1 July 1, 2010 MEMORANDUM

SUBJECT: CASAC Review of the Policy Assessment for the Review of the Particulate Matter National Ambient Air Qua lity Standards – Second Ex ternal Review Draft

FROM: Lydia N. Wegman, Director /s/ Health and Environmental Impacts Division Office of Air Quality Planning and Standards

TO: Holly Stallworth Designated Federal Officer Clean Air Sc ientific Advisory Committee EPA Science Advisory Board Staff Office

Attached is the draft document, Policy Assessment for the Revi ew of the Particulate Matter National Ambient Air Qua lity Standards - Second External Review Draft (Policy Assessment), prepared by the Environmental Protection Agency ’s (EPA) Office of Air Quality Planning and Standards (OAQPS) staff as part of EPA’s ongoing review of the national ambient air quality standards (NAAQS) for particulate matter (PM). This document will be the focus of a review by the Clean Air Scientific Advisory Committee (C ASAC) Particular Matter Review Panel (the Panel) on July 26-27, 2010. The second draft Policy Assessment presents co nsiderations and conclusions relevant for EPA’s review of the current primary (health-b ased) standards and secondary (welfare-based) standards for both fine and coarse particles. This draft document dr aws upon the evidence and information assessed and presented in the final Integrated Science Assessment for Particulate Matter (ISA) prepared by EPA’s National Center for Environmental Assessment and two final assessment documents prepared by OAQPS, the Quantitative Health Ri sk Assessment for Particulate Matter (Risk Assessment) and the Urban-Focused Visibility Asse ssment for Particulate Matter (Visibility Assessment). These three final documents reflect consideration of comments from the Panel and the public on earlier drafts. The second draft Policy Assessment reflects c onsideration of comments from the Panel, as well as public comments, on the first draf t Policy Assessment, which was reviewed by the Panel during teleconferences on April 8-9 and May 7, 2010. The main comments from the Panel on the first draft Policy Assessment were provide d to us in a May 17, 2010 letter (Samet, 2010). 1 These comments, and the changes made in the second draft Policy Assessment in response to them, are summarized in Attachment 1.

1 Samet, J. (2010). Letter from Clean Air Scientific A dvisory Committee to the Honorable Lisa P. Jackson, Administrator, US EPA. CASAC Revi ew of Policy Assessment for the Review of the PM NAAQS – First External Review Draft (March 2010). May 17, 2010.2 We will take comments from the Panel a nd the public on the second draft Policy Assessment into consideration in preparing a fina l Policy Assessment, which we plan to release in September, 2010. Our review of the PM NAA QS will conclude with Agency rulemaking. Our current schedule anticipates that proposed and final rules will be signed in February 2011 and October 2011, respectively.

Document Availability The second draft Policy Assessment is being made available to the Panel in the form of the attached electronic file, whic h 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 . Printed copies of this document will be sent to members of the Panel via Federal Express.

Charge to the Panel In their review, we ask the Panel members to focus on the charge questions listed in Attachment 2, though we would appreciate comments on other topics as well.

We look forward to discussing this second dr aft Policy Assessment w ith the Panel at our upcoming meeting in July. Should you have any que stions regarding this draft document, please contact Ms. Beth Hassett-Si pple (919-541-4605; email ha ssett-sipple.beth@epa.gov).

cc: Vanessa Vu, SAB, OA Holly Stallworth, SAB, OA John Vandenberg, ORD/NCEA-RTP Debra Walsh, ORD/NCEA-RTP Mary Ross, ORD/NCEA-RTP Lindsay Stanek, ORD/NCEA-RTP Jason Sacks, ORD/NCEA-RTP Beth Hassett-Sipple, OAQPS/HEID Zachary Pekar, OAQPS/HEID Pradeep Rajan, OAQPS/HEID Susan Lyon Stone, OAQPS/HEID Scott Jenkins, OAQPS/HEID Vicki Sandiford, OAQPS/HEID Meredith Lassiter, OAQPS/HEID Marc Pitchford, OAQPS/HEID Karen Martin, OAQPS/HEID Rosalina Rodriguez, OAQPS/HEID3 Attachment 1 CASAC comments on first draft PM Policy A ssessment and responses to those comments

The CASAC Panel’s comments and recommendati ons on the first draft of the PM Policy Assessment, as well as changes made in the s econd draft in response to those comments, are summarized below. Overarching comments a nd recommendations are summarized below, followed by comments and recommendations on chapters 2 through 4.

Overarching comments and recommendations The Panel made several overarching comme nts and recommendations, including:

 The document should be stream lined by relying more on the underlying scientific and technical documents and editing to reduce redundancy.

 The staff’s approach to reaching conclusions on policy options should be more explicit. In response to these comments, we have made extensive edits throughout the second draft Policy Assessment to streamline the document by reduci ng redundancy and by relying more extensively on references to the underlying scientific and technical documents. We have clarified the approaches to reviewing the standards (sections 2.1.3, 3.1.4, 4.1.3) and have added figures framing these approaches (Figures 2-1, 3-1, 4-1). Throughout the document we have more explicitly articulated the application of these approaches in reaching staff conclusions on the current and potential alternative standards. We have also added an executive summary and added sections discussing areas for future research and da ta collection (sections 2.5, 3.5, 4.5).

Chapter 2 (Primary Standards for Fine Particles) The Panel expressed agreement with a number of preliminary staff conclusions in the first draft Policy Assessment, expressing support for the following:

 Considering revisions to the current PM 2.5 primary standard to provide increased public health protection;

 Retaining PM 2.5 as the indicator for fine particles, while also encouraging research to provide information for futu re NAAQS reviews to inform our consideration of alternative size fractions as well as PM 2.5 components and sources;

 Retaining annual and 24-hour averaging times;

 Revising the form of the annual standard to eliminate spatial averaging; and

 Considering a suite of standard levels in which the annual standard would be the “generally controlling” standard to provide primary protection for both long- and shortterm PM 2.5 exposures, in conjunction with a 24-hour standard set to provide supplemental protection. Changes made in chapter 2 in the second draft Policy Assessment were primarily focused on streamlining the chapter as well as on improving and clarifying the approach for translating the epidemiological evidence into a basis for staff conclusions on the current and potential alternative standards. We have added a nu mber of figures that summariz e the available epidemiological evidence and air quality information (Figures 2- 2 to 2-9). We have also conducted air quality analyses to inform our discussion of form an d level. For the annual standard, we conducted analyses that focused on understanding potential im pacts on susceptible populations, including low income populations and minorities (section 2.3.3.1). For the 24- hour standard, we conducted air4 quality analyses to understand the differences in 98 th versus 99 th percentile forms (section 2.3.3.2) and to inform staff conclusions on level of the 24-hour standard (section 2.3.4.1).

Chapter 3 (Primary Standa rd for Coarse Particles) In reviewing the first draft PM Policy Assessment, the Panel expre ssed support for the following:

 Considering revisions to 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 informa tion for future NAAQS reviews to inform consideration of alternative sizes (e.g., PM 10-2.5 ) as well as components and sources;

 Retaining 24-hour averaging time; and

 Considering revising the form to a 98 th percentile form. We have made important revisions in the second dr aft Policy Assessment to the discussions of the current and potential alternative standards. We have added fi gures summarizing the available epidemiological evidence and air quality data to the discussion on adequacy of the current standard (Figures 3-2 and 3-3). We included a new discussion of potentia l alternative standard levels and staff conclusions. To facilitate this discussion, we added figures summarizing the available epidemiological evidence and air quality data (Figures 3-5 and 3-6) and we have conducted additional PM 10 air quality analyses (Figure 3-7, Table 3-2). In addition, we have expanded the discussion of considerations rela ted to the standard indicator (section 3.3.1), including an analysis of PM 10 and PM 10-2.5 air quality (Figure 3-4), and we have expanded the discussion of standard form (section 3.3.3).

Chapter 4 (Secondary Standard for PM-related Visibility) The Panel expressed agreement with a number of staff conclusions included in the fi rst draft Policy Assessment, including:

 Considering revisions to the current PM 2.5 standards to provide increased protection against PM-related visibility impairment;

 A one-hour averaging time, including dayl ight hours only, and excluding hours with relative humidity above 90%; and

 Considering a PM 2.5 light extinction indicator. In addition to the edits made to address the Panel’s overarching comments, we have addressed specific comments on chapter 4. The Panel recogni zed potential benefits in moving to a PM light extinction indicator as well as the lack of mo nitoring capabilities to support direct PM light extinction measurements at this time, and supporte d consideration of an alternative approach. In response, we have developed and evaluated an approach that uses an indicator based on using speciated PM 2.5 mass to calculate light extinction that allows the coupling of the PM light extinction indicator with PM air quality measurem ents based on the currently available PM mass monitoring infrastructure (Appendix B and section 4.3.1). In addition, in response to the Panel’s interest in additional analyses to better illustra te and evaluate the sim ilarities and differences between the wide range of alternative indices and forms of the standard (e.g., 1-hour daily maximum versus all dayli ght hours) being considered, and the policy implications of these options, we have incorporated an assess ment of the PM species componen ts that contribute to the high value days selected by different combin ations of indices/forms (Appendix C).5 Attachment 2 Charge to the Panel in Reviewing the Second Draft PM Policy Assessment

Our charge to the Panel in reviewing the seco nd draft Policy Assessment focuses on chapters 2 through 4. We ask the Panel to focus on the following char ge questions, though we would appreciate comments on other topics as well.

Chapter 2 (Primary Standards for Fine Particles)

1. Current Approach (section 2.1.3) :

a. What are the Panel’s views on the staff’s approach to 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 for consideration? b. Has staff appropriately applied this approach in reviewing the adequacy of the current standards (section 2.2) and potential alternative standards (section 2.3)? 2. Form of the Annual St andard (section 2.3.3.1):

a. What are the Panel’s views on the additional analyses conducted to characterize the potential for disproportionate impacts on su sceptible populations, including low income groups and minorities associated with spatial averaging allowed by the current annual standard? b. In light of these analyses, what are the Pane l’s views on staff’s conclusion that the form of the annual standard should be revi sed to eliminate spatial averaging? 3. Alternative Levels (section 2.3.4): What are the Panel’s views on the following:

a. The insights that can be gained into potential alternative stan dard levels by considering: i. Confidence bounds on concentration-response relationships? ii. Different statistical metrics that charac terize air quality distributions from multicity epidemiological studies? b. Potential alternative annual standard leve ls based on composite monitor distributions versus maximum monitor distributions?

c. Use of risk information in informing staff conclusions on alternative annual and 24- hour standard levels, including approaches used to assess overall confidence and potential bias in the risk estimates? d. Staff’s conclusion that alternative annual stan dard levels in the range of 13 to 11 μg/m 3 are most strongly supported by the available evidence and risk-based information?

e. Staff’s approach of focusing on peak-to-mean ratios to inform the level of a 24-hour standard that would provide supplemental protection to a generally controlling annual standard? f. Staff’s conclusion that consideration should be given to retaining the current 24-hour standard level of 35 μg/m 3 in conjunction with annual standard levels in the range of 13 to 11 μg/m 3 , and that consideration could also be given to an alternative 24-hour standard level of 30 μg/m 3 particularly in conjunction w ith an annual standard level of 11 μg/m 3 ? 4. Key Uncertainties and Areas for Future Research and Data Collection (section 2.5): What are the Panel’s views on the areas for future research and da ta collection outlined in this section, on relative priorities for research in these areas, and on any other areas that ought to be identified?6 Chapter 3 (Primary Standa rd for Coarse Particles)

5. Current Approach (sec tions 3.1.4, 3.2, 3.3) :

a. What are the Panel’s views on the approach to translating the available evidence and air quality information into the basis for reviewing the coar se particle standard? b. Has staff appropriately applied this approach in reviewing the adequacy of the current standard (section 3.2) and potential alternative standards (section 3.3)? 6. Adequacy of the Current PM 10 Standard (section 3.2): What are the Panel’s views on the alternative approaches presente d for considering the evidence and its uncertainties as they relate to the adequacy of the current standard? 7. Indicator (section 3.3.1): What are the Panel’s views on the approach taken to considering standard indicator and on staff’s conclusion that PM 10 remains an appropriate indicator in this review? 8. Form (section 3.3.3): What are the Panel’s views on the approach taken to considering the form of the standard and on staff’s conc lusion that revising the form to a 98 th percentile form would be appropriate for a 24-hour PM 10 standard meant to protect against exposures to thoracic coarse particles? 9. Level (section 3.3.4): What are the Panel’s views on the following:

a. The approach taken by staff to identify potential alternative PM 10 standard levels, in conjunction with a 98 th percentile form, including th e weight placed on different studies? b. Staff’s conclusion that the evidence most stro ngly supports standard levels around 85 μg/m 3 ?

c. The alternative approach to considering the evidence that could support standard levels as low as 65 μg/m 3 ? 10. Key Uncertainties and Areas for Future Research and Data Collection (section 3.5): What are the Panel’s views on the areas for future research and da ta collection outlined in this section, on relative priorities for research in these areas, and on any other areas that ought to be identified?

Chapter 4 (Secondary Standard for PM-related Visibility)

11. Current Approach (section 4.1.3) :

a. What are the Panel’s views regarding our a pproach for translating technical evidence and assessment results into the basis for a ssessing current fine particle standards and considering alternative standards to provi de protection against PM-related visibility impairment? b. Has staff appropriately applied this approach in reviewing the adequacy of the current standard (section 4.2) and potential alternative standards (section 4.3)? 12. Nature of the Indicator (section 4.3. 1): What are the Panel’s views on the following:

a. Staff’s consideration of the three indicat ors identified in th is section and our conclusions on the appropriateness of these in dicators for consideration in this review? b. The development and evaluation of a new appr oach that is based on using speciated PM 2.5 mass and relative humidity to calculate PM 2.5 light extinction by means of the IMPROVE algorithm?

c. The assessment approach and results comp aring the PM component s that contribute to the hours selected in the top percentiles for PM 2.5 mass and PM 10 light extinction?7 13. Alternative Levels and Forms (section 4.3.3): What are Panel view s on the following:

a. The performance assessment which focused on the Candidate Protection Levels of 64, 112, 191 Mm -1 for PM 2.5 light extinction and speciated PM 2.5 mass-calculated light extinction, and alternative levels of 10, 20, and 30 μ g/m 3 for PM 2.5 mass concentration? b. Use of three-year averaged 90 th and 95 th percentiles in conjunction with a 1-hour daily maximum form and use of three-year averaged 98 th percentile in conjunction with the all daylight hours form?

c. Insights to be drawn by comparing the PM components for hours included among the 10% highest for a 1-hour da ily maximum form with the hours included among the 2% highest for an all daylight hours form, for th e various indicators considered (Appendix C)? 14. Key Uncertainties and Areas fo r Future Research and Data Collection (section 4.5): What are the Panel’s views on the areas for future research and da ta collection outlined in this section, on relative priorities for research in these areas, and on any other areas that ought to be identified?