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March 9, 2010 

MEMORANDUM

SUBJECT: CASAC Review of the Policy Assessment for the Review of the Particulate Matter 

National Ambient Air Quality Standards -- First External 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 Scientific Advisory Committee 

 EPA Science Advisory Board Staff Office 

Attached is the draft document, Policy Assessment for the Review of the Particulate Matter 

National Ambient Air Quality Standards - First 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 (CASAC) Particular Matter Review Panel (the 

Panel), scheduled as a teleconference for April 8-9, 2010. 

The attached draft Policy Assessment document presents factors relevant to EPA’s 

review of the current primary (health-based) standards and secondary (welfare-based) standards 

for both fine and coarse particles. This draft document draws upon information assessed and 

presented in the final Integrated Science Assessment for Particulate Matter, prepared by EPA’s 

National Center for Environmental Assessment after undergoing review by the Panel and the 

public, and the second drafts of the Quantitative Health Risk Assessment for Particulate Matter

(Risk Assessment) and the Urban-Focused Visibility Assessment for Particulate Matter (Visibility 

Assessment), which will be reviewed at a meeting of the CASAC Panel scheduled for March 10-

11, 2010 in Research Triangle Park, NC. 

Following CASAC and public review of this first draft Policy Assessment, we will 

produce a second draft Policy Assessment for CASAC and public review, prior to preparing a 

final Policy Assessment in July 2010. Our review of the PM NAAQS will conclude with 

Agency rulemaking. Our current schedule anticipates that proposed and final rules will be 

signed in November, 2010, and July, 2011, respectively. 
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Document for Review 

We will send printed copies of the first draft Policy Assessment, described below, to 

members of the Panel. In addition, we request that you forward to the Panel the electronic file 

containing this document. This document will also be available on the EPA website: 

http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_2007_pa.html. Attached to this memorandum 

are charge questions to guide the Panel’s review of this document. 

 Policy Assessment for the Review of the Particulate Matter National Ambient Air Quality 

Standard - First External Review Draft 

Chapter 1 includes information on the purpose and background for this review, as well as 

an overview of the general approach and organization of the policy assessment. Chapters 

2 and 3 present staff observations and preliminary conclusions related to the review of the 

primary standards for fine and thoracic coarse particles, respectively. Each chapter 

begins with a discussion of policy assessment approaches and focuses on evidence-based 

considerations based on the updated scientific and technical information as assessed and 

presented in the final Integrated Science Assessment. In addition, chapter 2 also includes 

a discussion of quantitative risk-based considerations as assessed and presented in the 

second draft Risk Assessment. Preliminary staff conclusions are presented with regard to 

the adequacy of the current primary standards and potential alternative primary standards 

for consideration, in terms of indicators, averaging times, forms, and levels. Chapter 4 

focuses on PM-related visibility impairment, and presents staff observations and 

preliminary conclusions with regard to the adequacy of the current standards and 

potential distinct secondary standards for consideration, in terms of alternative indicators, 

averaging times, forms, and levels. This chapter focuses on the updated scientific and 

technical information as assessed and presented in the final Integrated Science 

Assessment as well as the quantitative analyses presented in the second draft Visibility 

Assessment. Chapter 5 focuses on other PM-related welfare effects, including effects on 

climate, ecological effects, and effects on materials, and presents staff observations and 

preliminary conclusions with regard to the adequacy of the current standards and the 

extent to which information is available to support consideration of alternative standards. 

We look forward to discussing this first draft Policy Assessment with the Panel at our 

upcoming teleconference in April. At the Panel’s request, we will provide a brief overview of 

this document at the meeting on March 10-11 to provide context for the Panel’s review of the 

second drafts of the Risk Assessment and Visibility Assessment at that meeting. Should you 

have any questions regarding this first draft Policy Assessment, please contact Ms. Beth HassettSipple (919-541-4605; email hassett-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 
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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 Rodriquez, OAQPS/HEID 

Attachment: 

Charge to the CASAC PM Review Panel for Review of the Draft PM Policy Assessment
Update 

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Charge to the CASAC PM Review Panel for Review of the First Draft Policy Assessment 

for the Review of the Particulate Matter NAAQS 

The first draft Policy Assessment (PA), conveyed to the CASAC PM Panel on March 9, 

2010, includes staff’s preliminary evaluation of the policy implications of the scientific assessment 

of the evidence presented in the Integrated Science Assessment (ISA) and the results of 

quantitative assessment based on analyses presented in the second draft Risk and Exposure 

Assessments (REAs). Consistent with CASAC’s comments on a preliminary draft Policy 

Assessment (September 2009) that encouraged the development of a document focused on key 

policy-relevant issues that draws from and is not repetitive of information in the ISA and REAs, 

staff has organized the discussion in the Policy Assessment around answering a series of policyrelevant questions. Taken together, staff’s responses to these questions support preliminary staff 

conclusions and the identification of policy options for consideration in our review of the primary 

and secondary PM NAAQS. 

We ask the CASAC PM Panel to focus on the charge questions below in their review of the 

first draft Policy Assessment, but we would appreciate comments on any other topics as well. 

Overarching Questions (related to Chapters 2, 3, 4, 5)

1. Organizational Structure 

a. Does the Panel find the introductory and background material, including that pertaining to 

previous reviews of the PM standards and the current review, to be clearly communicated 

and appropriately characterized? 

b. To what extent does the Panel find that the questions posed appropriately reflect the 

important policy-relevant issues for this review? Are there additional policy-relevant 

questions that should be addressed? 

c. What are the Panel’s views regarding the level of detail used to address these policyrelevant questions? Please comment on the extent to which the discussions are 

appropriately focused in addressing the questions. 

2. Technical Content 

a. Do the discussions accurately reflect and clearly communicate the currently available 

health and welfare effects evidence, including important uncertainties, as characterized in 

the final ISA? 

b. Do the discussions accurately reflect and clearly communicate policy-relevant information 

from the human health risk and visibility assessments, including important uncertainties, as 

characterized in the second draft REAs? 

Review of the Primary Standards for Fine Particles (Chapter 2)

3. Approach (section 2.1.3): Various approaches are described for translating different air 

quality metrics from epidemiological studies into the basis for reaching preliminary staff 

conclusions on the adequacy of the current PM2.5 standards and on alternative standards for 
Update 

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consideration. What are the Panel’s views regarding the appropriate weight to place on these 

various approaches; should specific approaches be afforded more or less weight? Are there 

additional approaches that should be considered? 

4. Adequacy of current suite of PM2.5 standards (section 2.2): 

What are the Panel’s views on the following: 

a. The appropriateness and characterization of the sets of long- and short-term PM2.5 exposure 

studies highlighted? (section 2.2.1) 

 Are there specific studies that should be given more or less emphasis? 

 Are there additional studies that should be focused on? 

 Does the Panel generally support placing greater weight on multi-city vs. single-city 

short-term exposure studies? 

 Does the Panel agree with the characterizations of PM2.5 air quality at which 

associations have been observed? 

b. The focus on persons with lower socioeconomic status as a susceptible population in 

addition to consideration of newly available evidence for susceptible populations identified 

in previous reviews (e.g., children, older adults, persons with pre-existing cardiac and 

respiratory disease)? (section 2.2.1) 

c. The preliminary staff conclusion that the estimated risks remaining upon simulation of just 

meeting the current suite of standards can reasonably be judged to be important from a 

public health perspective? (section 2.2.2) 

d. The relative roles of the annual and 24-hour standards in providing public health protection 

as informed by the quantitative risk assessment, specifically in focusing on simulation of 

estimated risks remaining upon just meeting the current suite of standards? (section 2.2.2) 

e. The integration of evidence-based and risk-based considerations to inform the preliminary 

staff conclusion that the available information clearly calls into question the adequacy of 

the current suite of PM2.5 standards and provides strong support for giving consideration to 

revising the current standards to provide increased public health protection? (section 2.2.3) 

5. Indicator (section 2.3.1): 

What are the Panel’s views on the following: 

a. The preliminary staff conclusion that it is reasonable to retain PM2.5 as an indicator for fine 

particles? 

b. The preliminary staff conclusion that the currently available information is too limited to 

support a distinct PM standard for ultrafine particles? 

c. The preliminary staff conclusion that the currently available information is not sufficient to 

support consideration of a separate indicator for a specific PM2.5 component or for the mix 

of fine particles from any specific source category, and that data are too limited to consider 

eliminating any component or source category from the mix of fine particles included in 

the PM2.5 mass-based indicator? 
Update 

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6. Averaging Times (section 2.3.2): 

What are the Panel’s views on the following: 

a. The preliminary staff conclusion that it is reasonable to retain annual and 24- hour 

averaging times? 

b. The preliminary staff conclusions that the currently available evidence is too limited to 

support additional averaging times to address sub-daily exposures or seasonal exposures? 

7. Forms (section 2.3.3): What are the Panel’s views on the utility of additional analyses to 

inform consideration of eliminating provisions included in the current form of the annual 

standard that allow for spatial averaging across monitors, specifically with regard to the 

potential for disproportionate impacts on susceptible populations with lower socioeconomic 

status? 

8. Levels (sections 2.3.4, 2.3.5, and 2.3.6): 

What are the Panel’s views on the following: 

a. The preliminary staff conclusions regarding alternative standard levels that are appropriate 

for consideration, and the rationale upon which those conclusions are based? 

b. The insights that can be gained from the quantitative risk assessment to inform our 

understanding of the roles that the annual and 24-hour standards play in providing public 

health protection, specifically in focusing on simulations of estimated risks remaining upon 

just meeting alternative suites of standards? (sections 2.3.4.2 and 2.3.5.2) 

c. The policy implications of the uncertainties associated with estimating risks, including 

potential underestimation of risk, in reaching conclusions regarding standards that would 

provide public health protection with an adequate margin of safety? 

d. A policy approach for identifying a suite of standard levels in which the annual standard 

would be the “generally controlling” standard to provide protection for both long- and 

short-term PM2.5 exposures, in conjunction with a 24-hour standard set to provide 

supplemental protection against days with high peak concentrations associated with 

localized “hotspots” and risk arising from seasonal emission that might not be controlled by 

a national annual standard? (section 2.3.6) 

e. Additional considerations that could inform our conclusions related to alternative suites of 

fine particle standards? 

Review of the Primary Standard for Thoracic Coarse Particles (Chapter 3)

9. Adequacy of the current 24-hour PM10 standard (section 3.2): 

What are the Panel’s views on the following: 

a. The preliminary staff conclusion that the available scientific evidence supports maintaining 

a standard that provides protection against health effects associated with exposure to 

thoracic coarse particles? 
Update 

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b. The various approaches described for translating the evidence and related uncertainties into 

the basis for conclusions on the adequacy of the current PM10 standard? 

c. The adequacy of the public health protection afforded by the current PM10 standard against 

exposures to thoracic coarse particles? 

 

10. Indicator (sections 3.3.1, 3.3.2, and 3.3.3): 

What are the Panel’s views on the following: 

a. The preliminary staff conclusion that it is appropriate to maintain a standard that provides 

protection against all thoracic coarse particles, regardless of their source of origin or 

composition? 

b. The appropriateness of maintaining an indicator that allows lower PM10-2.5 concentrations 

in urban areas than non-urban areas? 

c. The appropriateness of either a PM10 or PM10-2.5 indicator for a standard meant to protect 

against exposures to thoracic coarse particles? 

11. Averaging Time (section 3.3.4): What are the Panel’s views on the preliminary staff 

conclusions that the currently available evidence supports maintaining a 24-hour standard to 

protect against health effects associated with short-term exposures to thoracic coarse particles, 

and does not support consideration of a long-term thoracic coarse particle standard? 

 

12. Form (section 3.3.6): What are the Panel’s views on the preliminary staff conclusion that it is 

appropriate to consider a 98th percentile form for a revised 24-hour standard meant to protect 

against short-term exposures to thoracic coarse particles? 

13. Level (section 3.3.7): What are the Panel’s views on the appropriateness of considering 98th

percentile, 24-hour PM10 or PM10-2.5 concentrations in epidemiological study locations for 

identifying a range of potential alternative standard levels for consideration, recognizing the 

more limited air quality information available for PM10-2.5? 

Review of the Secondary PM2.5 Standards for Visibility-Related Effects (Chapter 4)

14. Adequacy (section 4.2): What are the Panel’s views on the preliminary staff conclusion that 

the currently available information clearly calls into question the adequacy of the current suite 

of PM2.5 standards to provide public welfare protection from unacceptable levels of visibility 

impairment, primarily in urban areas, and supports consideration of alternative standards to 

provide appropriate protection?

15. Indicator (section 4.3.1): 

What are the Panel’s views on the following: 

a. The appropriateness of considering PM light extinction and PM2.5 mass as indicators for a 

distinct secondary PM standard for visibility protection, and the relative advantages and 

disadvantages associated with each indicator? 
Update 

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b. The appropriateness of considering the contribution of coarse particles with respect to a 

potential PM light extinction indicator? 

16. Averaging times (section 4.3.2): 

What are the Panel’s views on the following: 

a. The preliminary staff conclusion that consideration should be given to a 1-hour averaging 

time? 

b. The advantages and disadvantages of focusing on a 1-hour daily maximum or each 1-hour 

average concentration during all daylight hours? 

17. Levels and Forms (section 4.3.3): 

What are the Panel’s views on the following: 

a. The preliminary staff conclusions regarding ranges of options with varying levels and 

forms in combination with different indicators (light extinction and PM2.5 mass-based 

indicators) and averaging times (1-hour daily maximum or each 1-hour average 

concentration during all daylight hours)? 

b. Additional approaches that could help inform our consideration of alternative levels and 

forms? 

Review of the Secondary Standards for Other Welfare-related Effects (Chapter 5) 

18. Climate (section 5.2): What are the Panel’s views on the preliminary staff conclusion that 

there is insufficient information to base a standard on climate impacts associated with current 

ambient PM concentrations? 

19. Ecological effects (section 5.3): What are the Panel’s views on the preliminary staff 

conclusion that data are insufficient to support establishing a distinct standard for ambient PM 

based on ecosystem effects not addressed in the ongoing NOx/SOx secondary NAAQS 

review? 

20. Material effects (section 5.4): What are the Panel’s views on the preliminary staff conclusion 

that no new evidence calls into question the adequacy of the protection afforded by the current 

suite of PM standards, and that there continues to be support for retaining an appropriate 

degree of control for both fine and coarse particles to provide protection against materials 

damage and soiling?