E B.1.c.vi ), the EPA propose d to modify section 4.1(a) of appendix N to separately list the levels of the primary and secondary annual PM 2.5

229 Before the introduction of continuous FEMs, when two or more samplers were collocated at the same site, monitoring agencies typically identified the sampler th at operated on the more frequent sampling schedule as the “primary” monitor for developing a single site record. However, due to concerns regarding the comparability of FEMs to FRMs operated in some monitoring agency networks, and as briefly discussed abov e and in more detail in section VIII.B.3.b.iii below, many monitoring agencies have kept the FRM as the “primary” monitor and delegated the continuous FEM (which samples more frequently, except in cases where the FRM operates on an “every day” schedule) to be the “supplemental” (non

- primary) collocated monitor. In such cases, FEM measurements reported on the FRM “off” days were technically considered “extra.” In light of this practice, EPA modified standing operating procedures whereby supplemental collocat ed FEM samples reported on the FRM “off” days would be considered “scheduled" and “creditable.” Thus, collocated FEM samples would count towards data capture rates (actually, increasing both the numerator and the denominator in the capture rate equation), and also would count towards identifying annual 98 th percentile concentrations. Further, if data from a supplemental collocated FEM are missing on an FRM “off” day (and no unscheduled FRM data are reported that day), the EPA proposed not to identify these as “scheduled” days consistent with current practice, and thus, reported data generated from the supplemental collocated continuous FEMs can only help increase data capture rates (77 FR 39001, June 29, 2012)). Formatted: Space After: 10 pt, Line spacing: Multiple 1.15 li, Widow/Orphan control, Adjust space between Latin and Asian text, Adjust space between Asian text and numbers Formatted: Normal***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 557 of 790 Formatted: Left standards. The final revised appendi x N incorporates this proposed change; this appendix N section now references the revised primary annual standard level of 12.0 μg/m 3 and the retained secondary annual standard level of 15.0 μg/m 3 . However, as discussed above with respect to the final deci sions decision to not implement establish a distinct secondary standard to provide protection for visibility impairment, the final appendix N now explicitly references all PM 2.5 secondary standard protection (that is, protection from visibility impairment and non

- visibility

- related welfare effects) to be provided by the revised annual standard with retained level of 15.0 μg/m 3 and the retained 24

- hour standard with retained level of 35 μg/m 3 . C onsistent with the final decision s to remove the option for spa tial averaging for the primary annual PM 2.5 standard (section I I I.F ) ) , as well as for the secondary annual PM 2.5 standard (section VI I.A.2 ), the EPA amend ed section 4.4 of appendix N to remove equations and associated instructions relat ing to spatial avera ging. With regard to assessments of data completeness, the EPA proposal included the incorporation of two additional data substitution tests 230 (making a total of three data substitution tests) into appendix N for validating annual and 24

- hour PM 2.5 design values otherwise deemed incomplete (via the 75 percent and 11 creditable sample minimum quarterly data completeness requirements)
. The EPA proposed to add these tests in order to codify existing practices currently included in guidance documents ( U. S. US EPA, 1999) and implemented as the EPA standard operating procedures , and further, to make the data handling procedures for PM 2.5 more consistent with the procedures used for other NAAQS
. While the need for data substitution will lessen as more continu ous
230 Data substitution tests are supplemental data completeness assessments that use estimates of 24

- hour average concentrations to fill in for missing data (i.e., “data substitution”). Formatted: Font: 10 pt

Formatted: Font: 10 pt***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 558 of 790 Formatted: Left
PM 2.5 monitors continue to be deployed in PM 2.5 networks, the EPA believes that these substitution procedures are important to ensure that available data, if incomplete, can be confidently used to make comparisons to the NAAQS. As noted in the EPA proposal, d ata substitution tests are diagnostic in nature; that is; they are only used in an illustrative manner to show that the NAAQS status based on incomplete data is reasonable. I f an “incomplete” As codified in section 4 of Appen dix N, data are substituted for missing data to produce a “test design value using substituted data ” which is compared to the level of the NAAQS. I f the test design value passes the diagnostic test, th is th e “incomplete” design value (without the data subs titutions) is then considered the true actual “complete and a valid ” design value. I f an incomplete design value
. I f an “ incomplete ” design value does not pass any stipulated data substitution test, then the original design value is still considered incomplete (and not valid for NAAQS comparisons). Previously , section 4.1(c) of appendix N specifie d only one data substitution test for validating an otherwise incomplete design value. Th at diagnostic test o nly appli ed to the primary and secondary annual PM 2.5 standard and only applies in instances of a violation ; this test is referred to as the “ over NAAQS” minimum quarterly value ” test and is used to determine if the NAAQS has not been met
. The two proposed additional data substitution tests were to be

a pplicable for making comparisons to the primary and secondary annual and 24

- hour PM 2.5 standards , specifically to show that the NAAQS had been met . One of these proposed tests uses collocated PM 10 data to fill in “slightly incomplete” 231 data records, and th e other uses quarter

- specific maximum values to fill in slig htly incomplete data records; these two test are referred to as the “ under NAAQS collocated PM 10 test” and

231 Slightly incomplete is defined as less than 75 percent but at least 50 percent quarterly data capture. Formatted: Font: 10 pt

Formatted: Font: 10 pt***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 559 of 790 Formatted: Left the “ under NAAQS maximum quarterly value test”, respectively. Both tests are designed to confirm that the PM 2.5 design value is valid and is less than the level of the NAAQS. The EPA received several comments on the proposed addition of the two “under NAAQS” data substitution tests ; to determine that the NAAQS was met . The majority of comments generally supported the proposed addition of the data substitution tests. However, one commenter questioned the general philosophy of all appendix N data substitution tests (i.e., the existing “over NAAQS” one test and the two proposed “ under NAAQS” ones test s ) by suggesting that there were more appropriate techniques for filling in for missing data that would result in better estimates of true design value level. The EPA believes that the three data substitution tests provided in the fina lized appendix N are all very conservative approaches to verifying verify that the NAAQS standards are either met or not met , and that they the test design values are not (and were never intended ) to be used as the best estimators of the actual expected design value level. concentration
. 232 Another commenter questioned, and argued against, the use of collocated PM 10 data in PM 2.5 data substitution tests. The commenter stressed was that this type of test is not consistent with those established for other po llutants. The commenter further argued that while PM 10 and PM 2.5 are both measurements of particulate matter, they are essentially different pollutants with different sources and different dispersion characteristics, and further, that the ratio of PM 2.5 to PM 10 varies spatially and temporally. In general, the commenter claimed that the EPA had o ffer ed no explanation in the

232 Appendix N states that when the data substitution tests are satisfied, then the NAAQS design values derived from reported PM 2.5 data which otherwise would be considered to be incomplete shall be considered valid for compar isons to the PM 2.5 NAAQS.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 560 of 790 Formatted: Left proposal preamble of why the use of PM 10 data were valid for a PM 2.5 data substitution test. The EPA believes that PM 10 data are appropriate for a PM 2.5 data substitution test. Because PM 2.5 data are a subset of PM 10 data, a PM 2.5 24

- hour average concentration should always be less than or equal to a collocated PM 10 24

- hour average concentration
. Even though the ratio of P M 2.5 to PM 10 may vary both temporally and spatially, that ratio should never exceed one. Because of the unique situation where one criteria pollutant (i.e., PM 2.5 ) is a theoretical subset of another pollutant (i.e., PM 10 ), the EPA therefore believes it app ropriate to incorporate a unique data substitution test that uses collocated PM 10 data as a conservative upper bound estimate for the missing PM 2.5 data. Therefore, the EPA believes it appropriate to incorporate a data substitution test that uses collocate d PM 10 data as a conservative upper bound estimate for missing PM 2.5 data. The EPA further acknowledges that due to current inconsistencies in the reference and equivalent methods for the two related pollutants and also because of usual collocation siting characteristics, there may be occasional a situations whereby a 24

- hour average PM 2.5 concentration actually exceeds a collocated 24

- hour average PM 10 concentration. However, the EPA notes that this situation is infrequent; in the recent 3

- year timeframe of 2009

- 2011, this situation only occurred in eight percent of the collocated PM 2.5 and PM 10 data pairs In general, the commenter claimed that the EPA had offered no explanation of why PM 10 data were valid for a PM 2.5 data substitution test. At the time of proposal, the EPA believed that PM 10 data would be appropriate for a PM 2.5 data substitution test. After consideration of public comments and additional air quality analyses, the EPA has decided that a collocated PM 10 test is largely redunda nt with the maximum quarterly value test and thus not necessary to include it in Appendix N. The***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 561 of 790 Formatted: Left EPA has analyzed the most recent three years of PM 2.5 and PM 10 data (2009

- 2011) and assessed the separate benefit of the PM 10 substitution routine compared to the maximum quarterly value test ( Schmidt, 2012 b). In this assessment of 2009

- 2011 PM 2.5 design values which did not meet the nominal data completeness requirements, the EPA found that the collocated PM 10 test was almost entirely redundant with the maximum quarterly value test. It was also very infrequently needed as a separate test. For the annual NAAQS, the maximum quarter value test in 100 cases resulted in a test design value (TDV max ) less than or equ al to 12.0 μg /m 3 . There were only two additional cases (i.e. 2 percent) when TDV max was greater than 12.0 μg /m 3 but the TDV associated with the collocated PM 10 test was less than 12.0 μg /m 3 . Similarly for the 24

- hour NAAQS, the maximum quarter value test in 116 cases resulted in a test design value (TDV max ) less than or equal to 35 μg /m 3 and again only 2 additional sites (less than 2 percent) passed the collocated PM10 test but not the maximum quarterly value test. Furthermore, the maximum quarterly value tests allowed the annual and 24

- hour design value to be validated approximately 5 times more often than through the use of the collocated PM 10 test. Accordingly, the EPA has decided to not include the collocated PM 10 data substitution tests in Appendix N, and thereby further simplify the data handling procedures for making comparisons to the annual and daily NAAQS
. With regard to identifying annual 98 th percentile concentrations for comparison to the primary and secon dary 24

- hour PM 2.5 standards, the EPA suggested in the propos al to simplify the procedures used with an approved seasonal sampling schedule. Specifically, the EPA proposed to eliminate the use of a special formula for calculating annual 98 th percentile con centrations with a seasonal sampling schedule and thereby proposed to use Formatted: Font color: Black, Not Superscript/ Subscript***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 562 of 790 Formatted: Left only one method for calculating annual 98 th percentile concentrations for all sites ( 77 FR 39002 , June 29, 2012 ). The proposal explained that with an approved seasonal sampling sche dule, a site is typically samples as required to sample during periods of the year when the highest concentrations are expected to occur, but less frequently during periods of the year when lower concentrations are expected to occur ( 77 FR 39002 , June 29, 2012 ). This type of sampling schedule generally leads to an unbalanced data record; that is, a data record with proportionally more ambient measurements (with respect to the total number of days in the sampling period) in the “high” season and proportional ly fewer ambient measurements in the “low” season. In the last review, the EPA revised section 4.5 of appendix N to include a special formula for computing annual 98 th percentile values when a site operates on an approved seasonal sampling schedule. This s pecial formula accounted for an unbalanced data record and was consistent with guidance documentation ( U.S. US EPA, 1999), and, where appropriate, with official OAQPS design value calculations (71 FR 61211, October 17, 2006). In cases where there is a balan ced 233 (or near

- balanced) data record, the special formula yields the same result as the regular procedure for calculating annual 98 th percentile concentrations. To qualify for a seasonal sampling schedule, monitoring agencies are required to

c ollocate c o - loc ate a continuous PM 2.5 instrument with the seasonal sampling FRM. Since the last review, there has been considerable deployment of continuous PM 2.5 FEM monitors. In situations where a PM 2.5 FRM monitor operating on a non

- daily periodic schedule (such as a 1

- day

- in

- 3 or a 1

- day

- in

- 6 schedule) is collocated with a continuous

233 A balanced data record has the same proportion of ambient measurements (with respect to the total number of days in the sampling period) in the “high” season as in the “low” season. Formatted: Font: 10 pt

Formatted: Font: 10 pt***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 563 of 790 Formatted: Left
PM 2.5 FEM monitor, data are combined based on procedures stated in section 3.0 of appendix N as modified , as discussed i n section VI VII .A.3 above. The end result of combining C ombining collocated FRM and FEM data is effectively an every - day results in a site

- based sampling frequency, hence resulting which samples everyday and results in a balanced data record. In such a cas e, if a site used a seasonal sampling schedule regime for the FRM monitor, these data would be balanced by the every

- day FEM data and there would be no need for the special formula for calculating annual 98 th percentile concentrations on the combined site data. In As EPA noted in the proposal, t he EPA note d that there were at that time are very few PM 2.5 FRM monitors that actually operated on an approved seasonal sampling schedule (only 15 sites out of approximately 1,000 total sites in 2010) and that for al most half of those sites ha d a , the collocated continuous instrument was a PM 2.5 FEM monitor ( 77 FR 39002 , June 29, 2012 ). The proposal stated that for the 3

- year period 2008 to 2010, the annual 98 th percentile concentrations calculated with the special formula at those 15 sites were approximately five percent lower than if the regular procedure was used
. The EPA also noted in the proposal that, in the last review, the Agency modified the monitoring r equirements for areas with an FRM operating on a non

- daily schedule such that, if

when the design values were within five percent of the 24

- hour PM 2.5 NAAQS, those areas would be required to increase the frequency of sampling to every day (40 CFR 58.12(d)(1 ); 71 FR 61165, October 17, 2006; 71 FR 61249, October 17, 2006). The In consideration of these facts, t he EPA proposed to simplify the data handling procedures for sites operating on a seasonal sampling schedule by eliminating the special formula and all references to it for the following reasons: (1) the small***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 564 of 790 Formatted: Left difference between 98 th percentile concentrations calculated using the special formula versus the regular procedure and the small number of sites currently using the special formula; (2) the EPA req uires every day sampling in areas with design values that are within five percent of the 24

- hour PM 2.5 NAAQS; and (3) FRMs operating on an approved seasonal sampling schedule are required to be collocated with a continuous PM 2.5 instrument (and if that ins trument were an FEM, the resulting combined site record would tend to be balanced over the year and thus the special formula would be superfluous
. ) ( 77 FR 39002 , June 29, 2012 ). Thus, the EPA proposal included only one method for calculating annual 98 th percentile concentrations, the “regular” table look

- up method specified in section 4.5(a)(1) of appendix N. In light of the rationale provided above and because there were EPA received no significant negative comments received against regarding the EPA p ro posal, the EPA has eliminated concludes it is appropriate to eliminate the special seasonal sampling 98 th percentile identification procedure from appendix N. The final revised appendix N specifies only one method for identifying annual 98 th percentile con centrations; the table look

- up method is now the only permitted technique for identifying annual 98 th percentile concentrations. B. Exceptional Events The EPA is finalizing primary annual PM 2.5 - specific deadlines in 40 CFR 50.14 by which air agencies 234 must flag ambient air quality data that they believe have been affected by exceptional events and submit initial descriptions of those events. The EPA is also finalizing the deadlines by which air agencies must submit detailed exceptional

234 References to “air agencies” are meant to i nclude state, local, and tribal air agencies responsible for implementing the Exceptional Events Rule. Formatted: Normal

Formatted: Font: 10 pt***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 565 of 790 Formatted: Left events documenta tion to support the exclusion of those data from the EPA’s monitoring

based determinations of attainment or nonattainment with the revised primary annual PM 2.5 NAAQS. The final exceptional events

- related schedule is aligned with the designations schedule, discussed in greater detail in section IX, and is promulgated as proposed and as supported by multiple commenters. W ithout revision s to 40 CFR 50.14,

a n air agency may not be able to flag and submit documentation for some relevant data either because the g eneric deadlines may have already passed by the time the new or revised NAAQS is promulgated or because the generic deadlines require documentation submission at least 12 months prior to the date that the EPA must make a regulatory decision. The EPA ackno wledges the concern raised by a few commenters that numerous wildfires occurred between 2010 and 2012 that air agencies may determine influenced ambien t air quality concentrations potentially affecting compliance with the revised primary annual PM 2.5 NAAQS , and that air agencies may want to submit detailed exceptional events documentation associated with these multiple wildfires. Commenters further noted that 1 year to provide documentation of these potential exceptional events may not be sufficient. The EPA believes that the promulgated schedules provide sufficient time for air agencies to submit information related to the annual standard and for the EPA to fully consider and act on the submitted information during the initial area designation process. Recently The EPA recently released draft exceptional events guidance that clarifies key provisions of the 2007 Exceptional Events Rule, provides examples of best practices, and streamlines the documentation development process , will help air agencies submit information in a timely manner. . The guidance provides***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 566 of 790 Formatted: Left approaches that are broadly applicable to all event/pollutant combinations and would apply to many PM events, including wildfire/PM combinations. Additionally, the EPA has posted several concurred upo n wildfire/PM exceptional event demonstration packages on its website at: http://www.epa.gov/ttn/analysis/exevents.htm . Considered together, the EPA believes this guidance will help air agencies su bmit information in a timely manner. 235 The EPA notes that under the promulgated schedule, except for events that occur in December 2012, air agencies will have more than 1 year to provide documentation for these potential events. The EPA intends to work wit h potentially affected areas to identify, screen, and prioritize events potentially influencing compliance with the primary annual PM 2.5 NAAQS and associated area designations
. Also in response to comments, the EPA is clarif ying that this preamble languag e and the associated promulgated exceptional events schedules apply only to the NAAQS that the EPA is newly promulgating or revising in this action, that is, the revised primary annual PM 2.5 NAAQS. The promulgated exceptional event schedule revisions do no t apply to the retained PM standards (i.e., secondary PM standards, primary 24

- hour PM 10 , primary 24

- hour PM 2.5 ). Further, the revised/extended exceptional event schedules apply only to those data the EPA will use to establish initial area designations for the revised primary annual PM 2.5 NAAQS. The “Treatment of Data Influenced by Exceptional Events; Final Rule” (72 FR 13560, March 22, 2007), known as the Exceptional Events Rule and codified at 40 CFR 50.14, contains generic deadlines for an air agency to submit to the EPA specified information about exceptional events and associated air pollutant concentration data. As

235 The EPA released draft exceptional events guidance documents (U.S. EPA, 2012e) for public comment via a Notice of Availability in the Federal Register on July 6, 2012 (77 FR 39959).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 567 of 790 Formatted: Left discussed in the proposal, w ithout revision s to 40 CFR 50.14, a n air agency may not be able to flag and submit documentation for some rele vant data because the generic deadlines may have already passed by the time the new or revised NAAQS is promulgated. Similarly, revisions to 40 CFR 50.14 are needed because air agencies may not be able to flag and submit documentation for events that occur red in December of 2013 by 1 year before the designations are made in 2014 as is required by the existing generic schedule requires. To support appropriate consideration of exceptional event data influencing ambient air quality concentrations potentially affecting compliance with the revised primary annual PM 2.5 NAAQS, the EPA is adopting revisions to 40 CFR 50.14 to change the submission dates for claimed exceptional events information affecting PM 2.5 data considered during the initial area designations p rocess under the promulgated revised primary annual PM 2.5 NAAQS
. As proposed, f or air quality data collected in 2010 or 2011, the EPA is extending to J uly 1, 201 3 the otherwise applicable generic deadlines of July 1, 2011 and July 1, 2012 , respectively, for flagging data and providing an initial description of an event ( 40 CFR 50.14(c)(2)(iii))
. The EPA is retaining the existing generic deadline in the Exceptional Events Rule of July 1, 2013 for flagging data and providing an initial description of events occurring in 2012. Similarly, the EPA is revising to December 12, 2013, the deadline for submitting documentation to justify exceptional events occurring in 2010 through 2012 and potentially influencing compliance with the revised primary annual PM 2.5 NAA QS
. The EPA believes these revisions/ extensions will provide adequate time for air agencies to review potential PM 2.5 exceptional events influencing compliance with the revised primary annual PM 2.5***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 568 of 790 Formatted: Left NAAQS from 2010 to 2012 , to notify the EPA by flagging the relevant data and providing an initial description in AQS, and to submit documentation to support claims for exceptional events. These schedule revisions will also allow the EPA to fully consider and act on the submitted information during the initial are a designation process. If a n air agency intends the EPA to consider in the revised primary annual PM 2.5 designations decisions whether PM 2.5 data collected during 2013 influenc e compliance with the primary annual PM 2.5 NAAQS , then the air agency must flag these data by the generic Exceptional Event Rule deadline of July 1, 2014
. The EPA is finalizing August 1, 2014, as th e deadline for submitting documentation to justify PM 2.5 - related exceptional events occurring in 201 3 and potentially influencing complia nce with the revised primary annual PM 2.5 NAAQS. The EPA believes that th ese deadline s provide air agencies with adequate time to review and identify potential exceptional events that occur in calendar year 2013 and for the EPA to fully consider and act on the submitted information during the initial area designation process. While the EPA will make every effort to designate areas for the primary annual PM 2.5 NAAQS on a 2 year schedule, the EPA recognizes that it may need up to an additional year for the designations process to ensure that states/tribes and the EPA base designations decisions on complete and sufficient information. If the EPA announces at a la ter date that it is extending the designations schedule beyond 2 years based on unavailability of data, the EPA will consider extending the 2013 exceptional event documentation submission schedule by promulgating additional revisions to 40 CFR 50.14.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 569 of 790 Formatted: Left Ther efore, using the authority provided in CAA section 319(b)(2) and in the Exceptional Events Rule at 40 CFR 50.14 (c)(2)(vi), the EPA is finalizing the schedule for data flagging and submission of demonstrations for PM 2.5 exceptional events data potentially influencing compliance with the revised primary annual PM 2.5 NAAQS considered for initial area designations under the promulgated primary annual PM 2.5 NAAQS as presented in Table 3.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 570 of 790 Formatted: Left Table 3. Revised Schedule for Exceptional Event Flagging and Documentat ion Submission for Data to be Used in Initial Area Designations for the 2012 PM 2.5 NAAQS NAAQS Pollutant/ Standard/(Level)/ Promulgation Date Air Quality

Data Collected for Calendar Year Event Flagging &

Initial Description Deadline Detailed

Documentation Submission Deadline PM 2.5 / Primary Annual Standard (12.0 μg/m 3 ) Promulgated December 14, 2012 2010 and 2011 July 1, 2013 December 12, 2013 2012 July 1, 2013 a December 12, 2013 2013 July 1, 2014 a August 1, 2014

a Thi s date is the same as the general schedule in 40 CFR 50.14. Note: The table of revised deadlines only applies to data the EPA will use to establish the initial area designations for the revised primary annual PM 2.5 NAAQS. The general schedule applies for all other purposes, most notably, for data used by the EPA for redesignations to attainment. C. Updates for Data Handling Procedures for Reporting the Air Quality Index There were no comments regarding the proposed u pdates for data handling procedures for reporting the AQI. However, two table footnotes that were part of the existing rule were inadvertently omitted from the proposal. The inadvertently dropped footnotes were footnotes 3 and 4 of Table 2 (“Breakpoints fo r the AQI”) of appendix G (“Uniform Air Quality Index (AQI) and Daily Reporting”) to Part 58. Since the footnotes are still applicable, the EPA has included them in the final rule. The final rule also codifies all changes identified in the EPA proposal reg arding data handling procedures for the AQI.
VIII. Amendments to Ambient Monitoring and Reporting Requirements The EPA is finalizing a number of changes to the ambient air monitoring, reporting, and network design requirements associated with the PM NAAQS
. Ambi ent Formatted: Space After: 12 pt***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 571 of 790 Formatted: Left PM monitoring data are used to meet a variety of monitoring objectives including determining whether an area is in violation of the PM NAAQS
. Ambient PM monitoring data are collected by state, local, and tribal monitoring agencies (“monitoring agencies ”) in accordance with the monitoring requirements contained in 40 CFR parts 50, 53, and 58
. This section discusses the monitoring changes that the EPA is finalizing to support the revised PM NAAQS summarized in sections II I .F, I V .F, and V I .F above
. The monitoring changes being finalized primarily relate to the revised primary PM 2.5 NAAQS. Several monitoring changes were proposed specifically in support of a potential distinct secondary PM 2.5 visibility index standard ; however, as explained in Section VI, EPA is not finalizing a distinct secondary NAAQS standard using a visibility index and therefore is not finalizing the monitoring changes that would have been necessary to support it. The EPA did not propose any monito ring changes associated with the PM 10 NAAQS and accordingly none are finalized is not adopting any in this final rule. A. Issues Related to 40 CFR Part 53 (Reference and Equivalent Methods) To be used in a determination of compliance with the PM NAAQS, PM data are typically collected using samplers or monitors employing an FRM or FEM
. The EPA also allows use of alternative methods where explicitly stated in the monitoring methodology requirements (appendix C of 40 CFR part 58), such as PM 2.5 ARMs which can be u sed to determine compliance with the NAAQS
. The EPA prescribes testing and approval criteria for FRM and FEM methods in 40 CFR part 53. 1. PM 2.5 and PM 10

- 2.5 Federal Equivalent Methods As described in the proposal, t he EPA continues to believe that an effec tive PM 2.5 monitoring strategy includes the use of both filter

- based FRM samplers and well

performing continuous PM 2.5 monitors
. Well

- performing continuous PM 2.5 monitors Formatted: Indent: First line: 0.5"***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 572 of 790 Formatted: Left would include both non

- designated continuous PM 2.5 monitors and designated Class III 236 continuous FEMs that meet the performance criteria described in table C

- 4 of 40 CFR part 53 when comparing to a collocated FRM operated by the monitoring agency . Only designated methods (i.e., FRMs, FEMs, and ARMs) are approved to be used in comparison to the NAAQS; however, non

- designated methods may be useful to meet other monitoring objectives (e.g., reporting the AQI). The use of Class III continuous FEMs at SLAMS is described in more detail in section VII I
. B. 3.b.ii below
. Monitoring agencies are encou raged to evaluate the quality of data being generated by FEMs and, where appropriate, to reduce the use of manual, filter

- based samplers to improve operational efficiency and to lower overall operating costs
. To encourage such a strategy, the EPA is workin g with numerous stakeholders including the monitoring committee of NACAA, instrument manufacturers, and monitoring agencies to support national data analyses of continuous PM 2.5 FEM performance, and where such performance does not meet data quality objecti ves, to develop and institute a program of best practices to improve the quality and consistency of resulting data. The EPA believes that progress is being made to implement well performing PM 2.5 continuous FEMs across the nation
. As noted in the proposal , the first few steps involved the EPA developing and approving the testing and performance criteria which were finalized in 2006, followed by instrument companies performing field testing and submitting applications to the EPA, and the EPA review and appro val, as appropriate, of Class III FEMs
. In the current step, monitoring agencies are testing and assessing the data

236 Class III refers to those methods for PM 2.5 or PM 10

- 2.5 that are employed to provide PM 2.5 or PM 10

- 2.5 ambient air measurements representative of one

- hour or less integrated PM 2.5 or PM 10

- 2.5 concentrations, as well as 24

- hour measurements determined as, or equivalent to, the mean of 24 one

- hour consecutive measurements.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 573 of 790 Formatted: Left comparability from continuous PM 2.5 FEMs
. While EPA did not propos e any changes to the performance or testing criteria in 40 CFR part 53 us ed to approve PM 2.5 continuous FEMs, the EPA did propose an administrative change to p art 53.9

– “Conditions of designations.” See 77 FR 39006. This section describes a number of conditions that must be met by a manufacturer as a condition of maintaining designation of an FRM or FEM
. Subsection (c) of this section reads , “ Any analyzer, PM 10 sampler, PM 2.5 sampler, or PM 10

- 2.5 sampler offered for sale as part of a FRM or FEM shall function within the limits of the performance specifications referred to in 40 CFR 53.20(a), 53.30(a), 53.50, or 53.60, as applicable, for at least 1 year after delivery and acceptance when maintained and operated in accordance with the manual referred to in 40 CFR 53.4(b)(3).” The EPA’s intent in this requirement is to ensure that monitoring methods work within performance criteria, which includes methods for PM 2.5 and PM 10

- 2.5 ; however, there wa s no s pecific reference to performance criteria for Class II 237 and III PM 2.5 and PM 10

- 2.5 methods
. T he EPA propose d to link the performance criteria referred to in 40 CFR part 53.35 associated with Class II and III PM 2.5 and PM 10

- 2.5 methods with this requirement for maintaining designation of approved FEMs
. The specific performance criteria identified in 40 CFR 53.35 for PM 2.5 and PM 10

- 2.5 methods are available in table C

- 4 to subpart C of 40 CFR part 53
. All comments received on this proposed change were support ive and EPA is finalizing this change. The implication of this change is that instrument manufacturers and air agencies operating the equipment will have a shared responsibility for approved
237 Class II refers to those methods for PM 2.5 or PM 10

- 2.5 in which integrated samples are taken by filtration and subjected to a subsequent filter condition ing process followed by a gravimetric mass determination, but which is not a Class I equivalent methods because of substantial deviations from the design specification of the sampler specified for reference methods in appendix L or O (as applicable) of par t 50 of the CFR.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 574 of 790 Formatted: Left FEMs to meet required performance criteria for at least the firs t 12 months of operation, which is the typical warranty period for an instrument. By having a shared responsibility for an FEM to meet the performance criteria , instrument companies and air agencies will both be motivated to ensure the best practices for installing, operating, and servicing an instrument are carried out according to the instrument company’s operating manual and other readily available materials 238 in support of each method. 2. Use of C hemical S peciation N etwork (CSN) Methods to Support the Proposed New Secondary PM 2.5 Visibility I ndex NAAQS The EPA had proposed to use CSN methods to support the proposed new secondary PM 2.5 visibility index NAAQS; howe ver, as explained in Section VI of this final rule, EPA is not finalizing the new secondary PM 2.5 visibility index NAAQS and therefore has no need to finalize the CSN methods to support such a standard. Despite our decision not to finalize formal requireme nts for CSN methods, this network remains a critical component in our PM monitoring program. The EPA, monitoring agencies, and external scientists and policy makers use PM 2.5 data from the CSN to support several important monitoring objectives such as: dev elopment of modeling tools and the application of source apportionment modeling for control strategy development to implement the NAAQS; health effects and exposure research studies; assessment of the effectiveness of emission reductions strategies through the characterization of air quality; and development of SIPs . The use of the CSN to support all of these objectives will continue. B. Changes to 40 CFR Part 58 (Ambient Air Quality Surveillance)
238 At the recent National Air Quality Conference in May of 2012, a training session on “Best Practices for Operating PM 2.5 Continuous FEMs” was conducted. Presentations from this session are publically available on EPA’s web site at: http://www.epa.gov/ttn/amtic/2012present.html
.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 575 of 790 Formatted: Left 1. Terminology Changes The EPA propose d to revise several terms as sociated with PM 2.5 monitor placement to ensure consistency with other NAAQS and to conform with long

- standing practices in siting of equipment by monitoring agencies
. (77 FR 39007). The EPA propose d to revoke the term “community

- oriented” and replace it with the term “area

- wide.” The term “community

- oriented,” while used within the description of the design criteria for PM 2.5 , is not defined and has not been used in the design criteria for other NAAQ S pollutants
. Appendix D to 40 CFR part 58 presents a functional usage of the term where sites at the neighborhood and urban scale area are considered to be “community

- oriented.” In addition, population

- oriented , micro

- or middle

- scale PM 2.5 monitoring may also be considered “community

- oriented” when determined by the Regional Administrator to represent many such locations throughout a metropolitan area
. The EPA propose d to replace this usage of “community

- oriented” with the term “area

wide” in the text of t

he PM 2.5 network design criteria and to define it in 40 CFR 58.1 to provide a more consistent usage of this concept throughout appendix D of 40 CFR part 58
. The Specifically, t

he EPA propose d that the terminology would read

– “Area

- wide means all monitors sited at neighborhood, urban, and regional scales, as well as those monitors sited at either micro

- or middle

- scale that are representative of many such locations in the same CBSA.” The EPA propose d to revoke the term “Community Monitoring Zone” (CMZ) and t o remove references to it in 40 CFR part 58
. Community monitoring zone is currently defined as “an optional averaging area with established, well defined boundaries, such as***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 576 of 790 Formatted: Left county or census block, within an MPA 239 that has relatively uniform concentrations of annual PM 2.5 as defined by appendix N of 40 CFR part 50 of this chapter
. Two or more community oriented state and local air monitoring stations (SLAMS) monitors within a CMZ that meet certain requirements as set forth in appendix N of 40 CFR part 50 may be averaged for making comparisons to the annual PM 2.5 NAAQS.” The EPA propose d to revoke this term and references to it since, as discussed in section VI I
. A .2 above, the EPA propos ed to eliminate all references to the now - revoked spatial averaging option throughout appendix N. Comments received on these terminology The one comment directly addressing the proposed rule changes were supportive ( from the one a state air agency that commented on it. ) supported the proposal. A few industry commenters noted the change in the context of how monitoring data are used to compare to the NAAQS, but did not provide either supportive or negative comments on these two address the proposed specific terminology changes. However, as explai ned in section III.E.3.a, several industry commenters did provide comments critical of EPA’s proposal to revoke spatial averaging which is related to revoking the term “Community Monitoring Zone”

. For the reasons explained above, the EPA is finalizing its proposed change to revoke the term “community

- oriented” and to replace it with the term “area

- wide.” The EPA is also finalizing its proposal to revoke the term “Community Monitoring Zone” (CMZ) and references to it in 40 CFR part 58.
2. Special Consideratio ns for Comparability of PM 2.5 Ambient Air Monitoring Data to the NAAQS
239 Monitoring Planning Area (MPA) means a contiguous geographic area with well established, well defined boundaries, such as a CBSA, county or State, having a common areas that is used for planning monitoring locations for PM 2.5 .***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 577 of 790 Formatted: Left In general, a mbient monitors must meet a basic set of requirements before the resulting data can be used for comparison to the NAAQS . T hese requirements include the presence and implem entation of an approved quality assurance project plan ; the use of methods that are reference, equivalent, or other approved method as described in appendix C to 40 CFR part 58 ; and compliance with the probe and siting path criteria as described in appendi x E to 40 CFR part 58
. While these 40 CFR part 58 requirements apply to a ny monitor that provides data for comparison to the NAAQS, only in the PM 2.5 monitoring requirements there are certain additional restrictions prescribed within the that apply only to P M 2.5 monitoring rules
. 240 These additional restrictions provide that sites must be “population

- oriented” for comparison to either the 24

- hour or annual NAAQS, and specifically for comparison to the annual NAAQS, sites must additionally be sited to represent area - wide locations
. There is a related provision that provides for comparing sites at micro

- or middle

- scales to the annual PM 2.5 NAAQS when the site is determined by the Regional Administrator to represent a larger region of localized high ambient PM 2.5 concentration
. The inclusion of these The se provisions have been in the PM 2.5 monitoring requirements regulations since the 1997 promulgation inception of the PM 2.5 NAAQS
. Nonetheless, these provisions and associated the fact that such monitoring requirements has resulted are not found in confusion when the requirements for all other criteria pollutants have created areas of uncertainty for the EPA and state, local, and tribal agencies consider the design of PM 2.5 that base implementation d ecisions on monitoring networks requirements through programs such as well as how unmonitored locations

240 These are referenced found in 40 CFR 58.30 (Special considerations for data comparisons to the NAAQS)
. Formatted: Subscript***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 578 of 790 Formatted: Left should be treated in dispersion modeling exercises such as PSD , SIP planning, and the calculation of transportation conformity budgets. For example, in developing modeling guidance to support near

- road transportation conformity modeling, the EPA struggled to determine how the identification of acceptable PM 2.5 receptor locations can be reconciled with the PM 2.5 monitoring regulations that reference potent ially acceptable (or unacceptable) monitoring locations that may, or may not, be considered unique for purposes of comparing to the annual PM 2.5 NAAQS . Accordingly, the EPA propose d to revise these particular PM 2.5 requirements for consistency with long

- standing practices in all other NAAQS pollutant monitoring networks, and to ensure that interpretation of the monitoring rules does not cause ambiguity in considering implementation examples that also include the trea tment of unmonitored areas
. (see 77 FR 39007

- 009). Each of these topics is described below.

a. Revoking Use of Population

- Oriented as a Condition for Comparability of PM 2.5 Monitoring Sites to the NAAQS

a. Eliminating the term “population oriented” from section 58.30 The EPA proposed to revoke the remove the term “populati on oriented” from section 58.30 so that there would no longer be an explicit requirement that PM 2.5 monitoring sites be “population

- oriented” for comparison to the PM 2.5 NAAQS. The EPA concluded noted that this requirement is inconsistent not entirely consistent with the definition of “ambient” used in the NAAQS. The EPA’s definition of ambient air is specified in 40 CFR 50.1

– “ Ambient air means that portion of the atmosphere, external to building s, to which the general public has access.” The EPA’s definition of “population

- oriented” is provided in 40 CFR 58.1

- “ Population

- oriented monitoring (or***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 579 of 790 Formatted: Left sites) means residential areas, commercial areas, recreational areas, industrial areas where workers from more than one company are located, and other areas where a substantial number of people may spend a significant fraction of their day.” The EPA’s intention in proposing to revok e the requirement that PM 2.5 monitoring sites be “population

- oriented” for comparison to the The NAAQS wa s to ensure that the monitoring rules do not have a different definition than the definition of are standards for concentrations “in the ambient air in 40 CFR 50.1 itself . We note that revok ing this term in no way changes the requirements in the PM 2.5 network design criteria, ” 241

— i.e., air to which will continue to focus on sites representing “area

- wide” locations; thus continuing to represent locations members of the public could be exposed

— and all monitors used for NAAQS regulatory purposes must be representative of ambient air concentrations. 242 Consistent with this requirement and the long

- standing pra ctice of monitoring agencies locating ambient monitors, the EPA’s experience is that PM 2.5 mo nitors are placed in areas that are representative of population exposures. There are no PM 2.5 monitors currently operating as “non

- population exposure . While the use of the term “population

- oriented” has little effect on how data from existing sites are t reated (as explained below there are no remaining sites designated as not being “population

- oriented”), the inclusion of this oriented” and the EPA does not believe that the requirement in the monitoring rules for

near - road monitoring (discussed in detail further below) will result in monitors that are not representative of population exposures. At the same time, the specification that certain PM 2.5 monitors must be “population

- oriented” in the rules has created substantial confusion in how to treat potent ial locations of exposure for NAAQS

- related regulatory
241 See 40 CFR part 50. 242 See, e.g., 40 CFR 58.1 (defining “federal reference method” as “a method for sampling and analyzing the ambient air for an air pollutant...”)***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 580 of 790 Formatted: Left requirements other than monitoring network design, such as in applying modeling

across as part of a PSD or SIP exercise
. 243 The EPA’s intention in proposing to remove the term “population oriented” from section 58.30 wa s to remove a potential source of inconsistency in the monitoring rules as they apply for all the NAAQS. As noted earlier, the NAAQS provide protection for the public health and welfare in areas where the public can be exposed. For all ot her criteria pollutants, the monitoring requirements have no such restriction on the comparability of a monitor. In the case of PM 2.5 however, the additional restriction of monitors being required to be “population

- oriented” for comparability to the NAAQS has existed. The term “population oriented” has lacked a quantitative definition (e.g., the interpretation of “substantial number” in the definition of “population

- oriented”), therefore monitoring agencies and those stakeholders who based implementation strategies and decisions on monitoring regulations have been uncertain about which locations would meet requirements described in §58.30, which do not exist for any other NAAQS. Monitoring agencies are also not in a position to precisely forecast where fu ture residential, commercial, or recreational development may occur, therefore requiring that PM 2.5 monitors that are to be compared to the NAAQS can only be located where “substantial numbers of people” live, work, or play (i.e., in the present tense) rep resents an
area . unwise limitation on the flexibility of monitoring agencies to revise their PM 2.5 networks to account for anticipated changes in demographics or development as well as a contradiction with the inherent applicability of the NAAQS in ambient air locations where the public has access (e.g., in any location outside the perimeter of a industrial

243 Examples incl ude dispersion modeling to support NAAQS attainment planning, associated SIP development, and the calculation of transportation conformity budgets.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 581 of 790 Formatted: Left facility). From an operational standpoint, we note that revok ing this term would not change the requirements in the PM 2.5 network design criteria
. To t he extent that the phrase “population

- oriented” served to emphasize the need for micro

- or middle

- scale monitors to be representative of locations with population exposure to be comparable to the annual NAAQS, the definition of ambient air, together with the requirement in revised section 58.30 that such sites must be “area

- wide” to be comparable to th e annual NAAQS, adequately serves the same purpose. By rev ising the PM 2.5 monitoring rules to ensure consistency with the long

- standing definition of ambient air applied to the other NAAQS pollutants , the EPA will be able to more clearly define how to trea t potential exposure receptors for other NAAQS regulatory requirements , regardless of whether monitoring exists or not
. In reviewing the impact that this change might have on the nation’s PM 2.5 monitoring network, the EPA notes that there are no remaining sites operating affirmatively as “non population

- oriented.” The last known non population

- oriented site at Sun Metro in El Paso Texas (AQS ID: 48

- 141

- 0053), was shut down in October 2010 and is in the process of being moved to a nearby neighborhood. Ther e were two commenters from air agencies on the issue of revoking population oriented as a condition for comparability of PM 2.5 monitoring sites to the NAAQS. One was fully supportive of the proposed change and the other stated out Public comments on this is sue were supported by air agencies and public health and environmental groups. Two commenters from state agencies supported the proposed change, with one noting further that regardless of a change it is still the air agency’s responsibility to plan a netw ork with sites that are appropriate for comparison to the NAAQS.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 582 of 790 Formatted: Left Most industry commenters did not support revoking “population

- oriented” as a condition for comparison to the NAAQS. Most comments raised concerns with using data from an area where potentially no one is exposed. Several public health and environmental groups supported revoking “ population oriented ” as a condition for comparability of PM 2.5 monitoring sites to the NAAQS stating that retaining such a policy is inconsistent with the text, purpose and intent of the Clean Air Act. Most industry commenters did not support revoking “population

oriented” as a condition for comparison to the NAAQS. Most of these comments raised concerns with using data from an area where potentially no one is exposed. In considering the public these comments on this aspect of the proposed rule, , the EPA agrees that it is appropriate for individual air agencies to provide a recommendation in the annual monitoring network plan regarding whether any site may or may not be appropriate for comparison to a the PM 2.5 (or any) NAAQS. The roles of the air agency and the EPA in this process of identifying whether a site is, or is not, consistent with the

ne twork plan requirements for a NAAQS are specified in the previously already

established monitoring requirements of §58.10. In this approval process, the air agency initiates the recommendations and the EPA has the responsibility to approve, as appropriate , any plans that provide for changes to the network. Regarding comments from industry commenters that monitors may be sited in areas that do not represent exposure of the public to PM 2.5 , if we revoke the requirement for sites to be population oriented to be compared to the NAAQS, the EPA maintains that all existing sites are already representative of population exposure. The EPA also asserts that any monitor an air agency deploys meeting our definition of ambient air will be***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 583 of 790 Formatted: Left located where the public is (o r may be) exposed. The EPA notes the supportive comments from the one air agency and several public health and environmental groups on revoking population oriented as a condition for comparability of PM 2.5 monitoring sites to the NAAQS. EPA disagrees with the industry comments. As noted above, monitors (including those for PM 2.5 ) must already meet the test of being representative of ambient air to be compared to the NAAQS, and thus such monitors meeting this test will be sited in locations where peopl e are already located, or where they could be exposed, whether or not the term “population oriented” appears in section 58.30. Moreover, as discussed below, comparisons to the annual PM 2.5 NAAQS can be only be from monitors “ that are representative of area

- wide air quality .” “Area

- wide” monitors are those at the neighborhood scale or larger, or at smaller scales if they are representative of many such locations in the same CBSA . The EPA anticipates that a monitor that is sited as representative of ambient air at the neighborhood scale or larger (or of ambient air at many smaller areas) will be representative of population exposure. This conclusion is further supported by the fact that all current monitors used for comparison with the PM 2.5 NAAQS are designa ted as “population

- oriented.” 244 After consideration of the public comments, the EPA is finalizing its decision to revoke use of “population

- oriented” as a condition for comparability of PM 2.5 monitoring sites to the NAAQS. The EPA is making this decision to provide for more consistency in the monitoring rules , to ensure the rules for comparability of PM 2.5 monitoring sites to the NAAQS are consistent with the definition of ambient air, and to remove an unnecessary

244 The last known non population

- oriented site at Sun Metro in El Paso Texas (AQS ID: 48

- 141

- 0053), was shut down in October 2010 and is in the process of being moved to a nearby neighborhood
.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 584 of 790 Formatted: Left requirement that was causing confusion in the monitoring regulations The EPA concludes that the “population

- oriented” language is unnecessary and inconsistent with other monitoring rules, and should therefore be removed
. b. Applicability of Micro

- and Middle

- scale Monitoring Sites to the Annual PM 2.5 NAAQS The EPA proposed clarifying language used in 40 CFR section 58.30 to determine clarify when data from PM 2.5 monitoring sites at micro

- and middle

- scale locations are comparable can be compared to the annual PM 2.5 NAAQS. The EPA’s intent in clarifying this language is was to provide consistency and predictability in the interpretation of the monitoring regulations which will minimize the burden on state monitoring programs as they plan and implement their monitoring programs. he . The EPA’s current rules , as specified in 40 CFR 58.30, state that “PM 2.5 data that are representative, not of area

- wide but rather, of relatively unique population

- oriented micro

- scale, or localized hot spot, or unique population

- oriented middle

- scale impact sites are only eligi ble for comparison to the 24

- hour PM 2.5 NAAQS. For example, if the PM 2.5 monitoring site is adjacent to a unique dominating local PM 2.5 source or can be shown to have average 24

- hour concentrations representative of a smaller than neighborhood spatial scal e, then data from a monitor at the site would only be eligible for comparison to the 24

- hour PM 2.5 NAAQS.” The EPA is We proposed clarifying language to explicitly state that measuring PM 2.5 in micro

- and middle

- scale environments near emissions of mobile s ources, such as a highway, does not constitute being impacted by a “unique” source

. Mobile and so could be compared to the annual PM 2.5 NAAQS. We explained that mobile sources are rather ubiquitous and there are many locations throughout an urban area wher e elevated exposures attributable to such sources could***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 585 of 790 Formatted: Left occur. Therefore, we proposed that in most cases the potential location for a PM 2.5 monitoring site, including micro

- and middle

- scale sites near roadways, would be eligible for comparison to the annu al NAAQS. The EPA’s existing definition of middle

- scale for PM 2.5, as specified in appendix D to 40 CFR part 58, already states, “(2) Middle scale

— People moving through downtown areas, or living near major roadways, encounter particle concentrations that would be adequately characterized by this spatial scale
. Thus, measurements of this type would be appropriate for the evaluation of possible short

- term exposure public health effects of particulate matter pollution
. In many situations, monitoring sites tha

t are representative of micro

- or middle

- scale impacts are not unique and are representative of many similar situations
. This can occur along traffic cor ridors or other locations in a r esidential district
. In this case, one location is representative of a number of small scale sites and is appropriate for evaluation of long

- term or chronic effects
. This scale also includes the characteristic concentrations for other areas with dimensions of a few hundred meters such as the parking lot and feeder streets ass ociated with shopping centers, stadia, and office buildings.” With the reference to “traffic corridors” and related text, the EPA emphasizes that this type of location, which is referred to as near

- road, should not be considered “unique.” We further noted that the existing definition of “middle scale” in appendix D to part 58 already indicates that traffic corridors can be middle scale, and hence not unique, and therefore comparable to the annual PM 2.5 NAAQS (as well as to the 24

- hour PM 2.5 NAAQS) (77 FR 3 9008). The EPA and monitoring agencies already have a process for approving PM 2.5 monitoring sites as described in the Annual Monitoring Network Plan due to the applicable EPA Regional Office by July 1 of each year (described in 40 CFR 58.10)
.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 586 of 790 Formatted: Left This exist ing process provides for identification of sites that are suitable and sites that are not suitable for comparison against the annual PM 2.5 NAAQS (§58.10 (b)(7)). This clarifying language will provide consistency between the PM 2.5 design criteria described in appendix D to 40 CFR part 58 and the example provided in the special considerations for data comparisons to the NAAQS network design (§58.30). This clarifying language will help to ensure a more consistent identification and a pproval of sites, and therefore provide a reduction in burden to monitoring agencies and EPA as annual monitoring network plans are prepared, reviewed, public comments are considered, plans are approved and implemented, and data are ultimately used. Air a gencies that commented on this aspect part of the proposed rule offered a variety of positions. One air agency stated that sites at these smaller scales should not be compared to the annual NAAQS. Another air agency stated that these sites should be conside red for comparison with the annual PM 2.5 NAAQS only when the air agency initiates a decision that such sites at these smaller scales are area

- wide , should they be compared to the annual NAAQS. Alternatively, a . A different air agency offered that all micro

- and middle

- scale sites should be compared to the annual NAAQS since the wording of the provision is problematic and will be difficult for agencies to implement. Industry commenters who offered comments on this aspect of the rule were largely against fina lizing such a provision. The major concern raised was that from their perspective such a provision combined with other related provisions represented an unwarranted tightening of the NAAQS. Some industry commenters pointed out that there are examples of u nique locations in near road environments and as such EPA should not presume that PM 2.5 monitors in these locations should be applicable to the***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 587 of 790 Formatted: Left annual PM 2.5 NAAQS. In considering comments on this part of the rule, and as described in the proposal, EPA note s that we there are ensuring consistency in our applicability already examples of treating where the States and EPA have determined certain micro

- and middle

- scale monitoring sites which will reduce the ambiguity of the monitoring regulations. This consistency is accomplished by ensuring locations as applicable to the annual NAAQS and others where they were determined as not applicable to the regulatory language cite d in annual PM 2.5 NAAQS. These cases exist where a State proposed and the section Special Considerations for Data Comparisons to the NAAQS Network Design (§58.30) is written in a manner Regional Administrator determine d th at is consistent with the longstandi ng definitions for either the micro

- and scale or middle

- scale in site did or did not represent many similar areas in a CBSA (40 CFR 58.30 and section 4.7 to Appendix D to Part , part 58
. ). The EPA also notes that the existing descriptions of the types of mic ro - and middle

scale sites which are unique and cited in §58.30 will remain in place are not being amended and that data from these types of sites would remain as not comparable to the annual PM 2.5 NAAQS. Accordingly, PM 2.5 data that are representative, no t of area

- wide but rather, of relatively unique population

- oriented microscale, or localized hot spots, or unique middle scale impact sites will only be eligible for comparison to the 24

- hour NAAQS. The EPA notes the supportive comments from several public health and environmental groups on the applicability of area

- wide Our proposal was to clarify language to explicitly state that measuring PM 2.5 in micro

- and middle

- scale monitoring sites environmen ts near emissions of mobile sources, such as a highway, does not***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 588 of 790 Formatted: Left constitute being impacted by a “unique” source and so the site could be compared to the annual PM 2.5 NAAQS
. After a review of the comments, the However, in light of public comments pointing out that there are cases where near

- road environments can be considered a unique location; EPA is not finalizing its decision on the applicability this part of area wide micro

- the rule language. Examples of such locations that are considered unique and mid dle

- scale monitoring sites should therefore not be considered applicable to the annual PM 2.5 NAAQS . As are explained later in section III.E.3.a on the form of the annual NAAQS, EPA notes that it took the variability in PM 2.5 concentrations from area

- wide micro

- and middle

- scale sites into account in setting the standard. Thus, the EPA disagrees with those comments indicating that this change would represent a tightening of the NAAQS. We are adding an example on the treatment of near road monitoring sites, indicating that they are generally representative of many such locations, and that consistent with our existing policy where micro

- and middle

- scale sites represent many such locations, these types of sites are comparable to the annual NAAQS. A key aspect of this decision also maintains the longstanding policy in siting and use of data from those PM 2.5 monitoring sites that are unique and therefore not comparable to the annual NAAQS. As described above, VIII.B.3.b.i. As noted in the preamble to the proposed rule (77 FR 39008

- 09), air agencies and the EPA will use the annual monitoring network plan described in 40 CFR 58.10 for identification and approval of sites that are suitable and sites that are not suitable for comparison against with the annual PM 2.5 NAAQS. The EPA disagrees with those comments that asserted that th e proposed change would have represent ed a tightening of the NAAQS. As explained in section III.E.3.a on Formatted: Font: Not Bold***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 589 of 790 Formatted: Left the form of the annual NAAQS, the EPA carefully conside red that areas such as traffic corridors were potential high exposure areas, since a significant fraction of the population, including at

- risk populations, live in proximity to major roads and should be afforded the degree of protection intended by the revisions to the form and level of the annual PM 2.5 standard being adopted . Monitoring in such areas as traffic corridors does not make the annual standard more stringent than intended , but rather affords the populations of such middle

- and micro

- scale are as (where determined to represent area

wide air quality) the requisite level of protection from long

- term exposure to PM 2.5 . 3. Changes to Monitoring for the National Ambient Air Monitoring System

a. Background As described in appendix D to 40 CFR part 58, the ambient air monitoring networks must be designed to meet three basic monitoring objectives: (a) Provide air pollution data to the general public in a timely manner
. Data can be presented to the public in a number of attractive ways including through air q uality maps, newspapers, Internet sites, and as part of weather forecasts and public advisories
. (b) Support compliance with ambient air quality standards and emissions strategy development
. Data from FRM, FEM, and ARM monitors for NAAQS pollutants will b e used for comparing an area’s air pollution levels against the NAAQS

. Data from monitors of various types can be used in the development of attainment and maintenance plans
. SLAMS, and especially National Core Monitoring Network (NCore) 245 station data, wil l be used to evaluate the regional air quality models used in developing emission strategies

245 NCore is a multi

- pollutant network that integrates several advanced measurements for particles, gases and meteorology ( U.S. EPA, 2011a, Appendix B, section B.4)
. Measurem ents required at NCore include PM 2.5 mass and speciation, PM 10

- 2.5 mass, ozone, CO , SO 2 , NO, NO y , and basic meteorology. Formatted: Indent: Hanging: 0.5"***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 590 of 790 Formatted: Left and to track trends in air pollution abatement control measures’ impact on improving air quality
. In monitoring locations near major air pollution sources, source

- oriented monitoring data can provide insight into how well industrial sources are controlling their pollutant emissions
. (c) Support for air pollution research studies
. Air pollution data from the NCore network can be used to supplement data collected by researchers working on health effects assessments and atmospheric processes or for monitoring methods development work. To support the air quality management work indicated in the three basic air monitoring objectives, a network must be designed with a va riety of types of monitoring sites
. Monitoring sites must be capable of informing managers about many things including the peak air pollution levels, typical levels in populated areas, air pollution transported into and outside of a city or region, and air pollution levels near specific

sources . Following is a listing of six general site types: (a) sites located to determine the highest concentrations expected to occur in the area covered by the network (highest concentration) ; (b) sites located to measure typical concentrations in areas of high population density (population oriented) ; (c) sites located to determine the impact of significant sources or source categories on air quality (source impact or source oriented) ; (d) sites located to determine genera l background concentration levels (general background) ; and (e) sites located to determine the extent of regional pollutant transport among populated areas (regional transport) ; and in support of secondary standards (welfare related impacts)
. b. Primary PM 2.5 NAAQS***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 591 of 790 Formatted: Left The EPA propose d to add a near

- road component to the PM 2.5 network design criteria and to clarify the use of approved PM 2.5 continuous FEMs at SLAMS. ii. Addition of a Near

- road Component to the PM 2.5 Monitoring Network The EPA proposed to add a near - road component to the PM 2.5 monitoring network
. (77 FR 39009). The EPA believes explained that there are gradients in near

roadway PM 2.5 that are most likely to be associated with heavily travelled roads ( particularly those with significant heavy

- duty diesel activity ) , and that the largest numbers of impacted populations are located in the largest CBSAs in the country (Ntziachristos et al., 2007; Ross et al., 2007; Yanosky et al., 2008 2009 ; Zwack et al., 2011). The EPA believes further noted that by addi ng a modest number of PM 2.5 monitoring sites that are leveraged with measurements of other pollutants in the near

- road environment, a number of key monitoring objectives will be supported, including collection of NAAQS comparable data in the near

- road envi ronment , support for long

term health studies investigating adverse effects on people, providing a better understanding of pollutant gradients impacting neighborhoods that parallel major roads, availability of data to validate performance of models simulat ing near

- road dispersion, characterization of areas with potentially elevated concentrations and/or poor air quality , implementation of a multi

- pollutant paradigm as stated in the NO 2 NAAQS proposed rule (74 FR 34442, July 15, 2009) , and monitoring goals c onsistent with existing objectives noted in the specific design criteria for PM 2.5 described in appendix D, 4.7.1(b) to 40 CFR part 58
. The monitoring methods that are appropriate for this purpose are an FRM, FEM, or ARM. The EPA recognizes recognize d that there are limitations in the ability of some***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 592 of 790 Formatted: Left of these methods to accurately measure PM 2.5 mass due to the incomplete retention of semi

- volatile material on the sampling medium (U.S. EPA, 2009a, section 3.4.1 .1)
. This limitation is relevant to the near

- roa d environment as well as to other environments where PM is expected to have semi

- volatile components . The EPA also recognizes recognize d that continuous PM 2.5 FEMs, which provide mass concentration data on an hourly basis, are better suited to accomplish th e goals of near

- road monitoring as they will complement the time resolution of the other air quality measurements and traffic data collected at the same sites
. In this regard, particular PM 2.5 FEMs are generally better suited for near

- road monitoring than FRMs
. However, filter

- based FRMs do offer some advantages which may be highly desirable for near

- road monitoring, such as readily available filters for later chemical analysis such as for elemental composition by x

- ray fluorescence and black carbon (BC) by transmissometry
. As a result of these tradeoffs, monitoring agencies are encouraged to select one or more PM 2.5 methods for deployment at near

– road monitoring stations that best meet their agencies monitoring objectives while ensuring that at least one of those methods is appropriate for comparison to the NAAQS (i.e., a FRM, FEM, or ARM). The EPA believes that by allowing monitoring agencies to choose the FRM, FEM, or ARM method(s) that best fits their needs, whether filter

- based or continuous, the data wi ll still be able to meet the objectives cited above while ensuring maximum flexibility for the monitoring agencies in the operation of their network. Additionally, the EPA recognizes that the near

- road sites would provide a valuable platform for evaluati ng emerging monitoring technologies and for measuring other pollutants besides PM 2.5 mass to enhance knowledge of exposure in the near road***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 593 of 790 Formatted: Left environment and to support the characterization and comparison of specific method readings in an emission

- rich envir onment. Further, i n its response to the EPA on a “Review of the “Near

- road Guidance Document

– Outline” and “Near

- road Monitoring Pilot Study Objectives and Approach” ( U.S. EPA, 2010i), the CASAC AAMMS cited several other measurements that may be useful or potentially linked to health and welfare effects such as BC, ultrafine particles, and particle size distribution (Russell and Samet, 2010b, pp. xi and xii)
. The EPA agrees with these recommendations and encourages monitoring agencies to include these meas urements, and others cited in the Subcommittee letter, where possible , in addition to the PM 2.5 mass measurement. The EPA also encourage s monitoring agencies to explore partnerships with instrument manufacturers and researchers to use the sites to evaluate the performance of emerging PM 2.5 monitoring methods in the near

- road environment, especially potential or current FEMs able to provide temporally resolved data and capture the semi

- volatile components of PM 2.5 . Such emerging PM 2.5 methods could be operat ed as SPMs 246 to provide comparisons to the EPA approved methods supporting compliance to advance the understanding of instrument performance in the near

- road environment. Monitoring agencies are also encouraged to partner with instrument manufacturers and researchers to operate monitors able to measure other PM properties relevant for the near

- road environment (e.g., ultrafine particles , BC) to provide additional information about exposure to PM in this environment. The EPA is interested in supporting monitoring agenci es willing to operate and report the data from these supplemental monitors. EPA
246 SPMs means a monitor included in an air agency’s monitoring network that the agency has designated a a special purpose monitor in it s monitoring network plan and in the Air Quality System database, and which the air agency does not count toward when showing compliance with the minimum monitoring requirements in appendix D to Part 58.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 594 of 790 Formatted: Left notes that the implementation of additional measurements, while encouraged, is completely voluntary to ensure maximum flexibility for state monitoring programs. The EPA belie ve s that requiring a modest network of near

- road compliance PM 2.5 monitors is necessary to provide characterization of concentrations in near

- road environments including for comparison to the NAAQS. These long

- term monitors will supplement shorter

- term net works operated by researchers to support the tracking of long

- term trends 247 of near - road PM 2.5 mass concentrations and other pollutants in near

road environments where people are exposed
. Therefore, the EPA propose d to require

near - roadway monitoring of PM 2 .5 at one location within each CBSA with a population of one million persons or greater

. The EPA believes that this network will be adequate to support the NAAQS since the largest CBSAs are likely to have greater numbers of exposed populations, a higher li kelihood of elevated near

- road PM 2.5 concentrations, and a wide range of diverse situations with regard to traffic volumes, traffic patterns, roadway designs, terrain/topography, meteorology, climate, surrounding land use and population characteristics
. Gi ven the latest population data available, th e proposed requirement would result in approximately 5 2 required near

- road PM 2.5 monitors across the country
. An indirect benefit of this network design is that monitoring agencies in these largest CBSAs are more likely to already have redundant monitors that could be relocated to the

247 For example, the emissions used for the PM NAAQS RIA modeling show that nationwide on

- road primary PM 2.5 emissions are expected to be reduced by 63% between 2007 and 2020. Additionally, the elemental carbon portion of the on

- road emissions is expected to drop by 81 percent between 2007 and 2020. Theref ore, we expect that measured near

- road PM 2.5 gradients will be much lower in the future as elemental carbon is a large fraction of the gradient , due to future impacts of existing mobile source controls.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 595 of 790 Formatted: Left

near - road environment , reducing costs for equipment and ongoing operation. 248 While only a single near - road PM 2.5 monitor is required within each of the CBSAs, agencies may elect to ad d additional PM 2.5 monitoring sites in near

- road environments. While the EPA recognizes recognize d that the location of maximum concentration of PM 2.5 exposure from roadway sources might differ from the maximum location of NO 2
or o t her pollutants, the EPA propose d to require that near

- road PM 2.5 monitors be collocated with the planned NO 2 monitors
. The NO 2 network design considers multiple factors that are also relevant for PM 2.5 concentrations ( i. e., average annual daily traffic , fleet mix , roadway design , congestion patterns, terrain, and meteorology ) and significant thought and review has already gone into its design, including pilot studies at five locations, and the development of a technical assistance document in conjunction with the affected monitor ing agencies and the CASAC AAMMS (Russell and Samet, 2010b) to support deployment
. Further, this collocation will allow multiple pollutants to be tracked in the near

- road environment. To the extent that air agencies are still determining the optimum location for their multi

- pollutant 249 near - road monitoring stations, EPA encourages consideration of sites that best reflect measurement of maximum concentrations associated with exposure of people living in areas that parallel major roads, to maximize the value of the data for use later in health studies. Therefore, while compromises may be necessary when siting a multi

- pollutant near road monitoring station, on balance, the EPA believes this is the most efficient and beneficial approach for deployment of this component of the network.

248 EPA Regional Administrator approval would be requ ired prior to the discontinuation of SLAMS monitors, based on the criteria described in 40 CFR 58.14(c). 249 NO 2 , CO, and now PM 2.5 measurements are all expected to be collocated at near

- road monitoring stations. Formatted: Font: 12 pt Formatted: Font: 12 pt, Not Superscript/ Subscript Formatted: Font: 12 pt Formatted: Font: 12 pt, Not Superscript/ Subscript Formatted: Font: 12 pt Formatted: Font: 12 pt, Not Superscript/ Subscript***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 596 of 790 Formatted: Left The EPA notes that the planned 52 near

- road monitors represent a small number of the total approximate 900 operating PM 2.5 monitoring stations across the count ry. The EPA could have considered proposing proposed more near - road sites, however, the addition of sites in lower population CBSAs is not expected to lead to much if any difference in characterization of air quality since the bump in PM 2.5 concentration

as sociated with near

- road environments in lower population CBSAs, which typically have correspondingly less travelled roads, is expected to be very small. The EPA could also have considered proposing proposed multiple sites in larger CBSAs; however, State

mon itoring programs are already working towards representative near

- road monitoring stations and there is a synergistic value in ensuring these measurements are collocated with multiple other measurements to serve the monitoring objectives noted above. Since EPA has already finalized requirement of CO monitoring at near

- road stations in CBSA’s with a population of 1 million or more at sites that are collocated with NO 2 , there would be less value in requiring any more than 52 PM 2.5 monitors as any more stations will not have CO for use in multi

- pollutant monitoring objectives (e.g., health studies and model evaluation). Ideally, near

- road sites would be located at the elevation and distance from the road where maximum concentration of PM 2.5 exposure occur s in t his environment, and within reasonable proximity to an other area - wide PM 2.5 compliance monitoring site at which a similar PM monitor is used (i.e., for comparison purposes) . However, specific PM 2.5 levels occur in this environment, representing locations wh ere populations are exposed; for example, in apartments and other housing; schools located along major roadways; industrial parks where workers exposed; and in recreational areas such as***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 597 of 790 Formatted: Left greenways, bikeways, and other park facilities that are often develop ed along roads. Specific to probe and siting criteria for near

- road PM 2.5 monitors, which is explained later in this section, EPA did not set additional criteria on what the elevation and distance requirements should be, beyond what is already defined for PM 2.5 or near - road NO 2 monitors for reasons explained above. Also, the EPA did not propose that the near

- road PM 2.5 monitors be located within a specific distance of other area

- wide sites; however, monitoring agencies are encouraged to consider that a near

- road site selected in accordance with monitoring requirements and also located in proximity to a robust area

wide site, such as an NCore station, would provide useful information in characterizing the near

- road contribution to multiple pollutants, includi ng PM 2.5 and tracking the decreasing trend that is expected in the PM 2.5 near - road gradient over time, due to future impacts of existing mobile source controls
. The timeline to implement the near

- road PM 2.5 monitors should be as minimally disruptive to on

- going operations of monitoring agency programs as possible recognizing monitoring agencies agency resource constraints , while still meeting the need to collect for near

- road PM 2.5 data in a timely fashion
. Since the near

- road PM 2.5 monitors were proposed to be collocated with the emerging near

- road NO 2 network that was scheduled to be operational by January 1, 2013 250 , the EPA believes it is appropriate to wait until after the near

- road NO 2 network is established before implementing the near

- road PM 2.5 monitor s. Therefore, the EPA propose d that each PM 2.5 monitor planned for collocation with a near

- road NO 2 monitoring site be implemented no later than January 1, 2015
.

250 The EPA has proposed a revised timeline for deployment of the near

- road NO 2 monitors, where all CBSAs with one million or more people are to have their first near

road NO 2 station operational by January 1, 2014 (77 FR 64244, October 19, 2012).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 598 of 790 Formatted: Left The EPA received comments from a number of air agencies, industrial groups, and environmental and public health organizations on its proposal to require PM 2.5 monitoring in near

- road environments. Among comments from air agencies, several commenters did not support the addition of near road monitoring with comments on citing the challenges of siting these stations and the additional cost it would require to operate the monitors. Several air agencies recognized the v alue of adding monitors to provide better characterization of exposures in near

- road environments, but recommend ed a slower deployment of the PM 2.5 monitors so that it can be phased in over a multi

- year period. Several air agencies recommended that the PM 2.5 monitoring in the near

- road environment be deployed on a phased

- in schedule with the first such monitors bein g required no sooner than one year after deployment of the NO 2 sites. These air agencies stated that the phasing in of the PM 2.5 monitors in the near road environment would allow more time to learn and share information on what worked best in deploying the NO 2 monitors at near

- road monitoring stations, since NO 2 is the first pollutant required to be monitored at near

- road stations. A few air agencies identified a need to more clearly support or require the maintenance of as much of the existing network of n eighborhood scale PM 2.5 monitoring sites as possible in regulatory text. These neighborhood scale PM 2.5 sites were identified by commenters as the most broadly representative sites for characterizing CBSA wide exposures that are supportive of a number of m onitoring objectives. A few air agencies also identified a need for flexibility in the proposed network design requirement that PM 2.5 near - road monitors must be collocated with the NO 2 monitors in the near

- road environment. The commenters suggested allowin g flexibility for air agencies to meet the requirement for Formatted: Default
Formatted: Not Superscript/ Subscript

Formatted: Not Superscript/ Subscript

Formatted: Not Superscript/ Subscript

Formatted: Not Superscript/ Subscript
Formatted: Not Superscript/ Subscript

Formatted: Not Superscript/ Subscript
Formatted: Not Superscript/ Subscript
Formatted: Not Superscript/ Subscript
Formatted: Not Superscript/ Subscript
Formatted: Not Superscript/ Subscript
Formatted: Not Superscript/ Subscript
Formatted: Not Superscript/ Subscript

Formatted: Not Superscript/ Subscript
Formatted: Not Superscript/ Subscript***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 599 of 790 Formatted: Left
PM 2.5 in a near

- road environment by siting at a different near

- road location where PM 2.5 concentrations are expected to be high. Most industry commenters did not support the addition of near

- road monitoring for PM 2.5 , citing again arguing that use of using data from such data should be for research purposes and, if used monitors, for comparison to the NAAQS, combined with other changes (i.e., elimination o f “population

- oriented” as a criteria for comp arison to the NAAQS and the elimination of spatial averaging) would represent, in their judgement, a collective tightening of the PM 2.5 NAAQS. A few of these commenters asserted that monitoring in the near

- road environm ent is not representative of ambien t air exposures. A few industry comments noted that if the EPA required PM 2.5 monitoring in the near

- road environment, any data collected should not be used for comparison to the NAAQS. One commenter stated it had no problem with monitoring in the near

- roa d environment, so long as any such monitoring used to compare to the PM 2.5 annual NAAQS is population

– oriented. One commenter stated that the decision to co

- locate with NO 2 monitors was based on convenience and the intent of the NO 2 near - road monitoring is to find the highest micro

- scale concentrations within a few meters of the most heavily travelled expressways, representing a unique situation. Environmental and public health groups strongly support the addition of PM 2.5 monitorin g to the near

- road environment. Commenters cited the large number of people that live in proximity to major roadways 251 in their support for adding these monitors,

251 One study identified that 45 million Americans live w ithin 300 feet of a major roadway
. or other source of mobile emissions. The commenters commenters ’ information is based on the American Housing Survey, which is available on the web at: http ://www.census.gov/housing/ahs/data/ahs2009.html
. The survey provides an estimate of the county’s housing units in the U.S. that are located with 300 feet of a highway with four or more lanes, or a railroad, or an airport. Formatted: Not Superscript/ Subscript Formatted: Not Superscript/ Subscript

Formatted: Not Superscript/ Subscript
Formatted: Not Superscript/ Subscript

Formatted: Not Superscript/ Subscript

Formatted: Not Superscript/ Subscript
Formatted: Not Superscript/ Subscript
Formatted: Not Superscript/ Subscript

Formatted: Not Superscript/ Subscript

Formatted: Not Superscript/ Subscript
Formatted: Not Superscript/ Subscript
Formatted: Not Superscript/ Subscript***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 600 of 790 Formatted: Left that such protection of people in these environments in long overdue, and that such data there fore be used for comparison to the NAAQS. Regarding comments from air agencies that the near

- road monitors are challenging to site and that there is additional cost in operating these monitors, the EPA maintains that the major challenges in siting would a lready be accomplished by implementing the required NO 2 monitoring stations in near

- road environments since the EPA fully expects that the PM 2.5 monitors will be placed at the NO 2 near roadway stations and has revised the PM 2.5 monitoring requirements cons istent with that expectation. The EPA also points out that the requirements for the minimum number of PM 2.5 monitors is unchanged and that in most cases the addition of near

- road PM 2.5 monitors can be accomplished by relocating an existing monitor, with no net increase in monitors. Thus, while we are requiring a new component of the PM 2.5 monitoring network, the overall size of the network is expected to remain about the same, and we expect that air agencies can meet this requirement by relocating existing lower

- priority monitors. In considering comments from air agencies on a schedule for implementing PM 2.5 monitors at near road monitoring stations, the EPA is persuaded by commenters from air agencies who stated that a phased deployment of the PM 2.5 monitor s would be a better approach as it would allow agencies to learn from the deployment of the NO 2 monitors and a first phase of PM 2.5 monitors. Phasing in the deployment of monitors is also consistent with previous CASAC advice (Russell and Samet, 2010b) on a schedule for deployment of near

- road NO 2 monitors. Regarding comments from air agencies on maintaining the neighborhood scale monitoring stations as the largest part of the network a s these sites are the most broadly Formatted: Not Superscript/ Subscript

Formatted: Not Superscript/ Subscript
Formatted: Not Superscript/ Subscript Formatted: Not Superscript/ Subscript Formatted: Not Superscript/ Subscript

Formatted: Not Superscript/ Subscript Formatted: Not Superscript/ Subscript

Formatted: Not Superscript/ Subscript

Formatted: Not Superscript/ Subscript
Formatted: Not Superscript/ Subscript
Formatted: Not Superscript/ Subscript
Formatted: Not Superscript/ Subscript
Formatted: Not Superscript/ Subscript
Formatted: Not Superscript/ Subscript

Formatted: Not Superscript/ Subscript***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 601 of 790 Formatted: Left representative of exposures across C BSAs, the EPA supports such a goal. Neighborhood scale monitoring sites remain the backbone of the PM 2.5 monitoring network and they will continue to represent over two thirds of the operating network following the deployment of the near

- road monitors. The EPA expects that each CBSA required to monitor for PM 2.5 will maintain its existing highest concentration area

- wide monitoring site (referred to as the design value site) and not attempt to move such sites to near

- road environments. Maintaining the area

- w ide and largely neighborhood scale design value sites is critical to the long

- standing goal of using data to support a variety of monitoring objectives. The EPA also recognizes that while every PM 2.5 monitor has value in some capacity at its current locati on, air agencies are expected to recommend relocation of monitors that are relatively low in priority to meet the near

- road requirement. Regarding comments from air agencies on the need for flexibility in the network design requirement that PM 2.5 near - road monitors must be collocated with the NO 2 monitors in the near

- road environment, the EPA points out that it prefers to maintain this requirement so that the multi

- pollutant data are available to support the monitoring objectives cited above. Howev er, the EPA also recognizes there may be cases where an air agency recommends siting their near

- road PM 2.5 monitor in another high concentration near

- road environment. The EPA believes such cases will be very limited, but that these situations can be suppo rted in one of two ways. First, EPA and the air agency can use their discretion to site two near

- road PM 2.5 monitors in the area. Second, the EPA can use its discretion in approving a deviation from the PM 2.5 monitoring requirements as already exists in th e network design criteria. Such deviations are to be Formatted: Not Superscript/ Subscript

Formatted: Not Superscript/ Subscript

Formatted: Not Superscript/ Subscript

Formatted: Not Superscript/ Subscript
Formatted: Not Superscript/ Subscript Formatted: Not Superscript/ Subscript

Formatted: Not Superscript/ Subscript

Formatted: Not Superscript/ Subscript
Formatted: Not Superscript/ Subscript***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 602 of 790 Formatted: Left approved by the Regional Administrator as described in section 4.7.1 of Appendix D to part 58. In considering public comments on the addition of PM 2.5 monitors to the near

road environment, the EPA poin ts out that a significant fraction of the population lives in proximity to major roads and agrees that these Regarding the comment that PM 2.5 monitors in near

- road environments were sited for convenience , which due to siting with NO 2 monitors a few meters f rom the road presents a unique situation, the EPA disagrees that these monitors were sited solely for convenience or that they would represent a unique situation within an urban area. On the initial point, t he EPA believes that the characterization of rep resentative maximum PM 2.5 concentration s due to on
- road mobile sources and the appropriate location of such PM 2.5 monitors will be the same approximate locations that are the focus of the near - road NO 2 network
. This is due to the fact that PM 2.5 , like NO X, is disproportionately influenced by heavy duty (HD) vehicles which are predominantly diesel fueled, when compared to light duty (LD) vehicles which are primarily gasoline fueled. Specifically, for both PM 2.5 and NOx, HD vehicles emit more of these two pollutants and their precursors on a per vehicle basis than LD vehicles. The EPA recognize d this fact in the near

- road NO 2 network by requiring states to consider the fleet mix of candidate road segments where near

- road monitoring might occur. In the des ign of the NO 2 near - road network where the PM 2.5 monitors will be installed, s tates were instructed to place a higher priority on those highly trafficked roads which have more diesel fueled vehicles using a metric called the fleet equivalent average annual daily traffic
. 252 As such, the Agency believes it is appropriate that required near

- road PM 2.5

252 See the Near

- road NO 2 Monitoring Technical Assistance Document at: http://www.epa.gov/ttn/amtic/files/nearroad/NearRoadTAD.pdf***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 6 03 of 790 Formatted: Left monitors would be located with near

- road NO 2 monitors as they are similarly influenced not only by fleet mix but also by total traffic count, congestion pattern s, roadway design, terrain, and meteorology. On the second point with regard to such sites representing a unique situation within an urban area, EPA points out that the determination of a near

road micro

- or middle

- scale site being considered to represent “area

- wide” air quality or “unique” will be made on a case by case basis with the monitoring agency providing such recommendations in their annual monitoring network plans described in §58.10. Examples of such “unique” micro

- and middle

- scale locations a re provided later in this section. We do not accept the comment that siting some monitors in near roadway environments makes the standard impermissibly more stringent. A significant fraction of the population lives in proximity to major roads. These expo sures occur in locations that represent ambient air for which the agency has a responsib ility to ensure the public is protected . Regarding comments that the addition of near

- road PM 2.5 monitoring sites, combined with the elimination of spatial averaging, and revoking “population

- oriented” as a criteria for comparison to the NAAQS, are a collective tightening of the NAAQS, as explained in section III.E.3.a, the EPA took these changes in to account in setting the standard. with an adequate margin of safety. Ignoring monitoring results from such areas (or not monitoring at all) would abdicate this responsibility. Put another way, monitoring in such areas does not make the standard more stringent, but rather affords requisite protection to the populations, amo ng them at

- risk populations, exposed to fine particulate in these areas. Thus, the EPA has made a determination to protect all area

- wide locations, including those locations with populations living near major roads that are representative Formatted: Default

Formatted: Not Superscript/ Subscript***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 604 of 790 Formatted: Left of many such loca tions throughout an area. As discussed above, EPA concludes that the requirement to locate monitors to represent ambient air, along with other siting requirements, will ensure that monitors represent PM 2.5 concentrations in areas of potential public exposu re. We do recognize, however, the possibility that some near

- road monitoring stations may be representative of relatively unique locations versus the more representative area

- wide situation mentioned above. This could occur because an air agency made a sit ing decision based on NO 2 criteria that resulted in the characterization of a microscale environment that is not considered area

- wide for PM 2.5 ; for example, due to proximity to a unique source like a tunnel entrance, nearby major point source, or other

re latively unique microscale hot spot. In these types of scenarios, air agencies would identify the site as a unique monitor comparable only to the 24

- hour PM 2.5 NAAQS per the language in section 58.30, and not comparable to the annual NAAQS, through the Ann ual Monitoring Network Plan process described earlier. Although EPA expects most

near - road PM 2.5 monitors to be sited to represent area

- wide conditions, since a vast majority of the near

- road stations have yet to be installed, we believe that providing suc h clarity and flexibility in siting and NAAQS comparability is warranted. After careful consideration of the public comments, the EPA is finalizing its decision to add PM 2.5 monitors to the near

- road monitoring stations. The EPA is finalizing this decision as the near

- road environment is an area where significant public exposure can occur, recognizing that this is a gap in the current PM 2.5 monitoring networks, and because these PM 2.5 monitors will be collocated with NO 2 monitors in the

near - road environmen t, there will not be a significant additional burden on the air Formatted: Default
Formatted: Not Superscript/ Subscript

Formatted: Not Superscript/ Subscript
Formatted: Not Superscript/ Subscript Formatted: Not Superscript/ Subscript***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 605 of 790 Formatted: Left agencies 253 . However, in recognition of the comments from air agencies above, EPA is finalizing a revised and phased schedule for deployment of the PM 2.5 monitors at near

road stations. A minimu m of one PM 2.5 monitor in each CBSA with a population ≥ greater than or equal to 2.5 million is to be collocated at a near

- road NO 2 monitoring station and must to be operational by January 1, 2015. The remaining CBSAs (i.e., those CBSAs with populations ≥ greater than or equal to 1M, but less than 2.5M) must operational by January 1, 2017. This schedule will ensure that air agencies have sufficient time to learn from deployment of the NO 2 monitors in near

- road environments, that the highest population CBSAs begin operating their PM 2.5 monitors in near

- road environments first, and that the remaining PM 2.5 monitors are deployed on the same schedule as the CO monitors (also, required by January 1, 2017 254 ). In consideration of the comments regarding maintaining n eighborhood scale monitoring sites as the largest portion of the network, the EPA is adding revising the wording of a requirement to maintain a portion of the network that requires at neighborhood scale or larger least one site to be in the an
area - wide loca tion of expected maximum concentration , to wording that states that such sites must be in an area

- wide location of expected maximum concentration while also being at the neighborhood or larger scale of representation
. iii. Use of PM 2.5 Continuous FEMs at SLAMS

The EPA propose d that each agency specify its intention and rationale to use or not use data from continuous PM 2.5 FEMs that are eligible for comparison to the NAAQS as part of its annual monitoring network plan due to the applicable EPA Region Office by July 1 each year
. The proposal also provide d that the EPA Regional Administrator would
253 The incremental one

- time cost of moving the 52 monitors required to be loc ated in the near - road environment is described in section X.B

– Paperwork reduction Act. 254 76 FR 54294, August 31, 2011 Formatted: Not Superscript/ Subscript
Formatted: Not Superscript/ Subscript
Formatted: Not Superscript/ Subscript
Formatted: Not Superscript/ Subscript

Formatted: Not Superscript/ Subscript
Formatted: Not Superscript/ Subscript
Formatted: Not Superscript/ Subscript
Formatted: Not Superscript/ Subscript
Formatted: Not Superscript/ Subscript***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 606 of 790 Formatted: Left be responsible for approving annual monitoring network plans where agencies have provided a re commendation that certain PM 2.5 FEMs be considered ineligible for comparison to the NAAQS
. In 2006, the EPA finalized new performance criteria for approval of continuous PM 2.5 monitors as either Class III FEMs or ARMs . At the time of proposal, the EPA ha d already approved six PM 2.5 continuous FEMs 255 and there are nearly 200 of these monitors already operating in State, local, and Tribal networks
. Monitoring agencies have been deploying and field

- testing these units over the last couple of years and the EPA recently compiled an assessment of the FEM data in relationship to collocated FRMs (Hanley and Reff, 2011; U.S. EPA, 2011a, pp. 4

- 50 to 4

- 51)
. As described in section V I .D.1.a.iii above, the proposal (FR 38983) , the EPA found that some sites with continuous PM 2.5 FEMs have an acceptable degree of comparability with collocated FRMs, while others had poor data comparability that would not meet the performance criteria used to approve the FEMs (71 FR 61285

- 61286, Table C

- 4, October 17, 2006)
. The EPA is encoura ging use of the FEM data from those sites with acceptable data comparability including for purposes of comparison to the NAAQS
. For sites with unacceptable data comparability, the EPA is working closely with the monitoring committee of the NACAA, instrumen t manufacturers, and monitoring agencies to document best practices on these methods to improve the comparability and consistency of resulting data wherever possible . Th e EPA believe s that the performance of many of these continuous PM 2.5 FEMs at locations with poor data comparability can be improved to a point where the acceptance criteria noted above can be met.

255 The EPA maintains a list of approved Reference and Equivalent Methods on its web site at: http://www.epa.gov/ttn/amtic/criteria.html
.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 607 of 790 Formatted: Left Given the varying data comparability of continuous PM 2.5 FEMs noted above, we believe that a need exists for flexibility in the approaches for ho w such data are used , particularly for the objective of determining NAAQS compliance
. Accordingly, we propose d that monitoring agencies address the use of data from PM 2.5 continuous FEMs in their annual monitoring network plans due to the applicable EPA Regional Office by July 1 of each year for any cases where the agency believes that the data generated by PM 2.5 continuous FEMs in their network should not to be compared t o the NAAQS
. The annual network plans would include assessments such as comparisons of continuous FEMs to collocated FRMs, and analyses of whether the resulting statistical performance would meet the established approval criteria
. Based on these quantitati ve analyses, monitoring agencies would have the option of requesting that data from continuous FEMs be excluded from NAAQS comparison subject to EPA approval ; however, these data could still be utilized for other objectives such as AQI reporting. The issu e exists of whether such data use provisions should be prospective only (i.e., future NAAQS comparability excluded based on an analysis of recent past performance) or a combination of retrospective and prospective (i.e., the implications of unacceptable FE M performance impacting usage of previously collected data as well as future data) . In the proposal, the EPA stated that in most cases, monitoring agencies should be restricted to addressing prospective data issues to provide stability and predictability i n the long

- term PM 2.5 data sets used for supporting attainment decisions
. However , in the first year after this proposed option would become effective, we indicated it would be appropriate to provide monitoring agencies with a one

- time opportunity to revie w already reported continuous PM 2.5 FEM data and request that data***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 608 of 790 Formatted: Left with unacceptable performance be restricted (retrospectively) from NAAQS comparability
. Accordingly, in the first year after this rule becomes effective, we propose d that monitoring agencie s have the option of requesting in their annual monitoring network plans that a portion or all of the existing continuous PM 2.5 FEM data, as applicable, as well as future data, be restricted from NAAQS comparability for the period of time that the plan cov ers. 256 In the proposal we stated that a nnual monitoring network plans in subsequent years would only need to cover new data for the period of time that the plan covers. As noted above, in cases where an agency is operating a PM 2.5 continuous FEM that is no t meeting the expected performance criteria used to approve the FEMs (71 FR 61285 to 61286, Table C

- 4, October 17, 2006) when compared to their collocated FRMs, an agency can recommend that the data not be used for comparison to the NAAQS
. However, all req uired SLAMS would still be required to have an operating FRM (or other well performing FEM , as evidenced by a prior collocation with an FRM ) to ensure a data record is available for comparison to the NAAQS
. In cases where a PM 2.5 continuous FEM was not mee ting the expected performance criteria, and the Regional Administrator has approved a recommendation that the FEM data not be considered eligible for comparison to the NAAQS, the data would still be required to be loaded to AQS; however, these data would b e identified distinctly from data used for comparison to the NAAQS
. The goal of proposing to allow monitoring agencies the opportunity to recommend not having data from PM 2.5 continuous FEMs as comparable to the NAAQS

256 Data from any PM 2.5 monitor being used to meet minimum monitoring requirements could not be restricted from NAAQS comparability.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 609 of 790 Formatted: Left is to ensure that only high quality d ata (i.e., data from FRMs which are already well established and new continuous FEMs that meet the performance criteria used to approve FEMs when compared to collocated FRMs operated in each agencies network) are used when comparing data to the PM 2.5 NAAQS
. Under the current monitoring regulations, a monitoring agency can identify a PM 2.5 continuous FEM as a n SPM, which allows the monitor to be operated for up to 24 months without its data being used in comparison to the NAAQS
. While 24 months should be suf ficient time to operate the monitor across all seasons, assess the data quality, and in some cases resolve operational issues with the instrument, it may still leave some agencies with m onitor s whose data are not sufficiently comparable to data from their FRMs
. In these cases there may be a disincentive to continue operating the PM 2.5 continuous FEM, especially in networks where the monitoring data are near the level of the NAAQS
. With the proposed provision , where a monitoring agency can recommend not having data from PM 2.5 continuous FEMs be comparable to the NAAQS, a monitoring agency can continue to operate their PM 2.5 continuous FEM to support other monitoring objectives (e.g., diurnal characterization of PM 2.5 , AQI forecasting and reporting), while working through options for improved data comparability while still providing data for comparison to the NAAQS from an FRM
. The EPA believes that an assessment of FEM performance should include several elements based on the original performance criteria . Th e Agency also believe s that certain modifications to the performance criteria are appropriate in recognition of the differences between how monitoring agencies operate routine monitors and how instrument manuf

acturers conduct required FRM and FEM testing protocols
. The details below summarize these issues
.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 610 of 790 Formatted: Left The EPA propose d to use the performance criteria used to approve the FEMs (71 FR 61285 to 61286, Table C

- 4, October 17, 2006) for those agencies that recomm end not having data from PM 2.5 continuous FEMs be comparable to the NAAQS
. To accommodate how routine monitoring networks operate, the EPA propose d that agencies seeking to demonstrate insufficient data comparability in an base their assessment base the ana lysis mainly on collocated data from FRMs and continuous FEMs at monitoring stations in their network . The EPA does not believe it is practical to utilize the requirement in table C

- 4 of 40 CFR part 53 for having multiple FRMs and FEMs at each site since s uch arrangements are not typically found in monitoring agency networks
. Accordingly, the requirement for assessing intra

- method replicate precision would be inapplicable
. Another consideration is the range of 24

- hour data concentrations, for instance, the performance criteria in table C

- 4 of 40 CFR part 53, provides for an acceptable concentration range of 3 to 200 μg/m 3

. However, the EPA note s that during an evaluation of data quality from two FEMs ( U.S. EPA, 2011a, p. 4

- 50), th e Agency found that including low concentration data w as helpful for understanding whether an intercept or slope was driving a potential bias in an instrument
. Therefore, the EPA propose d that agencies may include low concentration data (i.e., below 3 μg/m 3 ) for purposes of

e valuating the data comparability of continuous FEMs
. With regard to the minimum number of samples needed for the assessment, the EPA note s that a minimum of 23 sample pairs are specified for each season in table C

- 4 of 40 CFR part 53
. Having 23 sample pair s per season should be easily obtainable within one year for sites with a FRM operating on at least a 1 in 3 day sample frequency and we propose d that this requirement be applicable to the assessments being discussed here
. For sites on a one in 6 day***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 611 of 790 Formatted: Left sampl ing frequency, two years of data may be necessary to meet this requirement
. The EPA recognizes that it would be best to assess the data based on the most recently available information; however, having data across all seasons in multiple years will provide a more robust data set for use in the data comparability assessment; therefore , the EPA propose d that data quality assessments be permitted to utilize up to the last three years of data for purposes of recommending not having data from PM 2.5 continuous FE Ms be comparable to the NAAQS. The EPA recognizes that only a portion of continuous PM 2.5 FEMs will be collocated with FRMs, and it would be impractical to restrict the applicability of data comparability assessments to only those sites that had collocated FRM and FEM monitors
. In these cases, the monitoring agency will be permitted to group the sites that are not collocated with an FRM with another similar site that is collocated with an FRM for purposes of recommending that the data are not eligible for u se in comparison to the NAAQS
. Monitoring agencies may recommend having PM 2.5 continuous FEM data eligible for comparison to the NAAQS from locations where the method has been demonstrated to provide acceptable data comparability, while also recommending n ot having it eligible in other types of areas where the method has not been demonstrated to meet data comparability criteria
. For example, a rural site may be more closely associated with aged particles where volatilization issues are minimized resulting i n acceptable data comparability between filter

- based and continuous methods, while a highly populated urban site with fresh emissions with higher volatility may result in higher readings on the PM 2.5 continuous FEM that would not meet the expected performa nce criteria as compared to a collocated FRM
. In all cases where a monitoring agency chose to group***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 612 of 790 Formatted: Left sites for purposes of identifying a subset of PM 2.5 continuous FEMs that would not be comparable to the NAAQS, the assessment submitted with the annual moni toring network plan would have to provide sufficient detail to support the identification of which combinations of method and sites would, and would not, be comparable to the NAAQS, as well as the rationale and quantitative basis for the grouping and

recom mendation. Most comments received on this issue were from air agencies. All air agencies either supported the proposal or supported it with a recommendation to continue to allow for retrospective assessments to be used such that data would not be compared to the NAAQS, if such an assessment showed that the data were not of sufficient comparability to a collocated FRM such that the continuous FEM should not be compared to the NAAQS. One air agency supported the proposal, except though it had reservations abo ut how to best group sites together when a particular PM 2.5 continuous FEM is not collocated with a FRM. The EPA notes the support by air agencies to finalize this provision. EPA also notes that all commenters who offered input on the retrospective use o f assessments were supportive of allowing continued retrospective assessments in annual monitoring networks plans so that data may be recommended as excluded from comparison to the NAAQS under certain provisions. However, the EPA has some reservations abou t how and under what circumstances such an allowance should be made. The EPA notes the concern expressed from one agency about how to best group sites together when considering an assessment. On the issue of whether to allow data collected to be retrospect ively excluded***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 613 of 790 Formatted: Left from comparison to the NAAQS, the EPA notes there are a number of considerations, including that several air agencies support such a policy. The EPA has evaluated how this issue can be achieved and believes that some consideration should be allowed, but also wants to ensure there is a consistent and easily recognizable interpretation of such cases where air agencies recommend excluding already collected and reported data. To help illustrate the possible outcomes of how this could work conside r the following examples. Example 1: An agency finds that the bias between a collocated PM 2.5 continuous FEM and FRM are acceptable, but near the limit of that acceptability and then finds a year later that the assessment indicates that the bias is just outside the limit of that acceptability. Such relatively small changes where an assessment indicates flipping in or out of the acceptable bias are in themselves acceptable since the overall Data Quality Objectives (DQOs) can still be met. The overall DQOs can still be met since there are a number of other factors that feed into the DQOs such as precision, data completeness, and especially sample frequency, which when operating a continuous FEM is a daily sample. Daily sampling provides less uncertainty tha n sampling at the one

- in

- three day or one

- in

- six day sampling frequencies, which are routinely employed by filter

- based FRM samplers. Therefore, in this example the existing data should still be compared to the NAAQS, but the air agency should thoughtfully consider whether to recommend 257 and the EPA will consider whether to approve that any new data from PM 2.5 continuous FEMs are used in comparison to the NAAQS. If an air agency recommends to not use a PM 2.5 continuous FEM for comparison to the NAAQS, it wo uld need to ensure another approved method (i.e , ., a filter

- based FRM/FEM or other continuous FEM which is performing within acceptable performance criteria) is operating at the site or sites of interest. This would be
257 Through the annual moni toring network plan explained in §58.10.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 614 of 790 Formatted: Left expected for all SLAMS, but at a mini mum the design value monitoring station for the area of interest would be required to have another approved PM 2.5 method (i.e., an FRM, other filter

- based FEM, or other continuous FEM or ARM with acceptable data comparability) operating on the required sam ple frequency or more often for that location. Example 2: A PM 2.5 continuous FEM operated by an air agency is found to have a significant bias compared to a collocated FRM. If the air agency finds cause to invalidate the data (e.g., a flow sensor is found to be outside of acceptable limits), then it should invalidate the relevant data (i.e., data from the period going back to the last successful flow check or audit or other information that points to a cause that the flow sensor is not meeting its performan ce criteria) for all data uses and there is no follow

- up issue of retrospective analysis. A case of finding cause to invalidate data would be based on validation criteria found in an air agencies approved quality assurance project plan (QAPP). Example 3: A PM 2.5 continuous FEM operated by an air agency and previously identified as appropriate to compare to the NAAQS, is found to have a significant and unacceptable bias compared to a collocated FRM and there is no other reason to invalidate the data. That is , all other information points to the data being valid; however, there has been a significant shift in the comparability of the PM 2.5 continuous FEM compared to a collocated FRM (which itself is found to be operating correctly and data are valid). A signif

icant shift in the comparability would be noticeable by comparing assessments for a site from one year to the next and seeing a significant and unacceptable change in one of the key statistical metrics used in the evaluation (i.e., additive or multiplicati ve bias). Such a case of retrospectively recommending not using PM 2.5 continuous FEM data should also take into account all other available information that***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 615 of 790 Formatted: Left can help inform approving such a recommendation as part of an annual monitoring network plan. For e xample, do data from the PM 2.5 performance evaluation program data also suggest an unacceptable bias for a specific period of interest with this method as used in the air agencies network? Note: This type of assessment is often limited by the small number of samples taken in the PEP program relative to the large number of collocated samples expected when an FRM and PM 2.5 continuous FEM are collocated. In this type of example, the air agency might want to recommend not using the continuous FEM data for compa rison to the NAAQS; however, the continuous FEM data could be appropriate for use in reporting the Air Quality Index (AQI) or other data uses either as is or if statistically correlated 258 and corrected back to the collocated FRM. So in this last example, th e PM 2.5 continuous FEM data would be stored separately in the EPA’s data system so that they are eligible for use in AQI calculations, but not used in comparison to the NAAQS, if approved by the EPA. Again, the air agency should thoughtfully consider and s tate its position and rationale in the annual monitoring network plan on whether any future data should be compared to the NAAQS. Another issue to consider is the transparent and consistent use of PM 2.5 continuous FEM data from a method where one air agen cy recommends using the data for comparison to the NAAQS and another specifically recommends to not use it for comparison to the NAAQS. The use of the annual monitoring plans ensures that the process is transparent; however, it may not ensure a consistent approach if one agency recommends exclusion of data and another agency does not. For example, consider two
258 The EPA has had a long

- standing policy of allowing PM 2.5 continuous data to be statistically correlated and corrected to use in AQI reporting
. A report is available on this : See “ Data Quality Objectives (DQOs) for Relating Federal Reference Method (FRM) and Continuous PM 2.5 Measurements to Report an Air Quality Index (AQI), EPA

- 454/B

- 02

- 002, November 2002”.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 616 of 790 Formatted: Left adjacent air agencies operating the same make and model of a PM 2.5 continuous FEM, where one air agency recommends using data and the other air agency recommends not using it for comparison to the NAAQS. While on its face it may seem straightforward that a method with acceptable comparability to a collocated FRM should pe rform similarly in other air agency networks where they have similar aerosol composition and climate, in practice there are a number of other variables that affect data comparability. Such factors that lead to differences in comparability might include dif ferences in installation, training, development of SOPs, control of shelter conditions, maintenance of the continuous FEM, and performance of the FRMs which are being used as the basis of comparison to the continuous FEM. Also, there may be cases where the concentration levels are so far away from the level of the NAAQS (either substantially higher or lower) that it would not matter if the data are excluded or not, the same NAAQS determination would result. The EPA has considered these issues and in general believes that it would still be acceptable for one agency to use data for comparison to the NAAQS, while another agency does not, even if it’s the same method used in adjacent air agency networks. On the issue of grouping sites for purposes of allowing m onitors that are not collocated to be included when recommending a method should not be compared to the NAAQS, the EPA believes that it is not necessary to provide specific details on what criteria are necessary to group sites as air agencies are in the be st position to determine a recommendation of when such sites should or should not be grouped. However, to illustrate examples of possible ways to group sites, the air agency could take into account factors such as whether the sites are all in either a rura l or urban location, since urban***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 617 of 790 Formatted: Left locations tend to be impacted more directly by fresh emissions which are known to be more volatile, or whether there is consistency in the climate for the sites of interest as might be the case for sites near a large water body or at a high altitude. The EPA will consider these issues when evaluating air agency requests for approval. The EPA is finalizing its proposal to allow each air agency to specify its intention to use or not use data from continuous PM 2.5 FEMs that are eligible for comparison to the NAAQS as part of their annual monitoring network plan due to the applicable EPA Region Office by July 1 each year where adequate FRM data are available. The EPA’s approval of an annual monitoring network plan 259 as a whole, or in part, will constitute concurrence with an air agency’s recommendation to use or not use data from continuous PM 2.5 FEMs as eligible for comparison to the NAAQS , unless otherwise noted in the approval of the plan. The absence of an air agency statement specifying a position on use of data from a continuous PM 2.5 FEM for comparison to the NAAQS will be interpreted as meaning that the all such data are applicable for comparison to the NAAQS following the provisions in Part 50, Appendix N on data handling an d Part 58 on the monitoring requirements. In finalizing this decision the EPA will ensure, as proposed, that air agencies can identify already collected data from PM 2.5 continuous FEMs that should not be used for comparison to the NAAQS. After considering comments in support of allowing additional retrospective assessments, the EPA is also finalizing an approach of allowing for the continued use of retrospective assessments to inform when already collected data should not be compared to the NAAQS, if there has been a significant change in the assessment of that data from previous years.

259 Approval of an annual monitoring network plan is subject to approval of the EPA Regional Administrator as p rovided for in §58.10(a)(2).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 618 of 790 Formatted: Left

c. Revoking PM 10

- 2.5 Speciation Requirements at NCore Sites The EPA propose d to revoke the requirement for PM 10

- 2.5 speciation monitoring as part of the current suite of NCore monitoring requirements
. The requirement to monitor for PM 10

- 2.5 mass (total) at all NCore multi

- pollutant sites remains . PM 10

- 2.5 mass
m onitoring commenced on January 1, 2011 as part of the nationwide startup of the NCore network ( U.S. EPA, 2011a, p. 1

- 15). As part of the process to further define appropriate techniques for PM 10

- 2.5 speciation monitoring, a public consultation with the CASAC AAMMS on monitoring issues related to PM 10

- 2.5 speciation was held in February 2009 (74 FR 4196, January 23, 2009) . T he subcommittee noted the lack of consensus on appropriate sampling and analytical methods for PM 10

- 2.5 speciation and expressed concern that the Agency’s commitment to launch the PM 10

- 2.5 monitoring network without sufficient time to analyze the data from a planned pilot project was premature (Russell, 2009)
. Based on the noted lack of consensus on PM 10

- 2.5 speciation monitoring techniques, the Agency did implement a small pilot monitoring project to evaluate the available monitoring a nd analytical technologies
. The EPA pilot monitoring project was completed in 2011, with plans to analyze the data and prepare a final report on findings and recommendations in 201 3. At that time, the EPA will consider what PM 10

- 2.5 speciation sampling te chniques, analytical methodologies, and monitoring design strategies would be most appropriate as part of a potential nation

- wide monitoring deployment
. Such a deployment could be based on the NCore multi

- pollutant framework or some other strategy that all ows flexibility and targets measurements in areas with higher levels of coarse particles
.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 619 of 790 Formatted: Left All comments received from air agencies and multi

- state organizations were supportive of the removal of the PM 10

- 2.5 speciation requirement. A few industry commente rs raised concerns about the availability of PM 10

- 2.5 speciation data for research purposes. One environmental group opposed revoking the PM 10

- 2.5 speciation requirement and expressed the need for PM 10

- 2.5 data to support health effects research and future regulatory efforts. The EPA has considered the comments from air agencies that were all supportive of revoking the requirement , as well as the industry concern and environmental groups

concerns that PM 10

- 2.5 speciation data will not be available for resea rch. The In considering these comments, the EPA recognizes the importance of efforts to develop and evaluate speciation monitoring approaches for PM 10

- 2.5 given that t here is relatively little information available on the chemical and biological composition of PM 10

- 2.5 and on the health effects associated with the various components (U.S. EPA, 2009a, section 2.3.4). Without more information on the chemical speciation of PM 10

- 2.5 , the apparent variability in associations with health effects across locations is difficult to characterize (U.S. EPA, 2009a, section 6.5.2.3). However, the EPA believes that until a final report on the findings from the pilot study is completed in 2013 and the results of the study can be considered, PM 10

- 2.5 speciation is not ready for nationwide deployment. Therefore, the EPA is finalizing its decision to revoke the PM 10

- 2.5 speciation requirement at NCore stations. Given the continued importance of characterizing PM 10

- 2.5 species, and given that ongoing and future researc h will likely further inform the development of speciation methods, the appropriateness of requiring speciation monitoring for PM 10

- 2.5 will be revisited in future reviews.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 620 of 790 Formatted: Left d. Measurements for the Proposed New PM 2.5 Visibility Index NAAQS The EPA proposed requirements for sampling of PM 2.5 chemical speciation in states with large C BSAs. However, as explained in s ection VI, the EPA is not finalizing the proposed secondary PM 2.5 visibility i ndex NAAQS and therefore is not finalizing the proposed monitoring ch anges associated with that standard. 4. Revisions to the Quality Assurance Requirements for SLAMS, SPMs, and PSD

a . Quality Assurance Weight of Evidence The EPA propose d to use a weight

- of

- evidence approach for determining whether the quality of data is appropriate for regulatory decision

- making purposes . W hile t he EPA believes that it is essential to require a minimum set of checks and procedures in appendix A to support the successful implementation of a quality system, the success or failure of any one check or series of checks should not preclude the EPA from determining that data are of acceptable quality to be used for regulatory decision

- making purposes . Accordingly, the EPA proposed to include additional wording in appendix A to clarify the role th at appendix A generated data quality indicators have in the overall quality system that supports ambient air monitoring activities
. The EPA received eight comments on the weight of evidence approach with the majority of commenters endorsing the approach. One commenter felt that the “ paragraph, as written, undermines the importance of the quality control/quality assurance system dictated in Part 58
. ” Some that supported the approach also provided a word of caution that “ w hile a common sense approach to the assessment of quality data is important, minimum requirements are necessary to ensure scientifically

- defensible data is being used in decision making”. The EPA agrees with the commenter’s points that data should be subject to a minimum set of requirements for data collection, reporting and quality. In***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 621 of 790 Formatted: Left developing the weight of evidence approach , the EPA is not attempting to diminish the requirements of appendix A but rather ensure that other elements of a quality system that air agencies implement and are do cumented in their QAPP can also be used when judging whether data are valid for a particular monitoring objective. While the EPA considers the appendix A requirements the minimum for reporting, it is not the only data that the EPA and the air agencies use to judge quality. Therefore , if an appendix A requirement for some reason is not complete, the EPA concludes that it should not necessarily be the sole reason to declare the data invalid or unusable. One commenter who felt that the approach may be appropri ate also suggested that the language of the proposal was vague and may weaken the ability of air monitoring agencies to validate their own data and instead allows the EPA to make decisions regarding data validity. In the majority of cases when the quality of ambient air data is called into question, the EPA Regions and air agencies work together and reach consensus on data usability. The EPA agrees that the air agencies know more about their data and it is the air agencies responsibility to certify the data as valid. In most cases , the EPA and the air agencies will be in agreement on the validity and usability of this data. However, since the EPA is responsible for makin g final regulatory decisions concerning the NAAQS , in rare cases it may ultimately have to make a validity decision that the air agencies may not agree with. After consideration o f the general support received, the EPA will finalize the language as propose d. For the reasons explained above, the EPA concludes that this will not undermine the quality assurance system, but rather strengthen it. A few commenters, although supporting the weight of evidence approach, also commented that appendix A minimum require ments should not only apply to all air***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 622 of 790 Formatted: Left quality data collected by state, local, and tribal agencies, but also to “secondary” data collected by other monitoring efforts

. The EPA understands that this term is used by these commenters to either represent the C hemical Speciation and IMPROVE Network data being used to calculate light extinction for the secondary PM 2.5 visibility index NAAQS, or for criteria pollutant data collected by entities other than the state, local or tribal monitoring organizations. The EP A agrees with the comments that the appendix A requirements must apply to the CSN and IMPROVE data , if the data were being used for comparison to the secondary NAAQS, and included the term “PM 2.5 CSN” to refer to both networks. However, since as explained in Section VI, the secondary PM 2.5 visibility index NAAQS is not being finalized , the EPA will be removing any text related to the CSN and IMPROVE requirements from appendix A. If the term is being used by commenters to refer to criteria pollu tant data collected by entities other than the state, local or tribal monitoring organizations then the appendix A requirements, as has always been the case, apply to those monitors

. b. Quality Assurance Requirements for the Chemical Speciation Network The EP A propose d to include requirements for flow rate verifications and flow rate audits for the PM 2.5 CSN. Air agencies currently perform t hese audits even though they are not currently required. Thus , although they w ould be considered a new requirement, they are not new implementation activities. In addition, the CSN already includes six collocated sites which the EPA proposes to include in the 40 CFR part 58 appendix A requirements. The EPA propose d that PSD sites would not be required to collocate a second set of instruments for speciated PM 2.5 mass monitoring. There were no comments that specifically addressed the addition of collocation***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 623 of 790 Formatted: Left and flow rate requirements in appendix A for the chemical speciation network (CSN) . Since these flow rates have historically been included in the Agencies ’ CSN Network Quality Assurance Project Plan and implemented for many years, air agencies may not have considered them any additional burden on the program. However, as explained in S ection VI, the secondary PM 2.5 visibility index NAAQS is not being finalized; therefore, the EPA will not include these QA requirements into appendix A since the networks will not produce data to be used for NAAQS decisions.

c. Waivers for Maximum Allowab le Separation of Collocated PM 2.5 Samplers and Monitors The EPA proposed to allow waivers, when approved by the EPA Regional Administrator, for collocation of PM 2.5 samplers and monitors of up to 10 meters so long as the site is at a neighborhood s cale or larger. The EPA proposed to allow waivers for the maximum allowable distance associated with collocated PM 2.5 samplers and monitors. Ensuring PM 2.5 continuous FEMs and PM 2.5 FRMs meet collocation requirements (i.e., 1 to 4 meters for PM 2.5 samplers with flow rates of less than 200 liters/minute) can be challenging, since in some cases multiple instruments, FEMs installed in the shelter and FRMs installed on a platform, are being sited at the same station. The EPA believes that instruments spaced far ther apart could be maintained within the operational precision of the instruments, especially at sites located at larger scales of representation (e.g., neighborhood scale and larger). All comments received responded in support of the requirement allowin g up to 10 meter horizontal spacing for sites at a neighborhood or larger scale of representation. The EPA received no negative comments on this part of the proposal . During stakeholder presentations of the proposal, the EPA received a verbal comment that air agencies were***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 624 of 790 Formatted: Left also having difficulty meeting the one meter vertical criteria since PM 2.5 FEMs are typically housed in shelters with inlets extending through shelter roofs while the collocated FRM monitors are placed outside, usually on platforms somewh at lower to the ground
. After considering this comment, and further discussion with EPA O ffice of R esearch and Development on spacing requirements, the agency will amend the appendix A requirements to allow for a 1

- 3 meter vertical spacing which may be app roved by the Regional Administrator for sites at a neighborhood or larger scale of representation. In addition, the language will be amended to allow for waiver approvals during annual network plan approval processes. Alternatively, the existing waiver pro vision outlined in paragraph 10 of Appendix E may be used. 5. Revisions to Probe and Monitoring Path Siting Criteria

a. Near

- road Component to the PM 2.5 Monitoring Network The EPA propose d that the probe and siting criteria for the near

- road component

o f the PM 2.5 monitoring network design follow the same probe and siting criteria as the NO 2 near - road monitoring sites
. These requirements would provide that the monitoring probe be sited “...as near as practicable to the outside nearest edge of the traffic la nes of the target road segments; but shall not be located at a distance greater than 50 meters, in the horizontal, from the outside nearest edge of the traffic lanes of the target road segment” (section 6.4 of appendix E to 40 CFR part 58)

. The EPA receiv ed comments from several stakeholders on the probe and siting criteria for PM 2.5 monitors in the near

- road environment. One public health group offered detailed comments on the probe and siting criteria for PM 2.5 monitors in near

- road environments. While t

he commenter offered support for collocating the PM 2.5 monitors***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 625 of 790 Formatted: Left with NO 2 monitors in the near

- road environment, there was concern expressed regarding allowing monitors at sites of more than 15 meters from the traffic corridor which is the source of the air quality concern. The commenter points out that the EPA’s existing rules for siting localized hot spot sites in areas of highest concentration require sites at microscale locations which provide for a distance of no more than 15 meters from a major roadway . Several air agencies offered consistent comments that the inlet of the PM 2.5 monitors should be the same as that of the near

- roadway NO 2 monitors; however, one of the commenters suggested that the requirements for distance to the nearest vertical wall or obstruction should match the requirements for current micro and middle scale installations of PM 2.5 monitors. The concern expressed is that a wall or obstruction may disrupt the normal downwind flow across a roadway. In reviewing comments on probe and m onitoring path criteria for PM 2.5 monitors in near road environments, and whether to make any changes, the EPA has several issues to consider. One of the most important things to consider is what the intended network design of these monitors should be. As stated in the proposal our goal is to “better understand the health impacts of these (near

- road PM 2.5 ) exposures,” that a number of monitoring objectives can be supported by having near

- road PM 2.5 monitors, and that while it might be that the location of maximum concentration of PM 2.5 exposure from

near - roadway sources might differ from the maximum location of NO 2 or other pollutants, we proposed to require that the near

- road PM 2.5 monitors be collocated with the planned NO 2 monitors. The EPA did not propose to change the distance from obstructions for PM 2.5 monitors in its proposal. As we stated in the proposal, the planned NO 2 monitors are using several relevant***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 626 of 790 Formatted: Left factors that are also relevant for siting of PM 2.5 (e.g., ave rage annual daily traffic and fleet mix [accounting for heavy duty vehicles] by road segment) and that significant thought and review are going into the design of the near

- road stations. Therefore, the EPA is not persuaded that we should provide any additi onal constraints to the siting of the station (i.e., the distance from the roadway) than is already provided for in the NO 2 near - road monitor probe and monitoring path siting criteria. The EPA is concerned that additional constraints (i.e., to require site s within 15 meters of the road), might have some advantages, but also might unnecessarily eliminate otherwise useful near

- road locations that on balance might be a better candidate location. The EPA recognizes that there may be cases where the physical lo cation of a

near - road monitoring station is farther than 15 meters, but no greater than 15 50 meters from the roadway, but such cases are presumed to still be the most useful location for the siting of the NO 2 monitors, which we then proposed to collocate w ith PM 2.5 . Regardless of the actual distance of the inlet for the PM 2.5 monitor at the near

- road monitoring station, so long as it is collocated with the approved near

- road station for NO 2 and meets existing criteria, the EPA will consider this site to be appropriate as a near

- road PM 2.5 monitoring station. As explained in the proposal, there are a number of reasons to collect multi

- pollutant data in the near

- road environment. The EPA believes that these sites will be sufficient as representative maximum co ncentration sites for NO 2 and PM 2.5 in the

near - road environment and not necessarily the single maximum concentration location of each pollutant for an area. . As noted above, where an air agency believes a different location is a more appropriate site fo r a near - road PM 2.5 monitor, the EPA can use its discretion in approving a deviation from the PM 2.5 monitoring requirements as already***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 627 of 790 Formatted: Left exists in the network design criteria. A deviation would be appropriate for consideration where, for example, a state provides quantitative evidence de monstrating that peak ambient PM 2.5 concentrations would occur in a near

- road location which meets siting criteria but is not a near

- road NO 2 monitoring site . Such deviations are to be approved by the Regional Administrato r as described in section 4.7.1 of Appendix D to part 58. While it is still desirable for the near

- road stations to be as close to the road as practical, there may be differences in the scale of representation of the near

- road PM 2.5 monitor from one locati on to another, while the NO 2 near - road monitors are at the same scale of representation (i.e., micro

- scale) in different locations. This is a result of the scale of representation being based on the pollutant at a location and not the location alone. There fore, in cases where the station is 20 meters from a major road, the NO 2 measurement may still be micro

- scale, while the PM 2.5 measurement would be middle

scale if the average daily traffic count were sufficiently large enough. 260 If a site with both measure ments were 10 meters from a major road they would both be expected to be micro

- scale sites. In considering the comment on distance from obstructions, the EPA notes that a monitoring station with multiple measurements is effectively considered collocated fo r those measurements, even though the actual location of the inlets is slightly different from each other within the station. For example, a gas monitor (e.g., for carbon monoxide) may be pulling ambient air from a manifold with an inlet located on one par t of a station roof, while a PM monitor is pulling air directly from its inlet located a few meters away on the same roof. The EPA believes it is appropriate and consistent with the
260 See Table E

- 1 in Appendix E to Part 58 for defining the scale of representation of a PM sampler based on its distance to the nearest traffic lane and average daily traffic count.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 628 of 790 Formatted: Left public comment above on distance from obstructions to maintain the existin g requirements for distance from obstructions on a pollutant by pollutant basis, even if they are different for PM 2.5 and NO 2 monitors that will be at the same station. Air agencies will need to consider these distances from obstructions for each pollutant inlet probe (i.e., >1 meter for NO 2 monitors and >2 meters for PM 2.5 monitors) in locating monitors at the station. The EPA is maintaining the existing probe and siting criteria for PM 2.5 monitors; however, we are finalizing the provision that the required near

- road component of the PM 2.5 monitoring network design shall be collocated with a required NO 2 monitor at

near - road mo nitoring station. These near

- road NO 2 monitoring stations are to be sited “...as near as practicable to the outside nearest edge of the traffic lanes of the target road segments; but shall not be located at a distance greater than 50 meters, in the horizonta l, from the outside nearest edge of the traffic lanes of the target road segment” (section 6.4 of appendix E to 40 CFR part 58). The EPA is retaining the existing requirement that PM 2.5 inlets, including those at near road stations, must be >2 meters from obstructions
. \
. b. CSN Network As explained in Section VI, the EPA is not finalizing the proposed secondary standard based on a PM 2.5 visibility index and therefore will not be finalizing probe and siting criteria associated with the use of CSN measurements.

c. Reinsertion of Table E

- 1 to Appendix E The EPA propos ed to reinsert t able E

- 1 to a ppendix E of 40 CFR p art 58
. T his t able presents the minimum separation distance between roadways and probes or monitoring paths for monitoring neighborhood and urban scale ozone (O 3 ) and oxides of***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 629 of 790 Formatted: Left nitrogen (NO, NO 2 , NO x , NO y )
. This table was inadvertently removed during a previous CFR revision process . The only comments received on this topic were supportive of the reinsertion of table E

- 1; therefore, the EPA is finalizing the reinsert ion of this table, unchanged from its prior iteration, back into the CFR
. 6. Additional Ambient Air Monitoring Topics

a. Annual Monitoring Network Plan and Periodic Assessment In October of 2006, the EPA finalized new requirements for each state, or where applicable, local agency to perform and submit to their EPA Regional Offices an Assessment of the Air Quality Surveillance System (40 CFR 58.10)
. This assessment is required every five years
. The first required five year assessments were due to EPA Regional Offices by July 1, 2010
. The assessments are intended to provide a comprehensive look at each monitoring agenc y’ s ambient air monitoring network to ensure that the network is meeting the minimum monitoring objectives defined in appendix D to 40 CF R part 58, whether new sites are needed, whether existing sites are no longer needed and can be terminated, and whether new technologies are appropriate for incorporation into the ambient air monitoring network. 261 Since each agency has completed its first r equired five

- year assessment, and several monitoring rule requirements have either been added or changed since this requirement was added in 2006, the EPA th ought it wa s appropriate to review this requirement and solicit comment on any possible changes the EPA should consider that may improve the usefulness of the assessments
. Specifically, the EPA solicit ed comment 261 The EPA provides a link to these assessments on EPA’s website at: http://www.epa.gov/ttn/amtic/plans.html
. A detailed description of the requirements for the assessments is described in 40 CFR 58.10.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 630 of 790 Formatted: Left on ways to either streamline or add additional criteria for future assessments
. The EPA also propose d to remove references to “community monit oring zones” and “spatial averaging” in the annual monitoring network plans due to EPA Regional Offices by July 1 of each year
. The Agency propose d to remove these references since, as discussed in section VI I .A.2 above, the EPA propos ed to remove all references to the spatial averaging option throughout 40 CFR part 50 appendix N
. Consistent with these changes, the EPA also propose d to remove references to community monitoring zones under the annual monitoring network plans described in 4 0 CFR 58.10
. The EPA received comments from several air agencies on the five year assessments. Most comments on the five year assessments focused on the type and usefulness of assessment tools made available to air agencies during the last review. Of spec ific note were concerns that assessment tools used to evaluate networks on a regional or national basis do not provide the spatial resolution necessary to adequately assess state networks on a scale most useful to air agencies. This is especially true when attempting to evaluate smaller scale monitoring or pollutant gradients associated with near

- road and source oriented monitoring. Suggestions for improvement identified the need for the EPA to work closely with air agencies early in the next cycle of asses sments (due in 2015) so that any tools developed can be of benefit to the questions air agencies need to address for their programs. The EPA did not receive any comments on removing references to community monitoring zones specifically as it pertains to th eir listing in the annual monitoring network plans described in 40 CFR 58.10. 262 The EPA took comment on potential improvements to the five year assessments.

262 Comments on the substantive question of whether to revoke references to community monitoring zones were addressed in section VIII.B.1
.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 631 of 790 Formatted: Left All the recommendations received focused on the types of assessments to perform and ensuring that th e EPA works closely with air agencies so that assessments will be of benefit to the air agencies. No specific recommendations were made to add or remove any of the requirements of the five year assessments and consequently the EPA is not making any changes . The EPA intends to work with air agencies to ensure future tools are as helpful as practible practicable
. Consistent with the decision to end the practice of spatial averaging, the EPA is finalizing the removal of language that referenc es “community moni toring zones” and “spatial averaging” in the annual monitoring network plans due to EPA Regional Offices by July 1 of each year
. b. Operating Schedules The EPA generally requires PM 2.5 SLAMS to operate on at least a 1

- day

- in

- 3 sampling schedule, unless a red uced sampling frequency is approved such as might be the case with a site that has a collocated continuous operating PM 2.5 monitor. 263 However, in the 2006 monitoring rule amendments, the EPA finalized a new requirement for the operating schedule of PM 2.5 SL AMS sites (40 CFR 58.12)
. The new requirement stated that sites with a design value within plus or minus five percent of the 24

- hour PM 2.5 NAAQS must have an FRM or FEM operating on a daily sampling schedule
. This requirement was included to minimize any s tatistical error associated with the form of the 24

- hour PM 2.5 NAAQS (i.e., the 98 th percentile)
. In section II I .F, the Administrator is finalizing revisions to the level of the primary annual PM 2.5 NAAQS
. Accordingly, possible changes to sampling frequency requirements were also considered
.

263 All NCore stations must operate on at least a one

- in

- three day sample frequency for filter

- based PM sampling.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 632 of 790 Formatted: Left The EPA had previously considered how sample frequency affects the Data Quality Objectives in a consultation with the CASAC AAMMS in September of 2005 (70 FR 51353 to 51354, August 30, 2005)
. As a result of tha t consultation, the EPA proposed (71 FR 2710 to 2808, January 17, 2006) and finalized (71 FR 61236 to 61328, October 17, 2006) changes to the sample frequency requirements as part of the monitoring rule changes in 2006
. In that work, the EPA demonstrated t hat having a higher sample count is generally more useful to minimize uncertainty for a percentile standard than an annual average . Given the decision to strengthen the primary annual PM 2.5 NAAQS and the known burden of performing daily sampling using the filter

- based samplers that are still a mainstay in monitoring agency networks, the issue of needing daily sampling for sites that have design values close to the level of the 24

- hour PM 2.5 standard was reconsidered if the site already has a design value ab ove the level of the primary annual PM 2.5 NAAQS
. In a related issue, since the EPA finalized the requirement for daily sampling at sites within 5 percent of the 24

- hour PM 2.5 NAAQS in 2006, there has been confusion over the procedures for adjusting sample frequencies, where necessary, to account for variations in year

- to
- year design values
. Therefore, the EPA propose d to revise this requirement in the following ways: (1) The EPA propose d that monitors would only be required to operate on a daily schedule i f their 24

- hour design values we re within five percent of the 24

- hour PM 2.5 NAAQS and the site ha d a design value that wa s not above the level of the annual PM 2.5 NAAQS
. (2) The EPA propose d that review of data for purposes of determining applicability of this requirement at a minimum be included in each agency’s annual monitoring network plan described in 40 CFR 58.10 based on the***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 633 of 790 Formatted: Left three most recent years of ambient data that were certified as of the May 1 annual deadline
. However, monitoring agencies may r equest changes to sample frequency at any time of the year by submitting such a request to their applicable EPA Regional Office
. Changes in sampling frequency are expected to take place by January 1 of the following year . Increased sampling is expected to be conducted for at least three years, unless a reduction in sampling frequency has been approved in a subsequent annual monitoring network plan or otherwise approved by the Regional Administrator
. Comments received on the sample frequency requirements fo r PM 2.5 were from air agencies, who were generally supportive of the EPA’s proposed approach. The EPA is finalizing its proposal to modify the sample frequency requirements for triggering daily sampling so that only those areas with 24

- hour design values w ithin five percent of the 24

- hour PM 2.5 NAAQS and where the design value site is not above the level of the annual PM 2.5 NAAQS would be required to operate on a daily sample frequency. The EPA is also finalizing all other aspects of this part of the proposal.

c. Data Reporting and Certification for CSN and IMPROVE Data The EPA is not finalizing its proposal on minor changes to reporting and certification of data associated with CSN and IMPROVE networks since as explained in Section VI, EPA is not finaliz ing a secondary standard to support visibility impairment that would have used CSN and IMPROVE data. d. Requirements for Archiving Filters The EPA propose d to extend the requirement for archival of PM 2.5 , PM 10 , and PM 10

- 2.5 filters from manual low

- volume samplers (samplers with a flow rate of less than 200 liters/minute) at SLAMS from one year after data collection to five years after data***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 634 of 790 Formatted: Left collection
. The archive of low

- volume PM filters is an important tool resource for on

g oing research and development of emission control strategies and for use in health and epidemiology research
. During a workshop on Ambient Air Quality Monitoring and Health Research in 2008, retaining filters for laboratory analysis was identified as a key recommendation to provide daily measurements of metals and elements ( U.S. EPA, 2008d, pp. 17 to 21) . The EPA’s previous requirement of oneyear one - year is not sufficiently long for retrospective analysis of important episodes and for use in long

- term epide miology research . Since first initially requiring filter archival of low

- volume PM filters in 1997, the EPA has always recommended longer archiving of filters and most agencies are already doing so
. However, a small number of agencies have reported discardi ng older filters, despite the minimal cost of storing these filters. Since cold storage of a large number of filters may be cost prohibitive and of little benefit in retaining key aerosol species in the x

- ray fluorescence (XRF) analyses, the EPA proposed t o minimize the costs of retaining filters by only requiring cold storage during the first year after sample collection
. All comments received on this issue were from air agencies, which were largely supportive of such a change to this requirement. One ai r agency did report that it would present a hardship to store filters for such a long period of time as they did not have the room to support such a requirement. The EPA is finalizing the requirement for archival of PM 2.5 , PM 10 , and PM 10

- 2.5 filters from manual low

- volume samplers (samplers with a flow rate of less than 200 liters/minute) at SLAMS for a minimum of five years after data collection
. , with cold storage only required for the first 12 months of archiving. The EPA will work close ly***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 635 of 790 Formatted: Left with air agencies through its EPA Regional Offices and laboratories to support any air agency unable to store filters for the new five year requirement. IX. Clean Air Act Implementation Requirements for the PM NAAQS This section of the preamble discusses the general approach for air agencies 264 to meet certain CAA requirements for implementing the revised primary annual PM 2.5 NAAQS as part of the revised suite of NAAQS for PM. In accordance with CAA section 107(d), the PM NAAQS revisions trigger a process un der which states must and tribes may make recommendations to the Administrator regarding area designations, and the EPA will take final action on those designations. Under section 110 of the CAA and related provisions, states are also required to submit, f or EPA the EPA ’s approval, SIPs that provide for the attainment and maintenance of the revised NAAQS through control programs directed at sources of direct PM 2.5 and precursor emissions. If a state fails to adopt and implement the required SIPs by the time periods provided in the CAA, the EPA has responsibility under the CAA to adopt a Federal Implementation Plan (FIP) to assure that areas attain the NAAQS in an expeditious manner. Additionally, emissions sources and air agencies must address the revised PM NAAQS in the context of preconstruction air permitting requirements and the transportation conformity and general conformity processes. In addition to today’s revisions to the primary annual PM 2.5 NAAQS, the EPA is taking final action on a limited subset of implementation

- related program elements, to provide a workable transition to implementing the revised standards under the PSD permitting program and to clarify the anticipated schedule for initial area

264 This a nd all subsequent references to “air agency” are meant to include state, local and tribal agencies responsible for the implementation of a PM 2.5 control program.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 636 of 790 Formatted: Left designations. PSD implementation provision. To facilitate timely implementation of the PSD requirements resulting from the revised NAAQS, which would otherwise become applicable to all PSD permit applications upon the effective date of this final PM NAAQS rule, the EPA is finalizing a grandfatherin g provision for pending permit applications as originally proposed.
. This final rule incorporates revisions to the PSD regulations that provide for grandfathering of PSD permit applications that have been determined to be complete on or before December 14, 2012 or for which public notice of a draft permit or preliminary determination has been published as of the effective date of today’s revised PM 2.5 NAAQS. Accordingly, for projects eligible under the grandfathering provision, sources must meet the require ments associated with the prior primary annual PM 2.5 NAAQS rather than the revised primary annual PM 2.5 NAAQS. The EPA also proposed to implement a surrogacy approach for addressing PSD requirements associated with the proposed distinct secondary visibili ty index NAAQS. As described in section VI, the EPA is not finalizing a distinct secondary visibility index standard at this time and therefore the proposed surrogacy approach for implementing such a standard under the PSD program is unnecessary. Additiona lly, as discussed in section IV, today’s final rule does not include any changes to the existing PM 10 NAAQS. Accordingly, this section of the preamble does not include any discussion of implementation specifically related to the PM 10 NAAQS. Under the sched ule in section 107(d)( 1 ) of the CAA, as confirmed in this action, state Governors and tribes, if they choose, are required to submit their initial designation recommendations for the revised primary annual PM 2.5 NAAQS to the EPA no later than 1 year follow ing promulgation of the revised NAAQS (i.e., by December 13, 2013). The***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 637 of 790 Formatted: Left EPA will provide designation guidance to air agencies concurrent with, or very shortly after today’s final NAAQS rule to assist them in formulating their designation recommendations. T he EPA intends to complete initial designations for the revised primary annual PM 2.5 NAAQS by December 12, 2014 using available air quality data from the current PM 2.5 monitoring networks. In addition to describing the limited subset of NAAQS implementatio n elements PSD grandfathering provision being finalized in today’s rule and responding to associated public comments, this section of the preamble describes the EPA’s future plans for addressing the remaining aspects of implementation, such as infrastructur e SIP submittals and nonattainment area planning. In the proposed rule, the EPA solicited preliminary comment on some of the issues that the Agency anticipates will need to be addressed in future guidance or regulatory actions related to implementation of the revised PM 2.5 NAAQS. The EPA received comments on a few of these issues and, as explained in greater detail later in this section, the EPA either has considered or will consider, as appropriate, all substantive comments received as future guidance and regulations proposed rules are developed. A. Designation of Areas 1. Overview of Clean Air Act Designations Requirements After the EPA establishes or revises a NAAQS, the CAA requires the EPA and the states to take steps to ensure that the new or revised NAAQ S is met. The first step, known as the initial area designations, involves identifying areas of the country that either meet or do not meet the new or revised NAAQS along with the nearby areas contributing to violations. Section 107(d)(1) of the CAA states that, “By such date as the***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 638 of 790 Formatted: Left Administrator may reasonably require, but not later than 1 year after promulgation of a new or revised national ambient air quality standard for any pollutant under section 109, the Governor of each state shall ... submit to the A dministrator a list of all areas (or portions thereof) in the State” that designates those areas as nonattainment, attainment, or unclassifiable. 265 Section 107(d)(1)(B)(i) further provides, “Upon promulgation or revision of a NAAQS, the Administrator shall promulgate the designations of all areas (or portions thereof) ... as expeditiously as practicable, but in no case later than 2 years from the date of promulgation. Such period may be extended for up to one year in the event the Administrator has insufficien t information to promulgate the designations.” The term “promulgation” has been interpreted by the courts with respect to the NAAQS to be signature and widespread dissemination of a rule. By no later than 120 days prior to promulgating designations, the EP A is required to notify states of any intended modifications to their recommendations, including area boundaries, that the EPA may deem necessary. States then have an opportunity to demonstrate why the EPA's intended modification is inappropriate. Whether or not a state provides a recommendation, the EPA must timely promulgate the designation that it deems appropriate. While section 107 of the CAA specifically addresses states, the EPA intends to follow the same process for tribes that choose to make a reco mmendation to the extent practicable, pursuant to section 301(d) of the CAA regarding tribal authority, and the Tribal Authority Rule (63 FR 7254 ; , February 12, 1998). To provide clarity and consistency in doing so, the EPA issued a 2011 guidance memorandum on working with tribes during the designations

265 While the CAA says “designating” with respect to the Governor’s list, in the full context o f the CAA section it is clear that the Governor actually makes a recommendation to which the EPA must respond via a specified process if the EPA does not accept it.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 639 of 790 Formatted: Left process (Page, 2011). 2. Proposed Designations Schedules When the EPA proposed the new and revised PM NAAQS on June 29, 2012, the EPA indicated an intention to follow the standard 2

- year schedule for initial area designations for both the revised primary annual PM 2.5 standard and the proposed secondary PM visibility index standard, noting that promulg ating initial area designations for these standards on the same schedule would provide early regulatory certainty for states. Under this approach , the EPA intended to complete initial designations for both the revised primary annual PM 2.5 NAAQS and the sec ondary PM visibility index NAAQS by December 2014 using available air quality data from the current PM 2.5 and speciation monitoring networks using the most recent 3 consecutive years of certified air quality monitoring data (i.e., most likely data from 201 1

- 2013). The EPA’s June 29, 2012 , notice proposed new requirements for establishing

near - road PM 2.5 monitors in certain cities (section VII VII I .B.3.b.i of the proposal) and new requirements for each state with a CBSA over 1 million in population to add or relocate an existing CSN (or IMPROVE) monitoring site in at least one of its CBSAs to collect speciated PM 2.5 data to support implementation of the proposed secondary standard to address visibility impairment (section VII VI I I .A.2 of the proposal). The EPA anticipated that 3 consecutive years of air quality data from any near

- road monitoring sites or newly placed CSN (or IMPROVE) PM 2.5 speciated monitoring site would not be available until 2018. The timing for both of these proposed monitoring changes would preclude the use of the collected data in initial area designations, and therefore, the EPA stated in the proposal that initial area designations would not take into account***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 640 of 790 Formatted: Left monitoring data from any newly established near

- road monitoring sites, nor from n ewly established speciation monitoring sites. 3. Comments and Responses The EPA received numerous comments on the proposed designations schedules from states, state organizations, local air pollution control agencies, regional organizations, industry, environmental organizations, and health

- related organizations. Most commente rs expressed support for a standard 2

- year schedule for initial area designations for the primary annual standard. Several commenters also encouraged the EPA to consider an additional year for initial area designations associated with the proposed secondar y PM visibility index standard due to the lag in obtaining data from speciation monitoring networks, the variability in monitored relative humidity data, and the “unique” nature of the proposed secondary standard. For the reasons stated in section VI.D.2, the Administrator has decided not to establish the proposed distinct secondary standard to address visibility impairment, and therefore, the EPA will not promulgate initial area designations for a secondary PM visibility index standard. Because data are
cu rrently available from numerous existing PM 2.5 mass monitoring sites to determine compliance with the revised primary annual PM 2.5 NAAQS , the EPA believes it is appropriate to pursue a standard 2

- year schedule for initial area designations for the primary annual PM 2.5 NAAQS. The EPA also received numerous comments related to the use of data from the proposed new near

- road monitors in the d esignations process. Several commenters asked the EPA to clarify whether these data will be used if available for initial area designations. Others asked the EPA to provide guidance related to establishing***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 641 of 790 Formatted: Left boundaries for areas containing violating near

- roa d monitors. One commenter suggested that the EPA conduct dispersion modeling around transportation facilities in accordance with the EPA’s transportation conformity hotspot modeling guidance and use concentrations to determine attainment status for designa tions process. This same commenter also supported using modeling for unmonitored areas, e.g., communities near roadways. As previously stated, section As previously stated, the EPA does not believe that data from the new near

- road monitors will be availabl e for the EPA to consider within the timeframe for initial area designation provided by the CAA. S ection 107(d)(1)(B) of the CAA requires the EPA to designate areas no later than 2 years following promulgation of a new or revised NAAQS, or by December 2014 . (The CAA provides the Agency an additional third year from promulgation should there be insufficient information on which to make compliance determinations). For initial area designations for the primary annual PM 2.5 NAAQS, the EPA relies exclusively on monitoring data to identify areas to be designated nonattainment due to violations of the standards and then uses other information to identify areas contributing to violations
. in those areas
. See Catawba County v. EPA , 571 F.3d 12

- 13 (D.C. Cir. 2009) . As indicated in the notice for the proposed PM NAAQS proposal , the initial set of near - roadway PM 2.5 monitors are not expected to will be fully deployed until by January 2015, with the requisite 3 years of air quality data available in 2018. 266 The EPA intend s to proceed with initial area designations using 3 years of consecutive air quality data from the existing, area

- wide FRM/FEM/ARM PM 2.5 monitoring sites to complete designations by December 2014.

266 T he remainder of the near - road monitors in CBSAs with populations between 1 million but less than 2.5 million will be deployed by Jan uary 1, 2017.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 642 of 790 Formatted: Left The EPA intends to consider data from all PM 2.5 monitors me eting these criteria and would include near

- road data, if available. Consistent with previous area designations processes used in informing boundary decisions, the EPA would then use analyze a variety of area - specific factor analyses information 267 in determining which nearby areas contribute to a violation. As previously indicated, the EPA relies on monitoring data to identify areas to be designated nonattainment due to violations of the standards and does not intend to conduct or use dispersion modeli ng around transportation facilities or in unmonitored areas to determine whether an area is violating the primary annual PM 2.5 NAAQS for purposes of establishing nonattainment areas as this is not required by the statute. See Catawba County v. EPA , 571 F.3 d 12

- 13 (D.C. Cir. 2009) . The EPA intends to address the factor analysis use of area

- specific information and the boundary setting process, including the presumptive starting area boundary, in the designation guidance to the states, expected to be available shortly after promulgation of the PM NAAQS. 4. Final Intended Designations Schedules In this final rule, the EPA is setting a revised, more protective primary annual PM 2.5 NAAQS. After considering the public comments and for the reasons discussed above, the EPA intends to designate areas for the primary annual PM 2.5 NAAQS on a 2

- year schedule from signature of this final PM NAAQS rule, as prescribed in CAA section 107. 268 Under the schedule in section 107(d)(1) of the CAA, as confirmed in this action,

267 The EPA has used area

- specific factor analyses information to support boundary determinations by evaluating factors such as air quality data, emissions and emissions

related data, meteorology, geography/topography, and existing jurisdictional boundaries. This may include, as appropriate, information from non

- FRM/FEM/ARM monitors and air quality modeling, where available, to help define an appropriate boundary for areas contributing to FRM/FEM/AR M

- based monitored violations. 268 While the EPA intends to make every effort to designate areas for the primary annual PM 2.5 NAAQS on a 2

- year schedule, the EPA recognizes that new information may later Formatted: Font: 12 pt***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 643 of 790 Formatted: Left
state Governors and tribes, if they choose, are required to submit their initial designation recommendations for the revised primary annual PM 2.5 NAAQS to the EPA no later than 1 year following promulgation of the revised NAAQS (i.e., by December 13, 2013). The se recommendations should be based on air quality data from the years 2010 to 2012. If the EPA intends to make any modifications to a state's or tribe’s recommendations, the EPA is required to notify the state or tribe no later than 120 days prior to final izing the designation; this would be no later than August 14, 2014. States and tribes will then have an opportunity to demonstrate why the EPA's intended modification is inappropriate before the EPA makes the final designation decisions. Prior to the EPA’s signing a final rule by December 12, 2014, promulgating the initial area designations for the 2012 primary annual PM 2.5 NAAQS, data from 2013 may be available. If so, the EPA’s designations decisions will be based on air quality data from the years 2011 t o 2013. States and tribes may update their recommendations when these new data become available. In the proposal, the EPA stated its intention to provide technical information and guidance to states shortly after promulgation of the NAAQS to assist states and tribes in the development of their designation recommendations. The EPA understands that developing recommendations on appropriate nonattainment area boundaries is a significant effort for states, especially for states with little or no experience in PM 2.5 air quality planning. Therefore, the EPA plans to assist states throughout the designations process on technical and policy

- related issues through outreach efforts that will provide information and data sources relevant to making designations decisio ns. The EPA will arise that justifies the need for additional time, up to 1 additional year available based on insufficiency of data, to complete the process. Any subsequent change to the designations schedule would be announced.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 644 of 790 Formatted: Left include such information for the revised primary annual PM 2.5 NAAQS on the general PM 2.5 designations website at http://www.epa.gov/pmdesignations. The EPA also encourages states and tribes to consult with their EPA regional office as they develop their area recommendations. B. Section 110(a)(2) Infrastructure SIP Requirements The proposal described the CAA requirements for air quality management infrastructure SIPs that states must submit to the EPA within 3 years after promulgation of a new or revised primary standard. As discussed in the proposal, while the CAA allows the EPA to set a shorter time for submission of these SIPs, the EPA does not currently intend to do so. In the proposal, the EPA solicited comment on infrastructure SIP submitt al timing, in addition to “all aspects” of infrastructure SIPs, for the Agency to consider in developing future guidance. The EPA received comments recommending that the EPA provide states an additional 18 months to submit SIPs for any revised secondary st andard, but because the Agency is not revising the secondary NAAQS in this rule, the issue of whether or not to allow states extra time to submit infrastructure SIPs for the secondary NAAQS is now moot. The EPA received several comments on other aspects of infrastructure SIPs, which are being considered in the development of a forthcoming guidance document on section 110 infrastructure SIP requirements that will apply to all NAAQS, including the revised PM 2.5 NAAQS. In addition, the EPA may issue supplement al infrastructure SIP guidance specific to the revised PM 2.5 NAAQS if needed. C. Implementing the Revised Primary Annual PM 2.5 NAAQS in Nonattainment Areas In the proposal, the EPA described the basic CAA requirements that govern SIP submittals for nonattai nment areas (77 FR 39019

- 21; 38890, June 29, 2012 at 39019

- 21 ). The Agency did not propose any particular approach for implementing any revised PM 2.5***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 645 of 79 0 Formatted: Left standards, but rather indicated its intent to carry out a notice

- and

- comment rulemaking to propose and issu e a final implementation rule that will w ould spell out the implementation requirements for the revised primary annual PM 2.5 NAAQS and the revised monitoring regulations. The EPA acknowledges that several states and industry groups commented on the need for the EPA to issue an implementation rule, either in proposed or final form, simultaneous with this final PM NAAQS rule. Other commenters commented that the EPA should consult with states and local air agencies to develop the future implementation rule and to do so expeditiously, while another state commenter requested that the EPA commit to firm deadlines for issuing the future implementation rule and guidance related to infrastructure SIPs, among other things. We acknowledge The EPA acknowledge s states’ ne ed for timely guidance on how to implement the revised NAAQS. However, due to the number of unique and complex issues associated with the PM NAAQS proposal and uncertainty about the outcome of the final NAAQS, the EPA is not able to propose an implementati on rule or finalize any aspect of the implementation program beyond a limited subset of issues (related to the PSD permitting program and initial area designations) grandfathering provision discussed later in this section at this time. Because we agree that it is beneficial to engage with air agencies early in the rule development process, however, we have initiated such discussions to inform the upcoming proposed rule. The EPA intends to finalize the implementation rule around the time the initial area desi gnations process is finalized. One particular implementation

- related issue that the EPA sought preliminary comment on in the proposal was the concept of a transition period during which any changes in monitoring requirements would not affect attainment pl ans and maintenance***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 646 of 790 Formatted: Left plans for the 1997 and 2006 PM 2.5 NAAQS. The EPA received a range of comments both in support of and in opposition to such a concept. Upon further analysis of the potential effect of monitoring requirement changes, and in consideration of comments received, we believe that it will not be necessary to provide for such a transition period in the future implementation rule because the changes in monitoring requirements included in this final rule would not automatically affect attainment pl ans and maintenance plans for the 1997 or 2006 PM 2.5 NAAQS. Specifically, there are currently approximately ten PM 2.5 air quality monitors that have been identified as not comparable to the annual standard standard s as part of the annual state monitoring pl an revision process. If a state chooses to revise the status of one of these monitors in order to make it comparable to the annual standard standard s because it is determined to be representative of many other similar locations, it would propose a change in status for that monitor in the next revision of the state PM 2.5 monitoring plan (state revisions are due in June of each year). The EPA would then review and take action on the state's proposed change. The EPA believes that the monitoring plan revision pr ocess provides adequate procedural steps for identifying which monitors are to be comparable to the annual PM 2.5 standard standard s . Thus for this reason, there is no need to include any "transition period" in a future rule. The EPA appreciates the input re ceived from commenters on implementation issues and will take it into consideration as we continue to work with air agencies to develop our proposed implementation rule. I n developing the future implementation rule proposal , t he EPA also plans to address any potential impact of the monitoring requirement changes being finalized in this rule, particularly on attainment planning and development of attainment demonstrations by states, and in doing so, we will consider***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 647 of 790 Formatted: Left the preliminary comments received on this topic
. D. Prevention of Significant Deterioration and Nonattainment New Source Review Programs for the Revised Primary Annual PM 2.5 NAAQS The CAA requires states to include SIP provisions that address the preconstruction review of new stationary sources and the modification of existing sources. The preconstruction review of each new and modified source generally applies on a pollutant

- specific basis and the requirements for each pollutant vary depending on whether the area is designated attainment (or unclass ifiable) or nonattainment for that pollutant. Parts C and D of title I of the CAA contain specific requirements for the preconstruction review and permitting of new major stationary sources and major modifications, referred to as the PSD program and the no nattainment new source review (NNSR) program, respectively. Collectively, those permit requirements are commonly referred to as the “major NSR program” because of their applicability to new major stationary sources and major modifications. Today’s final r ule revising the primary annual PM 2.5 NAAQS will affect PSD permitting requirements as of the effective date of today’s final rule, [INSERT DATE 60 DAYS AFTER DATE OF PUBLICATION IN THE FEDERAL REGISTER] , which is also the effective date of the revised PM 2 .5 NAAQS. In addition, certain NNSR permitting requirements related to the revised PM 2.5 NAAQS will take effect on and after the effective date of any nonattainment area designation for PM 2.5 . In order to minimize potential delays for pending PSD permit ap plications and to provide a reasonable transition, the EPA is finalizing a grandfathering provision for PSD permit applications that have reached a specified milestone in the permitting process. This final rule incorporates revisions to the PSD regulations that provide for grandfathering of PSD***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 648 of 790 Formatted: Left permit applications for which the reviewing authority has determined the application to be complete on or before December 14, 2012 or for which the reviewing authority has first published public notice that a draft permit or preliminary determination for the permit has been issued prior to the effective date of today’s revised PM NAAQS. Accordingly, projects eligible under the grandfathering provisions provision must meet the requ irements associated with the prior primary annual PM 2.5 NAAQS rather than the revised primary annual PM 2.5 NAAQS. As discussed in more detail in the following sections, the EPA is not now making any changes to the PM 2.5 increments, nor are we revising any of the screening tools that are now used to implement PSD the major NSR program for PM 2.5 . These screening tools include the significant emission rate (“SER”), used as a threshold for determining whether a given project is subject to major NSR permitting re quirements under both PSD and NNSR; the significant impact levels (“SILs”), used to determine the scope of the required air quality analysis that must be carried out in order to demonstrate that the source’s emissions will not cause or contribute to a viol ation of any NAAQS or increment under the PSD program; and the significant monitoring concentration (“SMC”), a screening tool used to determine whether it may be appropriate to exempt a proposed source from the requirement to collect preconstruction ambien t monitoring data as part of the required air quality analysis. 1. Prevention of Significant Deterioration The PSD requirements set forth under part C (sections 160 through 169) of the CAA apply to new major stationary sources and major modifications locating in areas designated as “attainment” or “unclassifiable” with respect to the NAAQS for a particular***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 649 of 790 Formatted: Left poll utant. The EPA regulations addressing the statutory requirements under part C for a PSD permit program can be found at 40 CFR 51.166 (containing the PSD requirements for an approved SIP) and 40 CFR 52.21 (the federal PSD permit program). For PSD, a “major stationary source” is one with the potential to emit 250 tons per year (tpy) or more of any air pollutant, unless the source or modification is classified under a list of 28 source categories contained in the statutory definition of “major emitting facilit y” in section 169(1) of the CAA. For those 28 listed source categories, a “major stationary source” is one with the potential to emit 100 tpy or more of any air pollutant. A “major modification” is a physical change or a change in the method of operation o f an existing major stationary source that results in a significant emissions increase and a significant net emissions increase of a regulated NSR pollutant. Under PSD, new major sources and major modifications must apply best available control technology (BACT) for each applicable pollutant and conduct an air quality analysis to demonstrate that the proposed construction source or project will not cause or contribute to a violation of any NAAQS or PSD increments ( see CAA section 165(a)(3); 40 CFR 51.166(k); 40 CFR 52.21(k)). PSD requirements also include in appropriate cases an analysis of potential adverse impacts on Class I areas ( see sections 162 and 165 of the CAA). PSD permitting requirements generally first became applicable to PM 2.5 in 1997, on the e ffective date of the NAAQS for PM 2.5 (Seitz, 1997). The EPA’s regulations define the term “regulated NSR pollutant” to include any pollutant for which a NAAQS has been promulgated or that is otherwise identified as a constituent or precursor to a NAAQS pol lutant (40 CFR 51.166(b)(49); 40 CFR 52.21(b)(50)). 269 In addition, on May

269 Under various provisions of the CAA, PSD requirements are applicable to each pollutant subject to regulation under the CAA, excluding hazardous air pollutants. The***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 650 of 790 Formatted: Left 16, 2008, the EPA amended its rules r egulations to identify certain PM 2.5 precursors (SO 2 and NO x ) as regulated NSR pollutants and adopt other provisions, such as a significant emissio ns rate for PM 2.5 , to facilitate implementation of PSD and NNSR program requirements for PM 2.5 (73 FR 28321). 270 Air agencies were required to revise their SIPs by May 16, 2011 , to incorporate the required elements of the 2008 final rule. On October 20, 2010, the EPA again amended the PSD rules r egulations at 40 CFR 51.166 and 52.21 to add PSD increments as well as two screening tools for PM 2.5 – SILs and SMC (75 FR 64864). The October 2010 final rule became effective on December 20, 2010. T he EPA indicated that the SILs and SMC for PM 2.5 , while useful tools for program implementation, are not considered mandatory elements of an approvable SIP; thus, no schedule was imposed on states for addressing those screening tools in their PSD rules. Fo r the portions of the rule that addressed the PSD increments for PM 2.5 , states were required to submit the necessary SIP revisions (at least as stringent as the PSD requirements at 40 CFR 51.166) to the EPA for approval within 21 months from the date on wh ich the EPA promulgated the new PM 2.5 increments

– by July 20, 2012. The schedule for developing and submitting the revisions specifically for the adoption of new PSD increments in state PSD programs is prescribed by the CAA section 166(b). As of October 2 0, 2011, sources for which PSD permits have been issued pursuant to the federal PSD program at 40 CFR 52.21 have been required, where definition of “regulated NSR pollutant” also includes pollutants subject to any standard under section 111 of the CAA or any Class I or II substance subject to title VI of the CAA. 270 It s hould be noted that on October 25, 2012, the definition of “regulated NSR pollutant” was revised to remove the requirement that condensable PM be included when considering “particulate matter emissions.” Accordingly, the definition now requires condensable PM to be counted for PM 10 emissions and PM 2.5 emissions, and for “particulate matter emissions” only when required by the applicable New Source Performance Standard or SIP. ( S ee 77 FR 65107.) Formatted: Font: Italic***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 651 of 790 Formatted: Left applicable, to determine their impact on the PM 2.5 increments. The PSD program currently regulates emissions of PM using s everal indicators of particles, including “particulate matter emissions” (as regulated under various new source performance standards under 40 CFR part 60), “PM 10 emissions,” and “PM 2.5 emissions.” The latter two emission indicators are designed to be cons istent with the ambient air indicators for PM that the EPA currently uses to define the PM NAAQS. As already noted, the PSD program also limits PM 2.5 concentrations by regulating emissions of gaseous pollutants that result in the secondary formation of par ticulate matter. Those pollutants, known as PM 2.5 precursors, generally include SO 2 and NO x . In addition to the NAAQS revisions contained in today’s final rule, the EPA is finalizing certain clarifications to the existing monitoring regulations codified at 40 CFR 58.30 (Special considerations for data comparisons to the NAAQS). These clarifications are presented in detail in section VIII.B.2 of this preamble. The monitoring regulations provide a basis for determining whether specific monitoring sites are co mparable to specific NAAQS. By extension, the EPA has also used the principles for making these determinations for monitoring sites to guide permitting authorities in assessing the comparability of specific receptor locations involved in PSD air quality an alyses. Receptors are used in PSD modeling analyses to predict potential air quality impacts in the vicinity of the proposed new or modified facility and in some cases also at more distant Class I areas. Since the EPA interprets the regulation at 40 CFR 58 .30 to apply in this context, the EPA will continue to use the principles in the revised regulations in guiding PSD modeling analysis design. Accordingly, the EPA recommends that air agencies qualify or disqualify specific receptor locations used in PSD ai r quality analyses Formatted: Font color: Black, Not Superscript/ Subscript Formatted: Font color: Black, Not Superscript/ Subscript***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 652 of 790 Formatted: Left are evaluated consistent with the final monitoring provisions adopted in this regulation, and we intend to do so ourselves when we are the permitting authority regulations, as amended by today’s rule

. a. Transition Provision (Grandfather ing) i. Proposal As discussed previously in this preamble, today’s final rule establishes a revised level of the primary annual PM 2.5 NAAQS. 271 Longstanding EPA policy interprets the CAA and EPA regulations at 40 CFR 52.21(k)(1) and 51.166(k)(1) to generally require that PSD permit applications include a demonstration that new major stationary sources and major modifications will not cause or contribute to a violation of any NAAQS that is in effect as of the date the PSD permit is issued (Page, 2010a; Seitz, 1997). Thus, as a result of today’s final rule, any proposed major new and modified sources with permits pending at the time the PM 2.5 NAAQS changes take effect would be expected to demonstrate compliance with the revised standard, absent some type of transition provision exempting such applications from the new requirements. In order to provide for a reasonable transition into the new PSD permitting requirements that will result from the revision of the primary annual PM 2.5 NAAQS (primarily the requirement to demonstrate that emissions will not cause or contribute to a violation of the revised NAAQS) and the changes to the monitoring re quirements discussed earlier, the EPA proposed to add a grandfathering provision to the federal PSD program codified at 40 CFR 52.21 that would apply to certain PSD permit applications that are pending on the effective date of the revised PM 2.5 NAAQS. Spec ifically, the EPA

271 The EPA is also revising the form of the annual primary stand ard by removing the option for spatial averaging. However, this provision has played no role in PSD so its removal has no implications for PSD. Formatted: Font color: Black, Not Superscript/ Subscript

Formatted: Font color: Black, Not Superscript/ Subscript***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 653 of 790 Formatted: Left proposed to amend the federal PSD regulations at 40 CFR 52.21 to grandfather pending permit applications for which the Administrator or delegated air agency has published a public notice on the draft permit prior to the effective date of the revised PM 2.5 NAAQS. Qualifying applications could continue being processed in accordance with the PSD requirements applicable to the pre

- existing suite of PM NAAQS at the time the public notice on the draft permit was first published. The EPA also pro posed that air agencies that issue PSD permits under their own SIP

- approved PSD permit program should have the discretion to “grandfather” proposed PSD permits in the same manner under these same circumstances. Thus, the EPA also proposed to revise section 40 CFR 51.166 to provide a comparable exemption applicable to SIP

- approved PSD programs. In the preamble to the proposal, the EPA provided a detailed rationale and legal basis for the proposed grandfathering provision, also citing examples in which the EP A previously recognized that the CAA provides discretion for the EPA to grandfather PSD permit applications from requirements that become applicable while the application is pending (45 FR 52683, Aug. 7, 1980; 52 FR 24672, July 1, 1987; U
. S
. EPA, 2011c, pp
. 54 to 61). In summary, when read in combination, sections 165(a)(3), 165(c) and 301 272 of the CAA provide the EPA with the discretion to promulgate regulations to grandfather pending permit applications from having to address a revised NAAQS where necessar y to achieve a balance between the CAA objectives in order to protect the NAAQS on the one hand, and to avoid delays in processing PSD permit applications on the other. The EPA

272 Section 165(a)(3) of the CAA generally requires that no major emitting facility may be constructed unless the owner or operator demonstrates that emissions from construction or operation of such facility will not cause or contribute to a violation of any NAAQS or PSD increment. Section 165(c) of the CAA requires that the EPA grant or deny any completed permit application not later than one year after the date of filing of such complete application. Section 301 of the CAA authorizes the EPA to prescribe suc h regulations as are necessary to carry out the functions under the CAA.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 654 of 790 Formatted: Left has also construed section 160(3) of the CAA, which states that a purpose of th e PSD program is to “insure that economic growth will occur in a manner consistent with the preservation of existing clean air resources , ” to call for a balancing of economic growth and protection of air quality (70 FR 59587 to 59588 59582 , Oct. 12, 2005 at 59587 to 59588 ). The reasoning of those prior EPA actions is also applicable to the promulgation of revised PM NAAQS. In developing the proposed grandfathering provision, the EPA considered whether such a provision should include a sunset clause. A sunse t clause would add a time limit beyond which an otherwise eligible permit application would no longer be grandfathered from specified new PSD permitting requirements. Consistent with past grandfathering actions described above, the EPA did not propose to i nclude a sunset clause for the proposed grandfathering provision. ii. Comments and Responses The majority of commenters, including all industry and state agency representatives, supported the EPA’s proposed propos al to adopt a grandfathering provision base d on the purpose and rationale described in the preamble to the proposal. These commenters agreed that grandfathering certain pending PSD permit applications was reasonable to balance the CAA objectives to protect the NAAQS on one hand, and to avoid delays in processing PSD permit application application s on the other. They also agreed grandfathering provides a reasonable transition into the PSD requirements associated with the revised NAAQS. Industry commenters also indicated that such a provision was impor tant to economic growth and recovery, and was consistent with the purposes of the PSD program, i.e., to ensure that economic growth will occur in a manner***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 655 of 790 Formatted: Left consistent with preservation of air quality. Several state commenters pointed out that finalizing the revised PM 2.5 NAAQS without a grandfathering provision would result in a significant additional resource burden on both permit applicants and air agencies, which would have to reopen pending permit applications that have reached advanced stages in process ing to address the revised standard. The commenters further noted that there would likely be little if any environmental benefit afforded by such a process. One state agency commenter performed a preliminary review of recent PSD permitting actions and dete rmined that in all cases, the proposed primary annual PM 2.5 standard would not have led to tighter permit restrictions or reduced emissions, and that a re

- noticing of the preliminary permit decisions would accomplish nothing more than to change the margins of compliance. In other words, re

- noticing would have led to project delays with no reduction in PM 2.5 impacts. Four environmental group commenters (one representing a coalition of a health advocacy group and several environmental groups) opposed the prop osed grandfathering provision based either on concerns about further delay in implementation of the revised PM NAAQS or on a position that the proposed grandfathering provision exceeds the EPA’s statutory authority and is unlawful. Commenters challenging t he EPA’s legal authority to implement the proposed grandfathering provision contended that CAA sections 165 and 301 do not confer any authority on the EPA to grandfather PSD permit applications. The commenters asserted that CAA section 165(a) forecloses th e EPA’s proposed approach, specifically citing CAA section 165(a)(3)(B) which provides that no major emitting facility “may be constructed” unless the facility’s owner or operator demonstrates emissions from the facility will not cause or contribute to the violation of***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 656 of 790 Formatted: Left “any . . . national ambient air quality standard in any air quality control region.” These commenters further claimed that because Congress limited the applicability of the new PSD requirements in several ways, including specific grandfatheri ng relief for sources constructed before the enactment of the 1977 Amendments to the CAA, the EPA is not authorized to waive otherwise applicable statutory requirements (citing Andrus v. Glover Constr. Co. , 446 U.S 608, 116

- 17 (1980)). A subset of comment ers also stated that the EPA’s proposed grandfathering approach undermines the policy choices made by Congress in adopting the PSD program that 1) it is preferable to prevent air pollution from becoming a problem in the first place, and 2) controls should be installed when new sources are being constructed rather than as retrofits on existing sources. One commenter asserted that there is no conflict between CAA sections 165(a) and 165(c) as the EPA had implied; therefore, there is no need for the EPA to in voke the regulatory authority of CAA section 301. This commenter also concluded that the EPA’s rationale of balancing of economic growth and the protection of air quality pursuant to CAA section 160(3) was unlawful, and that the EPA had not adequately expl ained the considerations it sought to balance and how the proposal would achieve its goals. The same commenter questioned the EPA’s authority to leverage principles of equity and fairness in proposing the grandfathering provision. The commenter also object ed to the EPA’s rationale for choosing the public notice date of a draft permit as the milestone triggering the grandfathering provision, stating that the approach was contrary to statute because it would deprive interested persons of their statutory right to comment on elements of the application related to the current NAAQS.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 657 of 790 Formatted: Left The EPA does not agree with the interpretations of the CAA offered by the commenters opposing the proposed grandfathering provision. The EPA has previously exercised this discretion to establish grandfathering provisions in regulations. Indeed, the EPA has done so where provisions of the CAA contradict each other, citing the authority under section 301(a)(1) “to set transitional rules which accommodate reasonably the purpose and conce rns behind the two contradictory provisions” (45 FR 52676, August 7, 1980 at 52683). Furthermore, the EPA has noted and continues to recognize that even in the absence of a conflict between sections of the Act, “EPA would have the authority under section 3 01(a)(1) to exempt those projects in order to phase

- in new requirements on a reasonable schedule.” Id. at 52683 n. 5. There is a conflict or tension between certain provisions of the CAA that the EPA must reconcile in situations where the ability of air a gencies to complete action on a permit application within the statutory one

- year deadline is likely to be impeded if a new or revised NAAQS becomes applicable at a late stage in during the permit application review process. We do not agree with the commente rs’ arguments to the contrary. The CAA does not provide clear direction concerning how the EPA should apply section 165(a)(3) of the Act to NAAQS that become effective at such in circumstances where efforts to update a late stage in the permit application r eview process such that requiring applicants to address the new or revised NAAQS would jeopardize be time consuming and impede compliance with the CAA obligation to take action on the application within one year after the completeness determination. Since Congress has not precisely spoken to this issue, the EPA has the discretion to apply a permissible interpretation of the Act that balances the requirements in the Act to make a decision on a permit application***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 658 of 790 Formatted: Left within one year and to ensure that new and modified sources will only be authorized to construct after showing they can meet the substantive permitting criteria. Chevron, U.S.A., Inc. v. N

atural Res. Def. Council, Inc. , 467 U.S. 837, 843

- 44 (1984). Targeted grandfathering applicable to a specific NAAQS does not waive the statutory requirements in section 165(a)(3), as some commenters assert. Rather, the grandfathering provision makes clear which NAAQS are covered by this provision of the Act when it is applied to a permit application that has reached a late specific stage in the review process (i.e., the date the application is determined to be complete or the first date of publication of a public notice on the draft permit or preliminary determination ) before the effective a specified date of the revised NAAQS . Grandfathering resolves the question of how the EPA and other permitting authorities should interpret and apply section 165(a)(3) of the Act in the case of today’s PM NAAQS revisions considering the requirement of section 165(c) of the Act that reviewing authorities make a decision on a permit application within one year of the date the application was determined complete. This is not a question of whether section 165(a)(3) applies; it is a question of which NAAQS this requirement should cover in the case of a pending PSD permit. The EPA agrees that as a general rule, sections 165(a)(3) applies to “any NAAQS” that is effective as of the date a final PSD permit is initially issued (before any administrative appeal proceeding commences). However, these provisions cannot be read in isolation and should be construed in the context of other provisions in section 165 of the Act, such as sectio n 165(c). Since the EPA is required to give effect to all provisions of the Act, in those circumstances where a strict reading of sections 165(a)(3) would frustrate congressional intent that the EPA and other implementing air agencies act in a***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 659 of 790 Formatted: Left timely manne r, the Agency has the discretion to interpret the reach of section 165(a)(3) to be limited to particular NAAQS that were proposed or effective prior to specific significant milestones in the permitting process. Thus, the EPA does not agree with the view ex pressed by some commenters that section 165(a)(3) must be read strictly in all circumstances to apply to all NAAQS in effect on the date the EPA issues a final permit decision, regardless of other circumstances or other requirements of the CAA. Such a read ing fails to acknowledge or give meaning to section 165(c) of the Act. Legislative history illustrates congressional intent to avoid delays in permit processing. S. Rep. No. 94

- 717, at 26 (1976) ("nothing could be more detrimental to the intent of this sec tion and the integrity of this Act than to have the process encumbered by bureaucratic delay”). The EPA is also not persuaded that the presence of a grandfathering provision in section 168(b) precludes the EPA from establishing grandfathering exemptions i n other circumstances. The commenter’s reference to the Supreme Court’s observation that when “Congress expressly enumerates certain exceptions to a general prohibition, additional exceptions are not to be implied in the absence of evidence of a contrary l egislative intent,” Andrus , 446 U.S. at 616

- 17, is not persuasive here. The Court applied this principle in a circumstance where there was a provision of law “expressly relating to contracts of the sort at issue here.” Id. These are not the circumstances h ere. Section 168(b) of the Act does not expressly relate to the application of PSD permitting requirements to an application pending at the time of the promulgation of a new or revised NAAQS. Section 168(b) exempted facilities that were subject to permitti ng requirements under an earlier version of the PSD program created solely by the EPA***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 660 of 790 Formatted: Left regulation prior to the enactment of section 165 of the CAA and other provisions that expressly authorized and established the requirements of the PSD permitting program applicable today. This exemption operated to continue existing requirements for certain sources after a fundamental change in the statutory and regulatory regime under which such sources were required to obtain authorization to construct or modify major st ationary sources of air pollutants. Such an exemption does not expressly relate to the incorporation of a new requirement into the PSD program, under existing statutory authority, when the EPA promulgates a regulation that creates such a requirement. In th is case, the EPA is not grandfathering permit applications from the general prohibition in section 165(a) against commencing construction in the absence of a permit issued “in accordance with the requirements of this part.” The CAA does not contain any exp ress exemptions to the phrase “the requirements of this part” or from section 165(a)(3) of the Act that apply when the EPA promulgates a new or revised NAAQS. Furthermore, section 168(b) applied to sources that had commenced construction before new provisi ons of the CAA were enacted, whereas the grandfathering that the EPA proposed for purposes of the revised PM NAAQS is applicable to changes in regulatory requirements prior to the issuance of a permit. Thus, the adoption of a one

- time grandfather provision upon enactment of the statutory PSD program is clearly different from grandfathering when the EPA promulgates a new or revised NAAQS, which the Act does not address. The fact that Congress expressly enumerated an exemption in section 168 intended to ease transition upon enactment of the PSD provisions in the Act does not constrain the Agency with respect to offering reasonable transitional exemption provisions when EPA regulations create new PSD program requirements under those***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 661 of 790 Formatted: Left statutory provisions. The EP A agrees that the PSD program is based on the goals of preventing air pollution and installing controls when new sources are being constructed, but Section s ection 160(3) of the Act also states that a purpose of the PSD program is to “insure that economic g rowth will occur in a manner consistent with the preservation of existing clean air resources.” The EPA continues to construe this provision to call for a balancing of economic growth and protection of air quality. See 70 FR 59582, October 12, 2005 at 5958 7

- 88. Legislative history illustrates Congressional intent to avoid a moratorium on construction and delays in permit processing. The House Committee report describes how “the committee went to extraordinary lengths to assure that this legislation and the time needed to develop and implement regulations would not cause current construction to be halted or clamp even a temporary moratorium on planned industrial and economic development.” H.R. Rep. No. 95

- 294, 95th Cong., 1st Sess., at 171 (1977). As an illus tration of the lengths to which the committee went, the report lists five elements of the legislation, including the following statement: “to prevent disruption of present or planned sources, the committee has authorized extensive 'grandfathering' of both existing and planned sources.” Id. Furthermore, the Senate Committee report specifically discusses concerns about delays in program implementation. S. Rep. No. 94

- 717, at 26 (1976) (“nothing could be more detrimental to the intent of this section and the integrity of this Act than to have the process encumbered by bureaucratic delay”)

. In the 1980 PSD regulation, the EPA sought to strike a balance between competing goals of the CAA (45 FR 52683). The EPA explained that delaying certain construction “by im

posing new PSD requirements could frustrate economic***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 662 of 790 Formatted: Left development” and noted that the grandfathered projects “have a relatively minor effect on air quality.” Id. As a result, the EPA adopted a grandfathering provision that “would strike a rough balance betw een the benefits and costs of applying PSD to those projects.” Id. Although the EPA used issuance of permits previously required under the SIP in that case to determine eligibility for grandfathering, this precedent does not preclude the EPA from using ano ther milestone in the permit process to determine eligibility in order to strike the appropriate balance in a different situation. In 1980, the EPA concluded that determining eligibility for grandfathering based on a complete application might “exempt many more projects from review” in one particular situation addressed in 1980 and that this “would fail to give adequate expression to the interests behind section 165, especially the goal of protecting air quality.” Id. This precedent does not preclude the EPA from using the publication date of public notice of a draft permit or preliminary determination (or other milestone) in another circumstance where such a date would not exempt a large number of projects or have an adverse impact on air quality. The interests behind section 165 include both protection of air quality and timely decision

- making on pending permit applications. The EPA is seeking here to give effect to balance the requirements in the Act to make a decisi on on a permit application within one year and to ensure that new and modified sources will only be authorized to construct after showing they can meet the substantive permitting criteria. Moreover, this action is not based on an assertion of equitable power to disregard or override law, but rather on an interpretation of our statutory authority. In so doing, the EPA has in this case determined which regulatory requirements are covered by the statutory requirements that apply to a n application that has reached a specified milestone***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 663 of 790 Formatted: Left when the regulatory requirement was established. The EPA does not dispute that administrative agencies only have the powers conferred by statute. However, the EPA may interpret the statutory requirements consistent with Congressional intent and exercise its discretion in a thoughtful way in doing so. Thus, while an administrative agency in the executive branch does not have the equitable powers of a court, this does not necessarily mean an administrative agency cannot interpret its statutory authority to achieve equitable outcomes consistent with Congressional intent. Based on the foregoing, the EPA believes it has adequately explained its consideration of the CAA requirements related to both NAAQS protect ion and timely decision

- making on permit applications in designing the proposed grandfathering provision. As described below, the EPA is finalizing a grandfathering provision that applies to two categories of PSD permit applications : (1) those that the rev iewing authority has determined to be complete on or before December 14, 2012, or (2) those for which the reviewing authority has first published a public notice on the that a draft permit or preliminary determination , consistent with had been prepared prio r to the effective date of the revised PM NAAQS. In the proposal . The EPA selected this eligibility criterion because it represents a well

- documented point in time and is the latest and therefore most restrictive reasonable milestone in the permitting proc ess short of final permit issuance. As such , the EPA’s approach EPA proposed to balancing grandfather only the requirements in CAA sections 160 and 165 as finalized in this rule strongly favors NAAQS protection over exempting more projects from review under the revised PM NAAQS. As described in the proposal, before latter category, based on publication of a***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 664 of 790 Formatted: Left public notice on a draft permit or preliminary determination is issued for public comment, the applicant still has a reasonable opportunity to amend its permit application to address new or revised NAAQS that became effective while the reviewing authority’s preliminary review of the application was underway. Furthermore, the reviewing authority still has the opportunity to review additional material and re vise its fact sheet or statement of basis before beginning the public comment period on such a permit. However, if the EPA and other reviewing authorities were to require permit applicants to demonstrate that they will not cause or contribute to a violatio n of the revised PM NAAQS after the public comment period has begun, this would unduly delay the processing of the permit application by potentially requiring an additional public comment period and increased demand on the limited resources of the reviewin g authority at a time when it should be focused by the effective date of the final PM NAAQS. However, as described later in this section, based on considering consideration of public comments and preparing a final permit decision in order to conclude its re view of a permit application in a timely manner. These permit applications received on the proposal, the EPA decided to augment the grandfathering provision to include applications that had been determined to be complete on or before December 14, 2012, the date of signature of the final rule. P ermit applications qualifying under the final grandfathering provision must demonstrate that a qualifying new or modified source will not cause or contribute to a violation of the PM 2.5 NAAQS and increments in effect a s of the date the permit application is determined to be complete by the reviewing authority or as of the date the reviewing authority first publishes public notice of the draft permit or preliminary determination , depending on which prong of the grandfathering provision is***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 665 of 790 Formatted: Left applicable
. The grandfathering provision does not apply to any other applicable PSD requirements related to PM 2.5 . Sources with projects qualifying under the grandfathering provision will be required to install BACT for PM 2.5 em issions, demonstrate that project emissions will not cause or contribute to a violation of the PSD increments for PM 2.5 or the PM 2.5 NAAQS in effect at the time the permit application is determined to be complete or the public notice is first published on the draft permit or preliminary determination, and address Class I and additional impacts in accordance with the PSD regulatory requirements. Accordingly, the EPA does not expect that such a limited the grandfathering provision being finalized in today’s r ule will result in significantly different air quality impacts than would occur absent any type of grandfathering or transition provision. One commenter has submitted an analysis to support this conclusion. Finally, As described in the proposal and some of the comments received from state agencies, if the EPA disagrees that its rationale for choosing the publication date of the public notice on a draft and other reviewing authorities were to require permit applicants to demonstrate that they will not cause o r preliminary determination for public comment as the milestone triggering the contribute to a violation of the revised PM NAAQS after the public comment period has begun, this would unduly delay the processing of the permit application by potentially requi ring an additional public comment period and increased demand on the limited resources of the reviewing authority . The EPA disagrees with commenters who contend that grandfathering provision is contrary to statute because it would preclude public comment o n elements of the application related to the current NAAQS. This argument is essentially another means***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 666 of 790 Formatted: Left of challenging the EPA’s authority to implement any kind of grandfathering provision for phasing in new or revised NAAQS under the PSD program. With resp ect to an application grandfathered under the new provisions provided by today’s rule, interested persons will have the opportunity to comment on all aspects of PSD review for PM 2.5, including the air quality impacts associated with the revised NAAQS that became effective after the application was determined to be complete or after a public notice was published on the draft permit or preliminary determination , depending on which prong of the grandfathering provision applies . Section 165(a)(2) of the CAA and section 51.166(q)(2)(v) require an opportunity for the public to comment on “the air quality impact of the source” and “other appropriate considerations.” The grandfathering provision does not necessarily take away the ability of the public to comment on the impact the source may have on the revised NAAQS (including the standard proposed several months earlier) or the discretion of the permitting authority to consider these comments. However, as provided by the grandfathering provision established today in the EPA’s PSD regulations, a permit applicant is not required to complete an analysis after the start date of the public comment period applicable grandfathering milestone to demonstrate that it will not cause or contribute to a violation of the NAAQS that became effective after that date to obtain a permit. Thus, consistent with CAA section 165(a)(2), “the required analysis” will have “been conducted in accordance with regulation promulgated by the Administrator” and made available for public comment. Sever al of the commenters supporting the proposed grandfathering provision in general recommended that the EPA establish the grandfathering milestone as the date that a complete permit application is submitted (or that a submitted permit application is***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 667 of 790 Formatted: Left deemed c omplete by the reviewing agency) rather than the publication date of public notice for a draft permit or preliminary determination as proposed. These commenters pointed out the significant level of effort, resources and time involved in preparing all of th e information necessary for a complete permit application, including a BACT analysis, air quality analysis, additional impacts analyses, and a Class I area impact analysis. They claimed that it would be unfair to establish a grandfathering milestone past t he complete application date because the processes and timeframes involved in generating the draft permit or preliminary determination materials and publishing the public notice are largely out of the control of the permit applicant and vary from agency to agency. They further stated that requiring reevaluation of a proposed project to assess impacts with respect to the revised NAAQS after a permit application has been deemed complete would result in significant additional cost and delay
. Several such One in dustry commenter pointed out that the EPA’s proposed grandfathering approach could place considerable pressure on permit authorities to expedite review of publication of draft permits or decisions before adequate internal review was completed, which could result in subsequent withdrawal of the permit. Several commenters cited prior EPA grandfathering provisions that relied upon that milestone, including the 1987 PM 10 NAAQS (52 FR 24672, July 1, 1987) and the 1988 NO 2 increments (53 FR 40656, October 17, 199 8), and contended that the EPA had not justified the use of an alternative date for purposes of the proposed revisions to the PM 2.5 NAAQS. Some state commenters also indicated that the proposed draft permit public notice date milestone could result in add itional resource burden on the agency to expedite completion of draft permit packages and process public notices. Other state commenters***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 668 of 790 Formatted: Left supported the EPA’s proposed draft permit or preliminary determination public notice date as the appropriate grandfathe ring eligibility milestone, indicating that this approach would provide states and industry certainty on the NAAQS demonstration required during the PM 2.5 NAAQS transition period. We understand that using the The EPA acknowledges the comments raising

conc erns about an approach based solely on the public notice milestone date, and agrees that they warrant consideration of a different milestone date. Further, we agree that an alternate milestone for grandfathering based on the date a permit application is de termined to be complete versus the would address many of these concerns. Therefore, the EPA has modified its proposed approach to address these concerns. In particular, the EPA agrees with commenters that a substantial portion of the level of effort, resou rce investment, and time involved in the PSD permit process occurs during the process of preparing a PSD permit application and obtaining a completeness determination from the reviewing authority. Of particular importance is the issue of the time delay and the effect on permitting authorities to meet permit issuance deadlines, as previously noted. Commenters have persuaded the EPA that reevaluation of a proposed project to assess impacts with respect to the revised NAAQS after a permit application has been deemed complete would result in significant additional delay, thus frustrating the statutory requirement to complete action on a permit application within one year of the completeness date. We also agree with commenters that after the permit applicatio n completeness determination stage in the permitting process, the applicant must have completed all of the required technical demonstrations (including a BACT analysis, air quality analysis,***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 669 of 790 Formatted: Left additional impacts analyses, and Class I area impact analys e s ), a nd that the final stages of the permitting process prior to public notice (i.e., developing the draft permit or preliminary determination, developing supporting materials and publishing the public notice) are under the control of the permitting authority. Given the variable practices and timelines of permitting authorities in processing these final steps between permit application completeness and publication date of a public notice of on the draft permit or preliminary determination would likely pointed out by commenters, we agree that the proposed grandfathering approach could result in reduced inequitable and burdensome outcomes in some circumstances. The EPA has therefore concluded based on public comments that it should add an additional grandfathering m ilestone to avoid substantial additional burden for some PSD permit applicants and exempt a greater number of pending and delay for permit applications from review under the revised standard. We disagree that have reached a stage in the review process by wh ich significant resources have been expended to complete fundamental PSD analyses and demonstrations that would have to be redone. After a PSD permit application has been determined complete, it may be time consuming for the applicant t o amend its permit a pplication to address new or revised NAAQS promulgated after that date. The time required to both amend the application and review the amended application would impose unreasonable additional burden and delay upon the applicant and the reviewing authority. As a result, i f the EPA and other reviewing authorities were to require permit applicants to demonstrate that they will not cause or contribute to a violation of the revised PM NAAQS after the permit application is determined to be complete, or any later stage in the permitting process , this would unduly***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 670 of 790 Formatted: Left delay the processing of the permit application a nd place increased demand on the limited resources of the reviewing authority at a time when it should be focused on preparing the draft permit and supporting materials, preparing a public notice, considering public comments and preparing a final permit decision in order to conclude its review of a permit application in a timely manner. The EPA also agrees with commente rs’ concerns that the proposed grandfathering approach, based solely on the date of publication of a public notice on a draft permit or preliminary determination, could in some cases result in pressure on permitting authorities to expedite review of public ation of draft permits, resulting in additional burden on such permitting authorities and other potential adverse consequences. We note that expediting review is consistent with the requirement of section 165(c) of the CAA to process permit applications in a timely manner. We also observe that using the milestone of a completeness determination to determine eligibility for grandfathering could simply shift this pressure back to the stage in which a permitting authority is reviewing an application to determi ne if it is complete. A significant distinction, however that we are compelled by prior actions or by statute to establish any particular grandfathering eligibility milestone or that the complete application date is necessarily the appropriate milestone fo r grandfathering of PSD permit applications from new requirements associated with today’s revised PM NAAQS. As , is that the one

- year deadline for completing application on a permit does not begin to run until the date that a permit application is determin ed complete. Based on the comments received and the EPA’s consideration of those comments described previously above , the EPA sought has decided to strike modify the proposed***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 671 of 790 Formatted: Left grandfathering approach by adding a balance between competing goals second category of the CAA in several prior instances, including applications to the 1980 PSD regulations (45 FR 52676, August 7, 1980). Therein proposed qualifying criteria. Specifically, the EPA adopted is finalizing a grandfathering provision that used issuance of permit s previously required under the SIP to determine eligibility based on the rationale that this approach “would strike a rough balance between the benefits and costs of applying PSD to those projects.” The EPA also concluded that determining eligibility for grandfathering based on a complete application might “exempt many more projects from review” in one particular situation addressed in 1980 and that this “would fail to give adequate expression to the interests behind section 165, especially the extends gra ndfathering to permit applications that the reviewing authority has determined, on or before December 14, 2012 (the signature date of the final rule), to be complete. We are adding this category to our originally proposed category: permit applications for which the permitting authority has first published a public notice that the draft permit or preliminary determination has been prepared prior to the effective date of the revised PM NAAQS. We are adding eligibility criteria rather than wholly replacing wh at we proposed for two reasons. First, the EPA understands that there may be some permitting authorities that do not issue formal determinations that an application is complete. Applications in these jurisdictions that may in fact have been complete and fa r enough along in the review process that a public notice could be issued before the effective date of the revised NAAQS could be significantly delayed if the EPA removed the eligibility criteria based on the publication of the public notice. Second, given that the EPA proposed to establish eligibility for grandfathering based on the timing of the public notice, some permitting***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 672 of 790 Formatted: Left authorities and applicants may have anticipated that they had more time to take action to qualify for grandfathering and may have n ot acted as promptly as they could have to submit additional information or make a completeness determination. Retaining the proposed eligibility criteria avoids prejudice to parties that may have relied on the proposed rule in such a manner. For the seco nd eligibility criterion added in this final rule, the EPA chose to use the date an application is determined complete, as requested by several commenters. In several existing provisions in sections 51.166(i) and 52.21(i) of the EPA’s regulations, a pendin g application was able to quality for grandfathering if it was submitted before the applicable date but subsequently determined complete after that date. However, this historic approach can be cumbersome to implement and can lead to inconsistent implementa tion and potential abuse. These concerns stem from the fact that there is a time lag between submittal and the completeness determination during which there are typically additional data requests by the permitting authority and supplemental application mat erial submittals by the applicant. Therefore, it can be difficult to determine the specific date that the submitted application actually became complete; since this date could range from the initial submittal date, through a number of supplemental submitta l dates, to the date the permitting authority formally determines the application to be complete. The EPA has chosen to use the date an application is determined complete because this date is easier to identify and apply. For PSD permits issued under 40 CF R 52.21, the EPA’s regulations in 40 CFR part 124 define the effective date of an application as the date the permitting authority notifies the applicant that the application is complete. 40 CFR 124.3(f).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 673 of 790 Formatted: Left The EPA chose to base the second eligibility crite rion on the date this rule has been signed by the Administrator to avoid creating pressure on permitting authorities to determine applications complete. Such pressure could lead to premature findings of completeness and grandfathering of a larger number of applications than is warranted to avoid undue delays, thus increasing the air quality impact of the grandfathering provision. Notably, the one

- year deadline for completing application on a permit does not begin to run until the date that a permit applicat ion is determined complete. While Congress desired timely action on a permit application, the statute gives permitting authorities leeway to ensure they have all the necessary information to proceed expeditiously on a permit application before the clock st arts running. The goal of protecting air quality .” Id. As pointed out by commenters, can thus be fulfilled without compromising Congressional intent for timely action by conducting a careful review of an application to determine that it is complete. Appli cations that have not yet been determined complete may be supplemented to ensure the proposed source does not cause or contribute to a violation of the revised NAAQS without compromising compliance with the one

- year deadline in section 165(c). The EPA thus selected the signature date of the final rule to ensure the integrity of completeness determinations issued after the rule is signed and to limit the number of additional sources eligible for grandfathering. The final grandfathering provision appropriate ly balance s the objectives of CAA section 165 to protect of air quality and ensure timely decision

- making on permit applications , while also addressing concerns about resource burdens raised by commenters. In addition, a s pointed out by commenters, the final grandfathering provision also provides an approach that is more consistent with prior the EPA’s***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 674 of 790 Formatted: Left grandfathering actions, e.g., in the 1987 PM 10 NAAQS , wherein the EPA selected the date of application completeness for grandfathering projects from r equirements associated with the new NAAQS. These and other precedents, however, do not preclude the EPA from using the publication date of public notice of a draft permit or preliminary determination (or any other milestone) in another circumstance where i t would appropriately balance the interests of CAA section 165, including both protection of air quality and timely decision

- making on pending permit applications. The EPA proposed to establish grandfathering based on the first publication date of the pub lic notice on the draft permit or preliminary determination because, for the reasons explained above, that milestone strikes the appropriate balance between protection of the NAAQS and timely permit processing as required by the CAA. Additionally, there ar e a number of issues associated with using application completeness as the eligibility milestone for grandfathering that would complicate and potentially undermine the objectives of the grandfathering provision and the balance of these competing interests. First, the term “complete” application, although generally defined in the regulations ( see , e.g. , 40 CFR 51.166(b)(22); 40 CFR 52.21(b)(22)) has not been interpreted consistently among the many air agencies that implement the PSD program in state, local a nd tribal jurisdictions. Applications have been determined complete based on the submission of particular forms or documents alone (sometimes called “administrative completeness”) or based on a deeper assessment of whether those forms and documents contain adequate information to begin processing the application or propose a permit decision (sometimes described as “technical completeness”). The EPA has clarified that it reads the definition of “complete” to mean “technical completeness” (Page, 2012), but***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 675 of 790 Formatted: Left th is interpretation is not necessarily applied by all permitting authorities at this time. Furthermore, some air agencies do not have a formal application completeness process codified in their implementing regulations. Given these inconsistencies in the

mec hanisms and criteria for determining application completeness among reviewing agencies, the EPA does not believe that establishment of a grandfathering provision based on application completeness would provide a definitive, nationally

- consistent approach. Additionally, while some commenters pointed to potential burden associated with permit applicants pressuring reviewing authorities to expedite draft development and public notice publication, the EPA believes an equal or greater burden and potential abuse would result if the application completeness date were used as the eligibility milestone. Sources with projects much earlier in the planning process could be encouraged to hurriedly prepare and submit permit applications and pressure reviewing agencies to determine application completeness prior to the effective date of the revised PM NAAQS. Furthermore, this approach could provide an incentive for reviewing authorities to determine completeness of otherwise inadequate or incomplete applications, based on t

he varying agency criteria described above. Under that scenario, some sources would avoid having to evaluate the revised PM NAAQS without having reached the same level of completeness, threatening to tip the balance away from protection of the NAAQS and in favor of purely administrative and economic efficiency, which is not the balance of CAA provisions the EPA seeks to achieve. The EPA agrees with commenters that felt that use of the first publication date of the public notice of the draft permit or prelim inary determination will provide a more definitive and nationally

consistent milestone for grandfathering.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 676 of 790 Formatted: Left Regarding the need for a sunset clause for the grandfathering provision, the majority of commenters supported, as proposed, not including such a cla use, and no commenters specifically recommended that a sunset clause be established. Commenters pointed out that permit applicants and reviewing authorities already have strong incentives to issue final permits in a timely manner following the public notic e stage, and that a sunset clause would not add any meaningful incentive to expedite the permitting process, rather potentially causing additional delays. One commenter stated that permitting authorities have ample discretion, which they routinely use, to refuse to issue a draft permit if additional information is requested during a comment period or the agency itself wants additional information following publication of a draft permit or preliminary determination. The same commenter indicated that permitti ng authorities also have sufficient discretion to reopen permit proceedings if they consider information in an application to be stale. The EPA agrees with commenters that the addition of a sunset clause to the proposed grandfathering provision would not a dd meaningful additional incentive for sources or permitting authorities to expedite permitting processes. The EPA also agrees that a sunset clause could in fact result in further delays for permit actions that qualify for the proposed grandfathering provi sion in circumstances where unrelated and not reasonably avoidable factors cause final permit issuance to lapse beyond the sunset date. In such cases, the already delayed permit action would necessarily be further delayed to address PSD permitting requirem ents associated with the revised PM 2.5 NAAQS, potentially triggering a domino effect of newly applicable requirements. As such, the EPA believes a sunset clause would diminish the value of the grandfathering provision***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 677 of 790 Formatted: Left and likely introduce additional comple xities in relation to specific permit actions. A few industry commenters suggested, as an alternative to our proposed approach, that the EPA should effectively grandfather PSD permit actions from meeting requirements associated with the revised PM NAAQS by extending the effective date of the NAAQS by one year. These commenters argued that such an approach is preferable because it would address potential concerns about the inability of state agencies to implement the proposed grandfathering provision prior t o rule adoption and SIP approval. Several industry groups and representatives also commented that the EPA should not eliminate state discretion to grandfather individual permits even without an express exemption. The EPA disagrees with extending the effec tive date of the revised PM NAAQS by one year because this approach would entirely defer the important health benefits associated with the revised PM NAAQS. Further, as discussed in the proposal, the EPA does not anticipate any issues related to implementa tion of the grandfathering provision in SIP approved state/local jurisdictions. The EPA proposed and is finalizing a revision to 40 CFR 51.166 to provide a comparable exemption applicable to SIP

- approved PSD programs, and air agencies that issue PSD permit s under an EPA

- approved PSD permit program should have the discretion to “grandfather” proposed PSD permits consistent with these final rule provisions. Even absent an express grandfathering provision in state rules, states have the discretion to permit gr andfathering consistent with the federal regulations if the particular state’s laws and regulations may be interpreted to provide such discretion. 273 However, state SIPs may not be less stringent than federal

273 In one extraordinary case where the EPA had not previously adopted a grandfathering provision in regulations and had significantly exceeded the deadline in section 165(c) of***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 678 of 790 Formatted: Left requirements. Accordingly, the EPA believes that such discretion must be limited to applying grandfathering consistent with the federal rule provisions. iii. Final Action For the reasons articulated above, the EPA is finalizing a grandfathering provision under the PSD regulations that provides that qual ifying sources and modifications shall not be required to demonstrate that their proposed emissions will not cause or contribute to a violation of the revised primary annual PM 2.5 NAAQS but instead shall demonstrate that such emissions will not cause or co ntribute to the PM 2.5 NAAQS in effect on the date the public notice on reviewing authority determines the draft permit application to be complete or the date the public notice on the draft permit or preliminary determination is first published , depending on which prong of the grandfathering provision is applicable
. Under the final grandfathering provision, qualifying sources and modifications are those for which the reviewing authority has determined that the permit application is complete on or before Decem

ber 14, 2012 or the permitting authority has first published a public notice on the that a draft permit or preliminary determination is first published has been prepared prior to the effective date of today’s final revisions to the PM NAAQS. 274 The

the CA A, the EPA has taken the position that it may grandfather a specific source through adjudication, thus interpreting its regulations, as well as other authorities, to allow grandfathering in that extraordinary circumstance (U.S. EPA, 2011c, pp. 67 to 71). A lthough grandfathering without a specific exemption in regulations was justified based on the particular facts in that specific instance, the preferred approach is to enable grandfathering through express regulatory exemptions of the type proposed in this action (U.S. EPA, 2011c, p. 68). 274 There may be application completeness determinations or draft permits or / preliminary determinations for which a public notice was issued prior to October 20, 2011, which is the date that PM 2.5 increments became applicabl e requirements for any newly issued federal PSD permits under 40 CFR 52.21. It is not the EPA’s intention that the final grandfathering provision should relieve such a permit from the requirement to demonstrate compliance with those new PM 2.5 increments, f or which the EPA did not***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 679 of 790 Formatted: Left relevant p ublic notice requirements for the EPA and delegated agency issued permits are those in 40 CFR 124.10(c)(2), and the corresponding provisions for implementation

- plan approved agency permits are those in 40 CFR 51.166(q)(2)(iii). The grandfathering provision is being incorporated into the regulations at 40 CFR 52.21 and 51.166 to provide the same transition for the EPA, delegated jurisdictions, and implementation plan

- approved jurisdictions. The EPA is not establishing a sunset date for this grandfathering pr ovision. b. Modeling Tools and Guidance Applicable to the Revised Primary Annual PM 2.5 NAAQS Today’s final rule revising the level of the primary annual PM 2.5 NAAQS from 15.0 μg/m 3 to 12.0 μg/m 3 generally will require proposed new major stationary sources and modifications to take these changes into account as part of the required air quality analysis to demonstrate that the proposed emissions increase will not cause or contribute to a violation of the PM NAAQS. Upon the effective date of today’s final revisions to the PM NAAQS, proposed new major stationary sources and major modifications that are not grandfathered from the new requirements (as described in section IX.F.1.a) will be required to d emonstrate compliance with the suite of PM NAAQS, including the revised primary annual PM 2.5 NAAQS. PSD applicants are currently required to demonstrate compliance with the existing primary and secondary annual and 24

- hour PM 2.5 NAAQS and will need to con sider the impact of their proposed emissions increases on the revised primary annual PM 2.5 NAAQS. To assist sources and permitting authorities in carrying out the required air quality analysis for PM 2.5 under the existing standards, the EPA issued, on Marc h 23, adopt any grandfathering provisions but deferred implementation in accordance with the requirements of the CAA.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 680 of 790 Formatted: Left 2010, a guidance memorandum that recommends certain interim procedures to address the fact that compliance with the 24

- hour PM 2.5 NAAQS is based on a particular statistical form, and that there are technical complications associated with the ability of existing models to estimate the impacts of secondarily formed PM 2.5 resulting from emissions of PM 2.5 precursors (Page, 2010b). For the latter issue, the EPA recommended that special attention be given to the evaluation of monitored background air quali ty data, since such data readily account for the contribution of both primary and secondarily formed PM 2.5 from existing sources affecting the area. To provide more detail and to address potential issues associated with the modeling of direct and precurso r emissions of PM 2.5 , the EPA is now developing additional permit modeling guidance that will recommend appropriate technical approaches for conducting a PM 2.5 NAAQS compliance demonstration, which includes more adequate accounting for contributions from secondary formation of ambient PM 2.5 resulting from a proposed new or modified source’s precursor emissions. To this end, the EPA discussed this draft guidance in March 2012 at the EPA’s 10 th Modeling Conference. 275 Based on its review of comments received through the conference and further technical analyses, the EPA intends to issue final guidance by the end of calendar year 2012, prior to the effective date of t oday’s final PM NAAQS revisions. The EPA also received a number of industry and state comments on the PM 2.5 NAAQS proposal related to PM 2.5 air quality impact analyses and associated existing modeling tools and procedures. In general, commenters identified the lack of approved air quality modeling tools and procedures to predict the impacts of single source

275 The presentation on this draft guidance was posted on the EPA website at: http://www.epa.gov/ttn/scram/10thmodconf.htm
.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 681 of 790 Formatted: Left emissions on PM 2.5 concentration in ambient air as well as limitations associated with existing PM 2.5 modeling tools and guidance. Commenters recommende d the EPA address these existing issues and provide updated guidance through an open stakeholder process and preferably through notice

- and

- comment rulemaking. As described above, the EPA intends to issue revised PM 2.5 modeling guidance prior to the effecti ve date of today’s revised PM NAAQS to assist permit applicants and reviewing authorities in performing required air quality impact analyses. The EPA expects that this revised guidance will address all or most of the remaining issues related to PM 2.5 air q uality impact demonstrations under the PSD program, at least on an interim basis, until the EPA takes additional steps to improve existing regulatory models and procedures. To that end, the EPA is also pursuing regulatory updates to the Guideline on Air Qu ality Models (40 CFR part 51 Appendix W) to formalize new models and techniques as appropriate. The EPA recently granted a petition for rulemaking to specifically evaluate whether to incorporate into the Guideline new analytical technique technique s or mode ls for secondary PM 2.5 (McCarthy, 2012). The EPA anticipates that this rulemaking will be proposed by the end of calendar year 2014 or early in calendar year 2015.

c. PSD Screening Tools: Significant Emissions Rates, Significant Impact Levels, and Signifi cant Modeling Mo nitoring Concentration The EPA has historically allowed the use of screening tools to help facilitate the implementation of the NSR program by reducing the permit applicant’s burden and streamlining the permitting process for circumstances where emissions or concentrations could be considered de minimis . These screening tools, which all provide de minimis thresholds of some kind, include SERs, SILs, and a SMC. The EPA promulgated a SER for PM 2.5 in the 2008 final rule on NSR implementation a s part of the first phase of NSR***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 682 of 790 Formatted: Left amendments to address PM 2.5 (74 FR 28333, May 16, 2008). The PM 2.5 SER is used to determine whether any proposed major stationary source or major modification will emit sufficient amounts of PM 2.5 to require review under th e PSD program. 276 Under the terms of the existing EPA the EPA ’s regulations, the applicable SER for PM 2.5 is 10 tpy of direct PM 2.5 emissions (including condensable PM) and, for precursors, 40 tpy of SO 2 and 40 tpy of NO x emissions. 40 CFR 51.166(b)(23); 40 CFR 52.21(b)(23). This SER applies to permitting requirements based on both the annual and 24

- hour PM 2.5 NAAQS. The SERs are pollutant

- specific but not specific to the averaging time of any NAAQS for a particular pollut ant. Once it is determined that emissions resulting from the proposed new source or modification are significant for PM 2.5 , the permit applicant must complete an air quality analysis. 40 CFR 51.166(m)(1)(i); 40 CFR 52.21(m)(1)(i). The SIL helps to determi ne the scope of the required air quality analysis that must be carried out in order to demonstrate that the source’s emissions will not cause or contribute to a violation of any NAAQS or increment. The EPA promulgated SILs for PM 2.5 in 2010 under a final r ule that established increments, SILs, and a SMC for PM 2.5 (75 FR 64890 to 64894 64864 , October 20, 2010 at 64890 to 64894 ). Historically, the EPA and other permitting authorities have allowed permit applicants to determine the scope of analysis required t o satisfy section 165(a)(3) of the CAA by modeling their proposed emissions increase to predict ambient air quality impacts associated with that emissions increase, and by compar ing this predicted increase in ambient concentration of PM 2.5 to the applicabl e SIL, which is also expressed as an

276 The PSD rules provide that a source that would emit major amounts of any regulated NSR pollutant must undergo review for that pollutant as well as any other regulated NSR pollutant that the s ource would emit in significant amounts.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 683 of 790 Formatted: Left ambient PM 2.5 concentration over a prescribed averaging time consistent with the NAAQS and increments. The EPA notes that the current PM 2.5 SILs are the subject of a petition that challenges the EPA’s legal authority un der the CAA to develop and implement those SILs, and also alleges that the PM 2.5 SILs established by the EPA have not been adequately demonstrated to represent de minimis values. Sierra Club v. EPA, No. 10

- 1413 (D.C. Circuit Cir
. filed December Dec
. 17, 2010 ). In the course of this litigation, the EPA has recognized the need to correct the text addressing the use of the PM 2.5 SILs in the PSD regulations (40 C.F.R. 51.166(k)(2); 40 C.F.R. 52.21(k)(2)), and the EPA has asked the court to vacate and remand those provisions so that the EPA may correct them. However, the EPA does not believe this corrective action would preclude appropriate use of the PM 2.5 SILs in the interim. The EPA has not asked the court to vacate the SILs in section 51.165(b) of its regulatio ns. Furthermore, SILs that are not reflected in rules may be used if the permitting record provides adequate support that the values reflect a de minimis impact on air quality, consistent with the principles described in EPA memoranda establishing interim SILs for the one

- hour SO 2 and NO 2 NAAQS. 277 The revisions to the primary annual PM 2.5 NAAQS do not affect the continued used of the PM 2.5 SILs. Finally, the SMC, also measured as an ambient pollutant concentration (μg/m 3 ), is a screening tool used to determ ine whether it may be appropriate to exempt a proposed source from the requirement to collect pre

- construction ambient monitoring data as part of the required air quality analysis for a particular pollutant. The EPA promulgated the

277 Page, 2010c; Page, 2010d. The EPA provided similar advice before it finalized the proposed PM 2.5 SILs (Page, 2010b). See also, In re Mississippi Lime Co., PSD Permit Appeal 11

- 01, Slip. Op. at 34

- 41 (EAB August 9, 2011) and U.S. EPA, 2012 d
.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 684 of 790 Formatted: Left existing SMC for PM 2.5 i n 2010 on the basis of the defined minimum detection limit for PM 2.5 and the current information at that time concerning the physical capabilities of the PM 2.5 FRM samplers. In that rulemaking, the EPA addressed uncertainties introduced into the measuremen t of PM 2.5 due to variability in the mechanical performance of the PM 2.5 samplers and micro

- gravimetric analytical balances that weigh filter samples. Like the PM 2.5 SILs, the SMC was challenged by the Sierra Club in the same petition, and is currently und er review by the Court. In the proposal , the EPA did not propose any changes to the existing PM 2.5 SERs, SILs and SMC, but solicited preliminary comment on whether any such changes would be appropriate. The EPA also indicated that any changes to the PM 2.5 screening values would be addressed in a subsequent rulemaking that would specifically address various PSD implementation issues. The EPA received several comments from industry and state agencies regarding the existing PSD screening tools and the potenti al need to adjust associated values based on the revised primary annual PM 2.5 NAAQS. The majority of these commenters supported retaining the existing SERs, SILs and SMC for PM 2.5 (and PM 2.5 precursors in the case of the SERs), indicating that there was no compelling technical reason for revision based on the proposed revision to the primary PM 2.5 NAAQS. One industry commenter indicated that there might be a need to revise the annual PM 2.5 SILs based on the approach used in establishing the current value. H owever, this commenter and others recommended that any revisions to the PSD screening levels for PM 2.5 be accomplished through a separate notice

- and

- comment rulemaking. Several state commenters that supported retention of the current PM 2.5 SILs also urged the EPA to provide guidance on***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 685 of 790 Formatted: Left the use of those existing SILs. Two sets of collaborative comments, one from academic researchers and one from health and environmental advocacy groups, stated that the EPA should revise the current PM2.5 SERs, SILs and SMC t o reflect the revised NAAQS and true de minimis levels. Consistent with the proposal, the EPA is not making One set of collaborative comments from health and environmental advocacy groups stated that the EPA’s proposal to leave in place the PSD screening tools adopted with the previous PM NAAQS had no rational basis and was contrary to statutory requirements. Th e se commenters claim ed that the EPA has no statutory authority to establish SILs and SMC for PM 2.5 , which is the subject of current litigation in Sierra Club v. EPA , No. 10

- 1413 (D.C. Cir. filed Dec. 17, 2010). The EPA’s argument in support of the existing PSD screening tools is contained in a brief filed in that case, which is included in the docket for the final rule
. Id ., Brief of Respondent at 26

- 56 (June 26, 2012). These same commenters and one additional collaborative comment letter from academic rese archers also stated that the EPA should revise the current PM 2.5 SERs, SILs and SMC to reflect the revised NAAQS and true de minimis levels. T he EPA did not propose to make and is not finalizing any changes to the existing PM 2.5 SERs, SILs and SMC as part of this final rule. The EPA intends to consider the need for any future changes to these values in light of today’s revision of the primary annual PM 2.5 NAAQS and considering public comments received. The EPA will address any ch anges to the PM 2.5 SERs, SILs and SMC in a subsequent PSD implementation rulemaking if deemed necessary or appropriate. The EPA will determine the need for, and develop such rulemaking expeditiously, and any such forthcoming rulemaking will***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 686 of 790 Formatted: Left provide an addi tional opportunity for public comment on specific proposed revisions to the PSD screening tool values for PM 2.5 . Until any rulemaking to amend existing regulations is completed, permitting decisions should continue to be based on the SERs for PM 2.5 (and it s precursors) and the SILs and SMC for PM 2.5 in existing regulations. d. PSD Increments Section 166(a) of the CAA requires the EPA to promulgate “regulations to prevent the significant deterioration of air quality” for pollutants covered by the NAAQS. Amon g other things, the EPA has implemented this requirement through promulgation of PSD increments. The EPA promulgated PM 2.5 increments in 2010 to prevent significant air quality deterioration with regard to the primary and secondary annual and 24

- hour PM 2.5 NAAQS (75 FR 64864, October 20, 2010). The revision to the primary annual PM 2.5 NAAQS raises the question of whether the EPA should consider revising the annual PM 2.5 increments. The EPA does not interpret section 166(a) of the Act to require that the EPA revise existing increments whenever the EPA revises a NAAQS for the same pollutant and averaging time, 278 but the Agency interprets the Act to afford the EPA the discretion to do so. In the proposal, the EPA did not propose to revise the PM 2.5 increments. I n the meantime, the current PM 2.5 increments remain in effect, and PSD permitting should continue pursuant to the current increments, with a minimum of disruption to the permitting process when the revised NAAQS take effect. The EPA received few comments o n whether there was any need or justification to revise the existing PSD increments for PM 2.5 . Industry and state agency commenters

278 A United States District Court has upheld the EPA’s interpretation. See Order Granting Defendant’s Motion to Dismiss Mandatory Duty Claim, Wildearth Guardians v. Jack son, Case No. 11

- cv - 5651

- YGR (N.D. Cal. May 7, 2012). An appeal of this decision is now pending with the United States Court of Appeals for the Ninth Circuit.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 687 of 790 Formatted: Left generally supported retaining the existing increments. Commenters again recommended that any revisions to the PSD increments for PM 2.5 be accomplished through a separate notice

- and

- comment rulemaking. Consistent with the proposal, the T he EPA did not propose to make and is not making finalizing any changes to the existing PSD increments for PM 2.5 as part of this final rule. The EPA will consider whether it is appropriate to propose any revised PSD increments for PM 2.5 in the future. Any such forthcoming rulemaking will provide an additional opportunity for public comment on specific proposed revis ions to the PSD increments for PM 2.5 . Until any rulemaking to amend existing regulations is completed, permitting decisions should continue to be based on the PSD increments for PM 2.5 in existing regulations.

e. Other PSD Transition Issues Several industry commenters expressed concern that a permitting problem would result from the fact that, upon promulgation of the revised PM 2.5 NAAQS, ambient air quality monitoring data would show that for some areas, PM 2.5 concentrations exceed the revised NAAQS, althou gh those areas would not be formally designated as “nonattainment” until a later date pursuant to the designation process provided by the CAA. The commenters noted that sources locating in such areas would be required to obtain a PSD permit in order to con struct or modify, but could not do so because the requirement that the new or modified source must demonstrate that it will not cause or contribute to a NAAQS violation, even though the area would technically already be a in nonattainment area . The commente rs further noted that once the nonattainment designation is made, section 173 of the Act provides a nonattainment area permit***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 688 of 790 Formatted: Left program that specifies conditions under which a permit will be issued, including obtain ing offsetting reductions in emissions rath er than demonstrating through modeling or other analysis that the source will not cause or contribute to a violation of the NAAQS as required in PSD. Thus, the commenters urged the EPA to offer an interim approach that would avoid the imposition of an effe ctive construction ban on such areas until such time as the nonattainment area designations and the nonattainment NSR offset requirements are in place instead of the PSD requirements. Some of the commenters specifically requested that the EPA provide eithe r a surrogacy approach based on showing compliance with the pre

- existing annual PM 2.5 NAAQS or a PSD offset approach to avoid a construction moratorium in such areas. The commenters are correct in that areas already in violation of the revised annual PM 2.5 NAAQS upon the effective date of such NAAQS may not be formally designated nonattainment for two years or potentially longer in accordance with the statutory procedures for promulgating such area designations. In addition, it is the EPA’s longstanding pol icy that new and revised NAAQS must be implemented through the permitting process as of the NAAQS effective date (except for earlier projects that would qualify for any EPA

- authorized grandfathering). Accordingly, new major stationary sources and major mod ifications for which permits will be issued on or after the effective date of the revised annual PM 2.5 NAAQS must comply with the PSD requirement to demonstrate compliance with that and any other applicable NAAQS. We disagree, however, with the commenters ’ conclusion that such circumstances will result in “the imposition of an effective construction ban on such areas.” First, as already described, the EPA has promulgated is promulgating a grandfather grandfather ing***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 689 of 790 Formatted: Left provision that allows certain proposed new and modified sources to proceed with the permit process based on the requirements that were in effect previously, provided the permitting authority either has determined on the date when or before December 14, 2012 that the permit was application is complete or has proposed the permit (i.e., the date on which the draft permit or preliminary determination was has been noticed for public comment ). ) prior to the date the revised PM standards become effective, which is 60 days after publication in the Federal Register. The grandfathering provision thus will enable some sources to avoid issues associated with potential violations of the revised annual PM 2.5 NAAQS. Second, for those sources that are not eligible to be grandfathered under the new provision, exist ing permitting authorities have the discretion to consider offsetting emissions reductions at other sources as part of a demonstration that an individual source seeking a permit will not cause or contribute to violation of the NAAQS. See, Page (2010c). The EPA has historically recognized in regulations and through other actions that sources applying for PSD permit may utilize offsets as part of the required PSD demonstration, even though the PSD provisions of the Clean Air Act do not expressly reference offs ets in the same manner as the nonattainment NSR provisions of the Act. See, In re Interpower of New York, Inc ., 5 E.A.D. 130, 141 (EAB 1994) (describing an EPA Region 2 PSD permit that relied in part on offsets to demonstrate the source would not cause or contribute to a violation of the NAAQS). E xisting EPA regulations provide a procedure by which major stationary sources and major modifications locating in an area designated as attainment or unclassifiable for any NAAQS , and found to cause or contribute t o a NAAQS violation in any area, may***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 690 of 790 Formatted: Left utilize offsets to address such adverse impacts and ultimately be issued a permit. See 40 CFR 51.165(b). Specifically, paragraph (b)(3) of those regulations provides that the required permit program may include a provis ion allowing a proposed major source or major modification to reduce the impact of its emissions on air quality by obtaining sufficient emissions reductions to, at a minimum, compensate for its adverse ambient impact where the source or modification would otherwise cause or contribute to a violation of any NAAQS. On October 20, 2010, the EPA amended the requirements at 40 CFR 51.165(b) to define a significant impact with regard to the PM 2.5 NAAQS. See 75 FR 64864 at 64902. As noted by some of the commenters, the EPA addressed this same issue in 1987 when it promulgated a new set of NAAQS for PM 10 and revised 40 CFR 51.165(b) of the regulations. See 52 FR 24672 (July 1, 1987) at 24684, 24686

- 87, 24698. For PM 10 , the EPA made it clear that when a pro posed PSD source was found to cause or contribute to violation of the PM 10 NAAQS, the source would be required satisfy the requirements of 40 CFR 51.165(b) “to obtain, at a minimum, sufficient PM 10 emission offsets to compensate for the source’s ambient im pact in the area of the violation.” Such offsets were considered to satisfy the “cause or contribute to” language under section 165(a)(3)(B) of the CAA. Id. at 24698. 279 In response to comments concerning the

279 In 1980, the EPA had determined that statutory requirement under CAA section 165(a)(3)(B), pro viding that a proposed new or modified PSD source must demonstrate that it will not cause or contribute to a violation of any NAAQS, taken together with the requirements of section 110(a)(2)(D) of the CAA required all major stationary sources locating outs ide a nonattainment area but causing or contributing to a NAAQS violation to reduce the impact on air quality so as to assure attainment and maintenance of the NAAQS. In a footnote, the EPA further indicated that this offset requirement must apply to sourc es causing or contributing to a newly discovered NAAQS violation until the area is designated nonattainment. See 45 FR 31307 (May 13, 1980) at 31310. In this 1980 rule, EPA adopted section 51.18(k), which was later renumbered section 51.165(b). EPA***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 691 of 790 Formatted: Left appropriate criteria for applying this offset req uirement for PSD purposes, the EPA also stated that any emissions offsets used for PSD purposes must meet applicability criteria that are at least as stringent as the offset criteria set forth in the nonattainment NSR requirements for offsets under 40 CFR 51.165(a)(3). Id. at 24684. We continue to believe that reliance on the 40 CFR 51.165(a)(3) criteria is provide the most appropriate and necessary guide for determining the creditability of PSD offsets, including any offsets obtained to satisfy the PSD re quirements for the revised PM 2.5 NAAQS prior to any anticipated designation of any area as nonattainment with that NAAQS. Since the purpose for using offsets in PSD is to show that additional emissions from the proposed construction will not cause or contr ibute to a violation, the EPA has not codified a requirement that such offsets necessarily must meet the same criteria that apply to offsets under the nonattainment NSR program. In fact, the EPA has previously observed that, in the context of PSD, it may n ot be necessary for a permit applicant to fully offset the proposed emissions increase if an emissions reduction of lesser quantity will be sufficient to mitigate the proposed source ’ s adverse air quality impact on a modeled violation. Page (2010c); 44 FR 3274, January 16, 1979, at 3278. (“Although full emission offsets are not required, such a source must obtain emission offsets sufficient to compensate for its air quality impact where the violation occurs
. ”). This may be particularly true where anticipate d reductions from existing air quality regulations may mitigate the impacts of a proposed source ’ s emissi o ns by the time the source begins operating in an area that is expected to be designated nonattainment. This would need to
revised 51.165(b) in 1987 to expressly authorize an offset program to meet the requirements of section 110(a)(2)(D)(i), but this provision may also be interpreted to apply to section 165(a)(3)(B) of the CAA, consistent with EPA's reading of section 51.18(k) in 19 80.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 692 of 790 Formatted: Left be evaluated on a case

- by

- ca se basis. To the extent that any permit applicants may experience difficulties making the NAAQS compliance showing required to obtain a PSD permit in areas and as set forth in the Memorandum noted above, the EPA is committed to working with permitting auth orities and applicants to identify ways to apply offsets under the PSD program as necessary to meet PSD requirement s . 2. Nonattainment New Source Review Part D of Title I of the CAA pertains to the preconstruction review and permitting requirements for new major stationary sources and major modifications locating in areas designated “nonattainment” for a particular pollutant. Those requirements are commonly referred to as the NNSR program. The EPA regulations for the NNSR program are contained at 40 CFR 51. 165, 52.24 and part 51, appendix S. For NNSR, “major stationary source” is generally defined as a source with the potential to emit at least 100 tpy or more of a pollutant for which an area has been designated “nonattainment.” The NNSR program applies onl y to pollutants for which the EPA has promulgated NAAQS. Because the EPA has defined the PM NAAQS, and has established area designations for PM, in terms of two separate indicators

– PM 10 and PM 2.5 – each indicator is regulated separately for purposes of N NSR applicability. That is, for PM 10 , a “major stationary source” for NNSR applicability generally is a source that is located in a PM 10 nonattainment area and has the potential to emit at least 100 tpy of PM 10 emissions. 280 For PM 2.5 , a “major stationary so urce” for NNSR applicability is a source that is located in a PM 2.5 nonattainment area and has the potential to emit at least
280 In some cases, however, the CAA and the EPA’s regulations define “major stationary source” for nonattainment area NSR in terms of a lower emissions rate dependent on the pollutant. For PM 10 , for example, a source having the potential to emit at leas t 70 tpy of PM 10 is considered “major” if the source is located in a nonattainment area classified as a “Serious Area.”***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 693 of 790 Formatted: Left 100 tpy of direct PM 2.5 (“PM 2.5 emissions”) or any individual precursor of PM 2.5 . For a major modification, the NNSR rules r egulati ons rely upon SERs described previously in the PSD discussion in section IX.D.1. For NNSR, a major modification is a physical change or a change in the method of operation of an existing stationary source that is major for the nonattainment pollutant and r esults in a significant emissions increase and a significant net emissions increase of that nonattainment pollutant or any individual precursor of that pollutant. As described earlier, the EPA will be evaluating the existing SERs for PM 2.5 and PM 2.5 precur sors, and will determine whether there is any basis for proposing changes to any of the existing values. Any decision to propose changing the existing SERs in a future rulemaking would also apply to their use in the NNSR program requirements. The EPA has d esignated nonattainment areas for the existing primary annual and 24

- hour PM 2.5 NAAQS independently, and the EPA also approves redesignations to attainment separately for the two averaging periods. Thus, an area may be nonattainment for the annual standard and unclassifiable/attainment or attainment for the 24

- hour standard. In the p roposal, the EPA indicated that no formal policy has yet been developed to address this situation, but that the EPA presently believes that it is reasonable to require that only NNSR (and not PSD) applies for PM 2.5 in any area that is nonattainment for eit her averaging period. 281 The same situation would have existed with respect to the proposed secondary visibility index standard, had the EPA elected to finalize such a standard. Accordingly, the EPA indicated in the proposal that it intends to address this i ssue in a future NSR rulemaking, but invited preliminary comment on whether it is

281 H owever, transportation conformity requirements discussed in section IX.F below are dependent upon the averaging period(s) for which a n area is designated nonattainment.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 694 of 790 Formatted: Left appropriate to apply the NNSR program requirements for any pollutant that is designated nonattainment for at least one averaging period or at least one primary or secondary N AAQS for a particular pollutant. New major stationary sources or major modifications that trigger NNSR based on PM 2.5 emissions (or emissions of a PM 2.5 precursor) in a PM 2.5 nonattainment area must install technology that meets the lowest achievable emis sion rate (LAER); secure appropriate emissions reductions to offset the proposed emissions increases; and perform other analyses as required under section 173 of the CAA. Following the promulgation of any revised NAAQS for PM 2.5 , some new nonattainment are as for PM 2.5 may result. Where a state does not have any NNSR program or the current NNSR program does not apply to PM 2.5 , that state will be required to submit the necessary SIP revisions to ensure that new major stationary sources and major modifications for PM 2.5 undergo preconstruction review pursuant to the NNSR program. Under section 172(b) of the CAA, the Administrator may provide states up to 3 years from the effective date of nonattainment area designations to submit the necessary SIP revisions mee ting the applicable NNSR requirements. Nevertheless, permits issued to sources in nonattainment areas must satisfy the applicable requirements for nonattainment areas as of the effective date of the specific nonattainment designation; therefore, states who se existing NNSR program requirements, if any, cannot be interpreted to apply to the revised primary annual PM 2.5 NAAQS at that time will be allowed to issue the necessary permits in accordance with the applicable nonattainment permitting requirements cont ained in the Emissions Offset Interpretative Ruling at 40 CFR part 51, appendix S, which would apply to the revised PM 2.5 NAAQS upon its effective date ( see 73 FR 38321, May 16,***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 695 of 790 Formatted: Left 2008 at 28340). The EPA did not propose any type of PM 2.5 grandfathering provi sion at this time for purposes of NNSR. Several industry commenters recommended that the EPA establish a grandfathering provision for NNSR as was proposed under the PSD program. A subset of these commenters recommended that grandfathering be accomplished b y establishing an effective date for designations one year after initial publication in the Federal Register. However, no commenters provided any rationale or supporting basis for such a grandfathering provision or the underlying need for a transition into NNSR permitting for the revised PM 2.5 NAAQS. The EPA disagrees with commenters that recommended a grandfathering provision for NNSR requirements associated with the revised PM 2.5 NAAQS. As described in the proposal, the timetable for adopting new provisi ons under the state a state ’s NNSR program will not apply with regard to the revised NAAQS for PM 2.5 until such time that an area is designated nonattainment for a particular standard. Major NSR permits for PM 2.5 issued in areas newly designated as nonattai nment for the revised primary annual PM 2.5 NAAQS must, as of the effective date of such designation, meet the applicable NNSR requirements for PM 2.5 (Seitz, 1991). As such, there may be cases where applicants with PSD permit applications for PM 2.5 in progr ess will be required to revise their applications to address NNSR requirements for a newly designated PM 2.5 nonattainment area, and such revisions could result in additional resource burden and permit delays. However, the EPA believes at this time that suc h cases will be very limited , and in addition there is a substantial lead time between the effective date of the revised PM 2.5 NAAQS and the effective date of any associated new nonattainment***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 696 of 790 Formatted: Left designations for permit applicants and air agencies to anticipat e when the NNSR requirements will apply. Therefore, the EPA is not inclined at this time to pursue a rulemaking to establish a grandfathering provision for the revised PM 2.5 NAAQS under the NNSR program. The EPA will independently, and in consultation with other reviewing authorities, work with permit applicants on specific projects requiring additional measures to achieve a workable transition into NNSR permitting requirements. The EPA will also continue to consider whether a regulatory grandfathering may be come necessary for NNSR , and if determined to be, will undertake any such action as part of a subsequent NSR implementation rulemaking with additional opportunity for public comment. A few commenters ( industry and state ag ency) commenters addressed the issue of potential dual review (applying NNSR and PSD simultaneously) based on distinct designations for separate averaging times of the PM 2.5 NAAQS. These commenters generally agreed with the EPA’s conclusion that it was reas onable to apply only the NNSR permitting requirements to such situations and not PSD. Regarding the issue of potential dual review for multiple averaging times of the PM 2.5 NAAQS, since the proposal, the EPA has determined that existing regulations resolve this issue in favor of the conclusion suggested in the proposed rule. Based on the express terms of existing regulations, only the NNSR permit requirements, and not PSD, apply for the pollutant PM 2.5 in cases where the area is designated nonattainment for at least one averaging time of the PM 2.5 NAAQS. The federal PSD regulations provide that the PSD requirements (the requirements of paragraphs (j) through (r) of each section) “do not apply to a major stationary source or major modification with respect to a particular pollutant if the owner***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 697 of 790 Formatted: Left or operator demonstrates that, as to that pollutant, the source or modification is located in an area designated as nonattainment under section 107 of the Act.” 40 CFR 52.21(i)(2) and 40 CFR 51.166(i)(2) (e mphasis added ) . Thus, this provision expressly excludes from PSD any pollutant for which an area is designated nonattainment, without reference to a particular averaging period. For a number of years, it was the EPA’s practice to establish a single designation in an ar ea for a particular pollutant. Accordingly, if the area was not meeting the NAAQS for a particular averaging period, the area was designated nonattainment

— even though the area was likely meeting the NAAQS for one or more averaging periods for the same poll utant. The EPA’s statement in the proposal that we had not yet established a policy on the dual review question for PM 2.5 was based on the fact that we had only recently begun establishing designations for each averaging time in the case of the PM 2.5 NAAQS . However, at the time of the proposal, the EPA had not closely examined the applicability of the language in sections 51.166(i)(2) and 52.21(i)(2) in this context. After closer inspection prompted by the comments on this issue, we do not read these provis ions to authorize application of PSD to a pollutant when an area may be designated nonattainment for a particular averaging time, while also designated attainment or unclassifiable for a different averaging time for the same pollutant. As proposed, the EP A is not finalizing any changes under the NNSR program regulations as part of this final NAAQS rule. The EPA will consider the need for any changes to the NNSR program provisions and will implement any such changes as part of a future NSR implementation ru le and/or guidance. E. Transportation Conformity Program Transportation conformity is required under CAA section 176(c) to ensure that***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 698 of 790 Formatted: Left transportation plans, transportation improvement programs (TIPs) and federally supported highway and transit projects will n ot cause new air quality violations, worsen existing violations, or delay timely attainment of the relevant NAAQS or interim reductions and milestones. Transportation conformity applies to areas that are designated nonattainment and maintenance for transpo rtation

- related criteria pollutants: carbon monoxide, ozone, NO 2 , and PM 2.5 , and PM 10 . Transportation conformity for any revised NAAQS for PM 2.5 does not apply until 1 year after the effective date of the nonattainment designation for that revised NAAQS ( s ee CAA section 176(c)(6) and 40 CFR 93.102(d)). The EPA’s Transportation Conformity Rule (40 CFR part 51, subpart T, and 40 CFR part 93, subpart A) establishes the criteria and procedures for determining whether transportation activities conform to the SIP . The EPA is not making any changes to the transportation conformity rule in this rulemaking. The EPA notes that the transportation conformity rule already addresses the PM 2.5 and PM 10 NAAQS. The EPA will review whether there is a need to issue new or revi sed transportation conformity guidance in light of this final rule. In developing new or revised guidance the EPA will consider the comments related to implementation of the transportation conformity rule that were received in response to the proposal. As discussed in section VIII above, the EPA finalized certain clarifying changes to PM 2.5 air quality monitoring regulations. These changes are designed to align different elements of the monitoring regulations for consistency, which will help facilitate the interpretation of modeling results from quantitative PM 2.5 conformity hot

- spot analyses for the annual standards by clarifying which receptors are comparable to the NAAQS. Due to these changes to the monitoring regulations, the EPA will update its***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 699 of 790 Formatted: Left guidanc e on conformity quantitative PM 2.5 hot

- spot analyses as appropriate to make it consistent with the revised monitoring requirements (U
. S
. EPA, 2010j). The EPA intends that the current quantitative PM 2.5 hot

- spot guidance continues to apply to any quantitative PM 2.5 hot

- spot analysis that was begun before the effective date of these revisions to the monitoring regulations. Revised guidance on receptors to be compared to the annual PM 2.5 standards for quantitative PM 2.5 hot

- spot analyses would apply to any quantitative PM 2.5 hot

- spot analysis begun after the effective date of the revised monitoring regulations. Nonattainment and maintenance areas are encouraged to use their interagency consultation processes to determine whether an analysis for a give n project was started before the effective date of changes to the monitoring requirements. Applying the current guidance regarding whether or not a receptor can be compared to the annual PM 2.5 NAAQS to analyses that had begun before the effective date of c hanges to the monitoring regulations is consistent with how the conformity rule and guidance address the transitional period for new emissions factor models or local planning assumptions (40 CFR 93.110(a) and 93.111(b) and (c)). In both of those cases, ana lyses begun before the new model or data became available can be completed using the data and/or model that were available when the analyses began. The EPA rules allow this in order to conserve state resources by not making transportation planning agencies redo analyses simply because a model has been revised, new data have become available, or in this case, the EPA has revised its regulations for PM 2.5 monitoring. F. General Conformity Program General conformity is required by CAA section 176(c). This section requires that actions by federal agencies do not cause new air quality violations, worsen existing violations, or delay timely attainment of the relevant NAAQS or interim reductions and***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 700 of 790 Formatted: Left milestones. General conformity applies to any federal action (e.g., f unding, licensing, permitting, or approving), other than projects that are Federal Highway Administration (FHWA)/Federal Transit Administration (FTA) projects as defined in 40 CFR 93.101 (which are covered under transportation conformity described above), if the action takes place in a nonattainment or maintenance area for ozone, PM, NO 2 , carbon monoxide, lead, or SO 2 . General conformity also applies to a federal highway and transit project if it does not involve either Title 23 or 49 funding, but does invo lve FHWA or FTA approval such as is required for a connection to an Interstate highway or for a deviation from applicable design standards per 40 CFR 93.101. (The FHWA and FTA actions described here as not subject to general conformity are subject to trans portation conformity.) General conformity for the revised PM NAAQS will not apply until 1 year after the effective date of a nonattainment designation for that NAAQS. The EPA’s General Conformity Rule (40 CFR 93.150 to 93.165) establishes the criteria and procedures for determining if a federal action conforms to the SIP. With respect to the revised PM NAAQS, federal agencies are expected to continue to estimate emissions for conformity analyses in the same manner as they are estimated for conformity analy ses for the 1997 and 2006 PM NAAQS. The EPA’s existing general conformity regulations include the basic requirement that a federal agency’s general conformity analysis be based on the latest and most accurate emission emission s estimation techniques availab le (40 CFR 93.159(b)), and the EPA expects that this same principle will be followed for analyses needed for these revised PM NAAQS. When updated and improved emissions estimation techniques become available, the EPA expects the federal agency to use these th ose techniques. With this final rule, the EPA is making no changes to the general conformity***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 701 of 790 Formatted: Left rule as it already addresses the PM 2.5 and PM 10 NAAQS. As noted in the proposal, the EPA will review the need to issue guidance describing how the current confor mity rule applies in nonattainment and maintenance areas for the final revised primary annual PM 2.5 NAAQS. VI. X. Statutory and Executive Order Reviews A. Executive Order 12866: Regulatory Planning and Review and Executive Order 13563: Improving Regulation and Regul atory Review Under section 3(f)(1) of Executive Order 12866 (58 FR 51735, October 4, 1993), this action is an "economically significant regulatory action” because it is likely to have an annual effect on the economy of $100 million or more. The $100 million threshold can be triggered by either costs or benefits, or a combination of them. Accordingly, the EPA submitted this action to the Office of Management and Budget (OMB) for review under Executive Orders 12866 and 13563 (76 FR 3821, January 21, 201 1) , and any changes made in response to OMB recommendations have been documented in the docket for this action. The EPA prepared an analysis of the potential costs and benefits associated with this action. This analysis is contained in Regulatory Impact An alysis for the Proposed Revisions to the National Ambient Air Quality Standards for Particulate Matter , EPA 452/R

- 12

- 003. A copy of the analysis is available in Docket No. EPA

- HQ

- OAR

- 2010

- 0955. The estimates in the RIA are associated with the revised stan dard and alternative standard levels (in μg/m 3 ) of the primary annual PM 2.5 standards including: 13, 12, and 11 . Table 4 provides a summary of the estimated costs, monetized benefits , and net benefits associated with full attainment of these alternative st andards. Formatted: Indent: Left: 0", Numbered + Level: 1 + Numbering Style: I, II, III,

... + Start at: 10 + Alignment: Left + Aligned at: 0.25" + Indent at: 0.75"***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 702 of 790 Formatted: Left 

### Table 4. Total Costs , Monetized Benefits and Net Benefits in 20 20 ( millions of 2010 $) Full Attainment a 

### Alternative PM 2.5 

### Annual Standards (μg/m 3 

### ) Total Costs b 

### Monetized Benefits d 

### Net Benefits

3% Discount Rate c 

### 7%

Discount Rate 3%

Discount Rate 7%

Discount Rate 3%

Discount Rate d 

### 7%

Discount Rate
13 $11 to $100 $11 to $100 $1,300 to $2,900 $1,200 to $2,600 $1, 300 2 00 to $2, 800 9 00 $1,100 to

$2, 500 6 00 12 $53 to $350 $53 to 350 $4,000 to $9,100 $3,600 to $8,200 $ 4,000 3 , 7 00 to $ 8,800 9 , 0 00 $3, 600 3 00 to

$ 7,900 8 , 1 00 11 $320 to $1,700 $320 to $1,700 $13,000 to $29,000 $12,000 to

$26,000 $ 13 1 1 ,000 to

$ 27 2 9 ,000 $ 11 1 0 ,000 to

$ 25 2 6 ,000

a 

### These estimates reflect incremental emissions reductions from an analytical baseline that gives an “adjustment ” to the San Joaquin and South Coast areas in California for NOx emissions reductions expected to occur between 2020 and 2025, when those areas are expected to demonstrate attainment with the revised standards. Full benefits of the revised standards in those two areas will not be realized until 2025. b 

### The two cost estimates do not represent lower and upper bound estimates, but represent estimates generated by two different methodologies. The lower estimate is generated using the fixed

- cost methodology, which assumes that technological change and innovation will result in the availability of additional controls by 2020 that are similar in cost to t he higher end of the cost range for current, known controls. The higher estimate is generated using the hybrid methodology, which assumes that while additional controls may become available by 2020, they become available at an increasing cost and the incre asing cost varies by geographic area and by degree of difficulty associated with obtaining the needed emissions reductions. c 

### Due to data limitations, we were unable to discount compliance costs for all sectors at 3%. See s ection 7.2.2 of the RIA for addi tional details on the data limitations. As a result, the net benefit calculations at 3% were computed by subtracting the costs at 7% from the monetized benefits at 3%.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 703 of 790 Formatted: Left

d 

### The reduction in premature deaths each year accounts for over 90% of total monetized b enefits. Mortality risk valuation assumes discounting over the SAB

- recommended 20

- year segmented lag structure. Not all possible benefits or disbenefits are quantified and monetized in this analysis. B is the sum of all unquantified benefits. Data limitati ons prevented us from quantifying these endpoints, and as such, these benefits are inherently more uncertain than those benefits that we were able to quantify. The range of benefits reflects the range of the central estimates from two mortality cohort stud ies (i.e., Krewski et al. (2009) to Lepeule et al. (2012)).***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 704 of 790 Formatted: Left
B. Paperwork Reduction Act The information collection requirements in this final rule have been submitted for approval to the Office of Management and Budget (OMB) OMB under the Paperwork Reduction Act, 44 U.S.C. 3501 et seq . The information collection requirements are not enforceable until OMB approves them. The Information Collection Request (ICR) document prepared by the EPA for these revisions to part 58 has been as signed EPA ICR number 0940.26 . The information collected under 40 CFR part 53 (e.g., test results, monitoring records, instruction manual, and other associated information) is needed to determine whether a candidate method intended for use in determining a ttainment of the NAAQS in 40 CFR part 50 will meet the design, performance, and/or comparability requirements for designation as a n FRM or FEM . The EPA does not expect the number of FRM or FEM determinations to increase over the number that is currently us ed to estimate burden associated with PM 10 , PM 2.5 , or PM 10

- 2.5 FRM/FEM determinations provided in the current ICR for 40 CFR part 53 (EPA ICR numbers 0940.24). As such, no change in the burden estimate for 40 CFR part 53 has been made as part of this rulem aking. The information collected and reported under 40 CFR part 58 is needed to determine compliance with the NAAQS, to characterize air quality and associated health impacts, to develop emissions control strategies, and to measure progress for the air po llution program. The amendments finalized in this rule will revise the network design requirements for PM 2.5 monitoring sites, resulting in the movement of 21 monitors to established near

- road monitoring stations by January 1, 2015. The incremental burden associated with moving these 21 monitors that are required in 40 CFR part 58 (this is a

one - time cost of relocating the monitors) is $28,570. Burden is defined at 5 CFR Formatted: Font: Italic, Not Superscript/ Subscript***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 705 of 790 Formatted: Left 1320.3(b). State, local, and Tribal entities are eligible for State s tate assistance gra nts provided by the Federal f

ederal government under the CAA which can be used for monitors and related activities. An agency may not conduct or sponsor, and a person is not required to respond to, a collection of information unless it displays a currently valid OMB control number. The OMB control numbers for the EPA’s regulations in 40 CFR are listed in 40 CFR part 9
. To comment on the Agency's need for this information, the accuracy of the provided burden estimates, and any suggested methods for minimizin g respondent burden, the EPA has established a public docket for this rule, which includes this ICR, under Docket ID number EPA

- HQ

- OAR

- 2007

- 0492
. Submit any comments related to the ICR to the EPA and OMB. S end comments to the EPA at the Air and Radiation Docket and Information Center Docket in the EPA Docket Center (EPA/DC), EPA West, Room 3334, 1301 Constitution Ave., NW, Washington, DC. The EPA Docket Center Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday thr ough Friday, excluding legal holidays. The telephone number for the Reading Room is (202) 566

- 1744, and the telephone number for the Air and Radiation Docket and Information Center Docket is (202) 566

- 1742. An electronic version of the public docket is ava ilable at www.regulations.gov. Send comments to OMB at the Office of Information and Regulatory Affairs, Office of Management and Budget, 725 17 th Street, NW, Washington, DC 20503, A ttention: Desk Office for EPA. Since OMB is required to make a decision co ncerning the ICR between 30 and 60 days after [ INSERT DATE OF PUBLICATION IN THE F EDERAL REGISTER ] , a comment to OMB is best assured of having its full effect if OMB receives it by [ INSERT DATE 30 DAYS***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 706 of 790 Formatted: Left AFTER PUBLICATION IN THE FEDERAL REGISTER ]
. C. Regulatory Flexibility Act The Regulatory Flexibility Act (RFA) generally requires an agency to prepare a regulatory flexibility analysis of any rule subject to notice and comment rulemaking requirements under the Administrative Procedure Act or any other statute un less the agency certifies that the rule will not have a significant economic impact on a substantial number of small entities
. Small entities include small businesses, small organizations, and small governmental jurisdictions. For purposes of assessing the impacts of this rule on small entities, small entity is defined as: (1) a small business that is a small industrial entity as defined by the Small Business Administration’s (SBA) regulations at 13 CFR 121.201; (2) a small governmental jurisdiction that is a government of a city, county, town, school district or special district with a population of less than 50,000; and (3) a small organization that is any not
- for

- profit enterprise which is independently owned and operated and is not dominant in its field. After considering the economic impacts of this final rule on small entities, I certify that this action will not have a significant economic impact on a substantial number of small entities
. This final rule will not impose any requirements on small entiti es . Rather, this rule establishes national standards for allowable concentrations of particulate matter in ambient air as required by section 109 of the CAA
. See also American Trucking Associations v. EPA
. 175 F.3d at 1044

- 45 (NAAQS do not have significant impacts upon small entities because NAAQS themselves impose no regulations upon small entities)
. We continue to be interested in the potential impacts of***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 707 of 790 Formatted: Left the proposed rule on small entities and welcome comments on issues related to such impacts. D. Unfunded Mandates Reform Act This action contains no Federal mandates under the provisions of Title II of the Unfunded Mandates Reform Act of 1995 (UMRA), 2 U.S.C. 1531

- 1538 for s tate, local, or tribal governments or the private sector
. The action imposes no enforc eable duty on any s tate, local or tribal governments or the private sector beyond those duties already established in the CAA. Therefore, this action is not subject to the requirements of sections 202 or 205 of the UMRA
. This action is also not subject to the requirements section 205 of the UMRA because it contains no regulatory requirements that might significantly or uniquely affect small governments
. This action imposes no new expenditure or enforceable duty on any

s tate, local, or tribal governments or the private sector, and the EPA has determined that this rule contains no regulatory requirements that might significantly or uniquely affect small governments. Furthermore, in setting a NAAQS, the EPA cannot consider the economic or technological feasibi lity of attaining ambient air quality standards although such factors may be considered to a degree in the development of s tate plans to implement the standards
. See also American Trucking Associations v. EPA , 175 F. 3d at 1043 (noting that because the EPA is precluded from considering costs of implementation in establishing NAAQS, preparation of a Regulatory Impact Analysis pursuant to the Unfunded Mandates Reform Act would not furnish any information which the court could consider in reviewing the NAAQS)
. The EPA acknowledges, however, that any corresponding revisions to associated SIP requirements and air quality surveillance***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 708 of 790 Formatted: Left requirements, 40 CFR part 51 and 40 CFR part 58, respectively, might result in such effects
. Accordingly, the EPA will address, as appropriate, unfunded mandates if and when it proposes any revisions to 40 CFR parts 51 or 58. E. Executive Order 13132: Federalism This action does not have federalism implications
. It will not have substantial direct effects on the s tates, on the relations hip between the national government and the

s tates, or on the distribution of power and responsibilities among the various levels of government, as specified in Executive Order 13132
. The rule does not alter the relationship between the Federal government and the s tates regarding the establishment and implementation of air quality improvement programs as codified in the CAA
. Under section 109 of the CAA, the EPA is mandated to establish and review NAAQS; however, CAA section 116 preserves the rights of s tates to establish more stringent require ments if deemed necessary by a s tate
. Furthermore, this final rule does not impact CAA section 107 which establishes that the s tates have primary responsibility for implementation of the NAAQS
. Finally, as noted in section D (above) on UMRA, this rule does not impose significant costs on s tate, local, or Tribal governments or the private sector
. Thus, Executive Order 13132 does not apply to this action. However, as also noted in section D (above) on UMRA, the EPA rec ognizes that

s tates will have a substantial interest in this rule and any corresponding revisions to associated air quality surveillance requirements, 40 CFR part 58
. F. Executive Order 13175: Consultation and Coordination with Indian Tribal Governments Exec utive Order 13175, entitled ‘‘Consultation and Coordination with Indian Tribal Governments’’ (65 FR 67249, November 9, 2000), requires the EPA to develop an***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 709 of 790 Formatted: Left accountable process to ensure ‘‘meaningful and timely input by tribal officials in the development of regulatory policies that have tribal implications.” This rule concerns the establishment of national standards to address the health and welfare effects of particulate matter. Historically, the EPA’s definition of “tribal implications” has been limited to situations in which it can be shown that a rule has impacts on the tribes’ ability to govern or implications for tribal sovereignty. Based on this historic definition, this action does not have Tribal implications, as specified in Executive Order 13175 (65 FR 67249, November 9, 2000), i.e. because it does not have a substantial direct effect on one or more Indian tribes, since tribes are not obligated to adopt or implement any NAAQS. Never theless, we were aware that many tribes would be interest in this rule and we under took a number of outreach activities to inform tribes about the PM NAAQS review and off ered to two consult ations with tribes. Although Executive Order 13175 does not apply to this rule, the EPA undertook a consultation process including: prior to proposal on March 29,2012 we sent letters to tribal leadership inviting consultation on the rule and then sen t a second round of letters offering consultation after the proposal was issued on June 29, 2012 . No tribe requested a formal consultation with the EPA. W e conducted outreach and information calls to tribal environmental staff o n May 9, 2012 ; June 15, 2012 ; and August 1, 2012 . We also participated on the National Tribal Air Association call on June 28, 2012. As a result we received comments from the National Tribal Air Association , the Southern Ute Mountain Ute Tribe , and the Navajo Nation EPA. In general, these tribal organizations were supportive of the EPA’s proposal. G. Executive Order 13045: Protection of Children from En vironmental Health and Safety Risks***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 710 of 790 Formatted: Left This action is subject to Executive Order 13045 (62 FR 19885, April 23, 1997) because it is an economically significant regulatory action as defined by Executive Order 12866, and the EPA believes that the environmental h ealth or safety risk addressed by this action may have a disproportionate effect on children
. Accordingly, we have evaluated the environmental health or safety effects of PM exposures on children
. The protection offered by these standards is especially imp ortant for children because childhood represents a lifestage associated with increased susceptibility to PM

- related health effects
. Because children have been identified as an at
- risk population, we have carefully evaluated the environmental health effects of exposure to PM pollution among children
. Discussions of the results of the evaluation of the scientific evidence and policy considerations pertaining to children are contained in sections I II.B, II I .D, III.E, I V .B, and I V .C of this preamble . The revise d primary PM 2.5 NAAQS discussed above will provide greater public health protection, including increased protection for at

- risk populations such as children. H. Executive Order 13211: Actions that Significantly Affect Energy Supply, Distribution or Use This action is not a “significant energy action” as defined in Executive Order 13211, (66 FR 28355, May 22, 2001) because it is not likely to have a significant adverse effect on the supply, distribution, or use of energy
. The purpose of this action concerns th e review of the NAAQS for PM
. The action does not prescribe specific pollution control strategies by which these ambient standards will be met
. Su ch strategies are developed by s tates on a case
- by

- case basis, and the EPA cannot predict whether the control options selected by s tates will include regulations on energy suppliers, distributors, or users
.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 711 of 790 Formatted: Left
I. National Technology Transfer and Advancement Act Section 12(d) of the National Technology Transfer and Advancement Act of 1995 (NTTAA), Public Law 104

– 113, s ection 12(d) (15 U.S.C. 272 note) directs the EPA to use voluntary consensus standards in its regulatory activities unless to do so would be inconsistent with applicable law or otherwise impractical
. Voluntary consensus standards are technical standards (e.g., materials specifications, test methods, sampling procedures, and business practices) that are developed or adopted by voluntary consensus standards bodies
. The NTTAA directs the EPA to provide Congress, through OMB, explanations when the Agency deci des not to use available and applicable voluntary consensus standards. This final rulemaking involves technical standards for environmental monitoring and measurement
. Specifically, the EPA propos es to retain the indicators for fine (PM 2.5 ) and coarse (PM 1 0 ) particles
. The indicator for fine particles is measured using the Reference Method for the Determination of Fine Particulate Matter as PM 2.5 in the Atmosphere ( a ppendix L to 40 CFR part 50), which is known as the PM 2.5 FRM, and the indicator for coarse particles is measured using the Reference Method for the Determination of Particulate Matter as PM 10 in the Atmosphere ( a ppendix J to 40 CFR part 50), which is known as the PM 10 FRM
. To the extent feasible, the EPA employs a Performance

- Based Measurement System (PBMS), which does not require the use of specific, prescribed analytic methods
. The PBMS is defined as a set of processes wherein the data quality needs, mandates or limitations of a program or project are specified, and serve as criteria for selec ting appropriate methods to meet those needs in a cost

- effective manner
. It is intended to be more flexible and cost effective for the regulated community; it is also intended to***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 712 of 790 Formatted: Left encourage innovation in analytical technology and improved data quality
. Thou gh the FRM defines the particular specifications for ambient monitors, there is some variability with regard to how monitors measure PM, depending on the type and size of PM and environmental conditions
. Therefore, it is not practically possible to fully d efine the FRM in performance terms to account for this variability
. Nevertheless, our approach in the past has resulted in multiple brands of monitors being approved as FRM for PM, and we expect this to continue
. Also, the FRMs described in 40 CFR part 50 and the equivalency criteria described in 40 CFR part 53, constitute a performance

- based measurement system for PM, since methods that meet the field testing and performance criteria can be approved as FEMs
. Since finalized in 2006 (71 FR, 61236, October 1 7, 2006) the new field and performance criteria for approval of PM 2.5 continuous FEMs has resulted in the approval of six approved FEMs
. 282 In summary, for measurement of PM 2.5 and PM 10 , the EPA relies on both FRMs and FEMs, with FEMs relying on a PBMS appro ach for their approval
. The EPA is not precluding the use of any other method, whether it constitutes a voluntary consensus standard or not, as long as it meets the specified performance criteria. J. Executive Order 12898: Federal Actions to Address Environmental Justice in Minority Populations and Low

- Income Populations Executive Order 12898 (59 FR 7629, February 16, 1994) establishes federal executive policy on environmental justice
. Its main provision directs federal agencies, to the greatest exten t practicable and permitted by law, to make environmental justice part of their mission by identifying and addressing, as appropriate, disproportionately high

282 A list of designated reference and equivalent methods is available on EPA’s website at: http://www.epa.gov/ttn/amtic/criteria.html
.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 713 of 790 Formatted: Left and adverse human health or environmental effects of their programs, policies, and activities on minority populations and low

- income populations in the United States
. The EPA maintains an ongoing commitment to ensure environmental justice for all people, regardless of race, color, national origin, or income
. Ensuring environmental justice means not o nly protecting human health and the environment for everyone, but also ensuring that all people are treated fairly and are given the opportunity to participate meaningfully in the development, implementation, and enforcement of environmental laws, regulati ons, and policies . W e conducted an outreach and information call with environmental justice organizations o n August 9, 2012
. The EPA has identified potential disproportionately high and adverse effects on minority and/or low

- income populations related to P M 2.5 exposures . In addition, t he EPA has identified persons from lower socioeconomic strata as a n at
- risk population for PM

related health effects
. As a result, the EPA has carefully evaluated the potential impacts on low

- income and minority populations as discussed in section II I .E.3 .a of this preamble
. Based on this evaluation and consideration of public comments on the proposal, the EPA is eliminat ing the spatial averaging provisions as part of the form of the primary annual PM 2.5 standard to avoid poten tial disproportionate impacts on at

- risk populations
. The Agency expects this final rule w ill lead to the establishment of uniform NAAQS for PM
. The Integrated Science Assessment and Policy Assessment contain the evaluation of the scientific evidence and p olicy considerations that pertain to these populations
. These documents are available as described in the Supplementary Information section of this preamble and copies of all documents have been placed in the public docket for this action
.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 714 of 790 Formatted: Left
K. Congressional R eview Act The Congressional Review Act, 5 U.S.C. 801 et seq., as added by the Small Business Regulatory Enforcement Fairness Act of 1996, generally provides that before a rule may take effect, the agency promulgating the rule must submit a rule report, wh ich includes a copy of the rule, to each House of the Congress and to the Comptroller General of the United States. The EPA will submit a report containing this rule and other required information to the U.S. Senate, the U.S. House of Representatives, and the Comptroller General of the United States prior to publication of the rule in the Federal Register. A major rule cannot take effect until 60 days after it is published in the Federal Register. This action is a “major rule” as defined by 5 U.S.C. §804(2) . This rule will be effective [ INSERT DATE 60 DAYS AFTER DATE OF PUBLIC ATION IN THE FEDERAL REGISTER ] . References AAM (2012). Comments of the Alliance of Automobile Manufacturers on National Ambient Air Quality Standards for Particulate Matter; Proposed Rule. Docket No. EPA

- HQ

- OAR

- 2007

- 0492

- 9475. August 31, 2012. AASHTO (2012). Comments of the American Association of State Highw ay and Transportation Officials on National Ambient Air Quality Standards for Particulate Matter; Proposed Rule. Docket No. EPA

- HQ

- OAR

- 2007

- 0492

- 9506. August 31, 2012. Abt Associates Inc. (2001). Assessing Public Opinions on Visibility Impairment Due to Ai r Pollution: Summary Report. Available: http://www.epa.gov/ttn/oarpg/t1/reports/vis_rpt_final.pdf Abt Associates (2005). Particulate Matter Health Risk Assessment for Selected Urban Areas. Final Report. Bethesda, MD. Prepared for the Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, Contract No. 68

- D

- 03

- 002. EPA 452/R

- 05

- 007A. Available: http://www.epa.gov/ttn/naaqs/standards/pm/data/PMrisk20051220.pdf***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 715 of 790 Formatted: Left AAM (2012). Comments of the Alliance of Automobile Manufacturers on National Ambient Air Quality Standards for Particulate Matter; Proposed Rule. Docket No. EPA

- HQ

- OAR

- 2007

- 0492

- 9475. August 31, 2012. ACC (2012). Comments of the American Chemistry Council on National Ambient Air Quality Standards for Particulate Matter; Proposed Rule. Docket No. EPA

- HQ

OAR

- 2007

- 0492

- 9295/ August 29, 2012. AFPM (2012). Comments of the American fuel & Petrochemical Manufacturers on National Ambient Air Quality Standards for Particulate Matter; Proposed Rule. Docket No. EPA

- HQ

- OAR

- 2007

- 0492

- 9573. August 31, 2012. AHA et al. (2012). American Heart Association; American Lung Association; American Public Health Association; American Thoracic Society; Asthma and Allergy Foundation of America; Health Care Without Harm; March of Dimes; National Association of County and City Health Officials; Trust for America’s Health (2012). Letter to EPA Administrator Lisa P. Jackson re: Comments on the Proposed National Ambient Air Quality Standards for Part iculate Matter. August 31, 2012. Docket ID number EPA

- HQ

- OAR

- 2007

- 0492

- 9512. Air Alliance Houston et al., (2012). Air Alliance Houston, Alliance for Affordable Energy, Alliance for Health Promotion, American Bottom Conservancy; Center for Biological Divers ity; Chelsea Board of Health; Clelsea Collaborative; Citizens for Pennsylvania's Future; Clean Air Carolina; Clean Air Task Force; Clean Air Watch; Clean Water Action; Clean Water Action Michigan; Clean Water Action Rhode Island; Communities for a Better E nvironment; Conservation Law Foundation; Environment & Human Health, Inc.; Environment Illinois; Environment Northeast; Environmental and Energy Study Institute; Environmental Defense Fund; Fresh Energy; Green For All; Greenpeace USA; Hoosier Environmental Council; Improving Kids' Environment; Kentucky Resources Council; Massachusetts Climate Action Network; Midwest Environmental Advocates; Mining Impact Coalition of Wisconsin; Moms Clean Air Force; Mothers & Others for Clean Air; NAACP; National Resources Defense Council; National Wildlife Federation; New York Public Interest Research Group; Powder River Basin Resource Council; Respiratory Health Association; Safe Air for Everyone; Save Our Sky Blue Waters; Save the Dunes; Sierra Club; Southern Alliance for Clean Energy; Uranium Watch; US Climate Action Network; Valley Watch; Wasatch Clean Air Coalition; Western Environmental Law Center. Letter to EPA Administrator Lisa P. Jackson. Comments on the Proposed National Ambient Air Quality Standards for Particula te Matter. August 31, 2012. Docket ID number EPA

- HQ

- OAR

- 2007

- 0492

- 9402. ALA et al. (2012). Comments of the American Lung Association, Clean Air Council, Clean Air Task Force, Earthjustice, Environmental Defense Fund, Natural Resources Defense Council, Sier ra Club on EPA’s Proposed Revisions to the Primary National Ambient Air Quality Standards for Particulate Matter. Docket***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 716 of 790 Formatted: Left No. EPA

- HQ

- OAR

- 2007

- 0492

- 9826. August 31, 2012. AMC, et al. (2012). Comments of the Appalachian Mountain Club, the National Parks Conse rvation Association, and Earthjustice on National Ambient Air Quality Standards for Particulate Matter; Proposed Rule. Docket No. EPA

- HQ

- OAR

2007

- 0492

- 9562. August 31, 2012. API ( 2009). Comments of the American Petroleum Institute on the Integrated Science Assessment for Particulate Matter

– Second External Review Draft. Docket No. EPA

- HQ

- ORD

- 2007

- 0517

- 0079. October 13, 2009. API ( 2012). Comments of the American Petroleum Institute on National Ambient Air Quality Standards for Particulate Matter; Proposed R ule. Docket No. EPA

- HQ

OAR

- 2007

- 0492

- 9530. August 31, 2012. Armstrong BG. Effect of measurement error on epidemiological studies of environmental and occupational exposures. Occup Environ Med 1998, 55: 651

- 6. Arizona DEQ (2012). Comments of the Arizona De partment of Environmental Quality on National Ambient Air Quality Standards for Particulate Matter; Proposed Rule. Docket No. EPA

- HQ

- OAR

- 2007

- 0492

- 9492. August 31, 2012. Avol E; Gauderman WG; Tan SM; London SJ; Peters JM (2001). Respiratory effects of relo cating to areas of differing air pollution levels. Am. J. Respir. Crit. Care Med. 164: 2067

- 2072. BBC Research & Consulting (2003). Phoenix Area Visibility Survey. Draft Report. Available: http://www.azdeq.gov/environ/air/download/vis_021903f.pdf. Accessed 9/16/2008 Bell ML, Ebisu K, Belanger K (2007). Ambient air pollution and low birth weight in Connecticut and Massachusetts. Environ Health Perspect, 115: 1118

- 24. Bell ML; Ebisu K; Peng RD; Walker J; Samet JM; Zeger SL; Dominic F (2008). Seasonal and regional short

- term effects of fine particles on hospital admissions in 202 U.S. counties, 1999

- 2005. Am J Epidemiol, 168: 1301

- 1310. Bell ML (2009a). Personal comm unication with Dr. Michelle Bell. Annual PM 2.5 levels used in Dominici et al. 2006 and Bell et al. 2008. December 7, 2009. Docket No. EPA

- HQ

- ORD

- 2007

- 0517

- 0087. Bell ML, Ebisu K, Peng R, Samet J, Dominici F (2009b). Hospital Admissions and Chemical Composition of Fine Particle Air Pollution. Am J Respir Crit Care Med, 179: 1115

- 1120. Burnett RT; Brook J et al. (2000). Association between particulate

- and gas

- phas e components of urban air pollution and daily mortality in eight Canadian cities. Inhal. Toxicol. 12 Suppl 4: 15

- 39.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 717 of 790 Formatted: Left Burnett RT, Goldberg MS (2003). Size

- fractionated particulate mass and daily mortality in eight Canadian cities. In: Revised analyses of ti me - series studies of air pollution and health. Special report. May 2003. Boston, MA: Health Effects Institute; pp. 85

- 90. Available: http://www.healtheffects.org/news.htm
. Burnett RT, Stieb D, Brook JR, C akmak S, Dales R, Raizenne M, Vincent R, Dann T (2004). Associations between short

- term changes in nitrogen dioxide and mortality in Canadian cities. Arch Environ Occup Health, 59: 228

- 236. CARB (2012). Comments of the California Air Resources Board on Nat ional Ambient Air Quality Standards for Particulate Matter; Proposed Rule. Docket No. EPA

HQ

- OAR

- 2007

- 0492

- 1694. July 18, 2012. CA OEHHA (2012). Comments of the California Environmental Protection Agency, Office of Environmental Health Hazard Assessment on National Ambient Air Quality Standards for Particulate Matter; Proposed Rule. Docket No. EPA

- HQ

OAR

- 2007

- 0492

- 9882. August 28, 2012. Carroll RJ, Ruppert D, Stefanski LA
. (1995). Measurement error in nonlinear models. London, UK: Chapman and Hall Ltd , 19 95
. CBD (2012). Comments of the Center for Biological Diversity on National Ambient Air Quality Standards for Particulate Matter; Proposed Rule. Docket No. EPA

- HQ

OAR

- 2007

- 0492

- 9894. August 31, 2012. CDC (2004) Introduction and approach to causal inference . In: The health consequences of smoking: a report of the Surgeon General. Atlanta, GA: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health. Available: http://www.cdc.gov/tobacco/sgr/sgr_2004/chapters.htm (18 August, 2004). Available: http://www.cdc.gov/tobacco/data_statistics/sgr/2004/pdfs/tableofcontents.pdf
. Chaloulakou A; Kassomenos P; Grivas G; Spyrellis N (2005). Particulate matter and black smoke concentration levels in central Athens, Greece. Environ Int 31(5): 651

- 9. Chan CC; Chuang KJ; Chen WJ; Chang WT; Lee CT; Peng CM (2008). Increasing cardiopulmonary emergency visits by long

- range transported Asian dust storms in Taiwan. Environ Res, 106: 393

- 400. Chock DP; Winkler SL; Chen C. (2000). A study of the association between daily mortality and ambient air pollutant concentrations in Pittsburgh, Pennsylvania. J Air Waste Manag Assoc, 50: 1481

- 1500. Formatted: Font color: Auto, Not Superscript/ Subscript

Formatted: Font color: Auto***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 718 of 790 Formatted: Left CHPAC (2012). Comments of the Children’s Health Protection Advisory Committee on National Ambient Air Quality Standards for Part iculate Matter; Proposed Rule. Docket No. EPA

- HQ

- OAR

- 2007

- 0492

- 9944. September 10, 2012. Class of ’85 RRG (2012). Comments of the Class of ’85 Regulatory Response Group on National Ambient Air Quality Standards for Particulate Matter; Proposed Rule. Docke t No. EPA

- HQ

- OAR

- 2007

- 0492

- 9435. August 31, 2012 Colorado DPHE (2012). Comments of the Colorado Department of Public Health and the Environment on National Ambient Air Quality Standards for Particulate Matter; Proposed Rule. Docket No. EPA

- HQ

- OAR

- 2007

- 049 2

- 9353. August 31, 2012. CPC CPMC (2012). Comments of the Coarse Particulate Matter Coalition on National Ambient Air Quality Standards for Particulate Matter; Proposed Rule. Docket No. EPA

- HQ

- OAR

- 2007

- 0492

- 9491. August 31, 2012. Curl C (2009). Personal com munication with Cynthia Curl, MESA Air Project Manager, University Deck L; Lawson M (2010). Statistical analysis of Washington; email existing urban visibility preference studies. Memorandum to Beth Hassett

Sipple Vicki Sandiford , U.S. EPA , OAQPS regarding request for PM air quality data. August 10, 2009 /Office of Air Quality Planning and Standards from Leland Deck and Megan Lawson, Stratus Consulting Inc. February 3, 2010 . Docket No ID no . EPA

- HQ

- ORD OAR

- 2007

- 0517

- 0113 0492

- 0089
. DHEW (1969). Air Quality Crit eria for Particulate Matter. U. S. Department of Health, Education, and Welfare. Public Health Service, Environmental Health Service, National Air Pollution Control Administration, Washington, D.C. January 1969. Dockery DW, Pope CA III, Xu X, Spengler JD, Ware JH, Fay ME, Ferris BG Jr, Speizer FE (1993). An association between air pollution and mortality in six U.S. cities. N Engl J Med , 329: 1753

- 1759. Dockery DW, Cunningham J, Damokosh AI, Neas LM, Spengler JD, Koutrakis P, Ware JH, Raizenne M, Speizer FE (1996). Health effects of acid aerosols on North American children: respiratory symptoms. Environ Health Perspect , 104(5):500

- 5. DOI (2012). Comments of the United States Department of the Interior on National Ambient Air Quality Standards for Particulate Matter; Propose d Rule. Docket No. EPA

- HQ

- OAR

- 2007

- 0492

- 7970. August 23, 2012. Dominici F, Peng RD, Bell ML, Pham L, McDermott A, Zeger SL, Samet JM (2006a). Fine particulate air pollution and hospital admission for cardiovascular and respiratory diseases. JAMA, 295: 1127

- 1134. Dominici F (2006b). Letter from Dr. Francesca Dominici, Associate Professor of Biostatistics, Bloomberg School of Public Health, Johns Hopkins University, comments to the proposed rule. Docket ID number OAR

- 2001

- 0017

- 0988. March 21, 2006. Formatted: Normal, Indent: Left: 0", Hanging: 0.5", Space After: 12 pt

Formatted: Font: 12 pt, Not Superscript/ Subscript

Formatted: Font: 12 pt, Not Superscript/ Subscript***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 719 of 790 Formatted: Left Dominici F, Peng RD, Zeger SL, White RH, Samet JM (2007). Particulate air pollution and mortality in the United States: did the risks change from 1987 to 2000? Am J Epidemiol, 166: 880

- 8. Dominici F; Zeger SL; Janes H; Greven S (2012). Memo from Francesca Dominici, Harvard School of Public Health; Scott L. Zeger, The Johns Hopkins University; Sonja Greven, Ludwig

- Maximilians

- Universitat Munchen; and Holly Janes, University of Washington to Bryan Hubbell and Jason Sacks, U.S. EPA. Additional information to EPA for Ja nes et al. (2007) and Greven et al. (2011). November 28, 2012. Dow (2012). Comments of the Dow Chemical Company on National Ambient Air Quality Standards for Particulate Matter; Proposed Rule. Docket No. EPA

- HQ

OAR

- 2007

- 0492

- 8424. August 28, 2012. Eftim SE , Samet JM, Janes H, McDermott A, Dominici F (2008). Fine Particulate Matter and Mortality: A Comparison of the Six Cities and American Cancer Society Cohorts With a Medicare Cohort. Epidemiology, 19: 209

- 216. Ely DW; Leary JT; Stewart TR; Ross DM (1991). The establishment of the Denver Visibility Standard. Presented at Presented at: 84th annual meeting & exhibition of the Air & Waste Management Association; June; Vancouver, British Columbia. Pittsburgh, PA: Air & Waste Management Association; paper no. 91

- 48.4. EPRI (2012). Comments of the Electric Power Research Institute on National Ambient Air Quality Standards for Particulate Matter; Proposed Rule. Docket No. EPA

HQ

- OAR

- 2007

- 0492

- 9396. August 31, 2012. Frank N ( 2012 a ). Recommendations for sampling arti fact correction for PM 2.5 organic carbon. Memorandum to the PM NAAQS review docket. Docket number EPA

HQ

- OAR

- 2007

- 0492. June 14, 2012 2006). Retained Nitrate, Hydrated Sulfates, and Carbonaceous Mass in Federal Reference Method Fine Particulate Matter for Six Eastern U.S. Cities. J Air Waste Manage Assoc., 56: 500

– 511
. Frank N (2012a). Differences between maximum and composite monitor annual PM 2.5 design values by CBSA. Memorandum to the PM NAAQS review docket. Docket number EPA

- HQ

- OAR

- 2007

- 0492. December 2 012. Available: http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_2007_td.html
. Frank N (2012b). Reanalysis of the relationship between 24

- hour and 4

- hour visibility index levels. Memor andum to the PM NAAQS review docket. Docket number EPA

- HQ

- OAR

- 2007

- 0492. December 2012. Available: http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_2007_td.html
. Franklin M; Zeka A; S chwartz J (2007). Association between PM 2.5 and all

- cause and specific

- cause mortality in 27 U.S. communities. J Expo Sci Environ Epidemiol, 17: 279

- 287. Formatted: ReferenceFullCitation, Indent: Left: 0", First line: 0", Space After: 0 pt***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 720 of 790 Formatted: Left Franklin M; Koutrakis P; Schwartz J (2008). The role of particle composition on the association betwee n PM 2.5 and mortality. Epidemiology, 19: 680

- 689. Gauderman WJ; McConnell R; Gilliland F; London S; Thomas D; Avol E; Vora H; Berhane K; Rappaport EB; Lurmann F; Margolis HG; Peters J (2000). Association between air pollution and lung function growth in southern California children. Am J Respir Crit Care Med, 162: 1383

- 1390. Gauderman WJ; Gilliland GF; Vora H; Avol E; Stram D; McConnell R; Thomas D; Lurmann F; Margolis HG; Rappaport EB; Berhane K; Peters JM (2002). Association between air pollution and lu ng function growth in southern California children: results from a second cohort. Am J Respir Crit Care Med, 166: 76

- 84. Gauderman WJ; Avol E; Gilliland F; Vora H; Thomas D; Berhane K; McConnell R; Kuenzli N; Lurmann F; Rappaport E; Margolis H; Bates D; Pe ters J (2004). The effect of air pollution on lung development from 10 to 18 years of age. NEJM, 351: 1057

- 67. Gent JF , Koutrakis P , Belanger K , Triche E , Holford TR , Bracken MB , Leaderer BP (2009) Symptoms and medication us e in children with asthma and traffic

- related sources of fine particle pollution. Environ Health Perspect , 117: 1168

- 74. Georgia DNR (2012). Comments of the Georgia Department of Natural Resources on National Ambient Air Quality Standards for Particulate Matter; Proposed Rule. Docket No. EPA

- HQ

- OAR

- 2007

- 0492

- 9444. August 31, 2012. GMA (2012). Comments of the Georgia Mining Association o n National Ambient Air Quality Standards for Particulate Matter; Proposed Rule. Docket No. EPA

- HQ

OAR

- 2007

- 0492

- 3678. August 5, 2012. Gong H Jr ; Linn WS ; Clark KW ; Anderson KR ; Geller MD ; Sioutas C (2005). Respiratory responses to exposures with fine particulates and nitrogen dioxide in the elderly with and without COPD. Inhal Toxicol , 17(3):123

- 32. Goodman SN. (1993). P values, hypothesis tests, and likeli

- hood: implications for epidemiology of a neglected historical debate. American Journal of Epidemiology 137:48 5

– 496. Goodman SN. (1999). Towards evidence

- based medical statistics. 1: the P value fallacy. Annals of Internal Medicine 130:995

– 1004. Goss CH; Newsom SA; Schildcrout JS; Sheppard L; Kaufman JD (2004). Effect of ambient air pollution on pulmonary exacerb ations and lung function in cystic fibrosis. Am J Respir Crit Care Med, 169: 816

- 821. Greenland, S. (1998) Meta

- analysis. In: Rothman, K. J.; Greenland, S., eds. Modern epidemiology. Philadelphia, PA: Lippincott Williams & Wilkins; pp. 643

- 673. Formatted: Font: 12 pt, Not Superscript/ Subscript

Formatted: Font: 12 pt, Not Superscript/ Subscript Formatted: Font: 12 pt, Not Superscript/ Subscript***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 721 of 790 Formatted: Left Greven S; Dominici F; Zeger S ( 2012 2011 ). An Approach to the Estimation of Chronic Air Pollution Effects Using Spatio

- Termporal Information. Journal of the American Statistical Association. Vol. 106, No. 494. 396

- 406. Hanley T and Reff A (2011). Assessment of PM 2.5 FEMs compared to collocated FRMs. Memorandum to PM NAAQS review. Docket ID number EPA

- HQ

- OAR

- 2007

- 0492

- 0332. April 7, 2011. Available: http://www.epa.gov/ttn/naaqs/standards/pm/s_pm _2007_td.html
. Harnett WT (2009). Guidance on SIP Elements Required Under Sections 110(a)(1) and (2) for the 2006 24

- Hour Fine Particle (PM 2.5 ) National Ambient Air Quality Standards (NAAQS). September 25, 2009. Docket ID number EPA

- HQ

- OAR

2007

- 0492

- 0341. Available: http://www.epa.gov/ttn/oarpg/t1/memoranda/20090925_harnett_pm25_sip_110a1 2.pdf
. Hassett

- Sipple B and Stanek L (2009). Email to study authors of recent U.S, and Canadian epidemiological studies evaluating health effects associated with exposure to fine and thoracic coarse particles. May 2, 2009 and October 20, 2009. Docket ID numbers EPA

- HQ

- ORD

- 2007

- 0517

- 0050 and EPA

- HQ

- ORD

- 2007

- 0517

- 0104. Hassett

- Sippl e B; Rajan P; Schmidt M (2010). Analyses of PM 2.5 Data for the PM NAAQS Review. Memorandum to the PM NAAQS review docket. Docket ID number EPA

- HQ

- OAR

- 2007

- 0492

- 0077. March 29, 2010. Available: http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_2007_td.html
. HEI (2003). Commentary on revised analyses of selected studies. In: Revised analyses of time

- series studies of air pollution and health. Special report. Boston, MA: Health Effects Institute; pp. 255

- 290. Available: http://www.healtheffects.org/Pubs/TimeSeries.pdf . October 18, 2004. Henderson R (2005a). Letter from Dr. Rogene Henderson, Chair, Clean Air Scientific Advisory Committee to Honorable Stephen L. Johnson, Administrator, U.S. EPA. CASAC PM Review Panel’s Peer Review of the Agency’s Review of the National Ambient Air Quality Standards for Particulate Matter: Policy Assessment of Scientific and Technical Information (Second Draft PM Staff Paper, January 2005). June 6, 2005. EPA

- SAB

- CASAC

- 05

- 007. Docket ID number EPA

- HQ

- OAR

- 2001

- 0017

- 0393. Available: http://www.epa.gov/sab/pdf/casac

- 05

- 007.pdf
. Henderson R (2005b). Clean Air Scientific Advisory Committee (CASAC) Review of the EPA Staff Recommendations Concerning a Potential Thoracic Coarse PM Standard in the Review of the National Ambient Air Quality Standards for Particulate Matter: Policy Assessment of Scientific and Technical Information (Final PM OAQPS Staff Paper, EPA

- 452/R

- 05

- 005, June 2005). September 15, 2005. EPA

- SAB

- CASAC

- 05

- 012. Docket ID number EPA

- HQ

- OAR

- 2001

- 0017

-***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 722 of 790 Formatted: Left 0477. Available: http://yosemite.epa.gov/sab/s abproduct.nsf/3562FF25F05133FC85257084000B1 B77/$File/sab

- casac - 05

- 012.pdf
. Henderson R (2005c). Letter from Dr. Rogene Henderson, Chair, Clean Air Scientific Advisory Committee to the Honorable Stephen L. Johnson, Administrator, U.S. EPA. Clean Air Scienti fic Advisory Committee (CASAC) Advisory on Implementation Aspects of the Agency’s Final Draft National Ambient Air Monitoring Strategy (NAAMS) (December 2004). April 20, 2005. EPA

- SAB

CASAC

- 05

- 006. Available: http://yosemite.epa.gov/sab/sabproduct.nsf/FA9EBA6E90F17DBC8525700B005 520A5/$File/SAB

- CASAC

- 05

- 006_unsigned.pdf
. Henderson R. (2006a). Letter from Dr. Rogene Henderson, Chair, Clean Air Scientific Advisory Committee to the Honorable Stephen L. Johnson, Administrator, U.S. EPA. Clean Air Scientific Advisory Committee Recommendations Concerning the Proposed National Ambient Air Quality Standards for Particulate Matter. March 21, 2 006. EPA

- CASAC

- LTR

- 06

- 002. Docket ID number EPA

- HQ

- OAR

2001

- 0017

- 1452. Available: http://www.epa.gov/sab/pdf/casac

- ltr

- 06

- 002.pdf Henderson R; Cowling E; Crapo JD; Miller FJ; Poirot RL; Speizer F; Zielinski B (2006b). Letter from Clean Air Scientific Advisory Committee to the Honorable Stephen L. Johnson, Administrator, U.S. EPA. Clean Air Scientific Advisory Committee Recommendations Concerning the Final National Ambient Air Quality Standards fo r Particulate Matter. September 29, 2006. EPA

- CASAC

LTR

- 06

- 003. Docket ID number EPA

- HQ

- OAR

- 2007

- 0492

- 0051. Available: http://yosemite.epa. gov/sab/sabproduct.nsf/1C69E987731CB775852571FC00499 A10/$File/casac

- ltr

- 06

- 003.pdf
. Henderson R (2008). Letter from Dr. Rogene Henderson, Chair, Clean Air Scientific Advisory Committee to the Honorable Stephen L. Johnson, Administrator, U.S. EPA. Clean Air Scientific Advisory Committee Particulate Matter Review Panel’s Consultation on EPA’s Draft Integrated Review Plan for the National Ambient Air Quality Standards for Particulate Matter. January 3, 2008. EPA

- CASAC

- 08

- 004. Docket ID number EPA

- HQ

- OAR

- 2007

- 0 492

- 0018. Available: http://yosemite.epa.gov/sab/sabproduct.nsf/264cb1227d55e02c85257402007446a 4/76D069B8191381DA852573C500688E74/$File/EPA

- CASAC

- 08

- 004

- unsigned.pdf Herman SA, Perciasepe R (1999). State Implementation Plans: Policy Regarding Excess Emissions During Malfunctio ns, Startup, and Shutdown. Memorandum from Steven A. Herman, Assistant Administrator for Enforcement and Compliance Assurance, and Robert Perciasepe, Assistant Administrator for Air and Radiation to Regional Administrators, Regions I

- X. September 20, 199 9. Hill AB (1965). The environment and disease: association or causation? Proc. R. Soc. Med. 58: 295

- 300. Formatted: Font: 12 pt, Not Superscript/ Subscript***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 723 of 790 Formatted: Left Hopke PK; Ito K; Mar T; Christensen WF; Eatough DJ; Henry RC; Kim E; Laden F; Lall R; Larson TV; Liu H; Neas L; Pinto J; Stolzel M; Suh H; Paatero P; Thurston GD (2006). PM source apportionment and health effects: 1 Intercomparison of source apportionment results. J Expo Sci Environ Epidemiol, 16: 275

- 286. Host S; Larrieu S; Pascal L; Blanchard M; Declercq C; Fabre P; Jusot JF; Chardon B; Le Tertre A; Wagner V; Prouvost H; Lefranc A (2007). Short

- term Associations between Fine and Coarse Particles and Cardiorespiratory Hospitalizations in Six French Cities. Occup Environ Med, 18: S107

- S108. Howson, C; Urbach P (1993). Scientific Reasoning: The Bayesian Approach. 2nd ed. Chicago: Open Court Publishing Company. IMPROVE (1996). Improve Standard Operating Procedures, SOP 126, Site Selection. September 12, 1996. Available: http://vista.cira.colostate.edu/improve/publications/SOPs/ucdavis_sops/sop126.pd f
. Indiana DEM (2012). Comments of the Indiana Department of Environmental Management on National Ambient Air Quality Standards for Particulate Matter; Proposed Rule. Docket No. EPA

- HQ

- OAR

- 2007

- 0492

- 9398. August 31, 2012. ISEE (2012). Comments on EPA’s proposal to revise the Air Quality Standards for Particle Pollution (Particulate Matter). Letter from Annette Peters, President, International Society for Environme ntal Epidemiology to EPA Administrator Lisa P. Jackson. Docket No. EPA

- HQ

- OAR

- 2007

- 0492

- 9234. August 30, 2012. Islam T; Gauderman WJ; Berhane K; McConnell R; Avol E; Peters JM; Gilliland FD (2007). The relationship between air pollution, lung function and asthma in adolescents. Thorax, 62: 957

- 963. Ito K; Christensen WF; Eatough DJ; Henry RC; Kim E; Laden F; Lall R; Larson TV; Neas L; Hopke PK; Thurston GD (2006). PM source apportionment and health effects: 2 An investigation of intermethod variability in a ssociations between source - apportioned fine particle mass and daily mortality in Washington, DC. J Expo Sci Environ Epidemiol, 16: 300

- 310. Jackson L (2009). Memo from Administrator Lisa P. Jackson to Elizabeth Craig, Acting Assistant Administrator for OAR and Lek Kadeli, Acting Assistant Administrator for ORD. Process for Reviewing the National Ambient Air Quality Standards. May 21, 2009. Available: http://www.epa.gov/ttn/naaqs /pdfs/NAAQSReviewProcessMemo52109.pdf
. Jackson L J (2010). Letter from Administrator Lisa P. Jackson to Dr. Jonathan M. Samet, Chairman, Clean Air Scientific Advisory Committee. February 25, 2010. Docket ID number EPA

- HQ

- ORD

- 2007

- 0517

- 0127. Janes H; Domini ci F; Zeger SL ( 2007 a 2007 ). Trends in Air Pollution and Mortality: An***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 724 of 790 Formatted: Left Approach to the Assessment of Unmeasured Confounding. Epidemiology, 18: 416

- 423. Janes H; Dominici F; Zeger SL (2007 b ) . Partitioning Evidence of Association Between Air Pollution and Mortality: Author’s Response. Epidemiology, 18(4): 427

- 428. Jerrett M; Burnett RT; Ma R; Pope CA; Krewski D; Newbold KB; Thurston G; Shi Y; Finkelstein N; Calle N; Thun MJ (2005). Spatial analysis of air pollution and mortality in Los Angeles. Epidemiology , 16: 727

- 36. Kelly J; Schmidt M; Frank N; Timin B; Solomon D; Rao V (2012a). Technical Analyses to Support Surrogacy Policy for Proposed Secondary PM 2.5 NAAQS under NSR/PSD Program. Memorandum to EPA Docket No. EPA

- HQ

- OAR

- 2007

- 0492 through Richard Wayland , Director, Air Quality Assessment Division, U.S. EPA Office of Air Quality Planning and Standards. June 14, 2012. Available: http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_2007_td.h tml
. Kelly J; Schmidt M; Frank N (2012b). Updated comparison of 24

- hour PM 2.5 design values and visibility index design values. Memorandum to EPA Docket No. EPA

HQ

- OAR

- 2007

- 0492. Available: http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_2007_td.html
. Kennecott Utah Copper (2012). Comments of the Kennecott Utah Copper LLC on National Ambient Air Quality Standards for Particulate Matter; Proposed Rule. Docket No. EPA

- HQ

- OAR

- 2007

- 0492

- 9442. August 31, 2012. Killingsworth CR; Alessandrini F; Krishna Murthy GG; Catalano PJ; Paulauskis JD; Godleski JJ (1997). Inflammation, chem okine expression, and death in monocrotaline

- treated rats following fuel oil fly ash inhalation. Inhalation Toxicology. 9: 541

- 565. Kim JJ; Smorodinsky S: Lipsett M; Singer BC; Hodgson AT; Ostro B (2004). Traffic

related air pollution near busy roads: the East Bay children’s Respiratory Health Study. Am J Respir Crit Care Med, 170: 520

- 526. Klemm RJ; Mason R (2003). Replication of reanalysis of Harvard Six

- City mortality study. In HEI Special Report: Revised Analyses of Time

- Series Studies of Air Pollution and Health, Part II (pp. 165

- 172). Boston, MA: Health Effects Institute. Klemm RJ; Lipfert FW; Wyzga RE; Gust C (2004). Daily mortality and air pollution in Atlanta: two years of data from ARIES. Inhal Toxicol, 16 Suppl 1: 131

- 141. Krewski D; Burnett RT; G oldberg MS; Hoover K; Siemiatycki J; Jerrett M; Abrahamowicz M; White WH (2000). Reanalysis of the Harvard Six Cities Study and the American Cancer Society Study of particulate air pollution and mortality. A special report of the Institute’s particle epide miology reanalysis project. Cambridge, MA: Health Effects Institute. Available: http://pubs.healtheffects.org/view.php?id=6***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 725 of 790 Formatted: Left Krewski D; Jerrett M; Burnett RT; Ma R; Hughes E; Shi Y; Turner MC; Pope A C III; Thurston G; Calle EE; Thun MJ (2009). Extended Follow

- Up and Spatial Analysis of the American Cancer Society Study Linking Particulate Air Pollution and Mortality. HEI Research Report 140, Health Effects Institute, Boston, MA. Available: http://pubs.healtheffects.org/view.php?id=315
. Laden F; Neas LM; Dockery DW; Schwartz J (2000). Association of fine particulate matter from different sources with daily mortality in six U.S. cities. Environ Health Perspect, 108: 941

- 947. Laden F; Schwartz J; Speizer FE; Dockery DW (2006). Reduction in fine particulate air pollution and mortality: extended follow

- up of the Harvard Six Cities Study. Am. J. Respir. Crit. Care. Med. 173: 667

- 672. Laden F (2009). Personal communication with Dr. Francine Laden: Annual PM 2.5 levels used in the update of the Harvard Six Cities Study. May 21, 2009. Docket No. EPA

- HQ

- OAR

- 2007

- 0492

- 0122. Lanki T; Pekkanen J; Aalto P; Elosua R; Berglind N; D'Ippoliti D; Kulmala M; Nyberg F; Peters A; Picciotto S; Salomaa V; Sunyer J; Tiittanen P; Von Klot S; Forastiere F (2006). Associations of traffic

- related air pollutants with hospitalization for first acute myocardial infarction: the HEAPSS study. Occup Environ Med, 63: 844

- 851. League of Women Voters (2012). Comments of the League of Women Voters on National Ambient Air Quality Standards for Particulate Matter; Proposed Rule. Docket No. EPA

- HQ

- OAR

- 2007

- 0492

- 9505. Lepeule J, Laden F, Dockery D, Schwartz .J (2012). Chronic Exposure to Fi ne Particles and Mortality: An Extended Follow

- Up of the Harvard Six Cities Study from 1974 to 2009. Environ Health Perspect. 120: 965

- 970. Lipfert FW; Baty JD; Miller JP; Wyzga RE (2006). Lipfert, FW; Wyzga RE; Baty JD; Miller JP (2006a). Traffic density as a surrogate measure of environmental exposures in studies of air pollution health effects: long

- term mortality in a cohort of US veterans. Atmospheric Environment 40: 154

- 169. Lipfert F W; Baty JD; Miller JP; Wyzga RE (2006b). PM 2.5 constituents and related air quality variables as predictors of survival in a cohort of U.S. military veterans. Inhal Toxicol, Inhalation Toxicology. 18: 645

- 657. Lipfert FW; Baty JD; Miller JP; Wyzga RE (2006) . PM 2.5 constituents and related air quality variables as predictors of survival in a cohort of U.S. military veterans. Inhal Toxicol, 18: 645

- 657. Liu S; Krewski D; Shi Y; Chen Y; Burnett R (2007). Association between maternal exposure to ambient air poll utants during pregnancy and fetal growth restriction. J Expo Sci Environ Epidemiol, 17: 426

- 432.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 726 of 790 Formatted: Left Malm WC; Sisler JF; Huffman D; Eldred RA; Cahill TA (1994). Spatial and Seasonal Trends in Particle Concentration and Optical Extinction in the United States, Journal of Geophysical Research (Atmospheres), 99:1347

- 1370. Malm WC; Schichtel BA; Pitchford ML (2011). Uncertainties in PM 2.5 gravimetric and speciation measurements and what we can learn from them. J Air Waste Manag Assoc, 61(11): 1131

- 49. MANE

- VU (2012 ). Comments of the Mid

- Atlantic North East Visibility Union on National Ambient Air Quality Standards for Particulate Matter; Proposed Rule. Docket No. EPA

- HQ

- OAR

- 2007

- 0492

- 9364. Mar TF ; Ito K ; Koenig JQ ; Larson TV ; Eatough DJ ; Henry RC ; Kim E ; Laden F ; Lall R ; Neas L ; Stölzel M ; Paatero P ; Hopke PK ; Thurston GD (2006). PM source apportionment and health effects. 3. Investigation of inter

- method variations in associations between estimated source contributions of PM 2.5 and daily mortality in Phoenix, AZ. J Expo Sci Environ Epidemiol , 16:311

- 20 McCabe J (2011) . Regional Consistence for the Administrative Requirements of State Implementation Plan Submittals and the Use of Letter Notices. Memorandum from Janet McCabe, Deputy Assistant Administrator, EPA Office of Air and Radiation to Regional Administrators, Regi ons I

- X. April 6, 2011. Available: http://www.epa.gov/air/urbanair/sipstatus/docs/mccabeLltrRAs.pdf
. McCarthy, R. (2012). Letter from the Assistant Administrator, EPA Office of Air and Radiation to Mr. Robert Ukeiley. Subject: Petition to Initiate Rulemaking to Designate Air Quality Models. January 4, 2012. Available: Available: http://www.epa.gov/scram001/10thmodconf/review_material/Sierra_Club_Petitio n_OAR

- 11

- 002

- 1093.pdf McClellan R (2012). Comments of Roger O McClellan, Advisor, Toxicology and Human Health Risk Analysis on National Ambient Air Quality Standards for Particulate Matter; Proposed Rule. Docket No. EPA

- HQ

- OAR

- 2007

- 0492

- 9409. August 31, 2012. McConnell R; Berha

ne K; Gilliland F; London SJ; Vora H; Avol E; Gauderman WJ; Margolis HG; Lurmann F; Tomas DC; Peters JM (1999). Air pollution and bronchitic symptoms in southern California children with asthma. Environ. Health Perspect. 107: 757

- 760. McConnell R; Berhane K; Gilliland F; Molitor J; Thomas D; Lurmann F; Avol E; Gauderman WJ; Peters JM (2003). Prospective study of air pollution and bronchitic symptoms in children with asthma. Am J Respir Crit Care Med, 168: 790

- 797. McCubbin D (2011). Health Benefits of Alter native PM 2.5 Standards. July 2011
. Formatted: Font: 12 pt, Not Superscript/ Subscript***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 727 of 790 Formatted: Left Middleton N; Yiallouros P; Kleanthous S; Kolokotroni O; Schwartz J; Dockery DW; Demokritou P; Koutrakis P (2008). A 10

- year time

- series analysis of respiratory and cardiovascular morbidity in Nicosia, Cyprus: the effect o f short

- term changes in air pollution and dust storms. Environ Health, 7: 39. Miller KA; Siscovick DS; Sheppard L; Shepherd K; Sullivan JH; Anderson GL; Kaufman JD (2007). Long

- term exposure to air pollution and incidence of cardiovascular events in women. N Engl J Med , 356: 447

- 458. MOE

- Ontario (2012). Comments of the Ministry of the Environment for the Province of Ontario, Canada on Nationa l Ambient Air Quality Standards for Particulate Matter; Proposed Rule. Docket No. EPA

- HQ

- OAR

- 2007

- 0492

- 9409. August 31, 2012. Molenar JV; Malm WC; Johnson CE (1994). Visual air quality simulation techniques. Atmos Environ, 28(5): 1055

- 1063. NACAA (2012). C omments of the National Association of Clean Air Agencies on National Ambient Air Quality Standards for Particulate Matter; Proposed Rule. Docket No. EPA

- HQ

- OAR

- 2007

- 0492

- 9397. August 31, 2012. NAM et al. (2012). Comments of the National Association of Man ufacturers, Aluminum Association, American Chemistry Council, American Coke & Coal Chemicals Institute, American Forest & Paper Association, American Foundry Society, American Iron & Steel Institute, American Petroleum Institute, American Wood Council, BCC A Appeal Group, Brick Industry Association, Council of Industrial Boiler Owners, Corn Refiners Association, Hardwood Plywood and Veneer Association, Industrial Energy Consumers of America, Motor & Equipment Manufacturers Association, National Association f or Surface Finishing, National Federation of Independent Business, National Oilseed Processors Association, National Mining Association, North American Die Casting Association, Rubber Manufacturers Association, U.S. Chamber of Commerce, and Wisconsin Manuf acturers & Commerce on National Ambient Air Quality Standards for Particulate Matter; Proposed Rule. Docket No. EPA

- HQ

- OAR

- 2007

- 0492

- 9425. August 31, 2012. NEDA/CAP (2012). Comments of the National Environmental Development Association’s Clean Air Project on National Ambient Air Quality Standards for Particulate Matter; Proposed Rule. Docket No. EPA

- HQ

- OAR

- 2007

- 0492

- 9421. August 31, 2012. NESCAUM (2012). Comments of the Northeast States for Coordinated Air Use Management on National Ambient Air Quality Stan dards for Particulate Matter; Proposed Rule. Docket No. EPA

- HQ

- OAR

- 2007

- 0492

- 9366. August 31, 2012. Nevada DEP (2012). Comments of the Nevada Division of Environmental Protection, Department of Conservation and Natural Resources, on National Ambient Air Quality Standards for Particulate Matter; Proposed Rule. Docket No. EPA

- HQ

-***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 728 of 790 Formatted: Left OAR

- 2007

- 0492

- 9410. August 31, 2012. New York DOH/DEC (2012). Comments of the New York State Departments of Health and Environmental Conservation on National Ambient Air Quality Sta ndards for Particulate Matter; Proposed Rule. Docket No. EPA

- HQ

- OAR

- 2007

- 0492

- 9352. August 28, 2012. NTAA (2012). Comments of the National Tribal Air Association on National Ambient Air Quality Standards for Particulate Matter; Proposed Rule. Docket No. EP A

HQ

- OAR

- 2007

- 0492

- 9926. August 31, 2012. Ntziachristos L; Ning Z; Geller MD; Sheesley RJ; Schauer JJ; Sioutas C (2007). Fine, ultrafine and nanoparticle trace element compositions near a major freeway with a heavy

- duty diesel fraction. Atmospheric Environ ment, 41 (2007): 5684

- 5696. NYS DOH (2006). A study of ambient air contaminants and asthma in New York City, Final Report Part B: Air contaminants and emergency department visits for asthma in the Bronx and Manhattan. Prepared for: The U.S. Department of H ealth and Human Services, Agency for Toxic Substance and Disease Registry. NMA/NCBA (2012). Comments of the National Mining Association and the National Cattlemen’s Beef Association on National Ambient Air Quality Standards for Particulate Matter; Propose d Rule. Docket No. EPA

- HQ

- OAR

- 2007

- 0492

- 9382. August 31, 2012. NSSGA (2012). Comments of the National Stone, Sand & Gravel Association on National Ambient Air Quality Standards for Particulate Matter; Proposed Rule. Docket No. EPA

- HQ

- OAR

- 2007

- 0492

- 9345. Au gust 30, 2012. O’Connor GT; Neas L; Vaughn B; Katan M; Mitchell H; Crain EF; Evans R 3 rd ; Gruchalla R; Morgan W; Stout J; Adams GK; Lippmann M (2008). Acute respiratory health effects of air pollution on children with asthma in US inner cities. J Allergy Clin Immunol, 121: 1133

- 1139. Oklahoma DEQ (2012). Comments of the Oklahoma Department of Environmental Quality on National Ambient Air Quality Standards for Particulate Matter; Proposed Rule. Docket No. EPA

- HQ

- OAR

- 2007

- 0492

- 9373. August 30, 2012. Ostro BD ; Broadwin R; Lipsett, MJ (2003). Coarse particles and daily mortality in Coachella Valley, California. In: Revised analyses of time

- series studies of air pollution and health. Special report. Boston, MA: Health Effects Institute; pp. 199

- 204. Available: http://pubs.healtheffects.org/getfile.php?u=21
. Available: http://pubs.healtheffects.org/getfile.php?u=21. Page S (2010a). Applicability of the Federal Prevention of Significant Deterioration Permi t Requirements to New and Revised National Ambient Air Quality Standards. Memorandum from Stephen D. Page, Director, U.S. EPA Office of Air Quality Planning and Standards to Air Division Directors and Deputies, Regions I***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 729 of 790 Formatted: Left

- X. April 1, 2010. Available: http://www.epa.gov/region07/air/nsr/nsrmemos/psdnaaqs.pdf
. Page S (2010b). Modeling Procedures for Demonstrating Compliance with PM 2.5 NAAQS. Memorandum from Stephen D. Page, Director, U. S. EPA Office of Air Quality Planning and Standards. March 23, 2010. Available: http://www.epa.gov/region7/air/nsr/nsrmemos/pm25memo.pdf
. Page S (2010c). Guidance Concerning the Implem entation of the 1

- hour NO 2 NAAQS for the Prevention of Significant Deterioration Program. Memorandum from Stephen D. Page, Director, U.S. EPA Office of Air Quality Planning and Standards to Air Division Directors. June 29, 2010. Includes 2 attachments. Ava ilable: http:// http:// www.epa.gov/region07/air/nsr/nsrmemos/appwno2.pdf . Page S (2010d). Guidance Concerning the Implementation of the 1

- hour SO2 NAAQS for the Prevention of Significant Deterioration Program. Memorandum from Stephen D. Page, Director, U.S. EPA Office of Air Quality Planning and Standards to Air Division Directo rs. August 23, 2010. Includes 2 attachments. Available: http://www.epa.gov/region7/air/nsr/nsrmemos/appwso2.pdf . Page S (2011). Guidance to Regions for Working with Tribes during the Na tional Ambient Air Quality Standards (NAAQS) Designations Process. Memorandum from Stephen D. Page, Director, EPA OAQPS to Regional Administrators, Regions I

- X. December 20, 2011. Available: http://www.epa.gov/ttn/oarpg/t1/memoranda/20120117naaqsguidance.pdf
. Page S (2012). Timely Processing of Prevention of Significant Deterioration (PSD) Permits when EPA or a PSD

- Delegated Air Agency Issues the Permit. Memorandum from Steph en D. Page, Director, U.S. EPA Office of Air Quality Planning and Standards to Regional Air Division Directors. October 15, 2012. Available: http://www.epa.gov/region7/air/nsr/nsrmemos/timely.pdf Papp M (2012). Documentation of Measurement Uncertainty Esti mates of Collocated Chemical Speciation Network and IMPROVE Data for Use in the Secondary PM 2.5 Standard for Visibility. Memorandum to the PM2.5 June 13, 2012. Docket ID number EPA

- HQ

- OAR

- 2007

- 0492

- 0387. Available at: http://www.epa.gov/ttn/amtic/pmspec.html
. . Parker JD; Woodruff TJ; Basu R; Schoendorf KC (2005). Air pollution and birth weight among term infants in California. Pediatrics, 115: 121

- 128. Parker JD; Woodruff TJ (2008). Influences of study design and location on the relationship between particulate matter air pollution and birthweight. Paediatr Perinat Epidemiol, 22: 214

- 227. Parrish ZD; White JC; Isleyen M; Gent MPN; Iannucci

- Berger W; Eitzer BD; Kelsey JW; Mattina MI (2006). Accumulation of weathered polycyclic aromatic Formatted: Subscript

Formatted: Hyperlink, Font: 10 pt, Not Superscript/ Subscript

Formatted: Hyperlink, Font: 10 pt, Not Superscript/ Subscript Formatted: Font: 12 pt, Not Superscript/ Subscript Formatted: Font: 12 pt

Formatted: Font color: Black, Not Superscript/ Subscript Formatted: Font color: Black***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 730 of 790 Formatted: Left hydrocarbons (PAHs) by plant and earthworm species. Chemosphere, 64: 609

- 618. Patra M; Bhowmik N; Bandopadhyay B; Sharma A (2004). Comparison of mercury, lead and arsenic with respect to genotoxic effects on plant systems and the development of genetic tolerance. Environ Exp Bot, 52: 199

- 223. Peng RD; Chang HH; Bell ML; McDermott A; Zeger SL; Samet JM; Dominici F (2008). Coarse particulate matter air pollution and hospital admissions for cardiovascular and respiratory disea ses among Medicare patients. JAMA, 299: 2172

- 2179. Penttinen P; Vallius M; Tiittanen P; Ruuskanen J; Pekkanen J (2006). Source

- specific fine particles in urban air and respiratory function among adult asthmatics. Inhal Toxicol, 18: 191

- 198. Perez L; Tobias A; Querol X; Kunzli N; Pey J; Alastuey A; Viana M; Valero N; Gonzalez

- Cabre M; Sunyer J (2008). Coarse particles from Saharan dust and daily mortality. Epidemiology, 19: 800

- 807. Peters A; Dockery DW; Muller JE; Mittleman MA (2001). Increased particulate air pollution and the triggering of myocardial infarction. Circulation, 103: 2810

- 2815. Peters J; Avol E; Gauderman WJ; Linn WS; Navidi W; London S; Margolis H; Rappaport E; Vora H; Gong H Jr; Thomas DC (1999). A study of twelve southern California communities with differing levels and types of air pollution II Effects on pulmonary function. Am J Respir Crit Care Med, 159: 768

- 775. Pitchford M; Maim W; Schichtel B; Kumar N; Lowenthal D; Hand J (2007). Revised algorithm for estimating light extinction from IMPROVE particle speciation data. J Air Waste Manag Assoc, 57: 1326

- 36. Pitchford M (20 10). Assessment of the Use of Speciated PM 2.5 Mass

- Calculated Light Extinction as a Secondary PM NAAQS Indicator of Visibility. Memorandum to PM NAAQS review docket. November 17, 2010. Docket ID number EPA

- HQ

OAR

- 2007

- 0492

- 0337. Available: http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_2007_td.html
. Poole C (2001). Causal values. Epidemiology 12:139

– 41. Pope CA 3 rd ; Dockery DW (1992). Acute health effects of PM 10 pollution on symptom atic and asymptomatic children. Am Rev Respir Dis , 145(5): 1123

- 8. Pope CA 3 rd ; Thun MJ; Namboodiri MM; Dockery DW; Evans JS; Sp eizer FE; Heath CW (1995). Particulate air pollution as a predictor of mortality in a prospective study of U.S. adults. Am J Respir Crit Care Med, 151: 669

- 674. Formatted: Font: 12 pt, Not Superscript/ Subscript***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 7 31 of 790 Formatted: Left Pope CA 3 rd ; Burnett RT; Thun MJ; Calle EE; Krewski D; Ito K; Thurston GD (2002). Lung cancer, cardiopulmonary mortality, and long

- term exposure to fine particulate air pollution. JAMA, 287: 1132

- 1141. Pope CA 3 rd ; Burnett RT; Thurston GD; Thun MJ; Calle EE; Krewski D; Godleski JJ (2004). Cardiovascular mortality and long

- term exposure to particulat e air pollution: epidemiological evidence of general pathophysiological pathways of disease. Circulation, 109: 71

- 77. Pope CA 3 rd ; Ezzati M; Dockery DW (2009). Fine

- particulate air pollution and life expectancy in the United States. N Engl J Med, 360: 376

- 386. Pope CA Burnett RT (2007). Pope CA; Burnett RT (2007). Commentary: Confounding in Air Pollution Epidemiology: The Broader Context. Epidemiology, 18: 424

- 426. Pryor SC (1996). Assessing public perception of visibility for standard setting exercises
. Atmos Environ, 30: 2705

- 2716. PSR (2012). Comments on National Ambient Air Quality Standards for Particulate Matter; Proposed Rule. Submitted on behalf of Physicians for Social Responsibility by Alan H. Lockwood, Andrew S. Kanter, Catherine Thomasson, an d Barbara Gottlieb. Docket No. EPA

- HQ

- OAR

- 2007

- 0492

- 5763. August 13, 2012. Puett RC; Schwartz J; Hart JE; Yanosky JD; Speizer FE; Suh H; Paciorek CJ; Neas LM; Laden F (2008). Chronic particulate exposure, mortality, and coronary heart disease in the nurse s’ health study. Am J Epidemiol, 168: 1161

- 1168. Rabinovitch N; Zhang LN; Murphy JR; Vedal S; Dutton SJ; Gelfand EW (2004). Effects of wintertime ambient air pollutants on asthma exacerbations in urban minority children with moderate to severe disease. J A llergy Clin Immunol, 114: 1131

- 1137. Rabinovitch N; Strand M; Gelfand EW (2006). Particulate levels are associated with early asthma worsening in children with persistent disease. Am J Respir Crit Care Med, 173: 1098

- 1105. Raizenne M; Neas LM; Damokosh AI; Dockery DW; Spengler JD; Koutrakis P; Ware JH; Speizer FE (1996). Health effects of acid aerosols on North American children: pulmonary function. Environ Health Perspect, 104: 506

- 514. Rajan P, Schmidt M, Hassett

- Sipple B (2011). PM 2.5 Distributional Stat istical Analyses. Memorandum to PM NAAQS review docket. April 7, 2011. Docket ID number EPA

- HQ

- OAR

- 2007

- 0492

- 0333. Available: http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_2007_td.h tml
. Rom W (2012). Letter from Dr. William N. Rom and more than 350 doctors, nurses, scientists, and public health and medical professionals to EPA Administrator Lisa Formatted: Font: 12 pt, Not Superscript/ Subscript***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 732 of 790 Formatted: Left P. Jackson providing comments on the proposed revision of the PM NAAQS, August 31, 2012. Docket No. EPA

- HQ

- OAR

- 2007

- 0492

- 9755. August 31, 2012. Roosli M; Kunzli N; Braun

- Farlander C; Egger M (2005). Years of life lost attributable to air pollution in Switzerland: dynamic exposure

- response model. Int J Epidemiol, 34:1029

- 1035. Ross Z; Jerrertt M; Ito K; Tempalski B; Thurston GD (2007). A land use regression for predicting fine particulate matter concentrations in the New York City region. Atmospheric Environment 41 (2007) 2255

- 2269. Rothman, KJ; Greenland S., eds. (1998). Modern epidemiology. 2 nd ed. Philadelphia, PA: Lippincott

- Raven Publishers. Royall, RM (1997). Statistical Evidence: A Likelihood Paradigm. London: Chapman and Hall. Russell, A (2009). Letter from the Clean Air Science Advisory Committee (CASAC) Ambient Air Monitoring and Methods Subcommittee (AAMMS) to the Honorable Lisa P, Jackson, Administrator, U.S. EPA. Subject: Consultation on Monitoring Issues Related to the NAA QS for Particulate Matter. March 6, 2009. EPA

- CASAC

- 09

- 006. Docket ID number EPA

- HQ

- OAR

- 2007

- 0492

- 0088. Available: http://yosemite .epa.gov/sab/sabproduct.nsf/C446E60A1156E2DF8525757100780 CF4/$File/EPA

- CASAC

- 09

- 006

- unsigned.pdf
. Russell, A; Samet, J.M. ( 2010a). Letter from the Clean Air Science Advisory Committee (CASAC) Ambient Air Monitoring and Methods Subcommittee (AAMMS) to the Honorable Lisa P, Jackson, Administrator, U.S. EPA. Review of the White Paper on Particulate Matter (PM) Light Extinction Measurements. April 29, 2010. EPA

CASAC

- 10

- 010. Docket ID number. EPA

- HQ

- OAR

- 2007

- 0492

- 0189. Available: http://yosemite.epa.gov/sab/sabproduct.nsf/264cb1227d55e02c85257402007446a 4/92C9F5AA09A76A93852577150004A782/$File/EPA

- CASAC

- 10

- 01 0

- unsigned.pdf Russell, A; Samet, J.M. ( 2010b). Letter from the Clean Air Science Advisory Committee (CASAC) Ambient Air Monitoring and Methods Subcommittee (AAMMS) to the Honorable Lisa P, Jackson, Administrator, U.S. EPA. Review of the “Near

- road Guidance Document

- Outline” and “Near

- road Monit oring Pilot Study Objectives and Approach.” November 24, 2010. EPA

- CASAC

- 11

- 001. Docket ID number. EPA

- HQ

- OAR

- 2007

- 0492

- XXXX Available: http://yosemite.epa.gov/sab/sabproduct.nsf/ACD1BD26412312DC852577E50059 1B37/$File/EPA

- CASAC

- 11

- 001

- unsigned.pdf Formatted: Indent: Hanging: 0.5"

Formatted: Normal, Indent: Left: 0", Hanging: 0.5", Space After: 12 pt***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 733 of 790 Formatted: Left Savitz, DA; Tolo KA; Poole C (1994). Statistical significance testing in the American Journal of Epidemiology, 1970

– 1990. American Journa l of Epidemiology 139:1047

– 1052. Samet J (2009a). Letter from Dr. Jonathan M. Samet, Chair, Clean Air Scientific Advisory Committee to the Honorable Lisa P. Jackson, Administrator, U.S. EPA. Consultation on EPA’s Particulate Matter National Ambient Air Qu ality Standards: Scope and Methods Plan for Health Risk and Exposure Assessment. May 21, 2009. EPA

- CASAC

- 09

- 009. Docket ID number. EPA

- HQ

- OAR

- 2007

- 0492

- 0024. Available: http://yosemite.epa.gov/sab/sabproduct.nsf/723FE644C5D758DF852575BD0076 3A32/$File/EPA

- CASAC

- 09

- 009

- unsigned.pdf Samet, J (2009b). Letter from Dr. Jonathan M. Samet, Chair, Clean Air Scientific Advisory Committee to th e Honorable Lisa P. Jackson, Administrator, U.S. EPA. Consultation on EPA’s Particulate Matter National Ambient Air Quality Standards: Scope and Methods Plan for Urban Visibility Impact Assessment. EPA

- CASAC

- 09

- 010. Docket ID number. EPA

- HQ

- OAR

- 2007

- 0492

- 0 026. May 21, 2009. Available: http://yosemite.epa.gov/sab/sabproduct.nsf/0F63D7995F5850D5852575BD00778 69C/$File/EPA

- CASAC

- 09

- 010

- u nsigned.pdf
. Samet J (2009c). Letter from Dr. Jonathan M. Samet, Chair, Clean Air Scientific Advisory Committee to the Honorable Lisa P. Jackson, Administrator, U.S. EPA. Review of Risk Assessment to Support the Review of the Particulate Matter (PM) Prima ry National Ambient Air Quality Standards

– External Review Draft (September 2009). November 24, 2009. Docket ID number EPA

- HQ

- OAR

- 2007

- 0492

- 0065. Available: http://yosemite.epa.gov/sab/sabproduct.nsf/BC1ECC5D539EF72385257678006D 5754/$File/EPA

- CASAC

- 10

- 003

- unsigned.pdf
. Samet J (2009d). Letter from Dr. Jonathan M. Samet, Chair, Clean Air Scientific Advisory Committee to the Honorable Lisa P. Jackson, Administrator, U.S. EPA. Review of Particulate Matter Urban

- Focused Visibility Assessment (External Review Draft, September 2009). November 24, 2009. Docket ID number EPA

HQ

- OAR

- 2007

- 0492

- 0064. Available: http://yosemite.epa.gov/sab/sabproduct.nsf/15872217938041F685257678006A26 E3/$File/EPA

- CASAC

- 10

- 002

- unsigned.pdf Samet J (2009e). Letter from Dr. Jonathan M. Samet , Chair, Clean Air Scientific Advisory Committee to the Honorable Lisa P. Jackson, Administrator, U.S. EPA. CASAC Review of EPA’s Integrated Science Assessment for Particulate Matter

– First External Review Draft (December 2008). May 21, 2009. EPA

- CASAC

- 09

- 008. Docket ID number EPA

- HQ

- ORD

- 2007

- 0517

- 0120. Available: http://yosemite.epa.gov/sab/sabproduc t.nsf/264cb1227d55e02c85257402007446a 4/73ACCA834AB44A10852575BD0064346B/$File/EPA

- CASAC

- 09

- 008

- unsigned.pdf
. Formatted: Font: 12 pt, Not Superscript/ Subscript***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 734 of 790 Formatted: Left Samet J (2009f). Letter from Dr. Jonathan M. Samet, Chair, Clean Air Scientific Advisory Committee to the Honorable Lisa P. Jackson, Administrator , U.S. EPA. CASAC Review of EPA’s Integrated Science Assessment for Particulate Matter

– Second External Review Draft (July 2009). November 24, 2009. Docket ID number. EPA

- HQ

- ORD

- 2007

- 0517

- 0121. Available: http://yosemite.epa.gov/sab/sabproduct.nsf/264cb1227d55e02c85257402007446a 4/151B1F83B023145585257678006836B9/$File/EPA

- CASAC

- 10

- 001

- unsigned.pdf
. S amet J (2010a). Letter from Dr. Jonathan M. Samet, Chair, Clean Air Scientific Advisory Committee to the Honorable Lisa P. Jackson, Administrator, U.S. EPA. CASAC Review of Quantitative Health Risk Assessment for Particulate Matter

– Second External Review Draft (February 2010). April 15, 2010. Docket ID number EPA

- HQ

- OAR

- 2007

- 0492

- 0109. Available: http://yosemite.epa.gov/sab/sabprod uct.nsf/BC4F6E77B6385155852577070002F 09F/$File/EPA

- CASAC

- 10

- 008

- unsigned.pdf
. Samet J (2010b). Letter from Dr. Jonathan M. Samet, Chair, Clean Air Scientific Advisory Committee to the Honorable Lisa P. Jackson, Administrator, U.S. EPA. CASAC Review of Particulate Matter Urban

- Focused Visibility Assessment

- Second External Review Dr aft (January 2010). April 20, 2010. Docket ID number EPA

- HQ

- OAR

- 2007

- 0492

- 0110. Available: http://yosemite.epa.gov/sab/sabproduct. nsf/0D5CB76AFE7FA77C8525770D004 EED55/$File/EPA

- CASAC

- 10

- 009

- unsigned.pdf
. Samet J (2010c). Letter from Dr. Jonathan M. Samet, Chair, Clean Air Scientific Advisory Committee to the Honorable Lisa P. Jackson, Administrator, U.S. EPA. CASAC Review of Policy A ssessment for the Review of the PM NAAQS

– First External Review Draft (March 2010). May 17, 2010. Docket ID number EPA

HQ

- OAR

- 2007

- 0492

- 0113. Available: http://yosemite.epa.gov/sab/sabproduct.nsf/264cb1227d55e02c85257402007446a 4/E504EE3276D87A9E8525772700647AFB/$File/EPA

- CASAC

- 10

- 011

- unsigned.pdf
. Samet J (2010d). Letter from Dr. Jonathan M. Samet, Chair, Clean Air Scientific Advisory Committee to the Honorable Lisa P. Jackson, Administrator, U.S. EPA. CASAC Review of Policy Assessment for the Review of the PM NAAQS

– Second External Review Draft (June 2010). September 10, 2010. Docket ID number EPA

- HQ

- OAR

- 2007

- 0492

- 0256. Available: http://yosemite.epa.gov/sab/sabproduct.nsf/264cb1227d55e02c8525 7402007446a 4/CCF9F4C0500C500F8525779D0073C593/$File/EPA

- CASAC

- 10

- 015

- unsigned.pdf
. Sammons WAH; Saff R; Blackley WJ; Avery S; Kreilein N (2012). Comments on National Ambient Air Quality Standards for Particulate Matter; Proposed Rule , submitted by William A.H. Sammons, M.D.; Ronald Saff, M.D.; W.J. Blackley, Formatted: Font: 12 pt, Not Superscript/ Subscript

Formatted: Font: 12 pt, Not Superscript/ Subscript

Formatted: Font: 12 pt, Not Superscript/ Subscript

Formatted: Font: 12 pt, Not Superscript/ Subscript***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 735 of 790 Formatted: Left M.D.; Shayne Avery, M.D.; and Norma Kreilein, M.D. Docket No. EPA

- HQ

OAR

- 2007

- 0492

- 7555. Sarnat J; Marmur A; Klein M; Kim E; Russell AG; Sarnat SE; Mulholland JA; Hopke PK; Tolbert PE (2008). Fine part icle sources and cardiorespiratory morbidity: An application of chemical mass balance and factor analytical source

- apportionment methods. Environ Health Perspect, 116: 459

- 466. Sato M; Hansen J; Koch D; Lucis A; Ruedy R; Dubovik O; Holben B; Chin M; Novako v T (2003). Global atmospheric black carbon inferred from AAEONET. Presented at Proceedings of the National Academy of Science. Schilling JS; Lehman ME (2002). Bioindication of atmospheric heavy metal deposition in the Southeastern U.S. using the moss Thui dium delicatulum. Atmos Environ, 36: 1611

- 1618. Schisterman EF, Cole SR, Platt RW (2009). Overadjustment bias and unnecessary adjustment in epidemiologic studies. Epidemiology 20(4): 488

- 495. Schmidt M; Hassett

- Sipple B; Rajan P (2010) PM 2.5 Air Quality Analyses. Memorandum for the PM NAAQS Review (Docket EPA

– HQ

- OAR

- 2007

- 0492). July 22, 2010. Available: http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_2007_td.html Schmi dt M; Jenkins SM (2010). PM 10 and PM 10

- 2.5 Air Quality Analyses. Memorandum to PM NAAQS review docket. July 22, 2010. Docket ID number EPA

- HQ

- OAR

2007

- 0492

- 0128. Available: http://www.e pa.gov/ttn/naaqs/standards/pm/s_pm_2007_td.html Schmidt M (2011). PM 2.5 Air Quality Analyses

– Update: Memorandum to the PM NAAQS Review Docket. April 15, 2011. Docket ID number EPA

- HQ

- OAR

2007

- 0492

- 0340. Available: http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_2007_td.html
. Schmidt M ( 2012). Additional 2012a). Sensitivity Analysis of Long

- term Mean PM 2.5 Analyses Concentrations for Selected Long

- term Exposure Epidemiological Studies . Memorandum to PM NAAQS Review Docket No. EPA_HQ

- OAR

- 2007

- 0492. December 2012. Available: http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_2007_td.html
. Schmidt M (2012b). Evaluation of the PM 2.5 'Collocated PM 10 Data Substitution Routine, 2009

- 2011 . Memorandum to PM NAAQS Review Docket No. EPA_HQ

- OAR

2007

- 0492, December 2012. Available: http://www.epa.go v/ttn/naaqs/standards/pm/s_pm_2007_td.html
. Schneiderman ET; Myers MJ; Wilson L; Biden JR; King G; Kilmartin PF; Sorrell WH (2012). Comments of the State Attorneys General of New York, Delaware, New Mexico, Rhode Island, and Vermont on National Ambient Air Quality Standards for Particulate Matter; Proposed Rule. Docket No. EPA

- HQ

- OAR

- 2007

- 0492

- Formatted: Font color: Black, Not Superscript/ Subscript Formatted: Font color: Black Formatted: Font color: Black, Not Superscript/ Subscript***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 736 of 790 Formatted: Left 9385. August 31, 2012. Schreuder AB; Larson TV; Sheppard L; Claiborn CS (2006). Ambient woodsmoke and associated respiratory emergency department visits in Spokane , Washington. Int J Occup Environ Health, 12: 147

- 153. Schwartz J; Dockery DW; Neas LM (1996). Is daily mortality associated specifically with fine particles? J Air Waste Manage Assoc, 46: 927

- 939. Schwartz J; Coull B; Laden F; Ryan L (2008). The effect o f dose and timing of dose on the association between airborne particles and survival. Environ Health Perspect, 116: 64

- 69. Seitz J (1991). New Source Review Program Transitional Guidance. Memorandum from John S. Seitz, Director, EPA Office of Air Quality P lanning and Standards. Available: http:// www.epa.gov/region07/air/nsr/nsrmemos/trnsguid.pdf
. Seitz J (1997). Memorandum on the Interim Implementation of New Source Review Requirements for PM 2.5 . Memorandum from John S. Seitz, Director, EPA Office of Air Quality Planning and Standards. EPA Reference OZPMRH

- 2

- 97. Available: http://www.epa.gov/ttn/caaa/t1/memoranda/pm25.pdf
. Sheppard L; Levy D; Norris G; Larson TV; Koenig JQ (2003). Effects of ambient air pollution and nonelderly asthma hospital admissions in Seattle, Washington, 1987

- 1994. Epidemiology, 10: 23

- 30. Slaughter JC; Kim E; Sheppard L; Sullivan JH; Larson TV; Claib orn C (2005). Association between particulate matter and emergency room visits, hospital admissions and mortality in Spokane, Washington. J Expo Sci Environ Epidemiol, 15: 153

- 159. Smith A (2009). Comments to CASAC on Particulate Matter National Ambient A ir Quality Standards: Scope and Methods Plan for Urban Visibility Impact Assessment. Anne E. Smith, CRA International. Washington, DC. March 24, 2009. Prepared at the request of the Utility Air Regulatory Group. Docket ID number EPA

- HQ

- OAR

- 2007

- 0492

- 0015, Attachment I. Smith AE; Howell S (2009). An assessment of the robustness of visual air quality preference study results. CRA International. Washington, DC. http://yosemite.epa.gov/sab/sabproduct.nsf/B55911DF9796E5E385257592006FB 737/$File/CRA+VAQ+Pref+Robustness+Study+3+30+09+final.pdf South Carolina DHEC (2012). Comments of the South Carolina Department of Health and Environmental Control on National Ambient Air Quality Standards for Particulate Matter; Proposed Rule. Docket No. EPA

- HQ

- OAR

- 2007

- 0492

- 9469. August 31, 2012. Formatted: Font: 12 pt, Not Superscript/ Subscript***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 737 of 790 Formatted: Left South Dakota DENR (2012). Comments of the South Dakota Department of Environment and Natural R esources on National Ambient Air Quality Standards for Particulate Matter; Proposed Rule. Docket No. EPA

- HQ

- OAR

- 2007

- 0492

- 9360. August 31, 2012. Spiegelman D. Approaches to uncertainty in exposure assessment in environmental epidemiology. Annu Rev Public H ealth 2010, 31: 149

- 163. Stanek L; Hassett

- Sipple B; Yang R (2010). Southern Company (2012). Comments of the Southern Company on National Ambient Air Quality Standards for Particulate Matter Air Quality Data Requested from Epidemiologic Study Authors. Memor andum to PM NAAQS Review dockets EPA

- HQ

- ORD

- 2007

- 0517 and ; Proposed Rule. Docket No. EPA

- HQ

- OAR

- 2007

- 0492 . July 22, 2010

- 9365. August 31, 2012. Stanojevic S; Wade A; Stocks J; Hankinson J; Coates AL; Pan H; Rosenthal M; Corey M; Lebecque P; Cole TJ (2008). Reference ranges for spirometry across all ages: a new approach. Am J Respir Crit Care Med. 177: 253

- 260. Stratus Consulting (2009). Review of Urban Visibility Public Preference Studies: Final Report . Docket ID number No. EPA

- HQ

- OAR

- 2007

- 0492

- 0130. Availab le: http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_2007_td.html 0042. Texas CEQ (2012). Comments of the Texas Commission on Environmental Quality on National Ambient Air Quality Standards for Particulate Matter; Proposed Rule. Docket No. EPA

- HQ

- OAR

- 2007

- 0492

- 9522. August 31, 2012. Thomas D, Stram D, Dwyer J
. (1993). Exposure measurement error: influence on exposure - disease. Relationships and methods of correction. Annu Rev Public Health 1993 , 14: 69

- 93. Thurston G; Ito K; Mar T; Christensen WF; Eatough DJ; Henry RC; Kim E; Laden F; Lall R; Larson TV; Liu H; Neas L; Pinto J; Stolzel M; Suh H; Hopke PK (2005). Results and implications of the workshop on the source apportionment of P M health effects. Epidemiology, 16: S134

- S135. UARG ( 2009). Comments of the Utility Air Resources Group on the Integrated Science Assessment for Particulate Matter

– Second External Review Draft. Docket No. EPA

- HQ

- ORD

- 2007

- 0517

- 0077. October 13, 2009. UARG ( 2012). Comments of the Utility Air Resources Group on National Ambient Air Quality Standards for Particulate Matter; Proposed Rule. Docket No. EPA

- HQ

OAR

- 2007

- 0492

- 9483. August 31, 2012. Urban Air Initiative (2012). Comments on National Ambient Air Quali ty Standards for Particulate Matter; Proposed Rule. Docket No. EPA

- HQ

- OAR

- 2007

- 0492

- 9538. August 30, 2012.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 738 of 790 Formatted: Left U.S. EPA (1996). Air Quality Criteria for Particulate Matter. U.S. Environmental Protection Agency. Research Triangle Park, NC. EPA/600/P

- 95/001. Apr il 1996. Available: http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_cr_cd.html
. U.S. EPA (1997). Guidance for Network Design and Optimum Site Exposure for PM 2.5 and PM 10 . U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC 27711; EPA

- 454/R

- 99

- 022. December 1997. Available: http://ww w.epa.gov/ttn/amtic/files/ambient/pm25/network/r

- 99

- 022.pdf
. U.S. EPA (1999). Guideline on Data Handling Conventions for the PM NAAQS; EPA

454/R

- 99

- 008. U.S. EPA (2003). Guidance for Tracking Progress Under the Regional Haze Rule. U.S. Environmental Protection Agency, Office of Air Quality Planning and Standard, Research Triangle Park, NC 27711. Report no. EPA

- 454/B

- 03

- 004. September 2003. Available: http://www.epa.gov/ttn/oarpg/t1/memoranda/rh_tpurhr_gd.pdf
. U.S. EPA ( 2004 2004a ). Air Quality Criteria for Particulate Matter. National Center for Environmental Assessment, Office of Rese arch and Development, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711; report no. EPA/600/P

- 99/002aF and EPA/600/P

- 99/002bF. October 2004. Available: http://www. epa.gov/ttn/naaqs/standards/pm/s_pm_cr_cd.html
. U.S. EPA ( 2004b). The Particle Pollution Report: Current Understanding of Air Quality and Emissions through 2003. Office of Air Quality Planning and Standards, Research Triangle Park, NC. Report No. EPA 454

- R

- 04

- 002. December 2004. Available: http://www.epa.gov/airtrends/aqtrnd04/pmreport03/report_2405.pdf. U.S. EPA ( 2005). Review of the National Ambient Air Quality Standards for Particulate Matter: Policy Assessment of Scientific and Technical Information, OA QPS Staff Paper. Research Triangle Park, NC 27711: Office of Air Quality Planning and Standards. Report No. EPA

- 452/R

- 05

- 005a. December 2005. Available: http://www.epa.gov/ttn/naaqs/st andards/pm/s_pm_cr_sp.html
. U.S. EPA (2006a). Provisional Assessment of Recent Studies on Health Effects of Particulate Matter Exposure. National Center for Environmental Assessment, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, NC. Report No. EPA 600/R

- 06/063. July 2006. Available: http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=151826
. U.S. EPA (2006b). Air Quality Criteria for Lead

- Final Report. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R

- 05/144aF

- bF, October 2006. Available: http://www.epa.gov/ttn/naaqs/standards/pb/s_pb_cr_cd.html
. U.S, EPA (2006c). Report on Air Quality in Nonattainment Areas for 2003

- 2005 Covering Ozone, Particulate Matter, Carbon Monoxide, Sulfur Dioxide, Nitrogen Dioxide, and Lead: Techn ical Summary. U.S. Environmental Protection Agency, Formatted: Font color: Black, Not Superscript/ Subscript***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 739 of 790 Formatted: Left Research Triangle Park, NC. Office of Air Quality Planning and Standards. November 2006 , revised February 14, 2007. Available: http://www.epa.gov/airtrends/pdfs/20070214_aq_na_2003

- 2005.pdf http://www.epa.gov/airtrends/pdfs/20070214_aq_na_2003

- 2005.pdf
. U.S. EPA (2007a). Draft Integrated Review Plan for the National Ambient Air Quality Standards for Particulate Matter. Na tional Center for Environmental Assessment and Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, Research Triangle Park, NC. Report No. EPA 452/P

- 08

- 006. October 2007. Available: http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_2007_pd.html
. U.S. EPA (2007b). Ambient Air Monitoring Network Assessment Guidance, Analytical Techniques for Technical Assessments of Ambient Air Monitoring Networks. EPA 454/d

- 07

- 001. February 2007. Available: http://www.epa.gov/ttn/amtic/files/ambient/pm25/datamang/network

- assessment
guidance.pdf
. U.S. EPA (2008a). Integrated Review Plan for the National Ambient Air Quality Standards for Particulate Matter. National Center for Environmental Assessment and Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, Research Triangle Park, NC. Report No. EPA 452/R

- 08

- 004. March 2008. Available: http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_2007_pd.html
. U.S. EPA (2008b). Integrated Science Assessment for Particulate Matter: First Ex ternal Review Draft. National Center for Environmental Assessment

- RTP Division, Office of Air Quality Planning and Standards, Research Triangle Park, NC. EPA/600/R

- 08/139 and 139A. December 2008. Available: http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_2007_isa.html
. U.S. EPA (2008c). U.S. EPA. Integrated Science Assessment (ISA) for Oxides of Nitrogen and Sulfur Ecological Criteria (Final Report). U.S. Environmental Protection Age ncy, Washington, D.C., EPA/600/R

- 08/082F, December 2008. Available: http://www.epa.gov/ttn/naaqs/standards/no2so2sec/cr_isi.html
. U.S. EPA (2008d). Ambient Air Quality Monitoring a nd Health Research: Summary of April 16

- 17, 2008. Workshop to Discuss Key Issues. December 2008. EPA

452/S

- 08

- 001. Available: http://epa.gov/airsc ience/pdf/FINAL

- April

- 2008

- AQ

Health

- Research

- Workshop

- Summary

- Dec

- 2008.pdf
. U.S. EPA (2008e). Integrated Science Assessment for Oxides of Nitrogen

– Health Criteria (Final Report). U.S. Environmental Protection Agency, Washington, DC, EPA/600/R

- 08/071. Ju ly 2008. Available: http://www.epa.gov/ttn/naaqs/standards/nox/s_nox_cr_isi.html
. U.S. EPA (2008f). Integrated Science Assessment (ISA) for Sulfur Oxides

– Health Criteria (Final Report). U.S. Environmental Protection Agency, Washington, DC, Field Code Changed***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 740 of 790 Formatted: Left EPA/600/R

- 08/047F, 2008. Available: http://www.epa.gov/ttn/naaqs/standards/so2/s_so2_cr_isa.html
. U.S. EPA (2009a). I ntegrated Science Assessment for Particulate Matter: Final Report. National Center for Environmental Assessment

- RTP Division, Office of Research and Development, Research Triangle Park, NC. EPA/600/R

- 08/139F. December 2009. Available: http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_2007_isa.html
. U.S. EPA (2009b). Integrated Science Assessment for Particulate Matter: Second External Review Draft. National Center for Environmental Ass essment
- RTP Division, Office of Research and Development, Research Triangle Park, NC. EPA/600/R

- 08/139B. July 2009. Available: http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_2007_is a.html
. U.S. EPA (2009c). Particulate Matter National Ambient Air Quality Standards: Scope and Methods Plan for Health Risk and Exposure Assessment. Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency , Research Triangle Park , NC. EPA

- 452/P

- 09

- 002. February 2009. Available: http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_2007_pd.html
. U.S. EPA (2009d). Particulate Matter National Ambient Air Quality Stand ards: Scope and Methods Plan for Urban Visibility Impact Assessment. Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency , Research Triangle Park, NC. EPA

- 452/P

- 09

- 001. February 2009. Available: http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_2007_pd.html
. U.S. EPA (2009e). Risk Assessment to Support the Review of the PM Primary National Ambient Air Quality Standards

- External Review Draft . Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency , Research Triangle Park, NC. EPA

- 452/P

- 09

- 006. September 2009. Available: http://www.epa.gov/ttn/naaqs/standards /pm/s_pm_2007_risk.html
. U.S. EPA (2009f). Particulate Matter Urban

- Focused Visibility Assessment

– External Review Draft. Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency , Research Triangle Park, NC. EPA

- 452/P

- 09

- 005. September 2009. Available: http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_2007_risk.html
. U.S. EPA (2009g). Policy Assessment for th e Review of the Particulate Matter National Ambient Air Quality Standards

– Preliminary Draft. Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency , Research Triangle Park, NC. EPA

- 452/P

- 09

- 007. September 2009. Available: http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_2007_pa.html
. U.S. EPA (2009h). Risk and Exposure Assessment for Review of the Secondary National Ambient Air Quality Standards for Oxides of Nitrogen and Oxides of Sulfur. (Final Report). U.S. Environmental Protection Agency, Research Triangle Park,***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 741 of 790 Formatted: Left NC, EPA

- 452/R

- 09

- 008a. Available: http://www.epa.gov/ttn/naaqs/standa rds/no2so2sec/cr_rea.html
. U.S. EPA (2010a). Quantitative Health Risk Assessment for Particulate Matter

– Final Report . Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency , Research Triangle Park, NC. EPA

- 452/R

- 10

- 005. June 2010. Available: http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_2007_risk.html
. U.S. EPA (2010b). Particulate Matter Urban

- Focused Visibility Assessment

– Final Report. Office of A ir Quality Planning and Standards, U.S. Environmental Protection Agency , Research Triangle Park, NC. EPA

- 452/R

- 10

- 004. July 2010. Available: http://www.epa.gov/ttn/naaqs/standards/ pm/s_pm_2007_risk.html
. U.S. EPA (2010c). Policy Assessment for the Review of the Particulate Matter National Ambient Air Quality Standards

- First External Review Draft. Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency , R esearch Triangle Park, NC. EPA 452/P

- 10

- 003. March 2010. Available: http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_2007_pa.html
. U.S. EPA (2010d). Quantitative Risk Assessment for P articulate Matter

– Second External Review Draft . Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency , Research Triangle Park, NC. EPA

- 452/P

- 10

- 001. February 2010. Available: http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_2007_risk.html
. U.S. EPA (2010e). Particulate Matter Urban

- Focused Visibility Assessment

– Second External Review Draft . Office of Air Quality Planning and Standards, U.S. Environment al Protection Agency , Research Triangle Park, NC. EPA

- 452/P

- 10

- 002. January 2010. Available: http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_2007_risk.html
. U.S. EPA (2010f). Policy Assessment for the Review of the Particulate Matter National Ambient Air Quality Standards

- Second External Review Draft. Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency , Research Triangle Park, NC. EPA 452/P

- 10

- 007. June 2010. Available: http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_2007_pa.html
. U.S. EPA ( 2010g). White Paper on PM Light Extinction Measurements. Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency , Research Triangle Park, NC. January 2010. Available: http://yosemite.epa.gov/sab/sabproduct.nsf/264cb1227d55e02c85257402007446a 4/823a6c8842610e768525764900659b22!OpenDocument U.S. EPA ( 2010h). Risk and Exposure Assessment for Review of the Secondary National Ambient Air Quality Standards for Oxides of Nitrogen and Oxides of Sulfur. Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency , Research Triangle Par k, NC. EPA 452/R

- 09

- 008a/b. September 2009. Available: http://www.epa.gov/ttn/naaqs/standards/no2so2sec/cr_rea.html
.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 742 of 790 Formatted: Left U.S. EPA (2010i). White Paper regarding Draft Near

- road Guidanc e Document

– Outline and Draft Near

- road Monitoring Pilot Study Objectives & Approach. Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency , Research Triangle Park, NC. August 24. 1010. Available: http://yosemite.epa.gov/sab/sabproduct.nsf/0/9E0F3E9D727323C1852577890059 6432/$File/Review+Document+for+Sept.+29+

- +30,+2010+AAMMS +Meeting.pdf
. U.S. EPA (2010j). Transportation Conformity Guidance for Quantitative Hot

- spot Analyses in PM 2.5 and PM 10 Nonattainment and Maintenance Areas. U.S. EPA Office of Transportation and Air Quality, Transportation and Regional Programs Division. December 2010. EPA

- 420

- B

- 10

- 040. Available: http://www.epa.gov/otaq/stateresources/transconf/policy/420b10040.pdf
. U.S. EPA (2010k). Integrated Science Assessment for Carb on Monoxide (Final Report). U.S. Environmental Protection Agency, Washington, DC, EPA/600/R

- 09/019F, January 2010. Available: http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=218686
. U.S. EPA (2011a). Policy Assessment for the Review of the Particulate Matter National Ambient Air Quality Standards. Office of Air Quality Planning and Standards, U.S. Environmental Protection A gency , Research Triangle Park, NC. EPA 452/R

11

- 003. April 2011. Available: http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_2007_pa.html
. U.S. EPA (2011b). Policy Assessment for the Review of the Secondary National Ambient Air Quality Standards for Oxides of Nitrogen and Oxides of Sulfur. Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, Research Triangle Park, NC, EPA

- 452/R

- 11

- 005a, b. February 2011. Available: http://www.epa.gov/ttn/naaqs/standards/no2so2sec/cr_pa.html
. U.S. EPA (2011c). Responses to Public Comments on the Proposed Prevention of Significant Deterioration Permi t for the Avenal Energy Project. U.S. Environmental Protection Agency. May 2011. U.S. EPA (2011d). Integrated Science Assessment of Ozone and Related Photochemical Oxidants (Second External Review Draft). U.S. Environmental Protection Agency, Washington, D C, EPA/600/R

- 10/076B, 2011. September 2011. Available: http://www.epa.gov/ttn/naaqs/standards/ozone/s_o3_2008_isa.html
. U.S. EPA (2012a). Responses to Significant Comments on th e 2012 Proposed Rule on the National Ambient Air Quality Standards for Particulate Matter (June 29, 2012; 77 FR 38890). Docket Number EPA

- HQ

- OAR

- 2007

- 0492. U.S. Environmental Protection Agency. December 2012. Available: http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_index.html
. U.S. EPA (2012b). Provisional Assessment of Recent Studies on Health Effects of Particulate Matter Exposure. U.S. Environmental Protection Agency. Office of***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 743 of 790 Formatted: Left
Res earch and Development, National Center for Environmental Assessment. EPA/600/R

- 12/056A. December 2012. U.S. EPA (2012c). Report to Congress on Black Carbon. Office of Air and Radiation, Office of Air Quality Planning and Standards, U.S. Environmental Prote ction Agency, Research Triangle Park, NC, EPA

- 450/R

- 12

- 001. March 2012. Available: http://www.epa.gov/blackcarbon/
. Available: http://www.epa.gov/blackcarbon/
. U.S. EPA (2012d). Order Partially Granting and Part ially Denying the Petition for Objection to Permit for CF&I Steel, L.P. (EVRAZ Rocky Mountain Steel). U. S. Environmental Protection Agency. May 31, 2012. Available: http://www.epa.gov/region07/air/title5/petitiondb/petitions/evraz_response2011.p df
. U.S. EPA (2012e). Draft Guidance to Implement Requirements for the Treatment of Air Quality Monitoring Data Influenced by Exceptional Events. U.S. Environmental Protection Agency. June 2012. Available: http://www.epa.gov/ttn/analysis/exevents.htm. Vandenberg J (2009). CASAC Review of Integrated Science Assessment for Particulate M atter: Second External Review Draft. Memorandum from John Vandenberg, Director, National Center for Environmental Assessment, Research Triangle Park Division, U.S. EPA to Holly Stallworth, Designated Federal Officer, Clean Air Scientific Advisory Committee , EPA Science Advisory Board Staff Office. August 5, 2009. Docket ID no. EPA

- HQ

- ORD

- 2007

- 0517

- 0125. Viles HA; Gorbushina AA (2003). Soiling and microbial colonisation on urban roadside limestone: A three year study in Oxford, England. Building Environ, 38: 1217

- 1224. Villeneuve PJ; Chen L; Stieb D; Rowe BH (2006). Associations between outdoor air pollution and emergency department visits for stroke in Edmonton, Canada. Eur J Epidemiol, 21: 689

- 700. Wegman L (2011). Transmittal of Policy Assessment for the Review of the Particulate Matter National Ambient Air Quality Standards

– Final Document. Memorandum from Lydia N. Wegman, Director, Health and Environmental Impacts Division, Office of Air Quality Planning and Standards, U.S. EPA to Holly Stallworth, Desi gnated Federal Officer, Clean Air Scientific Advisory Committee, EPA Science Advisory Board Staff Office. April 20, 2011. Docket ID no. EPA

- HQ

OAR

- 2007

- 0492

- 0338. WESTAR (2012). Comments of the Western States Air Resources Council on National Ambient Air Q uality Standards for Particulate Matter; Proposed Rule. Docket No. EPA

- HQ

- OAR

- 2007

- 0492

- 9374. August 31, 2012. WHO (2008). Part 1: Guidance Document on Characterizing and Communicating***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 744 of 790 Formatted: Left Uncertainty in Exposure Assessment, Harmonization Project Document No. 6. Published under joint sponsorship of the World Health Organization, the International Labour Organization and the United Nations Environment Programme. WHO Press, World Health Organization, 20 Avenue Appia, 1211 Geneva 27, Switzerland. Woodruff TJ; Darr ow LA; Parker JD (2008). Air pollution and postneonatal infant mortality in the United States, 1999

- 2002. Environ Health Perspect, 116: 110

- 115. Yanosky JD; Paciorek CJ; Suh HH (2009). Predicting Chronic Fine and Coarse Particulate Exposures Using Spatiote mporal Models for the Northeastern and Midwestern United States. EHP, 117(4): 522

- 529. Zanobetti A; Schwartz J (2009). The effect of fine and coarse particulate air pollution on mortality: A national analysis. Environ Health Perspect, 117: 898

- 903. Zanobe tti A. (2009). Personal communication with Dr. Antonella Zanobetti; email to Jason Sacks, U.S. EPA, NCEA. June 1, 2009. Docket No. EPA

- HQ

- ORD

- 2007

- 0517

- 0064. Zeger S; McDermott A; Dominici F; Samet J (2007). Mortality in the Medicare population and chronic exposure to fine particulate air pollution. Johns Hopkins University. Baltimore. http://www.bepress.com/jhubiostat/paper133
. Zeger S; Dominici F; McDermott A; Samet J (2008). Mortality in the Medicare population and chronic exposure to fine particulate air pollution in urban centers (2000

- 2005). Environ Health Perspect, 116: 1614. Zwack LM; Paciorek CJ; Spengler JD; Levy JI (2011). Characterizing local traffic contributions to particulate air p ollution in street canyons using mobile monitoring techniques. Atomspheric Environment 45 (2011), 2507

- 2514. Formatted: Font: 12 pt***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 745 of 790 Formatted: Left Page 695 71 5 of 738 7 57

– PM NAAQS Proposed Rule List of Subjects 40 CFR Part 50 Environmental protection, Air pollution control, Carbon monoxi de, Lead, Nitrogen dioxide, Ozone, Particulate matter, Sulfur oxides. 40 CFR Part 51 Environmental protection, Administrative practices and procedures, Air pollution control, Intergovernmental relations 40 CFR Part 52 Environmental protection, Administrati ve practices and procedures, Air pollution control, Intergovernmental relations 40 CFR Part 53 Environmental protection, Administrative practice and procedure, Air pollution control, Intergovernmental relations, Reporting and recordkeeping requirements. 40 CFR Part 58 Environmental protection, Administrative practice and procedure, Air pollution control, Intergovernmental relations, Reporting and recordkeeping requirements

________________________________ Dated:

_________________________________ Lisa P. Jackson, Administrator Formatted: Line spacing: single, Widow/Orphan control, Adjust space between Latin and Asian text, Adjust space between Asian text and numbers, Tab stops: Not at 0" + 0.5" + 1" + 1.5" + 2" + 2.5" + 3" + 3.5" + 4" + 4.5" + 5" + 5.5" Formatted: Font: 10 pt, No underline***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 746 of 790 Formatted: Left For the reasons set forth in the preamble, chapter I of title 40 of the Code of Federal Regulations is amended as follows: PART 50

– NATIONAL PRIMARY AND SECONDARY AMBIENT AIR QUALITY STANDARDS 1. The authority citation for part 50 continues to read as follows: Authority: 42 U.S.C. 7401 et seq.

***** 2. Section 50.3 is revised to read as follows: § 50.3 Reference conditions. All measurements of air quality that are expressed as mass per unit volume (e.g., micrograms per cubic meter) other than for particulate matter (PM 2.5 ) standards contained in §§ 50.7, 50.13, and 50.18, and lead standards conta ined in § 50.16 shall be corrected to a reference temperature of 25 (deg) C and a reference pressure of 760 millimeters of

mercu ry (1,013.2 millibars). Measurements of PM 2.5 for purposes of comparison to the standards contained in §§50.7, 50.13, and 50.18, and of lead for purposes of comparison to the standards contained in §50.16 shall be reported based on actual ambient air volum e measured at the actual ambient temperature and pressure at the monitoring site during the measurement period. 2. 3. Table 1 in §50.14(c)(2)(vi) is revised to read as follows: § 50.14 Treatment of air quality monitoring data influenced by exceptional events. * * * * * (c) *** (2) *** (vi) *** Formatted: Indent: Left: 0.19"

Formatted: Indent: Left: 0.19"***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 747 of 790 Formatted: Left Table 1. Special Schedules for Exceptional Event Flagging and Documentation Submission for Data to be Used in Initial Designations for New or Revised NAAQS NAAQS Pollutant/ Standard/(Level)/ Promulgation Date Air Quality Data

Collected for Calendar Year Event Flagging &

Initial Description Deadline Detailed

Documentation Submission Deadline PM 2.5 /24

- Hr Standard (35 μg/m 3 ) Promulgated October 17, 2006 2004

- 2006 October 1, 2007 April 15, 2008

Ozone/8

- Hr Standard (0.075 ppm) Promulgated March 12, 2008 2005

- 2007 June 18, 2009 June 18, 2009

2008 June 18, 2009 June 18, 2009 2009 60 days after the end

of the calendar quarter in which the event occurred or February 5, 2010, whichever date occurs first. 60 days after the end

of the calendar quarter in which the event occurred or February 5, 2010, whichever date occurs first. NO 2 /1

- Hr Standard ( 100 pp b ) Promulgated February 9 , 20 10 2008 July 1, 2010 January 22, 2011

2009 July 1, 2010 a January 22, 2011 2010 April 1, 2011 July 1, 2011 SO 2 /1

- Hr Standard ( 75 pp b ) Promulgated June 22 , 20 10 2008 October 1, 201 0 June 1, 2011

2009 October 1, 201 0 June 1, 2011 2010 June 1, 2011 June 1, 2011 2011 6 0 d ays after the end

of the calendar quarter in which the event occurred or March 3 1, 2012, whichever date occurs first
. 6 0 d ays after the end

of the calendar quarter in which the event occurred or March 3 1, 2012, whichever date occurs first
. PM 2.5 / Primary Annual Standard (12 μg/m 3 ) Promulgated December 14, 2012 2010 and 2011 July 1, 2013 December 12, 2013 2012 July 1, 2013 a December 12, 2013 2013 July 1, 2014 a August 1, 2014

a This date is the same as the general schedule in 40 CFR 50.14.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 748 of 790 Formatted: Left

Note: The table of revised deadlines only applies to data EPA will use to establish the initial area designations for new or revised NAAQS
. The general schedule applies for all other purposes, most notably, for data used by the EPA for redesignations to at tainment
.
***** 3. 4. A dd § 50.18 to read as follows: § 50.18 National primary ambient air quality standards for PM 2.5 . (a) The national primary ambient air quality standards for PM 2.5 are 12.0 micrograms per cubic meter (μg/m 3 ) annual arithmetic mean concentration and 35 μg/m 3 24

- hour average concentration measured in the ambient air as PM 2.5 (particles with an aerodynamic diameter less than or equal to a nominal 2.5 micrometers) by either: ( 1 ) A reference method based on appendix L of this part and de signated in accordance with part 53 of this chapter; or ( 2 ) An equivalent method designated in accordance with part 53 of this chapter. (b) The primary annual PM 2.5 standard is met when the annual arithmetic mean concentration, as determined in accordance with appendix N of this part, is less than or equal to 12.0 μg/m 3

. (c) The primary 24

- hour PM 2.5 standard is met when the 98 th percentile 24

- hour concentration, as determined in accordance with appendix N of this part, is less than or equal to 35 μg/m 3

. 4. 5. Appendix N to part 50 is revised to read as follows: Appendix N to Part 50

— Interpretation of the National Ambient Air Quality Standards for PM 2.5 1.0 General (a) Thi s appendix explains the data handling conventions and computations necessary for determining when the national ambient air quality standards (NAAQS) for PM 2.5 are met, Formatted: Space After: 12 pt

Formatted: Indent: Left: 0.19"

Formatted: Indent: Left: 0.19"

Formatted: Font: Bold, Not Superscript/ Subscript Formatted: Font: Bold***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 749 of 790 Formatted: Left specifically the primary and secondary annual and 24

- hour PM 2.5 NAAQS specified in §50.7, 50.13, and 50.18
. PM 2.5 is defined , in general terms, as particles with an aerodynamic diameter less than or equal to a nominal 2.5 micrometers
. PM 2.5 mass concentrations are measured in the ambient air by a Federal Reference Method (FRM) based on a

ppendix L of this part, as applicable, and designated in accordance with part 53 of this chapter; or by a Federal Equivalent Method (FEM) designated in accordance with part 53 of this chapter; or by an Approved Regional Method (ARM) designated in accordanc e with part 58 of this chapter . Only those FRM, FEM, and ARM measurements that are derived in accordance with part 58 of this chapter (i.e., that are deemed “suitable”) shall be used in comparisons with the PM 2.5 NAAQS. The d ata handling and computation pr ocedures to be used to construct annual and 24

- hour NAAQS metrics from reported PM 2.5 mass concentrations , and the associated instructions for comparing these calculated metrics to the levels of the PM 2.5 NAAQS , are specified in sections 2.0, 3.0, and 4.0 of this appendix. (b) Decisions to exclude, retain, or make adjustments to the data affected by exceptional events, including natural events, are made according to the requirements and process deadlines specified in §§50.1, 50.14 and 51.930 of this chapte r. (c) The terms used in this appendix are defined as follows: Annual mean refers to a weighted arithmetic mean, based on quarterly means, as defined in section 4.4 of this appendix. The Air Quality System (AQS) is EPA’s official repository of ambient air data. Collocated monitors refers to two or more air measurement instruments for the same parameter (e.g., PM 2.5 mass) operated at the same site location, and whose place ment is***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 750 of 790 Formatted: Left consistent with § 53 .1 of this chapter. For purposes of considering a combined site record in this appendix, when two or more monitors are operated at the same site, one monitor is designated as the “ primary ” monitor with any additional monitors designated as “collocated.” It i s implicit in these appendix procedures that the primary monitor and collocated monitor(s) are all deemed suitable for the applicable NAAQS comparison; however, it is not a requirement that the primary and monitors utilize the same specific sampling and an alysis method. The c ollocated PM 10 data substitution test substitutes reported same - day PM 10 FRM/FEM daily values from the same site for missing scheduled PM 2.5 samples in data capture deficient quarters
. Combined site data record is the data set used for performing calculations in a ppendix N
. It represents data for the primary monitors augmented with data from collocated monitors according to the procedure specified in 3.0(d) of this appendix. Creditable samples are daily values in the combined site record that are given credit for data completeness . The number of creditable samples (cn) for a given year also governs which value in the sorted series of daily values represents the 98 th percentile for that year. Creditable samples i nclude daily values collected on scheduled sampling days and valid make

- up samples taken for missed or invalidated samples on scheduled sampling days
. Daily values refer to the 24

- hour average concentrations of PM 2.5 mass measured ( or averaged from hourly measurements in AQS ) from midnight to midnight (local standard time ) from suitable monitors
.. . Data substitution tests are diagnostic evaluations performed on an annual PM 2.5 NAAQS design value (DV) or a 24

- hour PM 2.5 NAAQS DV to determine if that metric t hose***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 751 of 790 Formatted: Left metric s , which is otherwise are judged to be based on incomplete (via the applicable 75 percent or 11 creditable sample minimum quarterly data capture requirements ), in accordance with 4.1(b) or 4.2(b) shall nevertheless be deemed complete and valid f or NAAQS comparisons, or alternatively, shall still be considered incomplete and not valid for NAAQS comparisons. There are three data substitution tests , the “maximum quarterly value” test, the “minimum quarterly value” test, and the “collocated PM 10 ” tes t. O nly one of the three tests needs to “pass” in order to validate the DV in question . These tests substitute actual same

- site extreme daily values for missing data in an incomplete year(s), calculate a revised “test DV” using the original plus substitute d data, and, if the test DV relays the same NAAQS status (i.e., meets or not meets) as the original (otherwise incomplete) DV, the test is deemed to have “passed” and since only one passing test is needed, the original DV (without the diagnostic data subst itutions) is then considered complete and valid for NAAQS comparisons. If the test DV relays a different NAAQS status as the original (otherwise incomplete) DV, the test is deemed to have “failed”, and if all applicable substitution tests are “failed” then the original DV will still be considered incomplete and not valid for NAAQS comparison s. There are two data substitution tests , the “minimum quarterly value” test and the “maximum quarterly value” test. Design values (DVs) are the 3

- year average NAAQS metrics that are compared to the NAAQS levels to determine when a monitoring site meets or does not meet the NAAQS , calculated as shown in section 4
.. . There are two separate DVs specified in this appendix : (1) The 3

- year average of PM 2.5 annual mean mass concentrations for each eligible monitoring site is referred to as the “ annual PM 2.5 NAAQS DV ”.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 752 of 790 Formatted: Left (2) The 3

- year average of annual 98 th percentile 24

- hour average PM 2.5 mass concentration values recorded at each eligible monitoring site is referred to as the “ 24

- hour (or daily) PM 2.5 NAAQS DV ”. Eligible sites are monitoring stations that meet the criteria specified in § 58.11 and § 58.30 of this chapter, and thus are approved for comparison to the annual PM 2.5 NAAQS . For the 24

- hour PM 2.5 NAAQS, all site loc ations that meet the criteria specified in § 58.11 are approved (i.e., eligible) for NAAQS comparisons. Extra samples are non - creditable samples
. They are daily values that do not occur on scheduled sampling days and that cannot be used as make

- up samples f or missed or invalidated scheduled samples
. Extra samples are used in mean calculations and are included in the series of all daily values subject to selection as a 98 th percentile value, but are not used to determine which value in the sorted list represents the 98 th percentile
. Make

- up samples are samples collected to take the place of missed or invalidated required scheduled samples. Make

- up s amples can be made by either the pri mary or the collocated monitor. Make

- up samples are either taken before the next required sampling day or exactly one week after the missed (or voided) sampling day. The maximum quarterly value data substitution test substitutes actual “ high ” reported dail y PM 2.5 values from the same site ( specifically, the highest reported non

- excluded quarterly value(s) (year non

- specific) contained in the combined site record for the evaluated 3

- year period ) for missing daily values
. The minimum quarterly value data sub stitution test substitutes actual “ low ” reported daily PM 2.5 values from the same site (specifically, the lowest reported quarterly value(s) (year non

- specific) contained in the combined site record for the evaluated 3

- year period )***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 753 of 790 Formatted: Left for missing daily values
. 98 th percentile is the smallest daily value out of a year of PM 2.5 mass monitoring data below which no more than 98 percent of all daily values fall using the ranking and selection method specified in section 4.5(a) of this appendix. Primary monitors are suitable monitors designated by a state or local agency in their annual network plan (and in AQS) to be as the default data source for creating a combined site record for purposes of NAAQS comparisons. If there is only one suitable monitor at a particu lar site location, then it is presumed to be a primary monitor. Quarter refers to a calendar quarter (e.g., January through March)
. Quarterly data capture rate is the p ercentage of scheduled samples in a calendar quarter that have corresponding valid repor ted sample values. Quarterly data capture rates are specifically calculated as the number of creditable samples for the quarter divided by the number of scheduled samples for the quarter, the result then multiplied by 100 and rounded to the nearest integer
. Scheduled PM 2.5 samples refers to those reported daily values which are consistent with the required sampling frequency (per § 58.12 of this chapter) for the primary monitor, or those that meet the special exception noted in 3.0(e). Seasonal sampling is the practice of collecting data at a reduced frequency during a season of expected low concentrations. Suitable monitors are instruments that use sampling and analysis methods approved for NAAQS comparisons. For the annual and 24

- hour PM 2.5 NAAQS, sui table monitors include all FRMs, and all FEMs/ARMs except those specific continuous FEMs/ARMs disqualified by a particular monitoring agency network in accordance with § 58.10(b)(13)***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 754 of 790 Formatted: Left and approved by the EPA Regional Administrator per §58.1 1 (e) of this chapt er. Test d esign v alue s (TDV) are numerical values that used in the data substitution tests described in 4.1(c)(i) , 4.1(c)(ii ) and 4. 2 (c)(i) to determine if the PM 2.5 NAAQS DV with incomplete data are judged to be valid for NAAQS comparisons. There are two TDVs: TDV min to determine if the NAAQS is not met and is used in the “minimum quarterly value” data substitution test and TDV max to determine if the NAAQS is met and is used in the “maximum quarterly value” data substitution test. These TDV’s are derived by substituting historically low or historically high daily concentration values for missing data in an incomplete year(s). Year refers to a calendar year. 2.0 Monitoring Considerations (a) Section 58.30 of this chapter provides special considerations fo r data comparisons to the annual PM 2.5 NAAQS. (b) Monitors meeting the network technical requirements detailed in § 58.11 of this chapter are suitable for comparison with the NAAQS for PM 2.5 . ( c ) Section 58.12 of this chapter specifies the required minimum frequency of sampling for PM 2.5 . Exceptions to the specified sampling frequencies, such as seasonal sampling, are subject to the approval of the EPA Regional Administrator and must be documented in the s tate or local agency Annual Monitoring Network Plan as required in § 58.10 of this chapter and also in AQS. 3.0 Requirements for Data Use and Data Reporting for Comparisons with the NAAQS for PM 2.5 (a) Except as otherwise provided in this appendix, all valid FRM/FEM/ARM PM 2.5 mass Formatted: Font: Bold, Not Superscript/ Subscript Formatted: Font: Bold

Formatted: Font: Bold, Not Superscript/ Subscript Formatted: Font: Bold***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 755 of 790 Formatted: Left concentration data produced by suitable monitors that are required to be submitted to AQS, or otherwise available to EPA, meeting the requirements of part 58 of this chapter including appendices A, C, and E shall be used in the DV calculations
. Generally, EPA will only use s uch data if they have been certified by the reporting organization (as prescribed by §58.15 of this chapter); however, data not certified by the reporting organization can nevertheless be used, if the deadline for certification has passed and EPA judges th e data to be complete and accurate. (b) PM 2.5 mass concentration data (typically collected hourly for continuous instruments and daily for filter

- based instruments) shall be reported to AQS in micrograms per cubic meter (μg/m 3 ) to at least one decimal pla ce . If concentrations are reported to one decimal place, additional digits to the right of the tenths decimal place shall be truncated . If concentrations are reported to AQS with more than one decimal place, AQS will truncate the value to one decimal plac e for NAAQS usage (i.e., for implementing the procedures in this appendix). In situations where suitable PM 2.5 data are available to EPA but not reported to AQS, the same truncation protocol shall be applied to that data. In situations where PM 2.5 mass data are submitted to AQS, or are otherwise available, with less precision than specified above, these data shall nevertheless still be deemed appropriate for NAAQS usage. If data (c) Twenty

- four

- hour average concentration s will be computed in AQS f rom submitted hourly PM 2.5 concentration data for each corresponding day of the year and the result will be stored in the first, or start, hour (i.e., midnight, hour ‘0’) of the 24

- hour period
. A 24

- hour average concentration shall be considered valid if a t least 75 percent of the hourly averages (i.e., 18 hourly values ) for the 24

- hour period are available
. In the event that less Formatted: Subscript***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 756 of 790 Formatted: Left than all 24 hourly average concentration s are available (i.e., less than 24, but at least 18), the 24

- hour average concentration shall be computed on the basis of the hours available using the number of available hours within the 24

- hour period as the divisor (e.g., 19 , if 19 hourly values are available ) . Twenty

- four

- hour periods with seven or more missing hours shall also be consi dered valid if, after substituting zero for all missing hourly concentrations, the resulting 24

- hour average daily value is greater than the level of the 24

- hour PM 2.5 NAAQS (i.e., greater than or equal to 35.5 μg/m 3 ). Twenty

- four hour average PM 2.5 mass c oncentrations that are averaged in AQS from hourly values will be truncated to one decimal place, consistent with the data handling procedure for the reported hourly (and also 24

- hour filter

- based) data
. (d) All calculations shown in this appendix shall be implemented on a site

- level basis
. Site level concentration data shall be processed as follows: (1) The default dataset for PM 2.5 mass concentrations for a site shall consist of the measured concentrations recorded from the designated primary monitor (s). All daily values produced by the primary monitor are considered part of the site record; this includes all creditable samples and all extra samples. (2) Data for the primary monitors shall be augmented as much as possible with data from collocated monitors
. If a valid daily value is not produced by the primary monitor for a particular day (scheduled or otherwise), but a value is available from a collocated monitor , then that collocated value shall be considered part of the combined site data record
. If more than one collocated daily value is available, the average of those valid collocated values shall be used as the daily value
. The data record resulting from this procedure is referred to as the “ combined site data record. ”***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 757 of 790 Formatted: Left (e) All daily values in a combine d site data record are used in the calculations specified in this appendix , ; however, not all daily values are given credit towards data completeness requirements
. Only creditable samples are given credit for data completeness
. Creditable samples include d aily values in the combined site record that are collected on scheduled sampling days and valid make

- up samples taken for missed or invalidated samples on scheduled sampling days
. Days are considered scheduled according to the required sampling frequency o f the designated primary monitor with one exception . The exception is, i f a collocated continuous FEM /ARM monitor has a more intensive sampling frequency than the primary FRM monitor, then samples contributed to the com bined site record from that continuou s FEM/ARM monitor are always considered scheduled and , hence , also creditable
. Daily values in the com bined site data record that are reported for nonscheduled days, but that are not valid make

- up samples are referred to as extra samples
. 4.0 Comparisons with the Annual and 24 - Hour PM 2.5 NAAQS 4.1 Annual PM 2.5 NAAQS (a) The primary annual PM 2.5 NAAQS is met when the annual PM 2.5 NAAQS DV is less than or equal to 12.0μg/m 3 at each eligible monitoring site. T he secondary annual PM 2.5 NAAQS is met when the an nual PM 2.5 NAAQS DV is less than or equal to 15.0 μg/m 3 at each eligible monitoring site
. (b) Three years of valid annual means are required to produce a valid annual PM 2.5 NAAQS DV. A year meets data completeness requirements when quarterly data capture

r ates for all four quarters are at least 75 percent. However, years with at least 11 creditable samples in each quarter shall also be considered valid if the resulting annual Formatted: Font: Bold, Not Superscript/ Subscript Formatted: Font: Bold Formatted: Font: Bold, Not Superscript/ Subscript Formatted: Font: Bold***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 758 of 790 Formatted: Left mean or resulting annual PM 2.5 NAAQS DV (rounded according to the conventions of

s ection 4.3 of this appendix) is greater than the level of the applicable primary or secondary annual PM 2.5 NAAQS. Furthermore, where the explicit 75 percent data capture and/or 11 sample minimum requirements are not met, the 3

- year annual PM 2.5 NAAQS DV sh all still be considered valid and complete if it passes at least one of the three two data substitution tests stipulated below
. (c) In the case of one, two, or three years that do not meet the completeness requirements of section 4.1(b) of this appendix and thus would normally not be useable for the calculation of a valid annual PM 2.5 NAAQS DV , the annual PM 2.5 NAAQS DV shall nevertheless be considered valid and complete if at least if one of the test conditions specified in 4.1(c)(i ), ) and 4.1(c)(ii ), and 4.1(c)(iii ) is met
. (i) An annual PM 2.5 NAAQS DV that is above the level of the NAAQS can be validated if it passes the minimum quarterly value data substitution test . This type of d ata substitution is permitted only if there are at least 30 days across the three matching quarters of the three years under consideration (e.g., collectively, quarter 1 of year 1, quarter 1 of year 2 and quarter 1 of year 3) from which to select the quarter

- specific low value
. Data substitution will be performed in all quarte r periods that have less than 11 creditable samples. Procedure : Identify for each deficient quarter ( i.e., those with less than 11 creditable samples) the lowest reported daily value for that quarter, looking across those three months of all three years under consideration
. If after substituting the lowest reported daily value for a quarter for (11

- cn) daily values in the matching deficient quarter(s) (i.e., to bring the creditable number for those quarters up to 11 ), the procedure yields a***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 759 of 790 Formatted: Left recalculated annual PM 2.5 NAAQS test DV (TDV min ) that is greater than the level of the standard, then the annual PM 2.5 NAAQS DV is deemed to have passed the diagnost ic test and is valid, and the annual PM 2.5 NAAQS is deemed to have been violated in that 3

- year period. (ii) An annual PM 2.5 NAAQS DV that is equal to or below the level of the NAAQS can be validated if it passes the maximum quarterly value data substitut ion test . This type of d ata substitution is permitted only if there are is at least 30 days across the three matching quarters 50 percent data capture in each quarter that is deficient of 75 percent data capture in each of the three years under consideration from which to select the quarter

- specific high value
. Data substitution will be performed in all quarter periods that have less than 75 percent data capture but at least 50 percent data capture . I f any quarter has less than 50 percent data capture then th is substitution test cannot be used. Procedure : Identify for each deficient quarter ( i.e., those with less than 75 percent but at least 50 percent data capture ) the highest reported daily value for that quarter, excluding

s tate
- flagged data affected by exc eptional events which have been approved for exclusion by the Administrator, looking across those three quarters of all three years under consideration
. If after substituting the highest reported daily PM 2.5 value for a quarter for all missing daily data i n the matching deficient quarter(s) (i.e., to make those quarters 100 percent complete), the procedure yields a recalculated annual PM 2.5 NAAQS test DV (TDV max ) that is less than or equal to the level of the standard, then the annual PM 2.5 NAAQS DV is deeme d to have passed the diagnostic test and is valid, and the annual PM 2.5 NAAQS is deemed to have been met in that 3

- year period. (iii) An annual PM 2.5 NAAQS DV that is equal to or below the level of the NAAQS can***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 760 of 790 Formatted: Left be validated if it passes the collocated PM 10 data substitution test
. Data substitution will be performed in all quarter periods that have less than 75 percent data capture but at least 50 percent data capture . I f any quarter has less than 50 percent data capture then this substitution test cannot be used. Procedure : Identify for each deficient quarter ( i.e., those with less than 75 percent but at least 50 percent data capture) , available collocated FRM/FEM PM 10 values reported for each PM 2.5 scheduled day that is missing a valid daily PM 2.5 value
. If there is more than one collocated daily PM 10 value present for a particular day (that is scheduled for measuring PM 2.5 but does not have a corresponding valid daily PM 2.5 value), then the highest of those multiple daily PM 10 values will be used as the s ubstituted value
. If , after substituting the available collocated daily PM 10 values for as many as possible missing daily PM 2.5 values in the deficient quarter(s), the procedure yields recalculated data capture rates of 75 percent or more, and a recalculated annual PM 2.5 NAAQS test DV less than or equal to the level of the standard, then the annual PM 2.5 NAAQS DV is deemed to have passed the diagnostic test and is valid, and the annual PM 2.5 NAAQS is deemed to have been met in that 3

- year period. (d) An annual PM 2.5 NAAQS DV based on data that do not meet the completeness criteria stated in 4(b) and also do not satisfy the test co nditions specified in section 4(c), may also be considered valid with the approval of, or at the initiative of, the EPA Administrator, who may consider factors such as monitoring site closures/moves, monitoring diligence, the consistency and levels of the daily values that are available, and nearby concentrations in determining whether to use such data. (e) The equations for calculating the annual PM 2.5 NAAQS DV s are given in section 4.4***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 761 of 790 Formatted: Left of this appendix. 4.2 Twenty

- four

- h our PM 2.5 NAAQS (a) The primary an d secondary 24

- hour PM 2.5 NAAQS are met when the 24

- hour PM 2.5 NAAQS DV at each eligible monitoring site is less than or equal to 35 μg/m 3

. (b) Three years of valid annual PM 2.5 98 th percentile mass concentrations are required to produce a valid 24

- hour PM 2.5 NAAQS DV. A year meets data completeness requirements when quarterly data capture rates for all four quarters are at least 75 percent. However, years shall be considered valid, notwithstanding quarters with less than complete data (even quarters with less than 11 creditable samples , but at least one creditable sample must be present for the year ), if the resulting annual 98 th percentile value or resulting 24

- hour NAAQS DV (rounded according to the conventions of section 4.3 of this appendix) is greate r than the level of the standard
. Furthermore, where the explicit 75 percent quarterly data capture requirement is not met, the 24

- hour PM 2.5 NAAQS DV shall still be considered valid and complete if it passes at least one of two applicable data substitutio n tests (i.e., the maximum quarterly value or collocated PM 10 data substitution tests). test. (c) In the case of one, two, or three years that do not meet the completeness requirements of section 4.2(b) of this appendix and thus would normally not be useable for the calculation of a valid 24

- hour PM 2.5 NAAQS DV , the 24

- hour PM 2.5 NAAQS DV shall nevertheless be considered valid and complete if either of if the test conditions specified in 4.2(c)(i) or 4.2(c)(ii) are met
. (i) A PM 2.5 24

- hour mass NAAQS D V that is equal to or below the level of the NAAQS can be validated if it passes the maximum quarterly value data substitution test . This type***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 762 of 790 Formatted: Left of d ata substitution is permitted only if there are is at least 30 days across the three matching quarters 50 perce nt data capture in each quarter that is deficient of 75 percent data capture in each of the three years under consideration from which to select the quarter
- specific high value . Data substitution will be performed in all quarter s that have less than 75 per cent data capture but at least 50 percent data capture . I f any quarter has less than 50 percent data capture then this substitution test cannot be used. Procedure : Identify for each deficient quarter ( i.e., those with less than 75 percent but at least 50 p ercent data capture) the highest reported daily PM 2.5 value for that quarter, excluding s tate
- flagged data affected by exceptional events which have been approved for exclusion by the Regional Administrator, looking across those three quarters of all three years under consideration
. If , after substituting the highest reported daily maximum PM 2.5 value for a quarter for all missing daily data in the matching deficient quarter(s) (i.e., to make those quarters 100 percent complete), the procedure yields a recalculated 3

- year 24

- hour NAAQS test DV (TDV max ) less than or equal to the level of the standard, then the 24

- hour PM 2.5 NAAQS DV is deemed to have passed the diagnostic test and is valid, and the 24

- hour PM 2.5 NAAQS is deemed to have been met in that 3

- year period. (ii) A 24

- hour PM 2.5 NAAQS DV that is equal to or below the level of the NAAQS can be validated if it passes the collocated PM 10 data substitution test
. Data substitution will be performed in all quarter periods that have less than 75 percent data capture but at least 50 percent data capture . I f any quarter has less than 50 percent data capture then this substitution test cannot be used. Procedure : Identify for each deficient quarter ( i.e., those with less than 75 percent but at least 50 percent data capture) , available collocated FRM/FEM daily PM 10 values reported***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 763 of 790 Formatted: Left for each PM 2.5 scheduled day that is missing a valid daily PM 2.5 value
. If there is more than one collocated daily PM 10 value present for a particular day (that is scheduled for measuring PM 2.5 but doesn’t have a corresponding valid daily PM 2.5 value), then the highest of those daily PM 10 values will be used as the substituted daily PM 2.5 value . Daily PM 10 values shall be truncated to integers if decimal places are reported. If , after substituting the available collocated daily PM 10 values for as many as possible missing daily PM 2.5 values in the deficient quarter(s), the procedure yields recalculated data capture rates of 75 percent or more, and a recalculated 24

- hour PM 2.5 N AAQS test DV less than or equal to the level of the standard, then the 24

- hour PM 2.5 NAAQS DV is deemed to have passed the diagnostic test and is valid, and the 24

- hour PM 2.5 NAAQS is deemed to have been met in that 3

- year period. (d) A 24

- hour PM 2.5 NAAQS DV based on data that do not meet the completeness criteria stated in 4(b) and also do not satisfy the test conditions specified in section 4(c), may also be considered valid with the approval of, or at the initiative of, the EPA Administrator, who may co nsider factors such as monitoring site closures/moves, monitoring diligence, the consistency and levels of the daily values that are available, and nearby concentrations in determining whether to use such data
. (e) The procedures and equations for calculating the 24

- hour PM 2.5 NAAQS DV s are given in section 4.5 of this appendix. 4.3 Rounding Conventions
. For the purposes of comparing calculated PM 2.5 NAAQS DV s to the applicable level of the standard, it is necess ary to round the final results of the calculations described in sections 4.4 and 4.5 of this appendix
. Results for all intermediate calculations shall not be rounded.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 764 of 790 Formatted: Left (a) A nnual PM 2.5 NAAQS DV s shall be rounded to the nearest tenth of a μg/m 3 (decimals

x.x 5 and greater are rounded up to the next tenth, and any decimal lower than x.x5 is rounded down to the nearest tenth). (b) Twenty

- four

- hour PM 2.5 NAAQS DV s shall be rounded to the nearest 1 μg/m 3 (decimals 0.5 and greater are rounded up to the nearest whol e number, and any decimal lower than 0.5 is rounded down to the nearest whole number). 4.4 Equations for the Annual PM 2.5 NAAQS. (a) An annual mean value for PM 2.5 is determined by first averaging the daily values of a calendar quarter using equation 1 of this appendix: Equation 1

Where: X – q,y = the mean for quarter q of the year y ; n q = the number of daily values in the quarter; and x i q,y = the i th value in quarter q for year y. (b) Equation 2 of this appendix is then used to calculate the site annual mean: Equation 2

Where:

y = the annual mean concentration for year y ( y = 1, 2, or 3); and

q,y = the mean for quarter q of year y (result of equation 1).
(c) The annual PM 2.5 NAAQS DV is calculated using equation 3 of this appendix.
.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 765 of 790 Formatted: Left Equation 3

Where:

= the annual PM 2.5 NAAQS DV ; and

y = the annual mean for year y (result of equation 2) (d) The annual PM 2.5 NAAQS DV is rounded according to the conventions in section 4.3 of this appendix before comparison s with the levels of the primary and secondary annual PM 2.5 NAAQS are made. 4.5 Procedures and Equations for the 24

- Hour PM 2.5 NAAQS (a) When the data for a particula r site and year meet the data completeness requirements in section 4.2 of this appendix, calculation of the 98 th percentile is accomplished by the steps provided in this subsection
. Table 1 of this appendix shall be used to identify annual 98 th percentile values. Identification of annual 98 th percentile values using the T able 1 procedure will be based on the creditable number of samples (as described below), rather than on the actual number of samples
. Credit will not be granted for extra (non

- creditable) s amples
. Extra samples, however, are candidates for selection as the annual 98 th percentile
. [The creditable number of samples will determine how deep to go into the data distribution, but all samples (creditable and extra) will be considered when making th e percentile assignment.] The annual creditable number of samples is the sum of the four quarterly creditable number of samples. Procedure : Sort all the daily values from a particular site and year by descending value
. (For example: (x[1], x[2], x[3], * * *, x[n]). In this case, x[1] is the largest number and***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 766 of 790 Formatted: Left x[n] is the smallest value.) The 98 th percentile value is determined from this sorted series of daily values which is ordered from the highest to the lowest number
. Using the left column of T able 1, determine the appropriate range for the annual creditable number of samples for year y (cn y ) (e.g., for 120 creditable samples per year, the appropriate range would be 101 to 150). The corresponding “n” value in the right column identifies the rank of the annual 98 th percentile value in the descending sorted list of site specific daily values for year y (e.g., for the range of 101 to 150, n would be 3). Thus, P 0.98, y = the n th largest value (e.g., for the range of 101 to 150, the 98 th percentile value wou ld be the third highest value in the sorted series of daily values
. Table 1
Annual number of creditable samples for year y (cn y ) The 98 th percentile for year y (P 0.98,y ), is the n th maximum 24

- hour average value for the year where n is the listed number 1 to 50 1 51 to 100 2 101 to 150 3 151 to 200 4 201 to 250 5 251 to 300 6 301 to 350 7 351 to 366 8 (b) The 24

- hour PM 2.5 NAAQS DV is then calculated by averaging the annual 98 th percentiles using equation 4 of this appendix: P 0.98 , y Equation 4

Where***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 767 of 790 Formatted: Left

0.98 = the 24

- hour PM 2.5 NAAQS DV; and P 0
. 98 , y = the annual 98 th percentile for year y
(c) The 24

- hour PM 2.5 NAAQS DV is rounded according to the conventions in section 4.3 of this appendix before a comparison with the level of the primary and secondary 24

- hour NAAQS are made. Part 5 1

— [ AMENDED ] P ART 51

— REQUIREMENTS FOR PREPARATION, ADOPTION, AND SUBMITTAL OF IMPLEMENTAT ION PLANS 5. 1. The authority citation for part 51 continues to read as follows: Authority : 23 U.S.C. 101; 42 U.S.C. 7401

- 7671 q. Subpart I

– [Amended] 6. 2. In §51.166, add paragraph (i)(10) to read as follows: §5 1 .1 66 Prevention of significant deterioration of air quality * * * * * (i) Exemptions
. (1) * * * * * * * * (10) The plan may provide that the requirements of paragraph (k)(1) of this section shall not apply to a stationary source or modification with respect to the national ambient air quality standards for PM 2.5 in effect on [ INSERT DATE 60 DAYS AFTER DATE OF PUBLICATION IN THE FEDERAL REGISTER] if : (i) The reviewing authority has determined a permit application subject to this section to be complete on or before December 14, 2012. Instead, the requirements in paragraph (k)(1) shall apply with respect to the national ambient air quality standards for PM 2. 5 in effect at the time the reviewing authority determined the permit application to be complete; or Formatted: Space After: 12 pt, Line spacing: single Formatted: Font: 10 pt

Formatted: Numbered + Level: 1 + Numbering Style: 1, 2, 3,

... + Start at: 1 + Alignment: Left + Aligned at: 0" + Indent at: 0.25"

Formatted: Numbered + Level: 1 + Numbering Style: 1, 2, 3,

... + Start at: 1 + Alignment: Left + Aligned at: 0" + Indent at: 0.25"***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 768 of 790 Formatted: Left (ii) The reviewing authority has first published before that date [ INSERT DATE 60 DAYS AFTER DATE OF PUBLICATION IN THE FEDERAL REGISTER] a public notice of a preliminary determination for the permit application subject to this section. Instead, the requirements in paragraph (k)(1) shall apply with respect to t he national ambient air quality standards for PM 2. 5 in effect at the time of first publication of a public notice on the preliminary determination.
* * * * * PART 52

—

AMENDED APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS 7. 1. The authority citation for part 52 continues to read as follows: Authority: 42 U.S.C. 7401, et seq. 8. 2. In §52.21, add paragraph (i)( 11 ) to read as follows: §52.21 Prevention of significant deterioration of air quality. * * * * * (i) * * * * * * * * (11) The requirements of paragraph (k)(1) of this section shall not apply to a stationary source or modification with respect to the national ambient air quality standards for PM 2.5 in effect on [ INSERT DATE 60 DAYS AFTER DATE OF PUBLICATION IN THE FEDERAL REGISTER] if the Administrator has first published before that date : (i) The Administrator has determined a permit application subject to this section to be complete on or before December 14, 2012. Instead, the requirements in paragraph (k)(1) shall apply with respect to the national ambient air quality Formatted: Indent: Left: 0.5"

Formatted: Underline, Not Superscript/ Subscript Formatted: Space After: 12 pt, Add space between paragraphs of the same style, Line spacing: single Formatted: Underline Formatted: Numbered + Level: 1 + Numbering Style: 1, 2, 3,

... + Start at: 1 + Alignment: Left + Aligned at: 0" + Indent at: 0.25" Formatted: Numbered + Level: 1 + Numbering Style: 1, 2, 3,

... + Start at: 1 + Alignment: Left + Aligned at: 0" + Indent at: 0.25"***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 769 of 790 Formatted: Left standards for PM 2. 5 in effect at the time the Administrator determined the permit application to be complete; or (ii) The Administrator has first published before [ INSERT DATE 60 DAYS AFTER DATE OF PUBLICATION IN THE FEDERAL REGISTER] a public notice that a draft permit subject to this section has been prepared. Instead, the requirements in paragraph (k)(1) shall apply with respect to the national ambient air quality standards for PM 2. 5 in effect on the date the Administrator first published a p ublic notice that a draft permit has been prepared.
* * * * * PART 53

— [AMENDED] PART 53

—

AMBIENT AIR MONITORING REFERENCE AND EQUIVALENT METHODS 9. 6. The authority citation for part 53 continues to read as follows: Authority: Section 301(a) of the CAA (42 U.S.C. sec. 1857 g(a)), as amended by sec. 15 (c)(2) of Pub. L. 91

- 604, 84 Stat. 1713, unless otherwise noted. 10. 7. In §53.9, revise paragraph (c) to read as follows: §53.9 Conditions of designation. * * * * * (c) Any analyzer, PM 1 0 sampler, PM 2.5 sampler, or PM 10

- 2.5 sampler offered for sale as part of an FRM or FEM shall function within the limits of the performance specifications referred to in §53.20(a), §53.30(a), §53.35, §53.50, or §53.60, as applicable, for at least 1 year af ter delivery and acceptance when maintained and operated in accordance with the manual referred to in §53.4(b)(3). * * * * * Formatted: Indent: Left: 0.5"

Formatted: Font: Not Bold

Formatted: Indent: Left: 0.19"

Formatted: Indent: Left: 0.19"***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 770 of 790 Formatted: Left PART 58

—

AMBIENT AIR QUALITY SURVEILLANCE 11. 8. The authority citation of part 58 continues to read as follows: Authority: 42 U.S.C. 7403 , 7405, 7410, 7414, 7601, 7611, 7614, and 7619. 12. 9. Section 58.1 is amended by adding in alphabetical order a definition for “Area

- wide” and by removing the definition for “Community monitoring zone (CMZ)” to read as follows: §58.1 Definitions. * * * * * Are a - wide means all monitors sited at neighborhood, urban, and regional scales, as well as those monitors sited at either micro

- or middle scale that are representative of many such locations in the same CBSA. * * * * * 13. 10. Section 58.10 is amended as follows:

a . By revising paragraph (a)(2). b. By adding paragraph (a)(8).

c. By adding paragraph (b)(13)
. d. By revising paragraph (c)
. e. By revising paragraph (d)
. §58.10 Annual monitoring network plan and periodic network assessment. (a) * * * (2) Any annual monitoring network plan that proposes SLAMS network modifications ( including new monitoring sites , new determinations that data are not of sufficient quality to be compared to the NAAQS, and changes in identification of monitors as suitable or Formatted: Indent: Left: 0.19"

Formatted: Indent: Left: 0.19"

Formatted: Indent: Left: 0.19"***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 771 of 790 Formatted: Left not suitable for comparison against the annual PM 2.5 NAAQS) is subject to the approval of the EPA Regional Administrator, who shall provide opportunity for public comment and shall approve or disapprove the plan and schedule within 120 days. If the State or local agency has already provided a public comment opportunity on its plan and has made no changes subsequent to that comment opportunity, and has submitted the received comments together with the plan, the Regional Administrator is not required to provide a sep arate opportunity for comment.

*** ( 8 ) (i) A plan for establishing near

- road PM 2.5 monitoring sites in CBSAs having 2.5 million or more persons, in accordance with the requirements of appendix D to this part , shall be submitted as part of the annual monitor ing network plan to the EPA Regional Administrator by July 1, 2014. The plan shall provide for these required monitoring stations to be operational by January 1, 2015
. (ii) A plan for establishing near

- road PM 2.5 monitoring sites in CBSAs having 1 millio n or more persons, but less than 2.5 million persons, in accordance with the requirements of appendix D to this part , shall be submitted as part of the annual monitoring network plan to the EPA Region al Administrator by July 1, 2016
. The plan shall provide for these required monitoring stations to be operational by Ja nuary 1, 2017. (b) * * * (13) The identification of any PM 2.5 FEMs and/or ARMs used in the monitoring agency’s network where the data are not of sufficient quality such t hat data are not to be compared to the NAAQS
. For required SLAMS where the agency identifies that the PM 2.5 Class III FEM or ARM does not produce data of sufficient quality for comparison to the NAAQS,***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 772 of 790 Formatted: Left the monitoring agency must ensure that an operating FR M or filter

- based FEM meeting the sample frequency requirements described in §58.1 2 or other Class III PM 2.5 FEM or ARM with data of sufficient quality is operating and reporting data to meet the network design criteria described in appendix D to this part
. (c) The annual monitoring network plan must document how s tate and local agencies provide for the review of changes to a PM 2.5 monitoring network that impact the location of a violating PM 2.5 monitor. The affected s tate or local agency must document the process for obtaining public comment and include any comments received through the public notification process within their submitted plan. (d) The s tate, or where applicable local, agency shall perform and submit to the EPA Regional Administrator an asse ssment of the air quality surveillance system every 5 years to determine, at a minimum, if the network meets the monitoring objectives defined in appendix D to this part, whether new sites are needed, whether existing sites are no longer needed and can be terminated, and whether new technologies are appropriate for incorporation into the ambient air monitoring network
. The network assessment must consider the ability of existing and proposed sites to support air quality characterization for areas with relat ively high populations of susceptible individuals (e.g., children with asthma), and, for any sites that are being proposed for discontinuance, the effect on data users other than the agency itself, such as nearby s tates and t ribes or health effects studies
. The s tate, or where applicable local, agency must submit a copy of this 5

- year assessment, along with a revised annual network plan, to the Regional Administrator
. The assessments are due every five years beginning July 1, 2010. * * * * ****E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 773 of 79 0 Formatted: Left 14. 11. Section 58.11 i s amended by adding paragraph (e) to read as follows: §58.11 Network technical requirements. * * * * * (e) State and local governments must assess data from Class III PM 2.5 FEM and ARM monitors operated within their network using the performance criteria described in table C

- 4 to subpart C of part 53, for any case cases where the data are identified as not of sufficient comparability to a collocated FRM, such and the monitoring agency requests that the FEM or ARM data should not be used in comparison to the NAAQS
. These assessments are re quired in the monitoring agency’s annual monitoring network plan described in §58.10(b) for any case cases where the FEM or ARM is identified as not of sufficient comparability to a collocated FRM. For these collocated PM 2.5 monitors t he performance criteria apply with the following additional provisions: (1) The acceptable concentration range (Rj), μg/m 3 may include values down to 0 μg/m 3

. (2) The minimum number of test sites shall be at least one; however, t he number of test sites will generally include all locations within an agenc y’ s network with collocated FRMs and FEMs or ARMs. (3) The minimum number of methods shall include at least one FRM and at least one FEM or ARM. (4) Since multiple FRMs and FEMs may not be present at each site ; the precision statistic requirement does not apply , even if precision data are available
. (5) All seasons must be covered with no more than thirty six consecutive months of data in total aggregated together. (6) The key statistical metric to include in an assessment is the bias (both additive and Formatted: Indent: Left: 0.19"***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 774 of 790 Formatted: Left multiplicative) of the PM 2.5 continuous FEM(s) compared to a collocated FRM(s). Correlation is required to be reported in the assessment, but failure to meet the correlation criteria, by itself, is n ot cause to exclude data from a continuous FEM monitor. 15. 12. Section 58.12 is amended by revising paragraph (d)(1)(iii) and by removing and reserving paragraph (f)(2) to read as follows: § 58.12 Operating schedules. * * * * * (d) * * * (1) *** (iii) Required SLAMS stations whose measurements determine the 24

- hour design value for their area and whose data are within plus or minus 5 percent of the level of the 24

- hour PM 2.5 NAAQS must have an FRM or FEM operate on a daily schedule if the th at
area ’s design value for the annual NAAQS is less than the level of the annual PM 2.5 standard
. A continuously operating FEM or ARM PM 2.5 monitor satisfies this requirement unless it is identified in the monitoring agency’s annual monitoring network plan as not appropriate for comparison to the NAAQS. (f) *** (2) Reserved * * * * * 16. 13. Section 58.13 is amended by adding paragraph ( f ) to read as follows: §58.13 Monitoring network completion. * * * * * ( f ) PM 2.5 monitors required in near

- road environments as described in appendix D to this Formatted: Indent: Left: 0.19"

Formatted: Indent: Left: 0.19"***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 775 of 790 Formatted: Left part, must be physically established and operating under all of the requirements of this part, including the requirements of appendices A, C, D, and E to this part , no later than: (1) January 1, 2015 for PM 2.5 monitors in CBSAs having 2.5 million persons or more; or (2) January 1, 2017 for PM 2.5 monitors in CBSAs having 1 million or more, but less than 2.5 million persons. 17. 14. Section 58.16 is amended by revising paragraphs (a) and (f) to read as follows: §58.16 Data submittal and a rchiving requirements. (a) The s tate, or where appropriate, local agency, shall report to the Administrator, via AQS all ambient air quality data and associated quality assurance data for SO 2 ; CO; O 3 ; NO 2 ; NO; NO y ; NO x ; Pb

– TSP mass concentration; Pb

– PM 10 m ass concentration; PM 10 mass concentration; PM 2.5 mass concentration; for filter

- based PM 2.5 FRM/FEM the field blank mass, sampler

- generated average daily temperature, and sampler

- generated average daily pressure; chemically speciated PM 2.5 mass concentrat ion data; PM 10

- 2.5 mass concentration; meteorological data from NCore and PAMS sites; average daily temperature and average daily pressure for Pb sites if not already reported from sampler generated records; and metadata records and information specified b y the AQS Data Coding Manual ( http://www.epa.gov/ttn/airs/airsaqs/manuals/manuals.htm ). The s tate, or where appropriate, local agency, may report site specific meteorological measurements generated by onsite equipment (meteorological instruments, or sampler generated) or measurements from the nearest airport reporting ambient pressure and temperature
. Such air quality data and information must be submitted directly to the AQS v ia electronic transmission on the specified quarterly schedule described in paragraph (b) of this Formatted: Indent: Left: 0.19"***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 776 of 790 Formatted: Left section. * * * * * (f) The s tate, or where applicable, local agency shall archive all PM 2.5 , PM 10 , and PM 10−2.5 filters from manual low

- volume samplers (sampl ers having flow rates less than 200 liters/minute) from all SLAMS sites for a minimum period of 5 years after collection
. These filters shall be made available for supplemental analyses , including destructive analyses if necessary, at the request of EPA or to provide information to s tate and local agencies on particulate matter composition
. Note: destructive chemical analysis may be necessary and are acceptable. Other Federal agencies may request access to filters for purposes of supporting air quality mana gement or community health

— such as biological assay
— through the applicable EPA Regional Administrator
. The filters shall be archived according to procedures approved by the Administrator, which shall include cold storage of filters after post

- sampling labo ratory analyses for at least 12 months following field sampling
. The EPA recommends that particulate matter filters be archived for longer periods, especially for key sites in making NAAQS

- related decisions or for supporting health

- related air pollution st udies
. * * * * * * * * * * Subpart C

— Special Purpose Monitors 18. 15. Section 58.20 is amended by revising paragraph (c) to read as follows: §58.20 Special purpose monitors (SPM). * * * * * (c) All data from an SPM using an FRM, FEM, or ARM which has operated for more than 24 months are eligible for comparison to the relevant NAAQS, subject to the Formatted: Indent: Left: 0.19"***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 777 of 790 Formatted: Left conditions of §58.11(e) and 58.30, unless the air monitoring agency demonstrates that the data c ame from a particular period during which the requirements of appendix A, appendix C, or appendix E to this part were not met, subject to review and EPA Regional Office approval as part of the annual monitoring network plan described in §58.10. * * * * * 19. 16. T he heading f or Subpart D is revised to read as follows: Subpart D

— Comparability of Ambient Data to the NAAQS 20. 17. Section 58.30 is amended by revising paragraph (a) to read as follows: §58.30 Special considerations for data comparisons to the NAAQS. (a) Compara bility of PM 2.5 data
. The primary and secondary annual and 24

- hour PM 2.5 NAAQS are described in part 50 of this chapter
. Monitors that follow the network technical requirements specified in §58.11 are eligible for comparison to the NAAQS
. subject to the ad ditional requirements of this section
. PM 2.5 measurement data from all eligible monitors are compar able to the 24

- hour PM 2.5 NAAQS ; . PM 2.5 measurement data from all eligible monitors that are representative of area

- wide air quality are compar able to the annual PM 2.5 NAAQS
. As specified in Consistent with appendix D to this part, section 4.7.1, when micro

- or middle

- scale PM 2.5 monitoring sites collectively identify a larger region of localized high ambient PM 2.5 concentrations ; for example, a PM 2.5 monitoring site located in a near

- road environment where there are many other similar locations in the same CBSA , such sites would be considered representative of an area

wide location and , therefore , eligible for compar ison to the annual PM 2.5 NAAQS
. PM 2 .5 measurement data from monitors that are not representative of area

- wide air quality but rather of relatively unique micro

- scale, or localized hot spot, or unique middle

- scale Formatted: Indent: Left: 0.19"

Formatted: Indent: Left: 0.19"***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 778 of 790 Formatted: Left impact sites are not eligible for comparison to the annual PM 2.5 NAAQS. PM 2.5 measurement data from these monitors are eligible for comparison to the 24

- hour PM 2.5 NAAQS
. For example, if a micro

- or middle

- scale PM 2.5 monitoring site is adjacent to a unique dominating local PM 2.5 source, then the PM 2.5 measurement data from such a site would only be eligible for comparison to the 24

- hour PM 2.5 NAAQS . Approval of sites that are suitable and sites that are not suitable for comparison with the annual PM 2.5 NAAQS is provided for as part of the annual monitoring network plan described in §58.10. * * * * * 21. 18. Appendix A to part 58 is amended as follows:

a . By redesignating the existing introductory paragraph in section 1 as paragraph ( b ) in section 1
. b. By adding paragraph ( a ) to section 1
. c. By revising paragraph s 3.2.5.6 , and 3.2.6.3
. d
. By revising Table A

- 1
. The revisions and additions read as follows: Appendix A to Part 58

— Quality Assurance Requirements for SLAMS, SPMs and PSD Air Monitoring 1. * * * ( a ) Each monitoring organization is required to implement a quality system that prov ides sufficient information to assess the quality of the monitoring data
. The quality system must, at a minimum, include the specific requirements described in this appendix of this subpart
. Failure to conduct or pass a required check or procedure, or a se ries of required checks or procedures, does not by itself invalidate data for regulatory decision making
. Formatted: Indent: Left: 0.19"***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 779 of 790 Formatted: Left Rather, monitoring agencies and EPA shall use the checks and procedures required in this appendix in combination with other data quality information, reports, and similar documents showing overall compliance with part 58 . Accordingly, EPA and monitoring agencies shall use a "weight of evidence" approach when determining the suitabil ity of data for regulatory decisions
. The EPA reserves the authority to use or not use monitoring data submitted by a monitoring organization when making regulatory decisions based on the EPA's assessment of the quality of the data . Generally , consensus bu ilt validation templates or validation criteria already approved in Quality Assurance Project Plans (QAPPs) should be used as the basis for the weight of evidence approach
. ( b) This appendix specifies the minimum quality system requirements applicable to SLAMS air monitoring data and PSD data for the pollutants SO 2 , NO 2 , O 3 , CO, Pb, PM 2.5 , PM 10 and PM 10

- 2.5 submitted to EPA
. This appendix also applies to all SPM stations using FRM, FEM, or ARM methods which also meet the requirements of appendix E of this part, unless alternatives to this appendix for SPMs have been approved in accordance with § 58.11(a)(2)
. Monitoring organizations are encouraged to develop and maintain quality systems more extensive than the required minimums
. The permit

granting authority for PSD may require more frequent or more stringent requirements
. Monitoring organizations may, based on their quality objectives, develop and maintain quality systems beyond the required minimum
. Additional guidance for the requirements reflected in this appendix can be found in the “Quality Assurance Handbook for Air Pollution Measurement Systems”, volume V olume II , part 1 (see reference 10 of this appendix) and at a national level in references 1, 2, and 3 of this appendix. * * * * ****E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 780 of 790 Formatted: Left 3.2. 5 * * * 3.2.5.6 The two collocated monitors must be within 4 meters of each other and at least 2 meters apart for flow rates greater than 200 liters/min or at least 1 meter apart for samplers having flow rates less than 200 liters/min to preclude airflow interference
. A

w aiver allowing up to 10 meters horizontal distance and up to 3 meters vertical distance (inlet to inlet) between a primary and collocated sampler may be approved by the Regional Administrator for sites at a neighborhood or larger scale of representation
. T his waiver may be approved during the annual network plan approval process. Calibration, sampling, and analysis must be the same for all the collocated samplers in each agenc y’s network. * * * * * 3.2.6* * * 3.2.6.3 The two collocated monitors must be within 4 meters of each other and at least 2 meters apart for flow rates greater than 200 liters/min or at least 1 meter apart for samplers having flow rates less than 200 liters/min to preclude airflow interference
. A waiver allowing up to 10 meters horiz ontal distance and up to 3 meters vertical distance (inlet to inlet) between a primary and a collocated sampler may be approved by the Regional Administrator for sites at a neighborhood or larger scale of representation taking into consideration safety, lo gistics, and space availability. This waiver may be approved during the annual network plan approval process. Calibration, sampling, and analysis must be the same for all the collocated samplers in each agenc y’s network. * * * * * and***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 781 of 790 Formatted: Left Table A

– 1 of Appendi x A to Part 58

— Difference and Similarities Between SLAMS and PSD Requirements Topic SLAMS PSD

Requirements 1. The development, documentation,

and implementation of an approved quality system 2. The assessment of data quality 3. The use of reference, equivalent, or approved methods 4. The use of calibration standards traceable to NIST or other primary standard 5. The participation in EPA performance evaluations and the permission for EPA to conduct system audits Same as SLAMS

Monitoring and QA Respons ibility State/local agency via the “primary

quality assurance organization” Source owner/operator. Monitoring Duration Indefinitely Usually up to 12 months. Annual Performance Evaluation (PE) Standards and equipment different

from those used for spanning, calibration, and verifications. Prefer different personnel Personnel, standards and equipment different from those used for spanning, calibration, and verifications. PE audit rate:

— Automated 100% per year 100% per quarter.

— Manual Varies depending on pollutant. See

Table A

– 2 of this appendix 100% per quarter. Precision Assessment:

— Automated One

- point QC check biweekly but

data quality dependent One point QC check biweekly.

— Manual Varies depending on pollutant. See

Table A

– 2 of this appendix One site: 1 every 6 days or every third day for daily monitoring (TSP and Pb). Reporting

— Automated By site

— EPA performs calculations

annually By site

— source owner/operator performs Formatted: Font: Bold, Not Superscript/ Subscript Formatted: Centered, Space After: 12 pt, Line spacing: single Formatted: Font: Bold***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 782 of 790 Formatted: Left

calculations each sampling quarter.

— Manual By reporting organization

— EPA

performs calculations annually By site

— source owner/operator performs calculations each sampling quarter.
* * * * * 22. 19. Appendix D to part 58 is amended as follows:

a . By revising paragraphs 4.7.1(b) and 4.7.1(c)(1)
. b
. By removing paragraph 4.7.5

c . By removing and reserving paragraph 4.8.2 Appendix D to Part 58

— Network Design Criteria for Ambient Air Quality Monitoring * * * * * 4.7.1* * * (b) Specific Design Criteria for PM 2.5 . The required monitoring stations or sites must be sited to rep resent area
- wide air quality
. These sites can include sites collocated at PAMS
. These monitoring stations will typically be at neighborhood or urban

- scale; however, micro

- or middle

- scale PM 2.5 monitoring sites that represent many such locations throughout a metropolitan area are considered to represent area

- wide air quality. (1) At least one monitoring station is to be sited at neighborhood or larger scale in an area of expected maximum concentration. (2) For CB SAs with a population over of 1,000,000 or more persons , at least one PM 2.5 monitor is to be collocated at a near

- road NO 2 station required in section 4.3.2 (a) of this appendix
. Formatted: Indent: Left: 0.19"***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 783 of 790 Formatted: Left (3) For areas with additional required SLAMS, a monitoring station is to be sited in an area of poor air quality. (4 ) Additional technical guidance for siting PM 2.5 monitors is provided in references 6 and 7 of this appendix. (c) *** (1) Micro

- scale . This scale would typify areas such as downtown street canyons and traffic corridors where the general public would be exp osed to maximum concentrations from mobile sources
. In some circumstances, the micro

- scale is appropriate for particulate sites
. SLAMS sites measured at the micro

- scale level should, however, be limited to urban sites that are representative of long

- term h uman exposure and of many such microenvironments in the area
. In general, micro

- scale particulate matter sites should be located near inhabited buildings or locations where the general public can be expected to be exposed to the concentration measured
. Emi ssions from stationary sources such as primary and secondary smelters, power plants, and other large industrial processes may, under certain plume conditions, likewise result in high ground level concentrations at the micro

- scale
. In the latter case, the m icro

- scale would represent an area impacted by the plume with dimensions extending up to approximately 100 meters
. Data collected at micro

- scale sites provide information for evaluating and developing hot spot control measures. * * * * * 4.7.5 [Removed]

* * * * * 4.8* * ****E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 784 of 790 Formatted: Left 4.8.2[Reserved] * * * * * 23. 20. Appendix E to part 58 is amended as follows:

a. By adding table E

- 1 to paragraph 6. b. By revising table E

- 4. Appendix E to Part 58

— Probe and Monitoring Path Siting Criteria for Ambient Air Quality Monitoring
* * * * * 6. * * * Table E - 1 o f

to Appendix E t o of Part 58. Minimum Separation Distance Between Roadways and Probes or Monitoring Paths for Monitoring Neighborhood and Urban Scale Ozone (O 3 ) and Oxides of Nitrogen (NO, NO 2 , NO x , NO y ) Roadway average daily tr affic, vehicles per day Minimum distance 1 (meters) Minimum distance 1,2 (meters) < 1,000 ............................... 10,000 ................................ 15,000 ................................ 20,000 ................................ 40,000 ................................ 70,000 ................................ > 110,000 ........................... 10 10 20 30 50 100 250 10 20 30 40 60 100 250 1 Distance from the edge of the nearest traffic lane
. The distance for intermediate traffic counts should be interpolated from the table values based on the actual traffic count. 2 Applicable for ozone monitors whose placement has not already been approved as of December 18, 2006. * * * * * 11. * * * Formatted: Indent: Left: 0.19"

Formatted: Left, Space After: 0 pt***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 785 of 790 Formatted: Left Table E

– 4 of Appendix E to Part 58

— Summary of Probe and Monitoring Path Siting Criteria

Pollutant Scale

(maximum monitoring path length, meters) Height from

ground to probe, inlet or 80% of monitoring path 1 (meters) Horizontal

and vertical distance from supporting structures 2 to probe, inlet or 90% of monitoring path 1 (meters) Distance

from trees to probe, inlet or 90% of monitoring path 1 (meters) Distance from

roadways to probe, inlet or monitoring path 1 (meters)

SO 2 3,4,5,6 Middle (300 m)

Neighborhood Urban, and Regional (1 km) 2

– 15 >1 >10 N/A

CO 4,5,7 Micro

[downtown or street canyon sites], micro [near

- road sites], middle (300 m) and Neighborhood (1 km). 2.5

– 3.5; 2

– 7;

2

– 15
. >1 >10 2

– 10 for downtown areas or street canyon microscale; ≤ 50 for near

- road microscale; see Table E

– 2 of this appendix for middle and neighborhood scales.
O 3 3,4,5 Middle (300 m)

Neighborhood, Urban, and Regional (1 km) 2

– 15 >1 >10 See Table E

– 1 of this appendix for all scales.
NO 2 3,4,5 Micro (Near

road [50

– 300 m ]) 2

– 7 (micro ) ); >1 >10 ≤50 for near

road micro

scale. Middle (300 m) 2

– 15 (all

other scales) Neighborhood, Urban, and Regional (1 km) See Table E

– 1 of this appendix for all other scales Ozone Neighborhood 2

– 15 >1 >10 See Table E

– 4 Formatted: Don't keep with next, Don't keep

lines together

Formatted: No widow/orphan control, Don't keep with next, Don't keep lines together Formatted: Don't keep with next, Don't keep lines together***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 786 of 790 Formatted: Left

precursors (for PAMS) 345 and Urban (1

km) of this appendix for all scales.

PM, Pb 3,4,5,6,8 Micro , Middle,

Neighborhood, Urban and Regional 2

– 7 (micro);

2

– 7 (middle PM 10

- 2.5 ); 2

- 7 for near

- road; 2

– 15 (all other scales) >2 (all scales,

horizontal distance only) >10 (all

scales) 2

– 10 (micro);

see Figure E

– 1 of this appendix for all other scales
. ≤50 for near - road N/A

— Not applicable. 1 Monitoring path for open pa th analyzers is applicable only to middle or neighborhood scale CO monitoring, middle, neighborhood, urban, and regional scale NO 2 monitoring, and all applicable scales for monitoring SO 2 ,O 3 , and O 3 precursors. 2 When probe is located on a rooftop, this sep aration distance is in reference to walls, parapets, or penthouses located on roof. 3 Should be greater than 20 meters from the dripline of tree(s) and must be 10 meters from the dripline when the tree(s) act as an obstruction. 4 Distance from sampler, probe, or 90 percent of monitoring path to obstacle, such as a building, must be at least twice the height the obstacle protrudes above the sampler, probe, or monitoring path
. Sites not meeting this criterion may be classified as middle scale ( see text). 5 Must have unrestricted airflow 270 degrees around the probe or sampler; 180 degrees if the probe is on the side of a building or a wall. 6 The probe, sampler, or monitoring path should be away from minor sources, such as furnace or incineration flues
. The s eparation distance is dependent on the height of the minor source's emission point (such as a flue), the type of fuel or waste burned, and the quality of the fuel (sulfur, ash, or lead content)
. This criterion is designed to avoid undue influences from min or sources. 7 For micro

- scale CO monitoring sites, the probe must be >10 meters from a street intersection and preferably at a midblock location. 8 Collocated monitors must be within 4 meters of each other and at least 2 meters apart for flow rates greater t

han 200 liters/min or at least 1 meter apart for samplers having flow rates less than 200 liters/min to preclude airflow interference, unless a waiver is in place as approved by the Regional Administrator pursuant to section 3 of Appendix A
. * * * * * Appe ndix F to Part 58 [Reserved] * * * * * * * * * * Appendix F to Part 58 [Reserved] * * * * ****E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 787 of 790 Formatted: Left 24. 21. Appendix G to Part 58 is amended as follows: a. By revising section 9. b. By revising section 10. c. By revising section 12, including table 2. d. By revising section 13. Appendix G to Part 58 - Uniform Air Quality Index (AQI) and Daily Reporting * * * * * 9. How Does the AQI Relate to Air Pollution Levels? For each pollutant, the AQI transforms ambient concentrations to a scale from 0 to 500. The AQI is keyed as appropriate to the national ambient air quality standards (NAAQS) for each pollutant. In most cases, the index value of 100 is associated with the numerical level of the short

- term standard (i.e., averaging time of 24

- hours or less) for each pollutant. The index value of 50 is associated with the numerical level of the annual standard for a pollutant, if there is one, at one

- half the level of the short

- term standard for the pollutant, or at the level at which it is appropriate to begin to provide guidanc e on cautionary language. Higher categories of the index are based on increasingly serious health effects and increasing proportions of the population that are likely to be affected. The index is related to other air pollution concentrations through linear interpolation based on these levels. The AQI is equal to the highest of the numbers corresponding to each pollutant. For the purposes of reporting the AQI, the sub

- indexes for PM 10 and PM 2.5 are to be considered separately. The pollutant responsible for t he highest index value (the reported AQI) is called the “critical” pollutant. 10. What Monitors Should I Use to Get the Pollutant Concentrations For Formatted: Indent: Left: 0.19"***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 788 of 790 Formatted: Left Calculating the AQI? You must use concentration data from State/Local Air Monitoring Station (SLAMS) or par ts of the SLAMS required by 40 CFR 58.10 for each pollutant except PM. For PM, calculate and report the AQI on days for which you have measured air quality data (e.g., from continuous PM 2.5 monitors required in Appendix D to this part). You may use PM

meas urements from monitors that are not reference or equivalent methods (for example, continuous PM 10 or PM 2.5 monitors). Detailed guidance for relating non

- approved measurements to approved methods by statistical linear regression is referenced in section 13 below. * * * * * 12. How do I calculate the AQI? i . The AQI is the highest value calculated for each pollutant as follows: a. Identify the highest concentration among all of the monitors within each reporting area and truncate as follows: (1) Ozone

– truncate to 3 decimal places PM 2.5 – truncate to 1 decimal place PM 10 – truncate to integer CO

– truncate to 1 decimal place SO 2 – truncate to integer NO 2 – truncate to integer
******E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 789 of 790 Formatted: Left 

### TABLE 2.

— BREAKPOINTS FOR THE AQI These breakpoints Equal these AQI’s O 3 

### (ppm) 8

- hour O 3 

### (ppm)

1

- hour 1 

### PM 2.5



### (μg/m 3 

### ) 24

- hour PM 10



### (μg/m 3 

### ) 24

- hour CO

(ppm) 8

- hour SO 2



### (ppb) 1

- hour NO 2



### ( ppb) 1

- hour AQI Category 0.000

- 0.059 .................. 0.0

– 12.0 0

- 54 0.0

- 4.4 0

- 35 0

- 53 0

- 50 Good 0.060

- 0.075 .................. 12.1

– 35.4 55

- 154 4.5

- 9.4 36

- 75 54

- 100 51

- 100 Moderate 0.076

- 0.095 0.125

-

0.164 35.5

– 55.4 155

- 254 9.5

- 12.4 76

- 185 101

- 360 101

- 150 Unhealthy for

Sensitive Groups 0.096

- 0.115 0.165

-

0.204 3 

### 55.5

- 150.4 255

- 354 12.5

- 15.4 4 

### 186

- 304 361

- 649 151

- 200 Unhealthy 0.116

- 0.374 0.205

-

0.404 3 

### 150.5

- 250.4 355

- 424 15.5

- 30.4 4 

### 305

- 604 650

- 1249 201

- 300 Very

Unhealthy ( 2 

### )............... 0.405

-

0.504 3 

### 250.5

- 350.4 425

- 504 30.5

- 40.4 4 

### 605

- 804 1250

- 1649 301

-

400 Hazardous ( 2 

### )............... 0.505

-

0.604 3 

### 350.5

- 500.4 505

- 604 40.5

- 50.4 4 

### 805

- 1004 1650

- 2049 401

-

500 1 

### Areas are generally required to report the AQI based on 8

- hour ozone values. However, there are a small number of areas where an AQI based on 1

- hour ozone values would be more precautionary. In these cases, in addition to calculating the 8

- hour ozone inde x value, the 1

- hour ozone index value may be calculated, and the maximum of the two values reported. 2 

### 8

- hour O 3 

### values do not define higher AQI values ( 301). AQI values of 301 or greater are calculated with 1

- hour O 3 

### concentrations. 3 

### If a different SHL for PM 2.5 

### is promulgated, these numbers will change accordingly. 4 

### 1

- hr SO 2 

### values do not define higher AQI values ( 200). AQI values of 200 or greater are calculated with 24

- hour SO 2 

### concentrations.***E.O. 12866 Review

- Draft Do Not Cite, Quote, or Release During Review***

Page 790 of 790 Formatted: Left Formatted: Font: Not Italic 13. What Additional Information Should I Know? The EPA has developed a computer program to calculate the AQI for you. The program prompts for inputs, and it displays all the pertinent information for the AQI (the index value, color, category, sensitive group, health effects, and cautiona ry language). The EPA has also prepared a brochure on the AQI that explains the index in detail (The Air Quality Index), Reporting Guidance (Technical Assistance Document for the Reporting of Daily Air Quality

– the Air Quality Index (AQI)) that provides as sociated health effects and cautionary statements, and Forecasting Guidance (Guideline for Developing an Ozone Forecasting Program) that explains the steps necessary to start an air pollution forecasting program. You can download the program and the guidan ce documents at www.airnow.gov . Reference for relating non

- approved PM measurements to approved methods ( Eberly, S., T. Fitz

- Simons, T. Hanley, L. Weinstock., T. Tamanini, G. Denniston, B. Lambeth, E. Michel, S. Bortnick . Data Quality Objectives (DQOs) For Relating Federal Reference Method (FRM) and Continuous PM 2.5 Measurements to Report an Air Quality Index (AQI). U.S. Environmental Protection Agency, Research Triangle Park, NC. EPA

- 454/B

- 02

- 002, November 2002) can be f ound on the Ambient Monitoring Technology Information Center (AMTIC) website, http://www.epa.gov/ttnamti1/
.