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From: Lydia W egman/RTP/USEPA/US To: nfrey@omb.eop.gov Cc: Beth Hassett - Sipple/RTP/USEPA/US@EPA, martin.karen@epa.gov, Scott

Jenkins/RTP/USEPA/US@EPA, wegman.Lydia@epa.gov Date: 06/05/2012 09:52 AM Subject: Fw: Final PM Policy Assessment - transmittal to CASAC PM Panel Nathan, Here are the documents that were sent to CASAC when we issued the final Policy Assessment. They include the final policy assessment and m y transmittal memo to CAS AC. Please let me know if you have any questions.2 April 20 , 20 1 1 **MEMORANDUM SUBJECT:**  Transmittal of Policy Assessment for the Review of the Particulate Matter National

Ambient Air Quality Standards

– Final Document **FROM:** Lyd ia N. Wegman , Director /s/

Health and Environmental Impacts Division Office of Air Quality

Planning and Standards **TO:** Holly

Stallworth Designated Federal Officer Clean Air Scientific Advisory Committee EPA Science Advisory

Board Staff Office Attached is the final document , Policy Assessment for the Review of the Particulate Matter National Ambient Air Quality Standar ds (Policy

Assessment , April 2011 ) , prepared by the Environmental Protection Agency ’s (EPA) Office of Air Qualit y Planning and Standards (OAQPS) staff as part of EPA’s ongoing review of the national ambient air quality standard s (NAAQS) for particulate matter ( PM ) . The Policy Assessment presents considerations and conclusions relevant for EPA’s review of the current primary (health - based) standards and secondary (welfare - based) standards for both fine and coarse particles . This final document draws upon the evidence and information assessed and presented in the Integrated Science Assessment for Particulate Matter (ISA) prepared by EPA’s National Center for Environmental Assessment and two risk and exposure assessment documents (REAs) prepared by OAQPS , th e Quantitative Health R isk Assessment for Particulate Matter (Risk Assessment) and the U rban Focused Visibility Assessment for Particulate Matter (Visibility Assessment) . 1 T hese three final documents reflect consideration of comments from the Clean Air Scientific Advisory Committee (CASAC) Particular Matter Review Panel (the Panel) and the public on earlier drafts . The Policy

Assessment reflects consideration of comments from the Panel, as well as public comments, on the second draft Policy Assessment, which was reviewed by the Panel at a meeting on July

26 - 27, 2010 . C omments from the Panel on the second draft Policy Assessment were provided to us in a September 10 , 2010 letter (Samet, 2010 a) . 2 These comments, and the

1 All documents related to the current PM NAAQS review are available at: http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_index.html . 2 Samet, J (2010 a). Letter from Dr, Jonathan M. Samet, Chair, Clean Air Scientific Advisory Committee to the Honorable Lisa P. Jackson, Administrator, US EPA. CASAC Review of Policy Assessment for the Review of the PM NAAQS

– Second External Revi ew Draft ( June 2010). September 1 0 , 2010. Available at: http://yosemite.epa.gov/sab/sabproduct.nsf/264cb1227d55e02c85257402007446a4/CCF9F4C0500C500F8525779D00 73C593/$File/EPA - CASAC - 10 - 015 - unsigned.pdf3

changes made in the final Policy Assessment in response to them, are summarized in the Attachment . **Availability of Final Document** The Policy

Assessment is being made available to the Panel in the form of the attached electronic file , which we request that you forward to members of the Panel. This document is also available on the EPA website: http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_2007_pa.html . Please accept m y gratitude for the advice the Panel has provided throughout our review of the Particulate Matter NAAQS. I look forward to continuing our productive relationship. Should you have any

questions regarding th e final Policy Assessment , please contact Ms. Beth Hassett - Sipple (919 - 541 - 4605 ; email - hassett - sipple.beth @epa.gov). cc: Vanessa Vu, SAB, OA Rosalina Rodriguez, OAQPS/HEID Karen Martin, OAQPS/HEID John Vandenberg, ORD/NCEA - RTP Debra Walsh, ORD/NCEA - RTP Mary Ross, ORD/NCEA - RTP Doug Johns, ORD/NCEA - RTP Lindsay Stanek , ORD/NCEA - RTP Beth Hassett - Sipple , OAQPS/HEID Zachary Pekar , OAQPS/HEID Pradeep Rajan , OAQPS/HEID Scott Jenkins, OAQPS/HEID Vicki Sandiford, OAQPS/HEID Meredith Lassiter, OAQPS/HEID Marc Pitchford, NOAA Chet Wayland, OAQPS/AQAD Phil L orang, OAQPS/AQPD Lewis Weinstock, OAQPS/AQAD Patrick Dolwick, OAQPS/AQAD James Hemby , OAQPS/AQAD1 **Attachment CASAC**  **C omments on**  **S econd**  **D raft PM Policy Assessment and**  **R esponses to**  **t hose**  **C omments**  T he CASAC PM Panel’s comments and recommendations on the second draft of the PM Policy Assessment , as well as changes made in the final document in response to those comments for chapters 2 through 4 , are summarized below . C hapter 2 (Primary

Standards for Fine Particles) The Panel expressed agreement with a number of staff conclusions in the second draft Policy Assessment , and support ed the following :  The general approach for translating the available epidemiological evidence, risk information, and air quality information into the basis for reaching conclusions on the adequacy of the current standards and on alternative standards that are appropriate for consideration;  Considering revisions to the current PM 2.5 primary standard to provide increased public health protection;  Returning to the strategy used in 1997 that considers a suite of standard levels in which the annual standard would be the “generall y controlling” standard to provide primary protection for health effects associated with both long - and short - term PM 2.5 exposures , in conjunction with a 24 - hour standard set to provide supplemental protection ;  Revising the form of the annual standard to eliminate spatial averaging; and  Revising the annual standard level within the range of 13 to 11 μg/m 3 in conjunction with retaining or revising the level of the 24 - hour standard within a range of 35 to 30 μg/m 3

. The Panel stated that these ranges were “supported by the epidemiological and toxicological evidence, as well as by the risk and air quality

information...” However, the Pane l re quested further clarification on the rationale for the combinations of annual and 24 - hour standards most strongl y supported by the currentl y available information, as well the rationale for excluding other combinations within the ranges considered.  In addition, the Panel encouraged staff to focus on information related to the concentrations that were most influential in generating the health effect estimates in individual studies to inform alternative annual standard levels (Samet, 2010 a , p. 2).  The P anel also commented that the approach presented in the second draft P olicy A ssessment to identify

alternative 24 - hour standard levels which focused on peak - to mean ratios was not relevant for informing the actual level (Samet 2010 a , p. 4) Changes made in chapter 2 in the final Policy Assessment were primarily focused on improving and clarifying the approach for translating the epidemiological evidence into a basis for staff conclusions on potential alternative standard levels and more clearl y articulating the basis for staff’s conclusions related to alternative standard levels that are appropriate for consideration . Specificall y, w e have updated and streamlined the discussion of the general approach used in the current review (section 2.1.3). W e have modified or added a number of figures that summarize the available epidemiological evidence , air quality information , and risk -based considerations (Figures 2 - 4 to 2 - 12 ).2

Inour discussion of evidence -based considerations to inform alternative annual standard levels (section 2.3.4.1), we expanded and clarified the different approaches for characterizing the range of PM 2.5 concentrations over which we have the most confidence in the associations observed in the epidemiological studies . Consistent with the Panel’s comments to consider more information from epidemiological studies related to the concentrations that were most influential in generating the health effect estimates in individual studies to inform staff conclusions on alternative annual standard levels that would provide appropriate protection for both long - and short - term exposures, we contacted several study investigators to obtain additional information on population - level data (i.e., health events, number of study participants) . In new anal ys es using distributional statistics, we considered these data in conjunction with air quality data to identify the broader range of PM 2.5 concentrations that were most influential in generating health effect estimates in epidemi ological studies , and , specificall y , the range of PM 2.5 concentrations below the long - term means over which we continue to have confidence in the associations observed in these epidemiological studies (Figures 2 - 7 and 2 - 8 and associated text) . Inour discussion of evidence -based considerations to inform potential alternative 24 - hour standard s , consistent with the Panel’s comments we focused on the epidemiological evidence from multi - and single - city short - term exposure studies to inform staff co nclusions on alternative 24 - hour standard levels appropriate to consider (section 2.3.4.1 , Figures 2 - 6 and 2 - 9 ) . Inaddition to the epidemiological evidence, we also considered air quality information to understand the implications of different combinations of alternative annual and 24 - hour standards that would support the policy

goal of focusing on a generall y controlling annual standard in conjunction with a 24 - hour standard that would provide supplementation protection (Figure 2 - 10) . Inthe second draft Policy Assessment, staff reached the preliminary conclusion that consideration should be given to alternative annual PM 2.5 standard levels in the range of 13 to 11 μg/m 3 , in conjunction with retaining the current 24 - hour PM 2.5 standard level of 35 μg/m 3 , and that consideration could also be given to an alternative 24 - hour PM 2.5 standard level of 30 μg /m 3 particularl y in conjunction with an annual standard of 11 μg/m 3

. As noted in section 2.3.4.3, staff conclusions in th e final P olicy A ssessment regarding alternative pairings of annual and 24 - hour standards that are appropriate to consider differ somewhat from the pairings of annual and 24 - hour standards discussed in the second draft P olicy A ssessment upon which the Panel based its advice. Inthe final Policy

Assessment, staff again concludes that consideration should be given to revising the current annual PM 2.5 standard level to a level within the range of 13 to 11 μg/m 3 . Staff further concludes that the evidence most strongl y supports co nsideration of an alternative annual standard level in the range of 12 to 11 μg/m 3 . In conjunction with consideration of an annual standard in the range of 12 to 11 μg/m 3 , staff concludes it is appropriate to consider retaining the current 24 - hour PM 2.5 s tandard level at 35 μg/m 3 . In conjunction with consideration of an annual standard level of 13 μg/m 3 , staff concludes there is limited support to consider revising the 24 - hour PM 2.5 standard level to somewhat below 35 μg/m 3 , such as down to 30 μg/m 3

. The se final staff conclusions reflect consideration of the Panel’s comments as well as public comments on the second draft Policy Assessment and additional anal ys es, as described above.3

Chapter 3 (Primary

Standard for Coarse Particles) Intheir review of the second draft Policy Assessment, the Panel recommended the following:  Revising the current PM 10 primary standard to provide increased public health protection against effects associated with exposures to PM 10 - 2.5 ;  Retaining PM 10 as the indicator for thoracic coarse particles, while also encouraging research to provide information for future NAAQS reviews to inform consideration of alternative sizes (e.g., PM 10 - 2.5 ) as well as components and sources;  Retaining the 24 - hour averaging time;  Revising the form to the 98 th percentile , while also noting that additional characterization is needed regarding the potential implications of such a change in form; and  Setting the level of the revised standard within the range of 75 to 65  g/m 3

. Changes made to chapter 3 since the second draft Policy Assessment have been focused largel y on improving and expanding the discussion of potential alternative standards in section 3.3. In sections 3.3.3 and 3.3.4, we have included additional anal ys is and discussion of the potential public health impacts of revising the form and level of the current PM 10 standard. Specificall y, section 3.3.3 discusses a new analysis of PM 10 and PM 10 - 2.5 air quality concentrations in U.S. locations and section 3.3.4 now includes an expanded discussion of PM 10 air quality concentrations in U.S. study locations. Section 3.3.4 also includes an expanded discussion of the relationship between the current standard level and 98 th percentile PM 10 concentrations. Figure 3 - 8 pres ents a regional breakdown of this relationship, and the integration discussion in section 3.3.4 now includes more extensive consideration of different approaches to characterizing this relationship. In addition, section 3.3.4 includes an expanded discussi on of potential alternative standard levels, more clearl y articulating the basis for staff’s conclusions related to alternative levels that are appropriate for consideration. C hapter 4 ( Secondary

Standard for PM - related Visibility ) The Panel expressed agreement with a number of staff conclusions included in the second draft Policy Assessment, including:  Considering revisions to the current PM 2.5 standards to provide increased protection against PM - related visibility impairment;  Considering a PM 2.5 light extinction indicator in preference to a PM 2.5 mass indicator; and  Considering secondary standards for a PM 2.5 light extinction indicator in a range of 20 to 30 deciviews. The Panel expressed its strong preference for direct ly measuring light extinction over using estimates based on mass measurements and recommended a fuller discussion of the reasons EPA staff believes this is not a feasible approach for this review. We have expanded the discussion of this issue and added a citation to the recommendation s of the advice we received from the Panel ’s Ambient Air Monitoring and Methods Subcommittee (Russell and Samet, 2010) . 3

3 Russell A, Samet JM (2010). Letter from the Clean Air Science Advisory Committee (CASAC) Ambient Air Monitoring and Methods Subcommittee (AAMMS) to the Honorable Lisa P, Jackson, Administrator, US EPA. Review of the White Paper on Particulate Matter (PM) Light Extinction Mea surements. April 29, 2010, Available at:4

In its review of the first draft P olicy A ssessment , the Panel agreed with the staff conclusion that PM effects on visibility can vary widel y and rapidly over the course of a day and such changes are almost instantaneousl y perceptible to human observers. 4 Based in part on this consideration, the Panel agreed that a 1 - hour averaging time would be appropriate to consider in conjunction with a directl y 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 monitoring methods that directly

measure light extinction . At that time, the Panel 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, 2010b , p. 19) . Thus, the P anel ’s views on averaging times that would be appropriate for consideration were predicated in part on the capabilities of monitoring methods that were available for the alternative indicators discussed in the draft PA. We have interpreted the Panel ’s vie ws on a multi - hour averaging time as extending to a sub - daily calculated PM 2.5 light extinction indicator since PM 2.5 mass measurements are also required for this indicator. Inpreparing the final Policy Assessment, EPA staff conducted anal ys es to better understand data quality issues associated with the use of continuous Federal Equivalent Methods (FEMs) that were considered as the basis for hourl y PM 2.5 mass measurements (section 4.3.1.1). Based in part on these anal ys es, EPA staff concludes that it is appropriate to consider a 24 - hour averaging time, in conjunction with a calculated PM 2.5 light extinction indicator and appropriatel y specified standard level (sections 4.3.2.2 and 4.3.2.4) . This conclusion reflects the judgment that PM 2.5 light extinctio n calculated on a 24 - hour basis is a reasonable and appropriate surrogate for sub - dail y PM 2.5 light extinction calculated on a 4 - hour average basis. This conclusion is also predicated on consideration of a 24 - hour average standard level which we have interpreted as providing information on the acceptability of day time visual air quality over an hourl y or multi - hour exposure period (section 4.3.4) . Other changes included in the final Policy Assessment include an anal ys is of the performance of two somewhat differentl y defined calculated PM 2.5 light extinction indicator s using 2007 - 2009 data (revised Appendix F), removal of detailed material from Chapter 4 regarding a PM 2.5 mass indicator (this material is still provided in Appendix E and several technical memos), and the addition of two new appendices, Appendix G and Appendix H. Appendix G discusses the us e of calculated 24 - hour average PM 2.5 light extinction as the indica tor and averaging period for a secondary PM 2.5 NAAQS that would be aimed at controlling dail y m aximum daylight 4 - hour average light extinction conditions. Appendix H provides information on the number and percentage of counties that likel y would not meet the current and alternative secondary standards, http://yosemite.epa.gov/sab/sabproduct.nsf/264cb1227d5 5e02c85257402007446a4/92C9F5AA09A76A938525771500 04A782/$File/EPA - CASAC - 10 - 010 - unsigned.pdf . 4 Samet J (2010b). Letter from Dr. Jonathan M. Samet, Chair, Clean Air Scientific Advisory Committee to the Honorable Lisa P. Jackson, Administrator, US EPA. CASA C Review of Policy Assessment for the Review of the PM NAAQS

– First External Rev i ew Draft (March 2010). May 17, 2010. Available at : http://yosemite.epa.gov/sab/sabproduct.nsf/264cb1227d55e02c85257402007446a4/E504EE3276D87A9E85257727 00647AFB/$File/EPA - CASAC - 10 - 011 - unsigned.pdf/ .5

similar to Appendices C and D which provides information related to the current and alternative primary standards. We note that since earlier drafts of this P olicy A ssessment did not include discussion of a calculated PM 2.5 indicator based on a 24 - hour averaging time, CASAC did not have a basis to express any

views regarding a 24 - hour averaging time .