UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C. 20460

OFFICE OF THE ADMINISTRATOR

SCIENCE ADVISORY BOARD

September 10, 2010

EPA-CASAC-10-015

The Honorable Lisa P. Jackson

Administrator U.S. Environmental Protection Agency 1200 Pennsylvania Avenue, N.W. Washington, D.C. 20460

Subject: CASAC Review of Policy Assessment for the Review of the PM NAAQS – Second External Review Draft (June 2010)

Dear Administrator Jackson:

The Clean Air Scientific A dvisory Committee (CASAC) Par ticulate Matter (PM) Review Panel met on July 26 – 27, 2010 and on August 2 5, 2010 in a public teleconference to review the Policy Assessment for the Review of the PM NAAQS - Second External Review Draft (June 2010). This letter highlights CASAC’s ma in comments on this document

, followed by consensus responses to the charge questions and co mments of individual Panel members.

This review of the Second Draft Policy Assessment completes the first cycle through the revised suite of NAAQS review documents and thus represen ts a major milestone. CASAC commends EPA staff for developing an ordere d and transparent basis for decision-making throughout the NAAQS revi ew process from the Integrated Science Assessment (ISA) to the Quantitative Health Risk Assessment and Urban Focused Visibility Assessment and then to the Policy Assessment . The Second Draft Policy Assessment was notably responsive to CASAC’s

comments on the first dr aft. At CASAC’s request, the cu rrent draft sets out the underlying decision-making algorith ms, greatly enhancing the transparency and readability of the document. EPA’s approach to reviewing the standard is explicitly articulated throughout the document, as are the key decision-making points and the eviden ce considered. CASAC’s major concerns, as expressed in our letter of May 1 7, 2010, have been addres sed. EPA staff are to be congratulated for building on CASAC’s suggestions and developing an assessment that provides a scientifically sound basis for making decisions on the primary and seconda ry PM standards.

Primary Standards fo r Fine Particles

CASAC supports the EPA staff’s conclusion in the Second Draft Policy Assessment that “currently available information clearly calls into question the adequacy of the current standards”.

For PM 2.5 , the current 24-hour primary standard is 35 μg/m 3 and the annual standard is 15 μg/m 3

. EPA staff also conclude that considerati on should be given to alternative annual PM 2.5 standard levels in the range of 13 – 11 μg/m 3 , in conjunction with retaining the current 24-hour PM 2.5standard 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 in conjunction with an annu al standard level of 11μg/m 3

. CASAC concludes that the levels under consider ation are supported by the epidemiological and toxicological evidence, as well as by the ri sk and air quality information compiled in the Integrated

Science Assessment (December 2009), Quantitative Health Risk Asse ssment for Particular Matter (June 2010) and summarized in the Second Draft Policy Assessment. Although 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). In addition, thes e combinations of annual/daily levels may not be adequately inclusive. It was not clear wh y, 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 . The rationale for the 24- hour/annual combinations proposed for the Administrator’s consid eration (and the exclusion of other combinations within the ranges contemplat ed) should be more clearly explained.

Primary Standard for Thoracic Coarse Particles

CASAC recommends that the primary standard for PM 10 should be revised downwards. While current evidence is limited, it is sufficie nt to call into question the level of protection afforded by the current standard (a 24-hour standard of 150 μg/m 3 ).

CASAC supports the EPA staff conclusion that it is appropriate to change the PM 10 standard to a 98 th percentile form because of its higher ra te of identifying areas in nonattainment while reducing the rate of misclassification. We do not agree that the available scientific evidence strongly supports the proposed up per bound standard level of 85 μg/m 3 . The Second Draft Policy

Assessment demonstrates that a 98 th percentile level of 85 μg/m 3 would be less stringent as compared to the current standard, protecting a sm aller fraction of the popul ation. In fact, on a population basis, results in the Second Draft Policy Assessment demonstrate that a 98 th percentile level between 75 and 80 μg/m 3 is comparable in the degree of protection afforded to the current

PM 10 standard. The cha nge in form will lead to changes in levels of stri ngency across the country, a topic needing further exploration. While recognizing scientific uncertainties, CASAC supports a lower level to provide enhanced protection, somewhere in the range of 75 – 65 μg/m 3 . We recognize that the Administrator will need to apply the Clean Air Act’s requirement for a “margin of safety” in a context of un certainty with respect to the health effects of thoracic coarse particles.

The Second Draft Policy Assessment concludes that PM 10 should continue to be the indicator for thoracic coarse particle s. While 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 ch ange in the indicator from PM 10 to one that directly measures thoracic coarse particles. To improve EPA’s scientific basis for the next NAAQS review, we recommend the deployment of a network of PM 10-2.5 sampling systems so that future studies will be able to expand the evidence base on this indicato r and facilitate assess ment of whether PM 10-2.5 should be

used as an appropriate indicator for thoracic coarse pa rticles. In concluding this letter, we elaborate further on the urgency of research on cer tain aspects of PM and health.

iiSecondary Standard for PM-R elated Visibility Impairment

CASAC supports the EPA staff conclusion that “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 incr eased public welfare protection.” The current secondary standards are identical to the current primary standards for fine and thoracic coarse particles. The detailed estimate s of hourly PM light extincti on under current conditions (and for assumed scenarios of meeting curre nt standards) clearly demonstrate that current standards do not protect against levels of visual air quality which ha ve been judged to be unacceptable in all of the available urban visibility preferen ce studies. EPA staff’ s approach for transl ating and presenting

the technical evidence and assessme nt results is logically conceived and clearly presented. The 20- 30 deciview range of levels chosen by EPA staff as “Candidate Protection Levels” is adequately supported by the evidence presented.

While the evidence shows that the current st andard does not adequately protect visibility, the choice of indicator for such protection was a subject of considerable discussion among CASAC panelists. The Second Draft Policy Assessment discusses three potential indicators: a PM 2.5 Mass Indicator, a Speciated PM 2.5 Mass-calculated Light Extinction I ndicator, and a Directly Measured

PM 2.5 Light Extinction Indicator. Overwhelmingly, CASAC would prefer the direct measurement of light extinction, the property of th e atmosphere that most directly re lates to visibility effects. It has the advantage of relating directly to the demons trated harmful welfare effect of ambient PM on human visual perception. However, in discussing the Directly Measured PM 2.5 Light Extinction Indicator with EPA staff, we learned that the time required to develop an official Federal Reference Method (FRM) for this indicator would postpone its implementation for years. Given the time lag associated with implementing th e Directly Measured Indicator, CASAC agrees with EPA staff’s preference for a Speciated PM 2.5 Mass-calculated Light Extinction Indicator. Its reliance on procedures that have already been implemented in the Chemical Specia tion Network (CSN) and routinely collected continuous PM 2.5 data suggest that it could be implemented much sooner than a directly measured indicator.

Areas for Future Research

The Second Draft Policy Assessment has identified scientific i ssues that will need to be addressed in order to improve EPA’s scientific ba sis for promulgating PM st andards in the future. As stated in our letter of May 17, 2010, CASAC urges the Agency to reinvigorate research that might lead to new indicators that may be more directly linked to the health and welfare effects

associated with ambient concentr ations of PM. CASAC also s uggests the ongoing collection of more comprehensive PM monitoring data, incl uding expanding the range of sizes to provide

information in the ultr afine particle range, and adding measurements of numbers, chemistry, species, and related emissions char acteristics of particles. CASA C strongly urges EPA to pursue research to develop a Federal Referen ce Method for a Directly Measured PM 2.5 Light Extinction Indicator and to develop baseline light extinction data so that it will be availa ble for the next 5 year review cycle. CASAC is available to provide advice on priorities for PM-related research.

iiiThank you for the opportun ity to comment on the Second Draft Policy Assessment . We look forward to receiving your response.

Sincerely,

/Signed/

Dr. Jonathan M. Samet, Chair

Clean Air Scientific Advisory Committee

ivNOTICE

This report has been written as part of the activ ities of the EPA's Clean Ai r Scientific Advisory Committee (CASAC), a federal advi sory committee independently chartered to provide extramural

scientific information and advice to the Administrator and othe r officials of the EPA. CASAC provides balanced, expert assessment of scientific matters related to issues and problems facing the Agency. This report has not been reviewed for ap proval by the Agency and, he nce, the contents of this report do not necessarily re present the views and policies of the EPA, nor of other agencies within the Executive Branch of the federal govern ment. In addition, any men tion of trade names or commercial products does not constitute a recommend ation for use. CASAC reports are posted on

the EPA Web site at: http://www.epa.gov/casac

.

vClean Air Scientific Advisory Committee

Particulate Matter Review Panel

CHAIR Dr. Jonathan M. Samet, Professo r and Chair, Department of Prev entive Medicine, University of Southern California, Los Angeles, CA

CASAC MEMBERS Dr. Joseph Brain, Philip Drinker Professor of Environmental Physiology, Department of Environmental Health, Harvard School of Public Health, Harvard University, Boston, MA

Dr. H. Christopher Frey, Professor, Department of Civil, Construction and Environmental Engineering, College of Engineering, Nort h Carolina State University, Raleigh, NC

Dr. Donna Kenski, 1 Data Analysis Director, Lake Michig an Air Directors C onsortium, Rosemont,

IL

Dr. Armistead (Ted) Russell, Prof essor, Department of Civil a nd Environmental Engineering, Georgia Institute of T echnology, Atlanta, GA

Dr. Helen Suh, Associate Professor, Harvard School of Public Hea lth, Harvard University, Boston,

MA

Dr. Kathleen Weathers, Senior Scientist, Cary Institute of Ecosystem Studies, Millbrook, NY

CONSULTANTS Dr. Lowell Ashbaugh, Associate Research Ecol ogist, Crocker Nuclear Lab, University of California, Davis, Davis, CA

Prof. Ed Avol, Professor, Preventive Medicine, K eck School of Medicine, Un iversity of Southern California, Los Angeles, CA

Dr. Wayne Cascio, Professor, Medicine, Cardiolo gy, Brody School of Medici ne at East Carolina University, Greenville, NC

Dr. David Grantz, Director, Botany and Plant Sciences and Air Pollution Research Center, Riverside Campus and K earney Agricultural Center, Univers ity of California, Parlier, CA

Dr. Joseph Helble, Dean and Pr ofessor, Thayer School of Engineering, Dartmouth College, Hanover, NH

Dr. Rogene Henderson, Senior Scientist Emer itus, Lovelace Respiratory Research Institute, Albuquerque, NM

vi 1 / Did not participate in this review.vii Dr. Philip Hopke, Bayard D. Cl arkson Distinguished Professo r, Department of Chemical Engineering, Clarkson University, Potsdam, NY

Dr. Morton Lippmann, Professo r, Nelson Institute of Enviro nmental Medicine, New York University School of Medicine, Tuxedo, NY

Dr. William Malm, Research Physicist, Nati onal Park Service Air Resources Division, Cooperative Institute for Research in the Atmosphere, Colorado St ate University, Fort Collins, CO

Mr. Charles Thomas (Tom) Moore, Jr., Air Qu ality Program Manager, Western Governors' Association, Cooperative Institute for Research in the Atmosphere, Colorado State University, Fort Collins, CO

Dr. Robert F. Phalen, Professor, Department of Community & E nvironmental Medicine; Director, Air Pollution Health Effects Laboratory; Profes sor of Occupational & Environmental Health, Center for Occupation & Environm ent Health, College of Medicine , University of California Irvine, Irvine, CA

Dr. Kent Pinkerton, Professor, Regents of the Univ ersity of California, Ce nter for Health and the Environment, University of California, Davis, CA

Mr. Richard L. Poirot, Environm ental Analyst, Air Pollution Cont rol Division, Department of Environmental Conservation, Vermont Agency of Natural Resources, Waterbury, VT

Dr. Frank Speizer, Edward Kass Professor of Medicine, Channing Laboratory, Harvard Medical School, Boston, MA

Dr. Sverre Vedal, Professor, Department of Environmental and Occupa tional Health Sciences,

School of Public Health a nd Community Medicine, Univers ity of Washington, Seattle, WA

SCIENCE ADVISORY BOARD STAFF Dr. Holly Stallworth, Designated Federal Offi cer, EPA Science Adviso ry Board Staff OfficeCASAC Responses to Charge Questions on the Second Draft Policy Assessment for the Review of the Particulate Matter NAAQS

Primary Standards for Fine Particles

1. Current Approach (Section 2.1.3) :

a. What are CASAC’s views on the staff’s approach to translating the available epidemiological evidence, risk informatio n, and air quality in formation into the basis for reaching conclusions on the adequacy of the current standards and on

alternative standards for consideration?

CASAC agrees with the approach as described in Section 2.1.3 and apprec iates the clarity with which the approach is detailed. The overview ofthe approach presented in Figure 2-1 is wellorganized, logical, and clear. CASAC agrees that it is appropriate to return to the strategy used in

1997 that considers the annual and the short-term st andards together, with the annual standard as the controlling standard, and the short-term standa rd supplementing the protection afforded by the

annual standard. CASAC commends th e expansion of the discussion on evidence of risk across life stages as well as of specific sus ceptibility risk factors and the use of empirical evidence and risk assessment findings together. CASAC considers it a ppropriate to place the greatest emphasis on health effects judged to be causal or likely causal in the analysis presented in the ISA. Finally, the statement that the data “call into question” the adequacy of the current standard could be more forcefully stated by concluding that the current standard is not protective.

b. Has staff appropriately applied this appr oach in reviewing the adequacy of the current standards (Section 2 .2) and potential alternative standards (Section 2.3)?

The staff has carefully followed this approach in reviewing the adequacy of the current standards and in considering potential alterna tive standards. The outline of the text of Section 2.3 follows the outline presented in the overview of the approach given in Figure 2-1.

2. Form of the Annual St andard (Section 2.3.3.1):

a. What are CASAC’s views on the additional analyses conducted to characterize the potential for disproportionate impacts on susceptible 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 CASA C’s views on staff’s conclusion that the

form of the annual standard should be revised to eliminate spatial averaging?

CASAC found the additional an alyses provided in the 2 nd draft PA to be helpful in understanding how spatial averaging differs relati ve to the highest average value from a single community site. This latter approach helps to ensure adequate protection of populations living in lower

socioeconomic areas and contribu tes an additional margin of sa fety for other populations. Although much of the epidem iological 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 the averaging process. Further, the number of su ch studies is likely to

1expand in the future. CASAC concludes that it is reasonable for EPA to eliminate the spatial averaging in the new PM 2.5 annual average standard.

3. Alternative Levels (Section 2.3.4): What are CASAC’s views on the following:

a. The insights that can be gained into po tential alternative st andard levels by considering:

i. Confidence bounds on concentr ation-response relationships?

CASAC commends the progr ess made in attempting to use co nfidence bounds in considering alternative levels of the standard, but also finds unresolved complexities. First, staff apparently made a comprehensive effort to identify releva nt studies for which b ounds were reported on concentration-response (C-R) relationships; this s hould be explicitly stated. Second, the statement

made in reference to what these bounds do not in dicate (“these analyses do not provide evidence of

a concentration below which the confidence interv al becomes notably wider and uncertainty in a C-R relationship substantially increases” [p.2-57] ) is contradictory to what they, in fact, do

indicate. The confidence bounds widen at lower concentrations be cause there are fewer data at such concentrations, as acknowledged by staff. Th is widening is of interest in characterizing precision of estimates as one source of uncerta inty. Third, CASAC does not agree with the

conclusion that these bounds canno t be used in considering altern ative levels of the PM NAAQS,

even with the limited C-R func tions shown. EPA Staff should be encouraged to integrate the

information available on relevant C-R confid ence bounds with that on study concentration distributions in arriving at a range of levels for consideration.

For the future, findings of epidemiological studies might be used in several ways in considering a range of levels for a NAAQS. It would be preferable to have in formation on the concentrations

that were most influential in generating the health ef fect estimates in individual studies. Less ideal, but still useful, would be information on the distribution of concentrations experienced by participants in the studies. For time-series studi es, because of the similar number of events (e.g., deaths) per day, this is likely to be the same as the PM concentration distribution; the situation is more complex for cohort studies in which exposur es of individuals change over time. Least preferable is using PM concentration distribution metrics, such as those used by EPA Staff in arriving at a range of levels for consideration. An attempt should be made, to the extent possible, to integrate this latter approach with aspects of the first two approaches, realizing that the reported study findings and data needed to accomplish this goal may not be readily available, and that interactions with investigators may be needed.

ii. Different statistical metrics that charac terize air quality distributions from multi-city epidemio logical studies?

2 The Second Draft Policy Assessment provides two alternatives, re ferred to as the composite

monitor and the maximum monitor. On the top of page 2-61, the text appears to be stating that, for the same air quality domain, the com posite monitor concentrations are less than those based on the maximum monitor approach, and an argument is made that an approach based on composite monitors has a “margin of safe ty” compared to the maximum mo nitor perspective. However, a judgment is made that data should be selected from the epidemiological studies for which the C-R relationships are “strongest,” and that concentra tions not more than one standard deviation belowthe long-term mean concentration should be used. The judgment, while not unreasonable, is not explained.

It is not clear why the lo wer bound to be considered is a range from the 10 th to 25 th percentiles, as opposed to, say, the 10 th percentile alone. In Fi gure 2-7, for long-term exposure studies, in the upper panel, the 10 th percentile annual mean concentrations range from approxi mately 9 to 11 μg/m 3 . The population-weighted values are 10 to 13 μg/m 3 . In both cases, the upper bounds of these ranges are for the high site, and the lower bounds are for th e composite monitor.

In summary, this section of th e report lacks clarity and focus on the key consideration of identifying ambient concentrations at which adverse effects are observed, in anticipation of supporting a range of concentrations that take in to account the statutory mandate to provide an adequate margin of safety.

b. Potential alternative annual standard levels based on composite monitor

distributions versus maximum monitor distributions?

The composite monitor approach is preferable because of its stab ility, and for the a dditional margin of safety it provides. The NAAQS should provide health protection for both long-term and shortterm health effects. It is not clear, for example, as to why the 24-hour level should be at least 2.5 times higher than the annual standa rd. Such a statement seems to be independent of consideration

of health effects. A statement is made on page 2-73, lines 26-27 that “based on this consideration” consideration should be given to retaining the 35 μg/m 3 24-hr level in conjunction with annual standards of 13 to 11 μg/m 3 . Setting aside the math problem here (e.g., 11*2.5 = 2 7.5, not 35), the rationale for the 2.5 times factor appears arb itrary and not based on health considerations.

c. Use of risk information in informing staff conclusion s on alternative annual and 24-hour standard levels, including appr oaches used to assess overall confidence and potential bias in the risk estimates?

The risk information provides valuable insights, and should be used in drawing conclusions. However, there is not symmetry between the evidence-based section and the risk-based section. .

The “evidence-based” section reaches the conclusion that alternative levels to be considered should be 11 to 13 μg/m 3 for the annual standard and 35 ug/m 3 for the 24-hour standard, and also a combination of 11/30 μg/m 3 for the annual/24-hour levels. Howe ver, the risk-based analysis does not systematically evaluate these combinations, omitting the 11/35 μg/m 3 and 11/30 μg/m 3

combinations. Furthermore, the text implies that a 10/35 ug/m 3 case was analyzed, but no results were reported. This difference between the ranges from the two sections reflects in part the

scenarios considered in the risk assessment. Whil e the Administrator’s consideration should not be

limited to those combinations th at were analyzed quantitatively, th e final policy assessment should be systematic and emphatic about providing conclusions regarding combinations of annual and daily levels that were not analyzed quantitativel y but that are recommende d for consideration.

3 The results of the risk assessments are presente d mainly in terms of percentage risk reduction compared to the current standard, in Figures 2- 11 and 2-12 for long-term and short-term effects, respectively. While this is useful information, it is not directly relevant to the setting of a NAAQS,given the goal of a NAAQS--to prot ect public health with an ad equate margin of safety. Additionally, the information on ri sk reduction might be better pres ented as the absolute numbers of deaths avoided rather than the percentage reduc tion under the various scenarios. The text should be rewritten to better reflect the utility and rele vance of the information on reduction of disease burden for determining the NAAQS.

This section should not only focus on the best estimate of risk, but the confidence intervals and non-quantified sources of bias, such as the role of socio-economic st atus (SES). See also Page 2- 35, lines 10-12, which indicates that sensitivity analysis of model sp ecification used in the risk assessment produce risk estimates that are a factor of 2 to 3 higher than the core risk estimates.

d. Staff’s conclusion that alternative annual standard levels in the range of 13 to 11

μ g/m 3 are most strongly supported by the available evidence and risk-based

information?

The rationale for the conclusion was well developed, but could use further justification, particularly in regard to the pairing of the 24-hour and annual standards. The risk assessment did not explore all

the combinations considered in the Policy Assessment

. While CASAC agrees with the range of 13 to 11 ug/m 3 , it finds less justification for the pairings proposed.

e. Staff’s approach of focusing on peak-to-mean ratios to inform the level of a 24- hour standard that would provide su pplemental protection to a generally controlling annual standard?

The peak-to-mean ratio merits consideration in pr oviding insight as to wh ether the annual or 24- hour standard would be controlling in a particular ar ea. It is not relevant to informing the actual

level to be selected for the 24-hour standard.

f. Staff’s conclusion that consideration shou ld be given to reta ining the current 24-

hour standard level of 35 μ g/m 3 in conjunction with annual standard levels in the range of 13 to 11 μ g/m 3 , and that consideration could also be given to an

alternative 24-hour st andard level of 30 μ g/m 3 particularly in co njunction with an

annual standard level of 11 μ g/m 3 ?

The conclusions are reasonable in relation to the criteria established by the Clean Air Act (CAA), and those developed by the OAQPS Staff that have been endorsed by CASAC. The choices within these options will need to be based on the Administrator's in terpretation of the CAA’s requirement for an adequate margin-of-safety. In other words, in the absence of thresholds in the dose-response relationships for the health outcomes of concern, how much public health impact resulting from exposure to ambient air PM 2.5 is acceptable under the CAA.

4 The least protective option (35-13 μg/m 3 ) would provide si gnificant additional public health

benefits in most of the U.S., in comparison to the current limits (35-15 μg/m 3 ). The most protective option (30-11 μg/m 3 ) would provide significant additional public health benefits to a larger part of the U.S. population in comparison to the current lim its (35-15 μg/m 3 ) and any of the intermediate options, but would not prevent at least some adve rse health effects amon g the most susceptiblesegments of the population, give n our current understanding of dose-response relationships.

4. Key Uncertainties and Area s for Future Research and Data Collection (Section 2.5):

What are CASAC’s views on the areas for future research and data collection outlined in this section, on relative priorities for researc h in these areas, and on any other areas that ought to be identified?

The key uncertainties and areas for future resear ch and data collection are well summarized in Section 2.5. The acknowledgement (at the top of page 2-87) that “Much of this research may depend on the availability of in creased monitoring data” is apt and appreciated. The opportunities for epidemiological research to effectively ad dress the knowledge gaps on the effects, and concentration-response relationships, of PM co mponents and source-related mixtures cannot be achieved without additional monitoring data to provide PM speciation and better temporal and spatial resolution. Only the EPA can provide the impetus and support for su ch an enhancement in air quality monitoring.

The research needs to address uncertainties in hea lth outcomes, exposure durations of concern, and susceptible populations that are also very nicely outlined are well targeted, and can be effectively studied in human populat ions. Such studies, to be most produc tive, will need the enhanced monitoring data, as recognized by EPA staff.

This section, as written, has more to do with future research prio rities than with uncertainties that influence impending decisions on revisions to the PM 2.5 NAAQS. The secti on outlines a very broad and ambitious research agenda . It would help to begin this section with a prioritized review of key uncertainties in order to help establish priorities among the sugges ted research topics. Obviously the key uncertainty is the range of conc entrations that are causing the observed health effects in the epidemiological studies, and the degree of certainty in effects at the lower concentrations along the C-R relationship. This uncertainty has necessitated using the

distributional measures of concentrations from th e epidemiology studies in attempting to make the link between the epidemiological findings and consid eration of alternative concentrations for the PM NAAQS. While this uncerta inty is reflected in two (p .2-88 and 2-90) of the many

recommendations for future res earch that C-R functions include confidence bounds, this uncertainty should be highlighted. We urge careful attention to priorities in relation to future revisions of the PM NAAQS, rather than a lengthy list of research topics.

CASAC finds the list to be appropriate, but al so suggests considerati on of the following:

• Generating time-activity data to support proba bilistic scenario-based exposure models, such as additional activity diary data to incorporate into the Consolidated Human Activity Database (CHAD).

5 • Characterizing indoor exposures to PM of ambi ent origin. For example, the penetration

of ambient PM 2.5 and PM 10 into indoor microenvironm ents (home, work, school, restaurant, bar, vehicle) should be better ch aracterized, particularly taking into account differences in penetration with respect to particle size and composition. Given the greater amount of time we spend in indoor vs. outdoor environments , the need for these data is compelling.• Addressing the bidirectional linkages betwee n climate change and concentration, size distribution and composition of PM in the PM 10 , PM 2.5 , and ultrafine particle (UFP) fractions. This would include assessing the relative effects of climate cooling due to aerosols (e.g., sulfate) vs. climate warmin g due to elemental carbon. Effects of increased wildfires, windbl own dust and pollen seasonality are also of interest.

• Continuing support of toxicological research in terms of chemical components, sources and subfractions (to include UFP). Toxi cological studies will address biological plausibility and give insights as to possib le mechanisms. Alth ough C-R relationships are a challenge to extrapolate from animal to human, animal studies do provide an

effective means to conduct controlled and well-characterized exposure scenarios to examine C-R relationships.

Primary Standard for Coarse Particles

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

a. What are CASAC’s views on the approach to translating the available evidence and air quality information into the basis for review ing the coarse particle

standard?

CASAC finds the second draft s uperior to the first draft revi ewed earlier; it demonstrates considerable progress and responsiveness to CA SAC's suggestions. The document is grounded on explicit data and clearly stated arguments. EPA staff has done its best to take the available evidence relating to exposure and health effects and to use them as the basis for reviewing the coarse particle standard.

There are inherent deficiencies whic h persist because of lack of data . Concentrations of the coarse particle fraction--particles between 2.5 and 10 mi crons—are usually estimated by subtraction and not measured directly. Moreover, given the limited data on coarse particles, much of the evidence

on health effects comes from in terpreting studies using PM 10 and assessing the extent to which the

health effects observed relate to the entire size range collected [including PM 2.5 ] or to only the coarse particle fraction.

b. Has staff appropriately applied this appr oach in reviewing the adequacy of the current standard (section 3.2) and potential alternative st andards (section 3.3)?

CASAC responds affirmatively to this question. The staff have noted the limitations of the data and used them in light of these li mitations to address the question of whether current standards are adequate. CASAC also finds that staff has ade quately discussed alternative standards and the consequences of applying them.

In toto , Chapter 3 reads well and is much improved. EPA staff has done its be st to describe an evidence-based approach for applying the limited amount of health effects evidence and air quality information in different US regions as a basis fo r reviewing the adequacy of the current coarse particle standard.

66. Adequacy of the Current PM 10 Standard (section 3.2): Wh at are CASAC’s views on the alternative approaches presented for consid ering the evidence and its uncertainties as they relate to the adequacy of the current standard?

The general consensus of CASAC is that consideration should be given to revising the current 24-

hour PM 10 standard. The rationale for this recommenda tion emerges from th e judgment that the current data, while limited, is sufficient to call into question the level of protection afforded the American people by the current standard. The opi nion hinges on the strength of associations in multi-city studies and positive trends in single city studies linking PM 10 exposure and health endpoints, and moreover that these health effect s can occur below the current standard. This approach gives significant weight to studies that have generally reported that PM 10-2.5 effect estimates remain positive when ev aluated in co-pollutant models . Likewise c ontrolled human exposure PM 10-2.5 studies showing decreases in heart rate variability and increa ses in markers of pulmonary inflammation are deemed adequate to support the plausibility of the associations reported in epidemiologic studies.

7. Indicator (Section 3.3.1): What are CAS AC’s views on the approach taken to considering standard indicator an d on staff’s conclusion that PM 10 remains an appropriate indicator in this review?

The majority of CASAC determined that there wa s insufficient evidence currently available to support a change in the indicator from PM 10 to PM 10-2.5 . However, CASAC vigorously recommends the implementation of plans fo r the deployment of a network of PM 10-2.5 sampling systems so that future epidemiol ogical studies will be able to more thoroughly explore the use of

PM 10-2.5 as a more appropriate indicator for thoracic coarse particles.

If a PM 10 indicator is retained, the Agency should co nsider limiting the Fede ral Reference Method to include only low volume PM 10 samplers, as high volume PM 10 samplers do not produce comparable results.

8. Form (Section 3.3.3): What are CASAC’s views on the approach taken to considering

the form of the standard an d on staff’s conclusion that revising the form to a 98 th
percentile form would be ap propriate for a 24-hour PM 10 standard meant to protect against exposures to thoracic coarse particles?

CASAC felt strongly that it is appropriate to change the statistical form of the PM 10 standard to a

98 th percentile form. Published work has shown that the percen tile form has greater power to identify non-attainment a nd a smaller probability of misclassif ication relative to the expected

exceedance form of the standa rd. This change in fo rm will lead to changes in levels of stringency across the country, a topic need ing further exploration.

9. Level (Section 3.3.4): What are CA SAC’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 the weight placed on different

studies?

7b. Staff’s conclusion that the evidence most st rongly supports stan dard levels around 85 μg/m 3 ?

c. The alternative approach to considering th e evidence that coul d support standard levels as low as 65 μg/m 3 ?

CASAC concurs that the approach in identifying potential alternative PM 10 standard levels are appropriate, with the discussion regarding the weight placed on different studies clearly and cogently presented. CASAC also considered that the proposed alternative standard levels of 85 and 65 ug/m 3 (based on consideration of 98 th percentile PM 10 concentration) could be justified.

CASAC, however, does not agree that scientific evidence most strongly supports an upper bound standard level of 85 μg/m 3 . As stated in the Second Draft Policy Assessment , scientific evidence supports the adoption of a standard at least as stringent as the current standard of 150 μg/m 3 based on one expected excee dance. Table A3 suggests that a 98 th percentile level of 85μg/m 3 is less stringent as compared to the current standard, protecting a smaller frac tion of the population. Results instead point to a 98 th percentile level between 75 and 80 μg/m 3 as comparable to the

current standard. CASAC further notes that settin g new 24-hour PM 10 standard levels should also consider the impact of corresponding changes in PM 2.5 standards, which will likely result in lower

24-hour PM 2.5 concentrations and lower measured PM 10 values. Thus, proportionately more coarse particle mass could be airborne at the standard level. Absent corresponding reduction in the PM 10 standard, these lower PM 2.5 concentrations would lessen the level of protection provided by the

PM 10 standard for exposure to PM 10-2.5

The Second Draft Policy Assessment does not adequately convey the possible rationale for selecting the lower end of the proposed range of levels. Therefore, the co nsiderations that might lead to selecting a PM 10 standard level more stringent than afforded by the current standard should be more clearly elaborated. These considerations focus on margin of safety, particularly as it relates to the impact and weight given to suggestive findings of causality, to findings of positive but statistically insignificant results, and to ex posure measurement erro r and other sources of uncertainty.

10. Key Uncertainties and Areas fo r Future Research an d Data Collection (Sec tion 3.5):

What are CASAC’s views on the areas for future research and da ta collection outlined in this section, on relative priori ties for research in these areas, and on any other areas that ought to be identified?

See comments on Chapter 2.

8 The key distinction for this chapter is the need to seriously focus on PM 10-2.5 for both mass and composition. CASAC looks forwar d to the planned implementation of mon itors that measure

PM 10-2.5 , rather than PM 10 . There is a critical need fo r national monitoring data on PM 10-2.5 in order to provide a basis for epidemiological studies that focus on this size fraction. Furthermore, there is a need for speciated data to sup port health effects research. Sp atial and temporal variability in coarse particle mass and com position need to be characteri zed. In addition, the national monitoring data will support a ba seline for ambient air quality in order to compare with health

effects data in order to assess whether ther e is a need for a more stringent standard.The research areas described in th e draft Section 3.5 are reasonable , but there needs to be strong emphasis on the critical need for coarse PM da ta, in order that the NAAQS can move beyond PM 10 as an indicator for thoracic coar se PM in a future NAAQS revision.

Another question to be considered is regarding what size cut-point s are most appropriate, and also regarding what specific components ar e of most interest or concern w ith respect to health effects.

There is a need for continuous mo nitoring of coarse PM (and of PM 2.5 ) in order to support health

effects studies and to be able to assess alternativ e forms of possible future standards.

Other challenges for future research: (a) it may be difficult to get useful data from rodent inhalation studies since they can breathe particles only up to about 2 to 3 mi crons into their lung airways; (b) getting good chemical characterization of the particle s will be a problem, since there are primary biological materials of potential in terest in the thoracic coarse size range.

Prioritization of the research topics is neede d, such as via a separate meeting or workshop.

Secondary Standard for PM-related Visibility

11. Current Approach (Section 4.1.3) :

a. What are CASAC’s views regarding our approach for translating technical evidence and assessment results into the basis for assessing current fine particle standards and considering alternative st andards to provide protection against PM-related visibility impairment?

The translation of technical evidence and assessme nt results as a basis fo r reviewing and revising the current secondary fine particle standard is logically conceived, clearly presented, and responsive to previous CASAC recommendations. The combined evidence-based and impactbased assessments effectively contrast and inte grate the various combinations of metrics for protecting urban visibility. Wh ile this approach is i nherently complex, it is clearly explained in the text and concisely summarized in Figure 4-1. The various tables and graphics in Chapter 4 and its associated appendices are helpful in communicating the i nherent complexity that results from the evaluation of so many possible co mbinations of indicators, averaging times, levels and forms.

b. Has staff appropriately applied this appr oach in reviewing the adequacy of the current standard (Section 4.2) and potentia l alternative standards (Section 4.3)?

The detailed estimates of hourly PM light extinction under curren t conditions and for “what if” scenarios of just meeting current standards clearly indicate that the current PM 2.5 standards do not protect against levels of visual air quality which ha ve been judged to be unacceptable in all of the available urban visibility preferen ce studies. The levels are too high, the aver aging times are too long, and the PM 2.5 mass indicator could be improved to correspond more closely to the light scattering and absorption properties of su spended particles in the ambient air.

9 While not discussed in detail in the Second Draft Policy Assessment , direct measurements of light extinction are the preferable indicator for an altern ate standard to make an accurate assessment of

the PM effect on urban visib ility. These measurements woul d provide timely and easy-to-understand results to address the protection of th e public welfare from PM impacts, but without a Federal Reference Method (FRM) adopted or in the development process – these data are not currently available for most urba n areas. Additional discussion of the timeline and process anticipated by EPA to advance di rect measurement of light exti nction monitoring methods to FRM status would be helpful.

Given this limitation, the detaile d estimates of PM light extincti on employed for 15 urban areas in the UFVA, and used to evaluate alte rnative new indicators including hourly PM 2.5 mass and “speciated PM 2.5 mass-calculated light extinction” in the Second Draft Policy Assessment are appropriate for the initial promul gation and first generation of re gulatory air quality analysis and planning; similar to the pr ocess for the Regional Haze Rule. The speciated PM 2.5 mass-calculated light extinction indicator produces hourly extincti on values quite similar to those resulting from more complex calculations, and it could be an appropriate indicator for a revised secondary standard, if employed on an interim basis until methods for direct light extinction measurements can be developed and deployed.

While the stated intent of the Second Draft Policy Assessment is “to provide as broad an array of options as is supportable by the available in formation”, the CASAC recommends providing

additional and more focused discu ssion of the policy implications that may be associated with selecting and implementing specific combinations of indicators, leve ls and forms from within this broad array of options. Some disc ussion should also be provided to i ndicate that reductions in light scattering aerosols could decrease light extincti on but increase radiative forcing, while reductions in light absorbing aerosols would decrease both light extinction and ra diative forcing. The contributions of anthropogenic controllable “S hort-Lived-Climate-Forcers” that contribute significantly to urban visibility impa irment would also be worthy of some attention in the analysis of policy implications.

12. Nature of the Indicator (Section 4.3. 1): What are CASAC’s view s on the following:

a. Staff’s consideration of the three indicato rs identified in this section and our conclusions on the appropriateness of thes e indicators for consideration in this

review?

b. The development and evaluation of a new approach 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 comparing the PM components that

contribute to the hours selected in the top percentiles for PM 2.5 mass and PM 10 light extinction?

As noted in past comments, CASA C strongly prefers directly meas uring light extinction to using

estimates based on mass m easurements (e.g., the other options provided in the Second Draft Policy

Assessment ). In their recent review, the Ambien t Air Monitoring and Methods Subcommittee (AAMMS) noted that there are co mmercial instruments available that provide light extinction measurements directly, and promising additiona l technologies may soon become available. The AAMMS also encouraged the EPA to begin the pr ocess of developing performance standards for PM light extinction measurements. However, a FR M for light extinction measurement does not yet

10exist, and as EPA does not view it as practical to develop an FRM in time for this rule making, CASAC recognizes that alternative appr oaches need to be considered.

A current weakness of the Second Draft Policy Assessment is that it does not explicitly state the

reasons that EPA does not curren tly recommend using a direct measur ement of light extinction. It also does not provide any indication that the prop osed mass-based indicato rs are intended for use on an interim basis, to be repl aced with direct light extincti on-based measurements as those methods are developed, tested and deployed. If staf f consider it impractical to develop performance

standards for an FRM in time for this round of ru le making, this should be clearly stated and a schedule for developing such performance standa rds and evaluating candid ate instruments should be specified well in advance of the next PM NAAQS review.

Assuming it is currently impracti cal to develop a FRM for direct measurements of PM light extinction in a sufficiently timely manner, CASAC agrees that for this rule making, a method to

estimate extinction based on measurements from continuous PM 2.5 monitors, preferably adjusted by PM 2.5 speciation and relative humid ity (RH) data, is appropri ate. The “speciated PM 2.5 masscalculated light extinction” method described in the Second Draft Policy Assessment appears to be a reasonable approach for estimatin g hourly light extinction. Fo r purposes of “near real time” visibility tracking, CASAC recommends consideri ng a simpler calculation in which historical, rather than concurrent, monthly or seasonal sp eciation averages would be used to estimate speciation for combining w ith real-time continuous PM 2.5 and RH data, even though the most recent speciation data woul d be used for developing plans fo r improving visibility. CASAC also recommends that the Agency consider developing the monthly or seasonal speciation estimates on a regional basis as well as on a site-specific basis, as this would allow light extinction estimates at all (>700) sites with continuous PM 2.5 data, rather than just the rela tively few sites with collocated

continuous PM 2.5 and speciation monitors.

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 alternativ e levels of 10, 20, and 30 μ g/m 3 for PM 2.5 mass concentration?

These are appropriate CPL and PM 2.5 levels. The CPL values were based on all visibility preference data that are available and bound the study results as represented by the 50% acceptability criteria. However, the presentati on could be improved by ex panding some of the tables to include 10 and 40 dv values, in that at 10 dv, no viewer found the scene to be unacceptable, and at 40 dv, virtually all viewers found all scenes to be unacc eptable. What would these dv levels correspond to in the context of PM 2.5 and the various percentile levels?

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?

11 While these levels may be approp riate, they are not well justif ied. A cursory argument was made

that the 90–95 th percentiles in conjunction with the 1-hour daily maximum identified similar daysand hours of non-compliance, as did the 98 th percentile in conjunction with all daylight hours, and this correspondence was a sufficient basis to pick these two approaches. It would be informative to compare all, or at that least the same, percentiles for both all da ys and the daily hourly daily maximum. These analyses should be informative as to whether one approach is preferred. Whether different sources might be identified, depending on use of daily average or maximum values has not been adequately addressed. For example, a significantly extended episode of low visibility might be attribut ed to a single source, such as a larg e wildfire or prescribed fire, which would result in the all hour, all day approach targeting only one large emission episode that occurred for only one or a few time periods. Fo r wintertime episodes in many cities of multi-day poor urban visibility conditions, the events can cr oss the end of the calendar year, tracking the highest daily hour for each day to form a full 3-year distribution of values (i.e., N = ~1,095) for which the compliance value is then compared to the percentile level selected by EPA.

c. Insights to be drawn by comparing the PM components for hours included among the 10% highest for a 1-hour daily maximum form with the hours included among the 2% highest for an all daylight ho urs form, for the various indicators considered (Appendix C)?

See comments above. Thes e two approaches appear to be simila r; however, it would be helpful to quantify the similarities as opposed to relying only on a qualitative di scussion. A scatter plot might be useful for the 14 sites that provides the averag e fractional contribution of a species in relation to the time metric used. Additionally, comparisons should be shown for the sp ecific days found in non-compliance by metric.

14. Key Uncertainties and Areas for Future Research and Data Collection (Section 4.5):

What are CASAC’s views on the areas for future research and data collection outlined in this section, on relative priorities for researc h in these areas, and on any other areas that ought to be identified?

The major areas of research and data collection needed to address key uncertainties related to a visibility-based secondary standard are nicely captured in Section 4.5 of the Second Draft Policy

Assessment . The section appropriately id entifies two major areas of n eed, one related to visibility preference, and one related to methods of measurement.

In the first category, preference studies, the de tails noted by EPA all id entify a strong need for additional urban visibility preference studies c onducted using consistent methodology. The range of 50% acceptability values discusse d as possible standards are based on just four studies (Figure 4-2), which, given the large spread in values, pr ovide only limited confidence that the benchmark candidate protection levels cover the appropriate ra nge of preference values. Studies using a range of urban scenes (including, but not limited to, ic onic scenes – “valued sc enic elements” such as those in the Washington DC stu dy), should also be considered.

12 In the second category related to methods of measurement, CASAC supports the proposal to conduct studies in several cities, pairing direct monitoring of light ex tinction with enhanced monitoring of PM size an d composition distributions (i.e., cont inuous PM speciation monitoring).

Additional work should also be conduc ted to understand the contribution of PM 10-2.5 in13 southwestern areas other than Phoenix, to address th e lack of information for scattering associated

with this fraction of PM 10 as is noted on page 4-30.

Underlying this overall discussion is a clear ne ed for better particle size – composition distribution information (i.e., particle composition distributions as a function of particle size). These data gaps are addressed in different ways in the discussion of future research needs elsewhere in the Second Draft Policy Assessment (Sections 2.5 and 3.5). Moreover, the development of continuous monitoring methods for specific PM components addr essed in Section 2.5 is equally applicable here. Improved understanding of size-dependent PM composition would also help address the questions related to the role of scattering and abso rbing aerosols in climate forcing that are raised

in Section 5.2.4.

Finally, a number of research and data collec tion topics overlap between the secondary PM NAAQS, and the PM 2.5 and PM 10 primary PM NAAQS. For example, the fraction of combustionrelated primary carbon PM species can be an im portant indicator of harmful health effects, visibility impairment and climate forcing.

With these characteristics, research to jointly quantify and reduce these primary PM carbon species

from combustion sources would a dvance the information available to the Administrator for her judgment about the necessary leve l of protection to be provided by the future PM NAAQS, to be assessed in the next review cycle.

CASAC suggests that EPA look for additional opportunities to align health and welfare improvement strategies simultaneously for common i ndicators, such that the next reviews of the PM and other NAAQS have not only the analyses of the eff ects of PM and other NAAQS indicators on health and welfare, but also includ e metrics useful for measuring progress toward

attainment.Appendix A: Compendium of Individual Comments

CASAC Particulate Matt er Review Panel on Policy Assessment for the Review of the Particulate Matter National Ambient Air Quality Standards (Second External Review Draft, June 2010)

Dr. Lowell Ashbaugh .................................................................................................... A-2

Mr. Ed Avol ................................................................................................................... A-5 Dr. Joseph D. Brain ...................................................................................................... A-9 Dr. Wayne Cascio ........................................................................................................ A-12 Dr. Christopher Frey .................................................................................................. A-17 Dr. Rogene Henderson ................................................................................................ A-26 Dr. Morton Lippmann ................................................................................................ A-30

Dr. William Malm ....................................................................................................... A-35

Mr. Tom Moore ........................................................................................................... A-40

Dr. Robert Phalen ....................................................................................................... A-43

Dr. Kent Pinkerton ..................................................................................................... A-44

Dr. Ted Russell ............................................................................................................ A-52 Dr. Frank Speizer ........................................................................................................ A-56

Dr. Helen H. Suh ......................................................................................................... A-61

Dr. Sverre Vedal .......................................................................................................... A-62

A- 1Dr. Lowell Ashbaugh

These comments are directed toward Chapters Four and Five of th e Policy Assessment. I was very pleased with this draft. EPA staff has done an excellent job of responding to CASAC comments and has produced a very readable and inform ative document. I have a few minor editorial

comments that I will enumerate below, but first I have a few more gene ral comments.

On pages 4-32/4-33 an unstated advantage of direct measurement of light extinction is the immediate response obtained. In contrast the process of collecting filters, analyzing them, and performing the data validation necessary to calculate reconstructed light extinction takes a significant amount of time. Dir ect measurement of light exti nction could provide immediate feedback to planning agencies an d could be used for alerts and be havior modification, if necessary. Furthermore, the increased analytical sensitivity achieved by sampling fo r longer periods makes speciated PM 2.5 calculated light extinction better for long er term averaging than for short term applications. This concept is particularly important in the ten-step simplifi ed approach outlined on pages 4-34/4-35. The inherent uncertainties in the speciated measurements used in this method might be significantly enhanced with this method. It would be important to perfo rm a critical analysis of these uncertain ties prior to using it.

The findings of the WACAP study described briefly on page 5-21 are important in identifying that the source of airborne contaminants is nearby emissions and not those transported from Eastern Europe or Asia. This should be highlighted to avoi d using scarce resources on projects that assume long-range transport is more important.

Page Line Comment 4-31 20 Change “wide spread” to “widespread” 4-36 15 insert “of” between “because” and “the differing” 4-38 25 add a space between “PM 2.5 ” and “mass”

4-39 9 remove the comma after “document” 4-40 9 add a space between “daylight” and “1-hour”

4-46 6 should this be “4 of the 14...”?

5-2 17 remove the comma after “1997”

5-5 3 remove the comma 5-9 7 change “effects” to “affects”

5-9 8 remove the comma after “thus” 5-9 33 change “are” to “is” 5-13 1 change “are” to “is”

5-13 14 add “comes” at th e beginning of the line

5-16 3-4 move “to” inside the numbered items (i.e. “are (1) to identify...and (2) to qualitatively

A- 2Charge questions

Chapter 4 (Secondary Standard for PM-related Visibility)

11. Current Approach (section 4.1.3) :

a. What are the Panel’s views regarding our ap proach for translating technical evidence and assessment results into the basis for assessing current fine particle st andards and considering alternative standards to provide protection against PM-related visibility impairment?

The approach is sound – it follows a logical step-b y-step process and is explained very well. Figure 4-1 provides an excellent road map of the approach.

b. Has staff appropriately app lied this approach in reviewing the adequacy of the current standard (section 4.2) and potential alternative standards (section 4.3)?

Yes, the approach is applied we ll. Staff has taken a complex proc ess and simplified in very well

into a readable document. I made a few comments above on secti on 4.3 regarding the advantages of direct light extinction measurement for fast response, and the suitability of speciated PM 2.5 calculated light extinction for longer term averages. In particular , the ten-step simplified approach for calculating hourly extinction is subject to high uncertainties th at should be analyzed prior to attempting to implement it.

12. Nature of the Indicator (sect ion 4.3. 1): What are the Panel’s views on the following:

a. Staff’s consideration of the th ree indicators identified in th is section and our conclusions on the appropriateness of these indicators for consideration in this review?

Staff has provided an excellent discussion of the merits of the three indi cators. I would only add that the direct light extincti on measurement can be accomplished immediately and could provide important feedback for encouraging behavior and emission adjustments that could curtail widespread air pollution events as they unfold.

b. The development and evaluation of a new approach that is based on using speciated PM2.5 mass and relative humidity to calculat e PM2.5 light extinction by means of the IMPROVE algorithm?

This approach is good when app lied to longer term averages, but I have reservations about its use for short term (hourly) applications. The inhere nt uncertainties in the measurements may be magnified significantly in the short term. This ne eds to be carefully evaluated prior to using it.

c. The assessment approach and results comparing the PM compon ents that contribute to the hours selected in the top percentiles for PM2.5 mass and PM10 light extinction?

This approach and assessment are well thought out and are presented well.

13. Alternative Levels and Form s (section 4.3.3): What are Pa nel views on the following:

a. The performance assessment whic h focused on the Candidate Pr otection Levels of 64, 112,

191 Mm -1 for PM2.5 light extinction and speciate d PM2.5 mass-calculated light extinction, and alternative levels of 10, 20, and 30 μ g/m 3 for PM2.5 mass concentration?

3 The logic behind this selection of Candidate Protection Levels is explained well; staff has done a commendable job of explaini ng the performance of the Alternativ e Standards. Table 4-5 is a clear representation of how the CPLs would perform in the 14 urban areas examined.

A-b. Use of three-year averaged 90t h and 95th percentiles in conj unction with a 1-hour daily maximum form and use of three-ye ar averaged 98th percentile in conjunction with the all daylight hours form?

The use of these percentiles and forms is explained well. Staff has done an excellent job of describing the steps used to get to this selection.

c. Insights to be drawn by comparing the PM components for hours included among the 10% highest for a 1-hour daily maxi mum form with the hours includ ed among the 2% highest for an all daylight hours form, for the vari ous indicators considered (Appendix C)?

This display of results is very informative. My primary complaint is that the labels on the graphs

are difficult to read because of the formatting necessary to fit them all on the page. The staff discussion explains the plots we ll; I had no proble m following it.

14. Key Uncertainties and Area s for Future Research and Da ta Collection (section 4.5):

What are the Panel’s views on the areas for fu ture research and data co llection outlined in this section, on relative priorities for researc h in these areas, and on any other areas that ought to be identified?

Staff responded very well to the panel’s request for a section on future research needs. I am especially pleased to see a disc ussion of the need for additional visibility preference studies to assess (or try to reduce) the differences in response between people in different urban areas. The call for a pilot light extinction monitori ng program is also highly important.

A- 4Mr. Ed Avol

General Comments

The second draft of th e Policy Assessment for PM is a ma rked improvement over the earlier

version. The discussions containe d within are more focused, more targeted, and by virtue of the presentation, more convincing. Staff has generall y been very responsive to comments provided on the first draft Policy Assessment.

In the course of presentation, there is repeated reference to “currently available scientific and

technical information” as the basi s for making informed judgments. This is entirely appropriate, but if there is not an assessment of missing gaps and data needs desired for the next review cycle (along with a subsequent commitment to devoting resources and energy to closing those gaps), progress will be slow in achieving the necessary or desired threshold of sufficient information on which to make additional informed and improved judgments. That is wh y Sections 2.5 and 3.5 (“Key Uncertainties and Areas for Future Research and Data Colle ction”) are such welcome and thoughtful additions, for which staff should be duly commended. This is a key element of encouraging substantive improvements in future review cycles, and shoul d be a part of every subsequent pollutant review.

That is not to say that the curre nt draft could not still be improved. There are still occasions in the text where there is a tendency to lapse into pr esentation of data, rather than referral to data presented in the ISA or RA docume nts. There are several sentences, paragraphs, and sections that meander a bit, and could be tightened up. The overall document could still be edited and reduced in length. That said, however, the formulation, approach, and presentations have significantly and positively evolved, and this genera l approach should be conceptua lly preserved for future policy assessments for other pollutants.

Specific Comments P1-12, lines 6-9 – The statement (and/or the thinking behind the st atement) is not well-expressed here. I would propose that the purpose for reviewi ng the emerging evidence on ultrafine particles is not to regulate PM2.5 “...or categories of fine par ticle sources...”, but rather to identify whether there is a basis for promulgating a health-protective standard for ultra-fine particles, which have a different constellation of sources, control strategi es, exposure pathways, and health outcomes than

PM2.5.

Pg 2-50, line32-34 – This question and answer seems like a circular argument. The fact that most studies utilize the annual and 24hr averaging times as the metric of analysis should not be seen as justification for having them. Ra ther, they are a reflection of the fact that they are the de facto “standard” metrics or “currency of the realm”.

Pg 2-52, line1-3 – This apparent inconsistency ra ises a possible question as to whether there is a lag effect of PM, with exposure leading to hospitalization in the winter, increased fragility or susceptibility, and increased risk of death several months later in the warm season, when PM is nearly as elevated.

A- 5Pg2-86, lines 19-21 – If this is not the appropriat e forum for discussion (a nd it arguably is not), then what is the appropriate forum to discuss/ present the research recommendations needed to meet standards implementation and strategy devel opment? This would seem to be a valuable discussion that should be held. Moreover, it should be tied closely to the review cycle of pollutants, in order to motivate continuing im provements in regulation and public health protection.

Pg 3-8, Figure 3-1 – This figure seems incomplete , with the several boxes at the bottom missing. Shouldn’t there be pathways and boxes for alterna tive and retained indicator, averaging time, form, and level options, respectively (so two possibilities for each element of the standard), and shouldn’t

that lead to a retention of or a lternatives to the current standard? The flow chart for review of the PM2.5 standard (Figure 2-1, Pg 2-12) is depicted in a similar but sligh tly different from, but shouldn’t these two figures be conceptually identical?

Minor Comments (typos, etc) The inherent writing style involves systematic (and arguably excessi ve) use of compound, complex, and sometime convoluted sentences throughout the document. Sentences fewer than

three or more lines are rare. This often makes it difficult for read ers to follow and understand the discussion. Multiple ideas are often conveyed with in one meandering statement. Improved efforts should be made to be clear, concise, and brief.

Pg ix, definition of FEV1 – this is not the change in FEV1 (which would be “delta’ FEV1), but

rather the volume of air exhaled in the first second of exhalation.

Pg xi, definition of PMx – 7th line should read “...di ameter are collected with an efficiency that

decreases...”

Pg 1-10, line 26 – replace “...we considered...” with “staff considered...”

Pg 1-11, line 6 – replace “...we revised...” with “...staff revised...”

Pg 1-11, lines 14-15 – were there really two seco nd drafts of the REA? Don’t you mean two drafts

of the REA?

Pg 2-3, lines 1-5 – Something is grammatically awkward or incorrect here. I suggest re-wording to read: “This conclusion was based on a key observa tion: most of the aggregated annual risk ...”

Pg 1-11, line 21 – replace “...we will...” to “...staff will...”.

Pg 1-11, line 25 – replace “We plan to release th e final...” with “Plans call for release of the

final...”

Pg 2-3, line 2 – insert comma after “...risk assessment...”

A- 6Pg 2-7 lines 23,27,34,... - This docum ent begins in the third person (“staff” determines or “staff” found this or that...), then gradually switches ove r to the first person (Our, we, ...). My personal opinion is that the third person is more appropriate, but consistency of presentation is another issue.

Pg 2-16, line 34 – Here, CVD is defi ned as cerebrovascular disease, but in the List of Acronyms at the start of the document, CVD is listed as cardiovascular disease.

Pg 2-22, line 29 – Delete “These studi es also...”, or complete the thought.

Pg. 2-45, line 14 – Based on current understanding (and the referenced text in the ISA), it’s the particle size, NOT the greater surface area, of UFPs that increases the potential to cross cell membranes and epithelial barriers. The current se ntence in the text here should be changed to

correct this.

Pg 2-69 footnote 52, lin e 4 – should read “in fact”, not “if fact”

Pg 3-27, lines 1-4 – The discussion in the section refers to “Western”, “East”, and “Southwest”, but the referred-to figure (Figure 3-4) is identifie d in terms of ”Mediterra nean”, “Dry”, “Dry Continental”, etc. The footnote on p3-26 explaining the designa tions identifies the Figure groupings by yet another way - specific states (e.g ., “The Mediterranean region includes CA, OR, WA.”) So, there are three slightly different desi gnations in the same disc ussion about overlapping (but not the same) areas (e.g., “Mediterranean ” seems to include both Southwest (CA) and Northwest (OR, WA) entries). If the inclusion of specific areas varies by definition in each of these three treatments, what are we to infer from the apparent variations between regions shown in the figure?

****************************************** Panel Charge Questions for the Primary Standards

1. Current Approach for Fine PM – Staff has gene rally done an excellent job in summarizing

the available evidence and revi ewing the adequacy of current and potential alternative

standards.

2. Form of the Annual Fine PM Standard – Th e issue of susceptible populations remains a challenging issue that cannot be minimized or ignored. Spatial averaging has the potential for reducing the importance of the potentia lly higher exposures encountered where susceptible populations may reside. Acco rdingly, in consideration of “allowing an adequate margin of safety”, this approach should not be used.

3. Alternate Level for Fine PM – Presen tation was appropriate and adequate.

4. Key Uncertainties for Fine PM – Staff shoul d be commended for an excellent job in developing this section. A prioritized lis ting of needs would be a next level of improvement, but the relative and varying pe rception of priorities may make this a challenging undertaking.

5. Current Approach for Coarse PM – Generally well done and convincing.

6. Adequacy of the Current PM10 Standard – Reasonable and logical approach with presentation of objective criteria and evidence on which to base current determinations.

7 7. Indicator of Coarse PM – The presentation seemed reasonable, in view of the available

evidence.

A-8. Form of the Coarse PM St andard – Seems reasonable.

9. Level of the Coarse PM Standard – Generally well-constructed presentation and discussion; Some questions remain as to why staff presented information in the 65-85ug/m3 range, but recommended the higher end of the range. Wher e and how does an “adequate margin of safety” for public health ente r into this recommendation?

10. Key Uncertainties for coarse PM – Excellent co mpilation of research needs to be addressed in the next/current cycle of research. As in the case of PM2.5 recommendations, prioritization might be us eful to apply/maximize th e use of limited resources.

A- 8Dr. Joseph D. Brain

Overall Assessment

The June 2010 draft of the PA for PM demonstrates considerable progress. EPA staff took seriously CASAC’s suggestions and this current ve rsion is much improved. Major concerns of

CASAC have been addressed. The nature of th e recommendations are clear, and the advice of EPA staff is clearly grounded on data and clearly stated arguments.

Answers to Charge Question 5: Current Approach for Coarse PM

Current Approach (secti ons 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 co arse particle standard?

The panel finds the second draft supe rior to the first draft discussed earlier. EPA staff has done its best to take the available evidence relating to ex posure and health effects and to use them as the basis for reviewing the coarse partic le standard. There are inherent deficiencies which persist. The coarse particle fraction--particles between 2.5 and 10--can only be esti mated by subtraction. Course particles are not measured directly. More over, the health effects studies suffer from an adjacent defect. We can only look at PM10 studies and try to estimate the extent to which the health effects observed relate to the entire size rang e collected or to only that fraction of coarse particles.

In toto , Chapter 3 reads well and is much improved. EPA staff has done its be st to describe an evidence-based approach for applying the limited amount of health effects evidence and air quality information in different US regions into a basis for reviewing the adequacy of the current coarse particle standard.

b. Has staff appropriately applied this approa ch in reviewing the adequacy of the current standard (section 3.2) and potential alternative standards (section 3.3)?

We believe that the answer to this question is yes. Given some deficiencies in data for both the exposure and health outcome side, the EPA staff has carefully delineated the limitations of the data available to them. They have done their best to use these data and to address the question of whether current standards are adequate. They al so do an excellent job of discussing possible alternative standards and the implications of applying them.

A New Concern Not Currently Adequately Addressed:

9 Page 3-1. This chapter focuses on “thoracic coarse particles,” which it defines as those particles with an aerodynamic mass me dian diameter between 10 microns a nd 2.5 microns. To what extent are the risks associated with partic les in this size range confined to the thorax? Particularly, during quiet breathing (primarily via the nose), there will be considerable deposition of these particles in the nose. What impact do they have on nasal inflammation and injury ? Do such particles interact with exposure to allergens? There is increasing evidence that some metals and even nanoparticles

A-can be transported from the nose through epithe lial and olfactory sensory neurons, through the olfactory bulb, to the brain. To what extent should we also wo rry about the impact of these particles on the nose and the CNS? It’s a little late to bring th is up, but this aspe ct should at least be acknowledged, if not in this document, at leas t in future versions. It should be on our radar

screen.

Minor Comments

Page ES1, Third Paragraph, Line 11. Ordinarily, one would give the lower end of the range first. Why not change this to “11-13 μg/m3.”

Page ES2, Four Lines from Bottom. There seems to be a missing verb. Shouldn’t this line read

“...there is sufficie nt information...”?

Page ix (List of Abbreviations), Line 11. Delete the words “change in.”

Page 2-32, Line 14. I’m not sure what staff means by the word “pea kiness.” It is sometimes used in relation to waveforms, particularly in relati on to speech, but I don’t know what it means in this

context. I’m also unclear as to wh at they mean in Line 15 by “rollb ack approach.” This is the first sentence of this paragraph, and is thus an import ant topic sentence. It should be rewritten and

clarified.

Adjacent Concerns

Discussions of the PM standard as well as this second draft of the PA raise long term generic issues. While not conveniently address is this document, I believe th at CASAC should begin thinking about these issues and make suggestions to solve them. We recognize that the time for implementation may be decades. Two topics come to mind:

1. PM Sampling Strategy The panel suggests a more rational design of exposur e assessment. This would involve thinking of the ideal size cuts to address size ranges of intere st. What should be th e cutpoints? Where and how should these devices be deployed? The goals would be a far more rational and useful design of exposure assessment, and one which would be coupled to the ne xt generation of health outcome studies. A long term process is needed in order for the next generation of sampling devices to be developed, calibrated, and deployed.

10 There is also a continuing cry for a more thoughtful assess ment of particle co mposition. There is increasing evidence that the extent of particle toxicity relates to the composition and solubility of the particles. There is also con cern about the most appropriate metr ic. Should standards really be mass-based or should they reflect numbers or surf ace area of particles? The composition issue is particularly relevant to discussions of coarse particles. How do we make the distinction between

those derived from fossil fuel co mbustion and resuspended crustal dus t? There is consensus that resuspended crustal dust is less toxic than co mbustion products. There are clear regulatory implications as well. It’s hard to regulate dust storms, but easier and more appropriate to regulate stationary and mobile sources.

A-2. Renewal of the Clean Air Act (CAA)

Pages 1-2 and 1-3 lucidly discuss the requirement s of the Clean Air Act. The first CAA was passed in 1963, and it was then am ended in 1966 and 1970. The next major re vision was in 1990. CASAC should contribute to the process of rene wing and refining the Clean Air Act. We have discussed inherent problems. We have discussed repeatedly some of the inherent problems with

the current version of the Clean Air Act. Some of the requirements simply cannot be met. Particularly for PM, we cannot protect all citizen s, particularly the most vulnerable ones, and protect them with an adequate margin of safe ty. We need to craft language which maximizes public health but is also consistent with what we know about health outcomes and PM exposure. We have not yet identified a threshold – an assu mption inherent in the current Clean Air Act.

We should also discuss whether regulating indivi dual pollutants makes sense. To what extent should mixtures be regulated? What about new ch emicals known to be toxic? These and other problems should be comprehensively addressed. Perhaps this is too big a job for CASAC, given its continuing responsibilities and the increased pace of activity in relation to criteria pollutants. But we should advocate for such a process, and suggest mechanisms to achieve it.

A- 11Dr. Wayne Cascio

General Comments:

The EPA staff has responded to the comments of CASAC and markedly improved the Policy

Assessment. The text is more focused and the rationale for the conclusions reached is now better justified. The text remains long but much easier to read. There remain many typographical errors that will undoubtedly identified in pr oof, but I would like to point out one reference that appears to be in error. The reference Zanobetti A, Schwar tz J. (2009) on 3-50 the correct citation is 117:898- 903. Epub 2009 Feb 13, rather than 117:1-40, 2008.

Chapter 2 (Primary Standards for Fine Particles)

1. Current Approach (section 2.1.3) : a. What are the Panel’s views on the sta ff’s approach to translating the available epidemiological evidence, risk information, and air quality informatio n into the basis for reaching conclusions on the adequacy of the current standards and on alternative standards

for consideration?

Comment: The approach is systematic, logical and explained clear ly. Figure 2-1 is very useful in conveying the details of the approach.

b. Has staff appropriately app lied this approach in reviewing the adequacy of the current standards (section 2.2) and potential alternative standards (section 2.3)?

Comment: The staff has been consis tent in their application of the approach described in section 2.1.3 and illustrated in Figure 2.1.3. The EPA staff has stru ck a good balance between the

evidence-based and risk-based considerations and associated uncertain ties to determine the adequacy of the current standards.

2. Form of the Annual St andard (section 2.3.3.1):

a. What are the Panel’s views on the additional analyses co nducted to characterize the potential for disproportionate impacts on susceptible populations, including low income groups and minorities associat ed with spatial averaging a llowed by the current annual

standard?

Comment: Some indi viduals with specific medi cal conditions, and children represent susceptible populations whose pathophysiologic response to PM exposure is enhanced. Individuals of low social position who reside disproportionately in ar eas of higher exposure might also share a greater susceptibility to the impact of PM exposure. The additional anal yses provided characterizing the potential for disproportionate impact on such a population allowed by spatial averaging is appropriate.

b. In light of these analyses, wh at are the Panel’s views on staff’s conclusion that the form of

the annual standard shou ld be revised to eliminate spatial averaging?

A- 12Comment: Based on the requirement to protect susceptible individuals it is appropriate 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 standard levels by considering: i. Confidence bounds on concentration-response relationships?

Comment: Figure 2-3 is useful in co nveying the confidence bounds on PM 2.5 C-R relationship. The figure would benefit from putting two panels on on e page and the third panel on a second page. The size of the images and associated text are too small to easily understand the message.

ii. Different statistical metrics that characte rize air quality distributions from multicity epidemiological studies?

Comment: Appropriate.

b. Potential alternative annual standard leve ls based on composite monitor distributions

versus maximum monitor distributions?

Comment: The composite monitor distributions appear to be quite robust and stable when compared to the maximum monitor dist ributions, and therefore is preferred.

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?

Comment: The risk inform ation particularly Figures 2-11 and 2-12 is described clearly and is utilized appropriately by the EPA staff to draw reasonable conclusi ons about the alternatives for

the annual and 24-hour standard levels.

d. Staff’s conclusion that alternative annual standard levels in th e range of 13 to 11 μ g/m3 are most strongly supported by the availabl e evidence and risk-b ased information?

Comment: An alternative annual standard level in the range of 13 to 11 μg/m 3 is supported by the available evidence and risk assessment. While a threshold does not appear to exist at lower concentrations the uncertainties do explode and li mit confidence of the ma gnitude of the health

effect at lower concentrations.

e. Staff’s approach of focusing on peak-to-mean ratios to inform the level of a 24-hour

standard that would provide supplemen tal protection to a gene rally controlling annual

standard?

Comment: This is a reasonable approach.

13 f. Staff’s conclusion that co nsideration should be given to retaining the current 24-hour

standard level of 35 μ g/m3 in conjunction with annual standa rd levels in the range of 13 to 11

A-μ g/m3, and that consideration could also be give n to an alternative 24-hour standard level of

30 μ g/m3 particularly in co njunction with an annual standard level of

11 μ g/m3?

Comment: Reducing the annual stan dard from 15 to 13 μg/m 3 is predicted to provide a significant public health benefit. Reducing the 24-hours standard from 35 to 30 μg/m3 is also predicted to provide significant public health benefit. The 30/11 option woul d provide the greatest protection to the largest number of people in the U.S., yet even this optio n will probably not offer optimal protection the most at risk popul ations, e.g. those with greater su sceptibility to the effects of PM.

4. Key Uncertainties and Areas for Future Re search and Data Collection (section 2.5):

What are the Panel’s views on the areas for fu ture research and data co llection outlined in this section, on relative priorities for researc h in these areas, and on any other areas that ought to be identified?

Comment: The Key uncertainties and areas for future research and data collection presented in section 2.5 are quite comprehensive and informativ e. Gaps in knowledge needed to eliminate uncertainties and improve risk assessment are identified in a wide range of areas including components and sources, ultrafine PM, co-pollutant exposures, exposure related factors, health effects, C-R relationships, and duration of e xposure, susceptible populations, genetic and epigenetic susceptibility, and social position. Moreover to answer the numerous questions related to the various issues described above, improvements are needed in data collection and monitoring methods as described on page 2- 89. To answer all of the polic y related questions will require a

vast amount of resources and time. For this reas on the EPA, the NIEHS and other relevant federal agencies should work collabora tively to establish priorities to determine which questions would provide the most cost-effective additions to our k nowledge to inform policy relevant questions and disease mechanisms needed and address this important public health issue.

Chapter 3 (Primary Standard for Coarse Particles)

General comment: In reviewing th e recently up-dated Chapter 3 it is agreed that EPA staff provided significant revisions in the 2nd draft Policy Assessment to the discussions of the current and potential alternative standa rds. The addition of Figures 3-2 and 3-3 that summarize the epidemiological evidence and air qu ality data relevant to the adequa cy of the current standard add considerably to understanding th e rationale for EPA’s conclusions. The discussion of potential alternative standard levels reads well and staff conclusions are well justified. The discussion was improved by a dding Figures 3-5 and 3-6 that summarized the epidemiological evidence and ai r quality data related to PM 10 and PM 10-2.5

.

5. Current Approach (sect ions 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 rev iewing the coarse particle standard?

14 Comment: The approach as outlined in Figure 3-1 provides a conc ise and logical approach to translating the available evidence and air quality information into th e review of the adequacy of the current standard. The approach is logical and relies on accumulate d evidence linking PM 10-2.5 to

A-adverse health effects. However, in contrast to the abundant evidence for PM 2.5 , the authors had to

contend with several serious limitations. These in clude limited epidemiological data specifically

related to PM 10-2.5 and very limited toxicological data in animal models, regional and spatial characteristics that complicate the generalization of exposures over a city or region, and a surrogate

measure of PM 10-2.5 , i.e. PM 10 that contains PM 2.5 . Nevertheless, the authors provide an excellent review of the evidence, and the va lue of that evidence in informing the risk for overall mortality and cardiovascular and respiratory effects.

b. Has staff appropriately app lied this approach in reviewing the adequacy of the current standard (section 3.2) and potential alternative standards (section 3.3)?

Comment: The EPA staff has utilized th e approach described successfully.

6. Adequacy of the Current PM10 Standard (section 3.2): What are the Panel’s views on the alternative approaches presented for considerin g the evidence and its uncertainties as they relate to the adequacy of the current standard?

Comment: It appears clear in reviewing the current literature and epidemiological studies that the present standard is not sufficient to protect h ealth. While uncertainties remain for many different reasons, the overall judgment is that the alternatives are likely to provide increased protection of

human health.

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 PM10 remains an appropriate indicator in

this review?

Comment: Given the availability of the health data, the associated health ri sk, and the present monitoring system, PM 10 is the only reasonable indicator fo r coarse PM at the present time.

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 st aff’s conclusion that revising the form to a 98th percentile form would be appropriate for a 24-hour PM10 standard meant to protect against exposures to thoracic coarse particles?

Comment: Based on the discussion provide by the EPA staff the 98 th percentile method appears to be the optimal form for the 24-hour standard.

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 PM10 standard levels, in conjunction with a 98th percentile form, including the weight placed on different studies?

Comment: Appropriate. This concentration-based st andard will be better matched to the health effects, will better compensate for missing data and as de scribed on page 3-31 is predicted to give “proportionally greater weight to days when concentrations are we ll above the level of the stand than to days when the con centrations are just above th e level of the standard.”

A- 15b. Staff’s conclusion that the evidence most strongly supports standard levels around 85

μ g/m3?

Comment: A standard around 85 μ g/m3 is easily supported by th e evidence and will generally provide equal protection to the current standard with some enhance improvement in some urban areas. Yet, such a standard will fail to protect a significant numbe r of individuals as indicated by the studies of Zanobetti and Schwartz (2009) an d Peng et al. (2008) where significant health impacts were measured with PM 10 98 th percentile concentration was 78 μg/m 3 and 68 μg/m 3
respectively. It is reasonable to consider a standard below 85 μg/m 3

.

c. The alternative approach to considering the ev idence that could suppor t standard levels as

low as 65 μ g/m3?

Comment: The available evidence pr ovides a justification for a 24-hour standard to lower values if positive but non-statistically significant associations are judged important, but justification near or below 65 μg/m 3 is weak. Ne w data from future studies will be necessary to resolve uncertainties in the vicinity of 65 μg/m 3 and at lower concentrations. Solutio ns might come in the form of more

direct measures of PM 10-2.5 and chemical characterization of the PM, and influence of co-pollutants.

10. Key Uncertainties and Area s for Future Research and Da ta Collection (section 3.5):

What are the Panel’s views on the areas for fu ture research and data co llection outlined in this section, on relative priorities for researc h in these areas, and on any other areas that ought to be identified?

Comment: Over the last several years, sufficie nt evidence has emerged regarding the adverse health effects of coarse PM, yet in contrast to fine PM the knowle dge base regarding coarse PM or

PM 10-2.5 is limited, and many significant gaps are pres ent in our understanding the C-R of its health effects. The key uncertainties pr esented in section 3.5 provide a broad overview of the areas of

information that are needed to fill these knowledge gaps and deve lop and justify more effective control strategies. Understanding sources and components of PM 10-2.5 , and modification of effects by co-pollutants is essential, and defining the concentration-response relationships accurately is extraordinarily important. Establishing the diff erential effects of PM mass on the various organ systems (heart, blood vessels, lungs, central nervous system, hematopoietic and immunity), reproduction and fetal development is key to understa nding the contribution the overall risks. Also consideration should be given to attaining a better understanding of the spatial distribution and

constituents of coarse PM and how they relate to local environments and huma n activity, such as traffic, industry or agriculture.

A- 16Dr. Christopher Frey

Charge Question 3: What are th e Panel’s views on the following:

Confidence bounds: The report seems to argue that there is not an adequate basis to consider concentration-response (C-R) confidence bounds quantitatively when developing or assessing potential alternative standard levels. However, as shown in Tables 2-2 and 2-3, 95 percent

confidence intervals are estimate d for the health effects endpoint s for long-term IHD mortality and short-term CV mortality a nd hospital admissions.

What is not entirely clear to the reader is what is m eant by “evidence-based considerations” and why this is different than “risk- based considerations.” The risk assessment is based also on evidence, so the dis tinction is not clear.

On page 2-57 it is stated that there are epidemiological studies th at report 95% confidence intervals

for the effect estimates. A statem ent is made, that is a bit unclear, as follows (lines 25-27): “these analyses do not provide evidence of a concentration below which the confidence interval becomes notably wider and uncertainty in a C-R relations hip substantially increas es.” Perhaps this statement is attempting to convey first the notion that the reported CIs are applicable to the range of ambient concentrations observed in the ep idemiological study, and that EPA is making a judgment that the CI’s should not be extrapolat ed to other values of ambient concentration. Second, the idea seems to be that if the C- R relationship would be applied to ambient concentrations that were not the basis of the sp ecific epidemiological stu dy, that the confidence intervals would widen. These assumpti ons could be stated more clearly.

The next sentence is even more un clear (p 2-57, lines 27-30). What is an “unacceptable degree of uncertainty”? What is a “continui ng C-R relationship”? The notion that “the possibility that an effects threshold may exis t becomes more likely” is likewise unclear. Sinc e the intended meaning is unclear, it is not possible to propose an alternative wording.

A key point is that there are fe w PM2.5 studies for which confiden ce bounds are reported for C-R functions. On page 2-58, lines 4-7 a purpose fo r the estimation of the CIs is given with an implication perhaps that somehow th ese CI’s are not relevant. It is not surprising, of course, that

the CI’s would widen as ambient concentration de creases into a range fo r which there are fewer ambient data. A point not discussed, however, is wh ether the confidence inte rvals widen such that the effects estimates are not statistically significant. Even if not statistically significant, is there an indication of an effect at the central tendency of the C-R relationship? Furthermore, there should be some discussion not only of the lower bound of the CI, but also of the u pper bound. This would be consistent with the statutory mandate that th e standard allow an “adequate margin of safety” that are “requisite to protect the public health.”

The Schartz et al. 2008 Fi gure 2 would be useful.

17 Different statistical metrics: The assessment provides two alternatives referred to as the composite

monitor and the maximum monitor. On the top of page 2-61, the text is a bit unclear but appears to be stating that, for the same air quality domain, th e composite monitor concentrations are less than

A-those based on the maximum monitor approach. An argument is made that an approach based on composite monitors has a “margin of safety” compar ed to the maximum monito r perspective. An implication is that if the maxi mum monitor approach is used, th en data from epidemiological

studies should be selected that are based on significant lower annual average concentrations. However, a judgment is made th at data should be selected from the epidemiological studies for which the C-R relationships are “strongest.” A judgment is made that c oncentrations not more than one standard deviation below the long-term mean concentration should be used. Although it

is reasonable to make some kind of judgment such as this, the j udgment should be explained. For example, it is not clear as to why one standard deviation was chosen, and no t, say, 1.65 standard deviations, 1.96 standard deviati ons, and so on. For ex ample, the information given in Table 2-4 implies that there are both author reported an d EPA analyzed air quality data well below the

“Mean-1SD”

Figures 2-7 through 2-8 provide useful informatio n regarding the frequency distribution of annual

mean concentrations. The lower panel of each figure is a bit uncle ar, but seems to be a population weighted version of the same air quality data. However, the sample sizes in the lower panels appear to be different than those in th e upper panel, which should be explained.

The text is somewhat confusing to the reader. For example, it is not cl ear as to why the lower bound to be considered is a rang e from the 10th to 25th percentile s, as opposed to, say, the 10th percentile alone. In figure 2-7, for long-term exposure studies, th e upper panel, the 10th percentile annual mean concentrations range from approxim ately 9 to 11 ug/m3. The population weighted values are 10 to 13 ug/m3. In both cases, the upper bounds of these ranges are for the high site,

and the lower bounds are fo r the composite monitor.

It is not clear to the reader that a standard deviation is any more or less arbitrary than a specific percentile of a frequency distribution, contra ry to the text on pa ge 2-65, lines 20-23.

A key point is made on page 2-6 8, lines 7-16, which seems to need more discussion, and needs to be discussed in the previous section regarding confidence intervals on th e C-R relationships. A key point to make clearly is regarding what is the lowest long-term ambient concentration and the

lowest short-term ambient concentr ation at which statistically significant effects are observed, and, furthermore, what are the lowest long-term and short-term concentra tions at which positive, even if not statistically significant, effects are observed.

The discussion of sensitive groups is very importa nt. However, this mate rial would seem to e more appropriate fit in the sec tion on confiden ce intervals.

18 In general, this section of the report is so mewhat confusing to the reader, because the key

consideration should be to select ambient concen trations at which adverse effects are observed, taking into account the statutory mandate to provide an adequate margin of safety. Much of this text seems to focus on what range of air quality data were the ba sis of the epidemiological study, but without an adequate tie-in to whether ther e are health effects associated with such concentrations. For example, page 2-72, paragraph of lines 6 to 14, the basic argument here is unclear. What is the “evidence” to support these numbers? Is the idea simply that the levels should not be chosen to be lower than approximate ly the 10th percentile of ambient concentrations observed in the epi studies? If so, then the text of this section could be shortened considerably.

A-If the maximum monitor approach is ultimately deemed to be less useful, then perhaps it need not

be included in the document.

b. Potential alternative annual standard levels ba sed on composite monitor distributions versus

maximum monitor distributions:

First, it is not at all clear as to why the annual standard should be “generally controlling.” The NAAQS should provide health protec tion for both long-term and short-term health effects. It is not clear, for example, as to why the 24-hour level shoul d be at least 2.5 times higher than the annual standard. Such a statement seems to be indepe ndent of consideration of health effects. A statement is made on page 2-73 , lines 26-27 that “based on this consideration” consideration should be given to retaining the 35 ug/m3 24-hr le vel in conjunction with annual standards of 13 to 11 ug/m3. Setting aside the math problem here (e .g., 11*2.5 = 27.5, not 35), the rationale here does not appear to be based on health effects, and thus appears not to be valid.

While it is useful to have insight as to what co mbinations of annual and 24 hour levels would lead to the annual standard being controlling in a gi ven area, it is not clear why the policy objective

should be set both levels such that the annual standard is generally controlling.

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?

There is a disconnect between the evidence-based section and the risk-based section that is confusing to the reader. The “e vidence-based” section reaches the conclusion that alternative levels to be considered should be 11 to 13 ug/m3 for the annual standard and 35 ug/m3 for the 24- hour standard, and also a combina tion of 11/30 for the annual/24-hour levels. However, the riskbased analysis does not systematically evaluate these combinations, om itting the 11/35 and 11/30 combinations. Furthermore, the text implies that a 10/35 case was analyzed, but no results are reported.

The results of the risk assessments are presente d mainly in terms of percentage risk reduction compared to the current standard, in Figures 2- 11 and 2-12 for long-term and short-term effects, respectively. While this is usef ul information, it is not relevant to the setting of a NAAQS. The goal of NAAQS is not to achieve relative risk reduction, but to protect public health with an adequate margin of safety. Thus, the risk charact erization should be based on absolute rather than relative numbers (e.g., number of premature deaths estimated under each scenario). Therefore,

much of the text need s to be revised.

This section should not only focus on the best estimate of risk, but the confidence intervals and non-quantified sources of bias, su ch as SES. See also Page 2- 35, lines10-12, which indicates that sensitivity analysis of model specification used in the the risk assessment produce risk estimates that are a factor of 2 to 3 highe r than the core risk estimates.

A- 19In cases where the 24-hour level would be cont rolling, it may be the case that there is less

confidence in the risk characteriza tion for the annual level. However, this in and of itself is not a reason as to why the 24-hour standard should not be controlling in such cases. A key policy question is whether having a 24-hour level be contro lling in these cases protec ts public health with an adequate margin of safety.

d. Staff’s conclusion that alternative annual standard levels in the range of 13 to 11 μ g/m3 are most strongly supported by the available evid ence and risk-based information?

Section 2.3.4.3 concludes that is appropriate to set levels so that the annual standard is generally controlling. However, it is not clear to the re ader as to how this conclusion was reached.

A conclusion is made that a lternative annual standards rangi ng from 13 to 11 ug/m3 are appropriate to consider. For internal consistency, a reason should be given as to why a level of 14 ug/m3 is not appropriate to consider. A level of 14/35 was considered in the risk assessment. Thus, the reader may wonder why this is set aside in the staff conclusions.

A conclusion is made to the effect that consider ation should be given to retaining the 24-hour level of 35 ug/m3 or to having a 30 ug/m3 level “particularly” in comb ination with an annual level of 11 ug/m3. It is not clear as to ho w this conclusion was reached, or why other combinations such as 13/30, 12/30, or 11/25 would not also be useful to consider.

The assessment is weakened by not having a quantitative risk asse ssment result for the 11/35 and 11/30 levels, or possibly for othe r combinations as noted above.

There should be discussion of potential sources of biases in the risk characterization, such as the

role of differences in distributi ons of low SES groups represente d in the epidemiological studies versus in the urban populations being analyzed.

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?

The key consideration should be the health effects evidence, rather than the peak-to-mean ratios. The ratios are useful in providing insight as to whether the annual or 24- hour standard would be controlling in a particular area, but it is not clear as to why the annual standard should be generally controlling.

f. Staff’s conclusion that consideration should be given to retaining the current 24-hour standard

level of 35 μ g/m3 in conjunction with annual standa rd levels in the range of 13 to 11 μ g/m3, and that consideration could also be given to an alternative 24-hour standard level of 30 μ g/m3 particularly in conjunction with an annual standard level of 11 μ g/m3?

This point is addressed above.

A- 20Charge Question 4: Key Uncertain ties and Areas for Future Resear ch and Data Collection (section 2.5): What are the Panel’s views on the areas for future research and data collection outlined in this section, on relative priorities for research in these areas, and on any other areas that ought to be

identified?

Response: The material presented here is generally r easonable. It would be nice to have all of this information to support future assessments.

A few additional points to mention are:

• Need for activity data to support probabilistic scenario-based exposure models, such as additional activity diary data to incorporate in to the Consolidated Hu man Activity Database (CHAD) • Characterization of indoor exposures to PM of ambient origin. For example, the penetration of ambient PM2.5 and PM10 into in door microenvironments (home, work, school, restaurant, bar, vehicle) should be better character ized, particularly taking into account differences in penetration with respect to particle size and composition. • How might climate change af fect the size distribution and composition of PM in the PM10, PM2.5, and UFP ranges?

What is lacking in this section is an idea of prio rities. What is outlined here is a very broad and ambitious research agenda. It wo uld help to start this section with a prioritized review of key uncertainties, in order to help establish prio rities among the suggested research topics.

Charge Question 10: Key Uncertainties and Ar eas for Future Research and Data Collection (section 3.5): What are the Panel’s views on the areas for future research and data collection outlined in this section, on relative priorities for research in these areas, and on any other areas that ought to be identified?

Response:

See comments on Chapter 2.

The key distinction for this chapter is the need to seriously focus on PM10-2.5 for both mass and composition. The CASAC looks forw ard to the planned implementatio n of monitors that measure PM10-2.5, rather than PM10. There is a critical n eed for national monitoring data on PM10-2.5 in order to provide a basis for epidemiological studie s that focus on this size fraction. Furthermore, there is a need for speciated data to support h ealth effects estimates. Spatial and temporal variability in coarse particle ma ss and composition need to be ch aracterized. In addition, the national monitoring data w ill support a baseline for ambient ai r quality in order to compare with

health effects data in order to assess whether there is a need for a standard.

The research areas described in th e draft Section 3.5 are reasonable , but there needs to be strong emphasis on the critical need for coarse PM data, in order that the NAAQS can move beyond

PM10 as an indicator for coar se PM in a future revision.

A- 21Another question to be considered is regardin g what size cut-points are appropriate, and also regarding what specific components ar e of most interest or concern w ith respect to health effects.

There is a need for continuous mon itoring of coarse PM (and of PM2 .5) in order to support health

effects studies and to be able to assess alternativ e forms of possible future standards.

Other challenges for future research : (a) it may be difficult to get useful data from rodent studies since they can breathe particles only up to a bout 4 to 5 microns; (b ) getting good chemical characterization of the particles will be a problem, since there are primary biological materials.

Prioritization is needed, such as vi a a separate meeting or workshop.

A- 22Dr. Joseph J. Helble

The Second Draft Policy Assessment is much more concise and readable than was the earlier draft. Text has been removed and replaced with appropri ate references to the IS A and other documents, and there is little overlap between sections. The length a nd clarity of this docu ment are now, in my view, appropriate for this Policy Assessment.

Charge Question 12: Nature of the Indicator (sect ion 4.3. 1): What are the Panel’s views on the following:

a. Staff’s consideration of the three indicators identified in this section and our conclusions on the appropriateness of these in dicators for considera tion in this review?

The three indicators – mass, direct measuremen t of extinction, and calculated extinction based on speciation and size data – are the thre e relevant indicators. Given the dependence of extinction on particle compos ition, the conclusions regardin g the relative inadequacy of a PM mass-only standard are appropriate. Di rect measurement of extinction is, of course, a direct measurement and relevant, and the r easonable match of the calculations based on speciated PM mass suggests that this latter indicator is also appropriate.

b. The development and evaluatio n of a new approach that is based on using speciated PM2.5 mass and relative humidity to calculat e PM2.5 light extinction by means of the IMPROVE algorithm?

Appropriate, as noted above. As discussed in the research needs section of the PA, better understanding of speciated PM2.5 ma ss distributions is needed.

c. The assessment approach and results comparing the PM components that contribute to the hours selected in the top percentiles for PM2.5 mass and PM10 light extinction?

The assessment approach, looking at contributio ns to PM mass v. contri butions to PM light extinction under different scenarios, is appropria te, as are the conclusions extacted from the study. My only comment is that the figures in Appendix 4C are difficult to read, the text used to describe each part isn’t particularly clear, and it appears that the captions of the relevant figures may be mislabeled (for exampl e, in each figure, it se ems that extinction is presented in parts a and d, not a and b – PA text is corr ect, figure caption is not)

A- 23Charge Question 14: Key Uncertainties and Ar eas for Future Research and Data Collection (section 4.5): What are the P anel’s views on the areas for futu re research and data collection outlined in this section, on relative priorities for research in these areas, and on any other areas that ought to be identified?

The major areas of research and data collection needed to address key uncertainties related to a visibility-based secondary standard are nicely capt ured in Section 4.5 of the PA. The section appropriately identifies two majo r areas of need, one related to visibility preference, and one

related to methods of measurement.

In the first category, preference studies, the de tails noted by EPA all id entify a strong need for additional urban visibility preference studies c onducted using consistent methodology. The range of 50% acceptability values discusse d as possible standards are based on just four studies (Figure 4-2), which, given the large spread in values, pr ovide only limited confidence that the benchmark candidate protection levels cover the appropriate ra nge of preference values. Studies using a range of urban scenes (including, but not limited to, ic onic scenes – “valued sc enic elements” such as those in the Washington DC stu dy), should also be considered.

In the second category related to methods of measurement, I support the proposal to conduct studies in several cities, pairing direct monitoring of light extinction with enhanced monitoring of PM size and composition distribu tions (i.e. continuous PM spec iation monitoring). Additional

work should also be conducted to understand the contribution of PM 10-2.5 in southwestern areas other than Phoenix, to address the lack of informa tion for scattering associated with this fraction of PM10 as is noted on page 4-30.

Underlying this overall discussion is a clear ne ed for better particle size – composition distribution information (i.e. particle composition distributions as a function of partic le size). It is addressed in different ways in the discussions of future res earch needs elsewhere in the PA (Sections 2.5 and 3.5), and the development of co ntinuous monitoring methods for specific PM components addressed in Section 2.5 is equally applicable he re. Improved understanding of size-dependent PM composition would also help addre ss some of the questions related to the role of scattering and absorbing aerosols in climate forcing th at are raised in PA Section 5.2.4.

A- 24Minor ed. Comments:

p. 2-89, line 16, missing “to” be tween “models” and “expand” ?

p. 4-13, line 25: “effects” is vague. De gradation would be a clearer term here.

p. 4-19, line 16, ) needed after “screen”

p. 4-33, line 33, delete “, and simplic ity” since the text is alread y describing “a simpler approach”

p. 4-35, line 15, first word, change “show” to “shown”

p. 4-36, line 15, insert of between “because” and “the differing”

p. 4-39, line 9, delete second pe riod at end of sentence

p. 4-41, line 3, change “areas” to “area”

p 4-46, line 2 delete apostrophe

p. 4-51, line 19, insert “data” between “component” and “to calculate”

p. 5-5, line 3, delete comma

p. 5-15, line 32, “review” ? – wouldn’t “ policy assessment” be correct here?

A- 25Dr. Rogene Henderson

Answer to charge questions assigned to me:

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 ai r quality information into the basis for reaching conclusions on the adequacy of the current standards and on alternative standards for consideration?

The Panel agrees with the approach as described in section 2.1.3 and appreciates the clarity with which the approach was described. The overview of the approach presented in Figure 2-1 is wellorganized and clear. The Panel agrees that it is appr opriate to go back to the approach used in 1997 to consider the annual and 24 hr standards toge ther, with the annual standard as the controlling

standard and the short-term standard intended to supplement the protection afforded by the annual standard. The Panel supports the Agency's co nsideration of evidence- based and risk-based

information as well as the uncertainties associ ated with both types of information. The Panel considers it appropriate to place the greatest emphas is on health effects judged to be causal or likely causal in the analysis presented in the ISA.

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)?

The staff has followed this approach in reviewin g the adequacy of the cu rrent standards and in considering potential alternative st andards. The outline of the text of section 2.3 follows the outline presented in the overview of the approach given in Figure 2-1.

6. Adequacy of the Current PM10 Standard (sec tion 3.2): What are the Panel’s views on the alternative approaches presented fo r considering the evidence and its uncertainties as they relate to the adequacy of the current standard?

Section 3.2 is exceptionally well wr itten. It includes a discussion of the studies that are most significant for the question for the ad equacy of the current standard. At the end, the authors offer two different approaches to analys is of the studies. The informa tion on the new studies related to coarse particles indicated differences in the robustness of the responses that left the answer to the question of adequacy of the current standard un certain. Therefore it wa s helpful to have the descriptions of two approaches to analysis of the data, as given at the end of the section.

Rogene Henderson July 15, 2010

General comment on 2nd draft PA:

A- 26I think this is a much-improved draft PA; the Agency has been responsive to the previous

comments of CASAC.

Answers to other charge questions:

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 ai r quality information into the basis for reaching conclusions on the adequacy of the current standards and on alternative standards for consideration? Good approach. b. Has staff appropriately applied this approach in reviewing the adequacy of the current standards (section 2.2) and potential alterna tive standards (section 2.3)?

Yes.

2. Form of the Annual St andard (section 2.3.3.1):

a. What are the Panel’s views on the additional anal yses conducted to characterize the potential for disproportionate impacts on susceptible popula tions, including low income groups and minorities associated with spatial averaging allo wed by the current annual standard?

Well done b. In light of these analyses, what are the Panel’s views on staff’s c onclusion that the form of the

annual standard should be revised to eliminate spatial averaging? Agree.

3. Alternative Levels (secti on 2.3.4): What are the Panel’ s views on the following: a. The insights that can be gained into potentia l alternative standard levels by considering:

i. Confidence bounds on concentr ation-response relationships?

ii. Different statistical metrics that charact erize air quality distributions from multi-city epidemiological studies? I agree with the discussion of these topics in the text.

b. Potential alternative annual standard levels ba sed on composite monitor distributions versus

maximum monitor distributions? I agree with the policy to focus on alternative levels that ar e just somewhat be low the long-term mean concentrations reported in the epidemiological studies using the composite monitor

distributions. c. Use of risk information in informing staff conc lusions on alternative annual and 24hour standard levels, including approaches used to assess over all confidence and poten tial bias in the risk

estimates?

This was well done.

d. Staff’s conclusion that alternative annual standard levels in the range of 13 to 11 μg/m3 are most strongly supported by the available evidence and risk-based information? I agree. 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? I agree.

A- 27f. Staff’s conclusion that consideration should be given to retaining the current 24-hour standard level of 35 μg/m3 in conj unction with annual standard levels in the range of 13 to 11 μg/m3, and that consideration could also be given to an alternative 24-hour standard level of 30 μg/m3 particularly in conjunc tion with an annual standa rd level of 11 μg/m3? Agree.

4. Key Uncertainties and Areas for Future Re search 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? I have nothing to add.

Chapter 3 (Primary Standard 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 coarse particle standard? I agree with the approach. 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)?

Yes.

6. Adequacy of the Current PM10 Standard (sec tion 3.2): What are the Panel’s views on the alternative approaches presented fo r considering the evidence and its uncertainties as they relate to the adequacy of the current standard? I liked the presentation of the two approaches for consideration of the data.

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 PM10 remains an appropriate indicator in this

review? I agree with the staff conclusions.

8. Form (section 3.3.3): What are th e Panel’s views on the approach taken to considering the form

of the standard and on staff’s c onclusion that revising the form to a 98th percentile form would be appropriate for a 24-hour PM10 st andard meant to protect against exposures to thoracic coarse particles? I agree.

9. Level (section 3.3.4): What are the Panel’s views on the following: a. The approach taken by staff to identify pot ential alternative PM10 standard levels, in conjunction with a 98th percentile form, including the weight placed on different studies? OK.

b. Staff’s conclusion that the evid ence most strongly supports standard levels around 85 μg/m3? I agree. c. The alternative approach to considering the evid ence that could support standard levels as low as 65 μg/m3?

A- 28I do not agree with this low a leve l because it places more weight on studies in which results were positive but not statis tically significant.

10. Key Uncertainties and Areas for Future Re search 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? I have nothing to add to this section.

A- 29Dr. Morton Lippmann

The 2 nd Draft PM PA is a great improvement over th e first. OAQPS Staff was very responsive to

the CASAC comments and recommenda tions on the first draft, and deserves to be commended for producing a clearly readable exposition of the scientif ic basis for its conclusions, as well as clearly

stated rationales for its recommendations.

I could only generate a relatively small number of specific suggestions for edits and/or changes for Chapters 2 and 3, which are enumerated below.

Page Line Comment

2-23 10 change “found” to “continued to find”.

2-23 17 insert a comma after “studies” an d insert “the increased” before “risk”. 2-32 14 insert a definition of “peakiness”. Does it have a specific meaning in the context of

this document? If so, what is it? 2-34 23,25 change “which” to “that”. 2-36 2 add to end of sentence: “but give greater weight to eastern and Midwestern populations.” 2-43 18 insert “and toxicological” after “epidemiological”. 2-44 20 insert “and humidity” after “concentrations”.

2-45 8 insert “collec tive” before “surface”. 2-45 21 change “i.e.,” to “within the”. 2-86 21 add to end of sentence: “, and w ill be the subject of a future document”. 2-87 27 change “ Exposure-related Factors.” to “Factors Influencing Exposures”. 2-89 1 change “Children” to “Age”, and add “and older adults” after “children” at end of

the line.

Charge Questions:

Chapter 2 (Primary Standards for Fine Particles)

1. Current Approac h (Section 2.1.3) : a. What are the Panel’s views on the sta ff’s approach to translating the available epidemiological evidence, risk information, and air quality informatio n into the basis for reaching conclusions on the adequacy of the current standards and on alternative standards

for consideration? The approach is sound.

b. Has staff appropriately app lied this approach in reviewing the adequacy of the current standards (section 2.2) and potential alternative standards (section 2.3)?

Yes.

2. Form of the Annual Standard (Section 2.3.3.1):

30 a. What are the Panel’s views on the additional analyses co nducted to characterize the

A-potential for disproportionate impacts on susceptible populations, including low income groups and minorities associat ed with spatial averaging a llowed by the current annual

standard? They were well conceive d and well articulated.

b. In light of these analyses, wh at are the Panel’s views on staff’s conclusion that the form of

the annual standard shou ld be revised to eliminate spatial averaging? The conclusion was well justified.

3. Alternative Levels (Secti on 2.3.4): What are the Pane l’s views on the following: a). The insights that can be ga ined into potential alternative st andard levels by considering:

i. Confidence bounds on conc entration-response relationships? Useful, and an appropriate choice.

ii. Different statistical metrics that charac terize air quality distributions from multi- city epidemiological studies? Useful, and highly approp riate for the purpose.

b). Potential alternative annual standard levels based on composite monitor distributions

versus maximum monitor distributions? The composite monitor approach is pr eferable because of its stability.

c). Use of risk information in informing staf f conclusions on alternative annual and 24- hour standard levels, including approaches used to assess overall confidence and potential bias in the risk estimates? The risk information provides valuable insights, and should be used in drawing conclusions.

d

). Staff’s conclusion that alternative annual standard levels in the range of 13 to 11 μ g/m 3
are most strongly supported by the availabl e evidence and risk-b ased information?

The rationale for the conclusion was well developed, and well justified.

e). Staff’s approach of focusing on peak-to-mean ratios to inform th e level of a 24-hour

standard that would provide supplemen tal protection to a generally controlling annual

standard? The approach is sound.

f). Staff’s conclusion that co nsideration should be given to retaining the current 24-hour

standard level of 35 μ g/m3 in conjunction with annual standa rd levels in the range of 13 to 11

μ g/m3, and that consideration could also be give n to an alternative 24-hour standard level of

30 μ g/m3 particularly in co njunction with an annual standard level of 11 μ g/m3?

The conclusions are reasonable in relation to the criteria established by the Clean Air Act (CAA), and those developed by the OAQPS Staff that have been endorsed by CASAC.

31 The choices within these options will need to be based on th e Administrators interpretation of the CAA’s requirement for a ma rgin-of-safety. In other words, in the absence of response thresholds, how much public health impact resulting from exposure to ambient air PM 2.5 is acceptable under the CAA.

A-The least protective option (35-13) would pr ovide significant additional public health benefits in most of the U.S., in comparison to the current limits (35-15), and these benefits would be greatest in the more humid pa rts of the U.S. The most protective option (30-11) would provide significant additional public health benefits to a larger part of th e U.S. population in comparison to the current limits (35-15) and any of the intermedia te options, but would not prevent at least some adverse health effects among the most su sceptible segments of the population.

The decision to be made on the selecti on among the alternative levels for the PM 2.5 NAAQS will need to be made j udiciously, with acknowledgment of its public health consequences. As compared to the previous round fo r PM, it is no longer justifiable to rely on residual uncertainties as a basis for confronting the need for a si gnificant advance in public health protection.

4. Key Uncertainties and Areas for Future Research and Data Collection (Section 2.5):

What are the Panel’s views on the areas for fu ture research and data co llection outlined in this section, on relative priorities for researc h in these areas, and on any other areas that ought to be identified? The key uncertainties and areas for future res earch and data collecti on are well summarized in Section 2.5. The acknowledgement (at the top of page 2-87) that “Much of this research may depend on the availability of in creased monitoring data” is apt and appreciated. The opportunities for epidemiological research to effectively ad dress the knowledge gaps on the effects, and concentration-response relationships, of PM co mponents and source-related mixtures cannot be achieved without additional monitoring data to provide PM speciation and better temporal and spatial resolution. Only EPA can provide the impetu s and support for such an enhancement in air quality monitoring.

The research needs to address uncertainties in health outcomes, exposure durations of concern, and susceptible populations that are also very nicely outlined are well targeted, and can be effectively studied in human po pulations. Such studies , to be most produc tive, will need the enhanced monitoring data that EPA has recogn ized as being needed, and that only EPA can provide.

Chapter 3 (Primary Standard 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 translatin g the available evidence and air quality information into the basis for reviewing the coarse particle standard? The Staff has done a good job of de scribing a suitable, evidence-based , approach for translating the

limited amount of relevant health effects eviden ce and air quality inform ation in different U.S. regions into a basis for reviewing the adequacy of the current coarse particle standard.

b. Has staff appropriately applied this a pproach in reviewing the adequacy of the current standard (section 3.2) and potential alternative standards (section 3.3)?

Yes.

6. Adequacy of the Current PM10 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?

32 They remind us of the reliance on uncertainties used by the previous Administ rator as an excuse to

A-discount the increasing evidence that exposures to thoracic coarse PM increases health risks.

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 PM10 remains an appropriate indicator in

this review? The document makes a good case for retaining PM 10 as an indicator for this round of 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 st aff’s conclusion that revising the form to a 98th percentile form would be appropriate for a 24-hour PM10 standard meant to protect against exposures to thoracic coarse particles? The document makes a good case for using the 98 th % form for this round of review

.

9. Level (section 3.3.4) : What are the Panel’s vi ews on the following: a. The approach taken by staff to identify pot ential alternative PM10 standard levels, in conjunction with a 98th percentile form, includi ng the weight placed on different studies? The approach outlined is a very reasonable one, and appropria te weights were given to the

available studies.

b. Staff’s conclusion that the ev idence most strongly supports standard levels around 85

μ g/m3.

This conclusion is not appropriate, insofar as it is base d on an average equivalence of PM 10 at 150

u g/m 3 for the 4 th highest concentration in 3 years, and 85 u g/m 3 for the 98 th % ile . Because of the well-documented differences in “peakiness” and the ratios of PM 2.5 to PM 10 in different parts of the U.S., there will be a less protectiv e limit for parts of the U.S. The ab sence of data on the adequacy of the present PM 10 NAAQS to protect against the adverse effects of PM 10-2.5 does not provide a basis for relaxing the thoracic coarse PM NAAQS for parts of the U.S.

c. The alternative approach to considering the evidence that could support standard

levels as low as 65 μ g/m3? The presentation of the evidence, as summarized in the text beginning on line 33 of page 3-42 is convincing, at least to this CASAC Panel reviewer, that a PM 10 level below 85 u g/m 3 is warranted, and a range of 75 to 65 u g/m 3 should be recommended for consideration.

10. (Section 3.5): Key Uncertaintie s and Areas for Future Rese arch and Data Collection

What are the Panel’s views on the areas for fu ture research and data co llection outlined in this section, on relative priorities for researc h in these areas, and on any other areas that ought to be identified?

33 The brief statement of the key un certainties and areas for future re search and data collection in Section 3.5 is very much on target, with one exce ption. That one is: “Anima l toxicological studies of long-term exposures (i.e ., months to years) to PM 10-2.5 would be useful”, as stated on page 3-46, lines 37 & 38. However, inhala tion exposures are not feasible in rodents because nearly all particles <2 u m would deposit in the nasal ai rways, and not penetrate into the lung parenchyma, and

those few that did woul d not have much deposition in the tracheobronchial airways. Exposure studies in animals by other routes of administration would have se vere limitations in terms of interpretation and risk assessment.

A-A- 34Dr. William Malm

The current draft PM PA is much improved over the first. EPA staff was for the most part responsive to CASAC recommendations. However, a few significant issues remain as outlined

below.

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 basi s for assessing current fine par ticle standards and considering alternative standards to provide protecti on against PM-related visibility impairment?

The combined evidence- and impact -based review nicely contrasts various approaches and metrics for protecting urban visibilit y. The three indicators; PM 2.5 extinction, reconstructed extinction, and mass concentration, pretty much cover the currently available metrics that could be used to set a standard. Averaging times are co nsidered, as are various percentile levels for both extinction and

mass concentration. The various metrics are compared to VAQ acceptability studies that were

carried out in four urban areas.

Detailed analysis was only presented for a subset of percentile levels and 1-hr da ily maximum levels versus maximums for all days. It is clear that contrasting and comparing all combinations would be overwhelming; however, the selection of a 90 th percentile for 1-hr maximum and a 98 th
percentile criteria for all daylight hours is not well jus tified, other than the two approaches yield

similar results. It would be he lpful to develop an easily underst ood statistic for each comparison, and then extend the contrasts and comparisons to more combinations of the percentile levels, metric forms, and maximum selections.

The EPA is to be comm ended for taking the VAQ acceptability st udies and applying the logit digit

model to the results in such a wa y as to more directly intercompa re the four studies and estimate various visibility acceptability levels. It would be of interest to further expand the analysis, using existing data, to see if there is a visibility index that represents visibility conditions independent of the type of scene being viewed, su ch that preference levels for all studies, when plotted against this index, would all yield the same response curve. If such an index could be identified, the currently available studies could be used to assess visibility levels in any urban area or setting, using this index. The relationship of this index to dv or extinction will necessarily be nonlinear; however, this approach would allow repres entative extinction levels to be examined for a variety of urban areas and/or landscape/urbanscape features.

In any case, I think the approach taken very clearly shows the li mitations of using the current PM 2.5 standards to protect against visibility impairme nt judged to be unacceptable by available VAQ acceptability studies.

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)?

For the most part they have.

A- 3512. Nature of the Indica tor (section 4.3.1): What are the Panel’s views on the following:

a. Staff’s consideration of the three indicators iden tified in this section and our conclusions on the appropriateness of these indicators for consideration in this review?

The three indicators, mass, reconstructed extin ction, and measured extinction, are appropriate indicators. However, it would be of interest to further expand th e analysis, using existing photos and preference data, to see if there is a visib ility index that represents visibility conditions independent of the type of scen e being viewed, such that prefer ence levels for all studies, when plotted against this index, would all yield the same response curve. If such an index could be identified, the current available studi es could be used to assess visib ility levels in any urban area or setting. The relationship to dv or extinction will necessarily be non linear; however, this approach would allow representative extinction levels to be examined for a variety of urban areas and/or landscape/urbanscape features.

b. The development and evaluation of a new approach that is based on usi ng speciated PM2.5 mass and relative humidity to calculate PM2.5 light extinction by means of the IMPROVE algorithm?

It has been demonstrated in many studies that it is possible to reconstruct extinction from speciated mass data if the relative humidity is known. The EPA has further demo nstrated that, in most cases, applying monthly average speciat ed mass data to hourly mass measurements and applying the IMPROVE algorithm results in a sim ilar estimate of hourly extinction values as would have been obtained by using the hourly speciated data directly.

c. The assessment approach and results comparin g the PM components that contribute to the hours selected in the top percentiles for PM2.5 mass and PM10 light extinction?

See comments in 11a and 13a. A qu antitative statistical index, repres entative of the good or not so good comparison between appro aches, should be developed.

13. Alternative Levels a nd Forms (section 4.3.3): What are Panel views on the following: a. The performance assessment which focused on the Candidate Protection Levels of 64, 112, 191 Mm-1 for PM2.5 light extinction and speciated PM2.5 mass-calculated light extinction, and alternative levels of 10, 20, and 30 μ g/m3 for PM2.5 mass concentration?

These are appropriate CPL and PM 2.5 levels. The CPL values were based on all visibility preference data that are available and bound the study results as represented by the 50% acceptability criteria. However, I think it would be worth it, but not necessarily essential, to expand some of the tables to include 10 and 40 dv values, in that at 10 dv, not anybody found the scene to be unacceptable, and at 40 dv, virtually everybody found the a ll scenes to be unacceptable.

What would these dv levels corre spond to in th e context of PM 2.5 and the various percentile levels?

36 b. Use of three-year averaged 90th and 95th percentiles in c onjunction with a 1-hour daily

maximum form and use of three-year averaged 98th percentile in conjunction with the all daylight

hours form?

A-These levels may very well be appropriate; howeve r, I don’t think they we re well justified. It seems that the cursory ar gument was that the 90–95 th percentiles in conjuncti on with the 1-hr daily maximum identified similar days an d hours of violation, as did the 98 th percentile in conjunction with all daylight hours, and th is correspondence was reason enough to pick these two approaches.

I think it would be informative to do all, or at that least the same , percentiles for both all days and daily max hr, contrast and compare the approaches , and then try to develop a self consistent argument of why one approach would be better than another. It doesn’t seem that this was done. The question of the implications of which sources might be identified as problematic as a function of all hours all days versus daily max hr has still not been adequate ly addressed. It was pointed out that the all hour, all day in some cases selected out multiple hours on the same da y. It seems that a significantly extended episode of lo w visibility might be a ttributed to a single source, such as a large wildfire or prescribed fire, which would resu lt in the all hour, all day approach targeting only one large emission episode that occurr ed for only one or a few time periods.

c. Insights to be drawn by comparing the PM components for hours included among the 10% highest for a 1-hour daily maximu m form with the hours included am ong the 2% highest for an all daylight hours form, for the variou s indicators considered (Appendix C)?

See comments above. Thes e two approaches appear to be simila r; however, it would be helpful to quantify the similarities as opposed to a qualitative discussion. Maybe a scatter plot for the 14 sites of the average fractional contribution of a species as a function of the vari ous approaches and some way of showing which days are selected in the context of all other days would be useful—some way of gaining insight into the kinds of visibility ep isodes that get selected.

14. Key Uncertainties and Area s for Future Research and Da ta 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?

Under “Visibility Preference”. I rep eat my comments under 11a. It would be of interest to further expand the analysis, using existing da ta, to see if there is a visibility index that represents visibility conditions independent of the type of scene bei ng viewed, such that pref erence levels for all studies, when plotted against this index, would all yi eld the same response curve. If such an index could be identified, the current available studies could be used to assess visibility levels in any urban area and setting, using this index. The relationship of this index to dv or extinction will necessarily be nonlinear; however, this approach woul d allow representative extinction levels to be examined for a variety of urban areas and/or landscape/urbanscape features.

Under “Urban Visibility Conditions ”. There isn’t any discussion of the role that clouds or atmospheric conditions might play in peoples’ visibility prefer ences as a function of PM. Visibility conditions associated with sky colo r and clouds could very well be significant normalizing features, making many or most urban settings similar. Any new visibility effects

assessments should include a variet y of atmospheric conditions other than clear skies, as was used

in the current studies.

A- 37Some specific comments:

Page 4.5: “The 2005 Staff Paper noted that a standard set at any specific PM2.5 concentration would necessarily result in visual ranges that vary somewhat in urban areas across the country, reflecting the variability in the correlations betw een PM2.5 concentrations and light extinction.” More than just correlations – the slope of the line between PM 2.5 and visual range will also vary.

Page 4.13, line18: One could us e a more up to date f(RH) curve in conjunction with the IMPROVE algorithm and “improve ” the equation significantly.

Line 35: The “refinements” in th e IMPROVE algorithm refl ect more than just the aging of organic aerosols. Might want to discuss the change in Roc and size distribution shifts of both OC and inorganic carbon as a function of aging.

Page 4.17, line 17: “These combine to make early morning th e most likely time for peak urban visibility impacts.” Probably sun angle is as important as or more important than the atmospheric

variables mentioned. Include discussion of sun an gle effects – forward/back scatter, illuminated and shadowed scenes, etc.

Page 4.18, 1 st paragraph: See comments under 11a. Here is where you could ha ve a discussion of scene-specific indices that characterize observers’ response functions. For example, such variables as modulation depth, JNCs, average contrast, and so forth. Then relate these variables to the modulation transfer function of the atmosphere an d, ultimately, extinction. This would show how

scene characteristics and illumina tion in conjunction w ith extinction contribute to preference.

Line 11: Atmospheric mixing ch aracteristics were also held constant. None of the studies addressed non-uniform haze, such as layered hazes.

Page 4.24, lines 10–12: It would be helpful to, at times, point out when real data is being used

versus modeled information.

Page 4.35, line 34: “...we believe...” There is no room for using words like belief in a scientific

document. A belief is not an adequate justification for any decisi on point! It is also bothersome to

read “...sufficiently similar results...” – especially in the context of “belief” to just ify an analysis approach. Quantify the concept!

Page 4.36: The general discussi on around the figures in 4C ar e difficult to follow primarily because the captions and axes in the figures are so small they cannot be easily read. Figures need to be improved and a clear and complete descript ion of these figures would be helpful before the discussion points.

Page 4.37: “While perception of change in visibility can occur in less than a minute, meaningful changes to path averaged light extinction occur mo re slowly and can be we ll represented by hourly averaging.” This may very well be true, but I think it is

A- 38conjecture.. I haven’t seen any ev idence in the literature for making th is statement, certainly not in the absolute way that it is stated. I am not sure this argument is adequate justification for a 1-hr averaging time.

Page 4.39, lines 18-28: What are the emission control strategy impli cations of this discussion? If not here, I would think a discussion of what sources might be preferentially controlled as a function of regulation form and type would be appropriate.

Page 4.40: “ We noticed a close correspondence...” Here, and throughout the document, there are a number of qualitative statements such as this . What is a close correspondence? Make it quantitative. A close correspondenc e means different thin gs to different peop le. Some would say

a correlation of 0.5 constitutes a close correspondence, while others might make this judgment only if the correlation was 0.9 or greater.

Page 4.41, lines 1-8: Might do a scatter plot of mass fraction from differen t approaches using the 14 sites as individual data points.

Page 4.51: “Additionally, prior to the next PM NAAQS review and as part of the planning for additional preference and valuation survey studies, a literature revi ew of recent social science literature could usefully be conducted to asse ss the state of knowledge of view exposure mechanisms, and the psychologica l and behavioral effects associ ated with viewed stimuli.” Good

recommendation! Needs to be done.

A- 39Mr. Tom Moore

Thanks to the author team for a great effort on the 2 nd draft of the Policy Assessment - much more

readable than the 1 st draft.

Specific Comments on Section 4:

Page 4-1, lines 11-16: The disc ussion of the considerations be hind “...staff conclusions on a range of alternative secondary standards appropriate...” should note that federal, state, and local air quality management agencies have been analyzing cumulative and individual pollutants’ impacts on visibility under the National Environmental Polic y Act, the New Source Review, Prevention of Significant Deterioration, Best Available Retrof it Technology, and Regional Haze Rule programs over the past 25 years. While the Administrator’s d ecision must draw upon th e factors listed in this paragraph, air quality manageme nt to improve visibility by controlling PM to reduce light extinction impacts would utilize well-developed me thodologies and control methods – perhaps not as difficult a “...public welfare policy judg ment..” as the current text would suggest.

Page 4-3, lines 1-2: Data av ailable in 1997, especially in ur ban areas, were not based on an existing primary or secondary PM 2.5 NAAQS. These data were very limited for the purposes of forecasting improvement “... to some degree...” in ur ban PM-caused visibility impairment. The 1997 PM2.5 primary NAAQS le d to the first effort, funded by EPA and implemented by state and local air agencies to more completely and r outinely characterize urba n PM2.5 composition across the nation. The expansion of the IMPROVE networ k in 2000-01 to support the implementation of the Regional Haze Rule led to a much fuller unde rstanding of Class I area impacts from urban sources and regions. The forecas ts of PM-caused urban visibility improvements from the 24-hour average PM2.5 secondary NAAQS proposed at 50 μg /m3 in 1996 were highl y speculative, and the 24-hour average secondary PM2.5 NAAQS of 65 μg/m3 adopted by EPA in 1997 was even less protective of PM-caused visibility impairment.

Page 4-3, lines 14-17: This se ntence is not necessarily true, as the requirements for air quality planning and attainment of the NAAQS are more timely and in st atute, while the Regional Haze program is required under a less stringent administ rative rule with a long time horizon. If and when secondary PM NAAQS are prom ulgated to separately protec t visibility in [monitored] urban/small town/rural areas, testing of the hypothe sis that the Regional Ha ze program adopted in rule under §169A and 169B of th e CAA “...can be more responsive to the factors contributing to regional differences in visibility...” can be done. PM-c aused visibility impairment in urban/small

town/rural areas is both an effect and a source.

40 Page 4-3, lines 19-24: While in 1997, “...a regional haze program , in conjunction with secondary

standards set identical to the suite of PM2.5 primary standard s, would provide appropriate protection for visibility in non-Class I areas.” c onceptually would provide protection from PM welfare impacts on visibility in the ambient environment, the EPA had little or no urban PM2.5 mass or composition data at the time to make th is assertion. The Regional Haze analyses and planning effort since that time suggest that an administrative rule with a 60+-year implementation

time frame will not lead to the more timely and necessary redu ctions in PM causing welfare visibility impacts in urban/small town/rural ar eas. Instead the Region al Haze program guidance

A-from EPA addresses primarily stationary point so urces, and states have accounted for the national mobile source control programs adopted by EPA primarily to attain the various primary NAAQS. The lesson learned from Regional Haze is that if impacts from PM on “non -Class I area” visibility are occurring as EPA’s 2010 PM ISA and UFVA an alyses suggest, then a secondary PM NAAQS to protect visibility is now nece ssary - different in form, aver aging time, level, and perhaps indicator from the primary PM NAAQS, along with the requisite analyses to develop emission control plans to complement the Regional Haze program.

Page 4-4, line 2: Replace “local” with “sub-regional”.

Page 4-4, line 3: Replace “City of Denver” with “Colorado Front Range urban areas from Fort Collins to Colorado Springs”.

Page 4-4, lines 5-8: While it is reasonable to asse rt now that visibility would improve in a “...urban area near a mandatory Class I Federal ar ea ... by implementation of the current visibility regulations...” [which include ongoing implementati on of stationary point source controls under the NSR, PSD, BART and Regional Haze programs], the urban area-specific nature and causes of PM-caused visibility impairment may not be addr essed appropriately and proportionally since we have never had a specifically-v isibility-protective PM NAAQS. This sentence also does not belong in the 1997 section, it is an analysis of the current situation.

Page 4-4, line 12: After “...impair ment”, add “known at that time”.

Page 4-4, lines 17-18: After “...EPA”, insert “recommended separate and more stringent, but promulgated” before “revised”. Re move “the” and “by making them”.

Page 4-4, line 29: Remove “D enver” – should instead be ment ioned in or around line 3 above.

Page 4-10, diagram: This diagram is a helpful depiction of the overall process followed by EPA in preparing the secondary welfare PM NA AQS analysis for vi sibility impacts.

Page 4-18, line 3: After “...extinction”, insert “b y PM” before “...is an...”. In the same sentence, after ...that”, remove “by itself does not directly tran slate into a” and insert “is a direct measure of the public welfare effect, but setting a secondary welfare PM NAAQS for li ght extinction is not a

sufficient measure of the...”.

Page 4-18, line 3: After “Li ght extinction”, insert “by PM”, then after “...atmospheric property that...”, delete “by itself does not directly translat e into a” and replace with “ is a direct measure of the” before “public welfare eff ect”. Insert a following sentence: “Promulgation of a secondary welfare PM NAAQS for light extin ction gives definition to the dimensions of urban visibility impairment effects by defining the measurement meth od(s) to characterize th e indicator, as well as the form, level, and averaging time.”

Page 4-18, line 4: After “...mean ingful”, insert “and the public policy effect evaluated by using”

before “in the context...”. Delete “in” before “the context”.

A- 41Page 4-18: line 6: After “The perception”, inse rt “of some representative group of individuals”

before “of the...”.

Page 4-18, end of line 13: Insert a new sentence , something like: “Further, the “scenic-ness” of a given scene is a setting- and context-based valu e judgment by an indivi dual. Those individual judgments should be part of a large a nd representative sample size distribution.

Page 4-21: line 12: After “...which is by far the best of the four studies”, insert “due to the large sample size” and modify the reminder of the se ntence to make a list including “least noisy” and “most representative”.

Page 4-29, line 13: After “...air quality conditi ons.”, continue the senten ce by adding “by mass, not species contribution to light extinction”. Futu re change in species’ magnitudes and/or source mix are not likely to be proportional.

Page 4-31, line 23: Delete “...Chemical Speciation Network (CSN)...” – it does not produce hourly average mass concentrations. It would be more accurate to note the sampling schedule and averaging time for CSN in a separate sentence.

Page 4-38, line 34: The assertion that averaging for 3 years is sufficient “...to provide stability...” is not supported, particularly as NAAQS are change d to more stringent levels. The 3-average is much less than generally accepted climatological averaging periods of 7 to 10 years, nor is the 3- averaging period source-independent. If the long-tim e formulation of the compliance time period for the various NAAQS over a 3-ye ar period is due to the NAAQS review and air quality planning requirement in the Clean Air Act, it should be stated as such – espe cially in the Policy Assessment. The effect of climate change and expected futu re variations in climat e will also reduce the “stability” of a 3-year average.

Page 4-39, line 10: After the sentence ending in “... values.”, insert a new sentence: “Such studies

were done in the absence of an EPA secondary PM NAAQS set to pr otect the public from welfare impacts of impaired urban visibility.”

Page 4-47, table starting line 4: Modify the table to remove “Mm-1” from every data cell. Does the coloring apply to more values than are currently “colored in”?

Page 4-49, line 2: After the se ntence ending “...Administrator.”, in sert a clause to start the next sentence “As there is no explicit protection for this impact at present,” before “we recognize...”.

Page 4-50, after line 12: Add a “(7)” describing what would be expected to be learned and the associated EPA activities to support the gatheri ng and analysis of new knowledge through the promulgation, initial implementation, and the first r ound of “nonattainment plans” to implement this secondary welfare PM NAAQS for visibility over the 5 years from October 2011 through

2016.

42 Page 4-52: Noted there are only 17 references for Section 4 of the Policy Assessment, while

Section 5 where no action is recommended has 41 – ar e there more references to add for Section 4?

A-Dr. Robert Phalen

I. General Comments on P.A. draft 2

a. As expected,the Staff has prepared a lucid and elegant seco nd draft of the P.A.

b. I am struck by the limitations placed on th e Staff in framing the P. A., and concerned that readers may believe that several potentially adverse secondary health consequences have been evaluated along with the direct health effects, when they have not. Thus , I recommend adding an explicit informative statem ent to the P.A., or the cover letter, such as: "Due to statute, case-law, and policy decisions , it should be noted that this Policy Assessment addresses only the direct adverse health effect s of PM mass fractions. Thus, secondary public health effects, such as:(1)the potential health effects of compliance actions on jobs, and the availability of goods and services ;(2)the potential health effects at locations that have positive (rather than negative)health asso ciations with PM mass; and (3) the potential health effects of changes in PM mass on other air contaminants (e .g. UFP counts, and airb orne acidity), are not considered. In short, the range of potential uni ntended secondary adverse consequences have not

been evaluated in this document. Thus the re commendations herein may, or may not, improve overall public health."

Such a statement would both help readers to unde rstand the current state of evolution of the NAAQS-setting process, and help guide the way for its future improvement. It also states, for those who may not appreciate what the P.A does, and does not, achieve.

c. On pg. 3-14, lines 9 - 13: Strike the sentence,"It is possibl e that such differences in particle composition could affect particle toxicity,...". Numerous studies have shown that particle composition definitely, not "possibl y" affects particle toxicity.

d. On pg. 3-44, line 26: For the sake of transparency add, "from the direct adverse effects of individual criteria air pollutants" after "public health".

II. Charge Question no. 5

a. The approach is o.k. b. the application of the approach is o.k.

A- 43Dr. Kent Pinkerton

The Second External Review Draf t of the Policy Assessm ent for the Review of the Particulate Matter National Ambient Air Quality Standards is a well-written docum ent that brings to focus the

most relevant scientific evidence and technical information in determin ing whether and how to revise the PM standard for the country. The ch apters of the Policy Assessment document are well organized to address primary st andards for fine particles (PM 2.5 ) and thoracic coarse particles (PM 10-2.5 ), as well as secondary standa rds for PM-related visibility impairment and non-visibility welfare effects. This second draft of the polic y assessment is greatly improved over the first

version. The staff is to be co mmended for their efforts to addre ss each of the concerns of CASAC in this second version of the policy assessment.

Charge Question #4: Key uncertainties and areas for future research and data collection. What are

the Panel’s views on the areas for future research and data collec tion outlined in this section on relative priorities for research in these areas an d on any areas that ought to be identified?

This section of the document provides a list of area s for future health-related research, along with some of the key uncertainties, mo del development and data collection needs, as well as research and data collection efforts that should be pursued in the future. The list is excellent, but dwells predominantly on those areas to provide further epidemiological evidence of PM-related health effects. Although appropriate and highly desirable, future studies should also include toxicological studies to provide defi ning and confirming evidence for the biological plausibility of PM-related

health effects. These studies sh ould be based on the same premise as posed for the future need for epidemiological evidence in terms of components and sources of PM, the influence of particle size as well as co-pollutant interactions with a particular emphasis on ozone.

This section further recommends new research and analyses for exposure related factors which include intra-city and inter-city differences relate d to various PM componen ts and size fractions, all excellent points. However, future consideratio n should also be given to particle transport and aging as a potentially important factor to alter part icle effects and toxicity as well. Consideration

for new research should also enco mpass the interaction of climate conditions (i.e. climate change and temperature) on PM incidence, concentrati ons and distribution, includi ng factors leading to desertification (dust formation), increased wild fires and secondary particle formation. An important research consideration is to further ev aluate how ultrafine particles contribute to the

PM 2.5 particle size fraction, both te mporally and spatially as thes e particles undergo accumulation and/or aggregation. The recomme nded future monitoring measuremen ts of the section are briefly stated, but are timely and relevant. Model de velopment to improve models for estimating PM 2.5 mass and composition are clearly import ant as a future research priority.

A- 44Mr. Rich Poirot

Pre-Meeting Review Comments on 2n d Draft PM Policy Assessment

Generally, I thought the second draft PAD was a substantial impr ovement on the first draft – logically reasoned, clearly and concisely presen ted, and responsive to previous CASAC review comments. My pre-meeting comm ents are primarily focused on Chapter 4 (secondary visibility standards) and also respond to charge questio n 9 on the proposed rang e of levels for a PM 10 primary standard.

“Controlling” Annual PM 2.5 vs. 24-hour Peaks I also wanted to confess ignorance and request cl arification on the rationale for the proposed need to “pair” the annual and 24-hour PM 2.5 standards such that the annual standard would remain the “controlling” standard. I don’t und erstand why this is logical or desirable, as it would seem

inconsistent with the observati ons of separate kinds of effect s resulting from acute and chronic exposures to PM 2.5 pollution. It also seems like this has become, is becoming or soon will become a less desirable air quality manage ment approach as progress is made (and continues with CAIR) on reducing the large regional source influences most important for high annual concentrations over large areas. The scatter plot Figure 2-10 (p age 2-75) and the Figure 2-9 box/whiskers on the preceding page do seem to indicate th at a majority of US sites have 98 th percentile 24-hour

concentrations which are about 2.5 times their annua l means, but that there are a number of sites particularly in the Northwest that have ratios of 3.5 to 1 or higher. Taking a closer look at data from that region, I think many of these sites are in relatively deep mountain valley locations, with strong winter seasonal early mo rning peaks under stagnation/ inve rsion conditions. Much of the “peakiness” here is due to wood-smoke, other h eating fuel burning and gasoline motor vehicle and diesel exhaust, which not only reach much higher th an average concentrations on bad days but see even more extreme short-term hourly morning pe aks during rush hour. Are these sources, their associated carbonaceous aerosols, and extreme temporal exposure re gimes so benign that control

efforts should focus instead on the summer ammonium sulfate th at tends to dominate chronic exposures in areas which exceed annual stan dards but not the curre nt 24-hour standard?

I also think there could be an important conf lict here with health messaging and public

communication. States and municipalities issue daily air qu ality forecasts and during pollution events issue air quality alerts, advi sories, action days, etc. based on the “Air Quality Index” which is directly linked to the levels of the NAAQS (and for which EPA still hasn ’t provided official guidance relative to the current 24-hour PM 2.5 NAAQS of 35). At a mini mum this guidance needs to be updated, and it and the short term standard s hould reflect short-term concentrations at which effects may be expected for sens itive groups – regardless of whethe r a controlling annual standard is useful for other purposes.

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 PM10 standard levels, in conjunction with a 98th percentile form, including the weight placed on different studies?

45 Given the limitations in currently available coarse particle epidemiological studies, the absence of statistically significant results in many of the mortality and morbidity studies, and the stated intent

A-to focus more on urban than rural coarse particles by retaining a PM 10 indicator (tricky, but I think I like it for now): the approach taken to id entify a range of levels for a revised PM 10 standard, using

a 98 th percentile form, generally appears to be reasonable.

b. Staff’s conclusion that the evidence most strongly supports standard levels around 85

μ g/m3?

Part of the stated justification for the upper en d of the range was the ab sence of statistically significant positive associations between PM 10-2.5 and mortality in single-city studies with 98 th
percentile PM 10 concentrations below this level. While there is some logic to use this to help determine an upper bound level, it should also be recognized that th ere were a number of mortality and morbidity studies showing relatively consiste nt positive, but non-significant results at lower levels, and that there are a number of factors which will tend to push epi results for coarse particles toward the null hypothesis. PM 10-2.5 is not measured very precisely, especially when compared to

PM 2.5. The spatial representativeness of PM 10-2.5 measurements is also very limited, relative to the density of measurements and difficult to asso ciate with large populations. There are also

substantial differences between indoor and outdoor concentrations of PM 10-2.5 , as outdoor concentrations don’t penetrate indoors very e fficiently and as there are also often large, independent indoor sources of coarse particles, further complicating accurate human exposure

assessments. All of the above w ill tend to push results toward null and/or make them difficult to confirm with high statistical confiden ce in areas with lower ambient air PM 10-2.5 concentrations. Thus the upper bound of 85 μg/m 3 may not provide much of a margin of safety.

46 Another part of the justification for the upper end of the range was the stated intent of not weakening the existing PM 10 standard of 150 μg/m 3 with an “expected exceedance” form, while transitioning to a more stable (and less sample-size dependent) 98 th percentile form. I think there is at least a wee bit of logic to this (don’t weaken the status quo) argument , as there is no strong evidence for loosening the current standard. Ho wever, I don’t agree that this logic necessarily

leads to a 98 th percentile form at 85 μg/m 3 . This judgment seems to be primarily supported by the Figure 3-7 (page 3-39) scatter plot comparing expected exceedance design values with 98 th
percentile design values for the sa me recent 3-year periods (the la rge solid symbols, incidentally, make it hard to really see the data here). The fa irly broad scatter indicates that there is a lot of variability in the relationship and that there is no singl e “equivalence point” for comparing the two metrics; at the 150 μg/m 3 level of the current standard, the 98 th percentile counterparts range from about 30 to 130 μg/m 3 . A regression line (which doesn’t appear to fit the data very well) intersects the 150 μg/m 3 expected exceedences level at a 98 th percentile level of about 85 μg/m 3 and so this is taken as the point of “equivalence” and used to support the selection of 85 μg/m 3 as the upper

bound for a 98 th percentile level. It looks to me like there are many more points below this line than above it – that would be afforded less, an d in some cases much le ss protection that they

receive under the current standard . From Table 3A-1 in Appendix 3A, it can be noted that the population protected by current 150 μg/m 3 expected exceedance PM 10 standard is 32,169,000, and that this would be reduced by about 30% to a pr otected population of 22,73 6,000 if an “equivalent”

98 th percentile level of 85 μg/m 3 were selected. The 98 th percentile form in Ta ble 3A-1 that affords protection to a population that comes closest to th at afforded by the current standard is 75 μg/m 3

and I think new 98 th percentile standards at levels above 75 μg/m 3 should be recognized as weakening the current standard. So again, I think the upper bound is not especially well justified.

A-c. The alternative approach to considering the ev idence that could support standard levels as

low as 65 μ g/m3?

I think the rationale for this lower bound is reas onable, and might be further strengthened by noting that there may be good reasons fo r absence of significant results, an d that the relative consistency among many studies finding positive but non-significant results is supportive, and by noting that a standard at this level would reduce, but not eliminate the number of sites for which a 98 th percentile

form would weaken the current standard. 11. Current Approach (section 4.1.3) : a. What are the Panel’s views regarding our ap proach for translating technical evidence and assessment results into the basis for assessing current fine particle st andards and considering alternative standards to provide protection against PM-related visibility impairment?

The approach for translating an d presenting the technical evidence and assessment results is logically conceived and clearly presented. The va rious tables and graphics in Chapter 4 and its associated appendices are very helpful in communi cating the inherently co mplex information that unavoidably results from the evalua tion of so many optional combina tions of indicators, averaging times, levels and forms.

b. Has staff appropriately app lied this approach in reviewing the adequacy of the current standard (section 4.2) and potential alternative standards (section 4.3)?

The detailed estimates of hourly PM light extinction under curren t conditions and for “what if” scenarios of just meeting current standards clearly indicate that these current standards do not protect against levels of visual air quality which ha ve been judged to be unacceptable in all of the available urban visibility preference studies.

Given the limitation that there are not currently available methods for directly measuring the preferred indicator of PM light extincti on, the alternative indicators of hourly PM 2.5 mass or estimated hourly PM 2.5 light extinction (composition and humidity-adjusted hourly PM 2.5 mass) are logical choices for a revised secondary standard. Each indicator has advantages and disadvantages compared to the other. In my opini on, the pragmatic advantages that a PM 2.5 mass indicator might

have over the estimated PM 2.5 extinction indicator are understated. I also think that there may be reasonable approaches to further simplify the estimated extinction approach that would not significantly compromise its benef its as an effective regulatory me tric. See answer to 12b below.

12. Nature of the Indicator (sect ion 4.3. 1): What are the Panel’s views on the following:

a. Staff’s consideration of th e three indicators identified in this section and our conclusions on the appropriateness of these in dicators for consideration in this review?

47 Generally, the 3 indicators evaluated are logical options which essentially span a range from directly measured PM extinction (theoretically ideal but currently impractical) to directly measured (dried) PM 2.5 mass (easy to implement but not directly representative of visibility effects). The “simplified” estimated PM 2.5 extinction option is a sort of compromise between the two measurement extremes, although I think that other less complex intermediate options could also be

considered.

A-b. The development and evaluation of a new approach that is based on using speciated PM2.5 mass and relative humidity to calculat e PM2.5 light extinction by means of the IMPROVE algorithm?

While this is an approach that could be implemented using existing measurements, I think there may be simpler alternatives that would produce similar results and which should be evaluated. Reflecting back on the comparison of hourly PM 2.5 mass vs. hourly PM lig ht extinction in Table D1 of the UFVA document, it can be noted that the average correlation (R 2 ) is 0.70 across all 14 urban areas (excluding St. Louis w ith its questionable data) – which I’ ll first argue is not really all that bad, and is way tighter than the relationships between any other primary or secondary pollutant NAAQS indicator and any associat ed effect. A numbe r of adjustments could improve upon the quality of an hourly PM 2.5 mass indicator, but each adjustment adds complexity, and the currently proposed adjustments are very complex for a regula tory metric, and would require combining data

from continuous PM 2.5 , filter FRM PM 2.5 , speciation PM 2.5 (3 filters) and relative humidity measurements (and could only be applied at sites wh ere all of the above were measured). In many states, the continuous data are adjusted to be FRM-like prior to submittal to AQS, but that is typically conducted after the end of each calendar quarter. While th e need to use FRM filter data might be eliminated by use of continuous FEM instruments, the proposed use of the (concurrent month) speciation data has the added disadvantage of delaying the availability of the estimated

extinction estimate until several m onths after real time. I questi on whether the added complexity and time delay is justif iable compared to simple r adjustment approaches.

One simpler approach would be to develop (by regression of hourly PM 2.5 mass and RH vs. the

estimated PM 2.5 light extinction) a generic “aerosol f(RH)” function. This could be done using historical data on a site-specific or regional basi s, and calculated on a se asonal, or even monthly basis if need be. The resulting equations c ould be used to convert continuous FEM PM 2.5 mass and

RH data to estimated PM 2.5 extinction in near-real time. A slightly more co mplex variation on this would be to use the historical speciation data – ag ain on a seasonal basis if warranted, on either a site-specific or regional basis, to develop quar terly composition estimates. These would include seasonal estimates of the hygroscopic mass fractio ns which could be multiplied by the measured mass and enhanced by IMPROVE f(RH) functions. A third vari ation would be to discard the current RH data and instead use historical hourly RH averages – again on a quarterly or monthly basis and expressed as site-specific or regional averages. Following some what the logic of the regional haze rule, the use of climatologically derived RH and f(RH) functions might reproduce actual hourly PM light extinction less perfectly, but might still be a better regulatory metric. Arguably it would be more effective to reduce con centrations of hygroscopic species on months and hours of day when the combin ations of pollutant concentrat ion and RH have tended (and will tend) to be highest, rather than the specific month and hour of day when an extreme event

occurred.

48 I’m confident that any of the above approaches would represent a substantial improvement over

the use of fine mass alone as an estimator of visibility effects, but the calculations would be simpler and could be done one time, in advance, so that the resultant es timated light extinction could be reported in near-real time, employed as a public communication tool, compared to realtime extinction measurements as they evolve (o r as ASOS scattering data become available at

A-higher resolution, which is happening now), etc. If regional average equations worked reasonably well, an advantage would be to allow the extinction estimates to be made at all (> 550) continuous

PM 2.5 sites – not just the (<200) sites with speciati on data (and far fewer, I suspect where FRM and CSN – running every 3 rd day are collocated with continuous PM 2.5

.

This reminds me to suggest that it could be useful to see a table or map indicating the numbers and locations of Continuous, FRM and Speciation PM 2.5 sites and indications of where all the above (with the filters running every 3 rd day) are collocated (maybe also including continuous PM 10 if there are many of those ou t there collocated with PM 2.5

.

c. The assessment approach and results comparing the PM compon ents that contribute to the hours selected in the top percentiles for PM2.5 mass and PM10 light extinction?

The approach and results compar ing PM components that contri bute to the highest extinction percentiles are logically contrived and clearly pres ented. As a practical matter, I don’t think its likely that states or mu nicipalities will develop va stly different source control strategies based on relatively subtle differences in the regulatory metrics. For example, it’s unlikely that a lot of effort would be “wasted” on visibility-inefficient attempts to control fine soil if a PM 2.5 mass indicator was selected. Nor are there practical options for su b-daily reductions in hygroscopic sulfates and/or nitrates that might be directed toward “the wrong hours” if a mass indicator, or a percentile based on all daylight hours was employed.

13. Alternative Levels and Form s (section 4.3.3): What are Pa nel views on the following: a. The performance assessment whic h focused on the Candidate Pr otection Levels of 64, 112, 191 Mm-1 for PM2.5 light extinction and specia ted PM2.5 mass-calculated light extinction, and alternative levels of 10, 20, and 30 μ g/m3 for PM2.5 mass concentration?

These ranges of levels for PM 2.5 light extinction, estimated extinction and fine mass indicators are logically derived, and the performance assess ments for exceeding/ attaining these various candidate protection levels are clearly presented. Various combinations of CPLs and percentiles could be considered which would affect the sp atial extent, frequency and severity of nonattainment of a visibility-related secondary st andard. Because visib ility is so sensitive to impairment by concentrations of fine particles and associated water (i.e. particles as they exist in the ambient air), it should be expected that levels of PM light extinction considered “acceptable” to human observers would be exceeded relatively fre quently in many areas and by relatively high margins in some areas. Attaining specific threshold conditions may be especially difficult and require very long-term strategies in areas subject to frequent high humidity, stagnation or inversion conditions, or persistent regional transport in fluences. Consequently, guidance provided by EPA on the expected pace, or rate of progress towa rd attaining the secondary standard in the implementation phase is likely to become an im portant component of the standard’s ultimate performance, which would modify the “stringency” of any specific combination of level and form.

49 As indicated previously, there may be some advantages to using a PM 2.5 mass indicator (at least on

an interim basis until more direct PM light extinction methods can be developed a nd evaluated). Compared to an extinction indi cator, a mass indicator would tend to de-emphasize somewhat the importance of hygroscopic sulfate and nitrate scattering aerosols, which tend to impair visibility

A-(and as Ted points out exert a cooling effect on cl imate) over relatively large areas, and emphasize the relative importance of more locally produced carbonaceous ae rosols which might have both visibility and climate benefits. A mass indicator w ould also somewhat redu ce the differences in stringency between the East and West, and at a gi ven level might be somewh at more feasible to attain in the more humid (and po ssibly less scenic) East while affording greater protection in the dryer (and more scenic) West. Th is option might be wort h considering if EPA is not able to utilize a “progress-based” approach in implementing a secondary standard.

b. Use of three-year averaged 90t h and 95th percentiles in conj unction with a 1-hour daily maximum form and use of three-ye ar averaged 98th percentile in conjunction with the all daylight hours form?

The illustrations provided indicat e that the choice between a 90 th or 95 th percentile with a 1-hour daily maximum form or a higher 98 th percentile based on all daylight hours does not re ally seem to have much effect on the species implicated or the kinds of control strategies that would be most effective. I don’t really think the different “sus ceptible population” expos ure arguments make are especially compelling either, and believe a choi ce between these two func tionally similar options could be made for other reasons. For example, the single worst daylig ht hour is a simpler calculation, although it would also be more susceptible to measurem ent noise that effects some of

the continuous PM 2.5 mass measurement instruments.

c. Insights to be drawn by comparing the PM components for hours included among the 10% highest for a 1-hour daily maxi mum form with the hours includ ed among the 2% highest for an all daylight hours form, for the vari ous indicators considered (Appendix C)?

See answer to B above. Note that I’ve also sugge sted alternative approaches for estimating hourly extinction that would permit simpler and more tim ely hourly extinction es timates. Occasionally these simpler estimates could be distorted – for ex ample if a moderate forest fire or fine dust impact was occurring during a peri od of high humidity and historically projected high sulfate concentration. Use of the single worst hour per day would simplify the task of identifying and correcting such occasional outliers.

14. Key Uncertainties and Area s for Future Research and Da ta Collection (section 4.5):

What are the Panel’s views on the areas for fu ture research and data co llection outlined in this section, on relative priorities for researc h in these areas, and on any other areas that ought to be identified?

Generally, I think this section is very good and id entifies several important research needs for the near future. Often however, the best laid plans...never get funded. In this case I think expanded visibility preference studies and establishing a small pilot urban visib ility monitoring network (which includes some support fo r instrument development and evaluation) would be extremely

valuable.

Post-meeting Review Comments on Second Draft PM PAD

PM 10 Indicator for Coarse Particles

A- 50This didn’t get discussed at the 7/25-26/10 meetin g, but I wanted to suggest, belatedly, that in revising the PM 10 standard, EPA should consider specifying the low volume PM 10 method as the sole federal reference method (FRM). Curre ntly, both low volum e and high volume PM 10 methods are designated as FRMs, although they have consistently been de monstrated to produce different results in field and laboratory comparisons – with the high volume method typically showing lower concentrations. For an example showing differences of 25% to 35% in an area with very high

PM 10 and coarse mass concentrations , see: Ono, D.M., E. Hardebec k, J. Parker, and B.G. Cox (2000) Systematic Biases in Measured PM 10 Values with U.S. Envir onmental Protection AgencyApproved Samplers at Owens Lake, California, J. Air & Waste Manage. Assoc. 50 :1144-1156. For an example showing differ ences of about 20% from an area with relatively low PM 10 and coarse mass, see the example below from Burlington, VT.

Wind tunnel

tests have generally

demonstrated similar results and show the hi volume PM 10 samplers can have cut points significantly less 10 microns, especially under hi gh wind conditions. The recently established FRM

for PM 10-2.5 (by difference) specifies low volume PM 10 (and PM 2.5 ) samplers. If the PM 10 standard is revised with the intention of providing better pr otection against coarse pa rticle effects, it would be a timely opportunity limit the FRM to low- volume samplers. This would afford better protection, assure more consistent data across spac e and time, increase the collection of and assure better consistency with PM 10-2.5 measurements, and produce samples on Teflon (rather than quartz)

filters more conducive to speciation analysis - for PM 10 and for PM 10-2.5 (by difference).

A- 51Dr. Ted Russell

Overall, this draft of the PM PAD is much improved and lays the foundation for informing the revision of the PM standards, providing both a sy nopsis of the prior documents and the procedure used to develop suggestions for th e revisions. Their conclusions are generally supported by the information in the prior documents and have been responsive to CASAC’s prior comments as well. My areas of disagreement/concern are ra ther specific as discussed below.

My major concern has to do with consideration fo r the potential of the tightening of the standards to exacerbate climate warming if the appropriate fraction of PM is not pr eferentially controlled.

This concern has to do most with the level at which the secondary standard. Decreasing light scattering aerosols will improve vi sibility, but increase radiative forc ing. It would be better to focus on reducing light absorbin g aerosols to both improve visi bility and potentially reduce warming (there is uncertainty about the latter). There is also a growing body of evidence that EC is more strongly associated with various health impacts, so in the implementation, focusing on EC

controls would be a win-win.

Chapter 3

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 PM10 remains an appropriate indicator in

this review?: As noted previously, I view the use of PM 10 as a reasonable choice as laid out by

the PAD.

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 st aff’s conclusion that revising the form to a 98th percentile form would be appropriate for a 24-hour PM10 standard meant to protect against exposures to thoracic coarse particles? Using a multiyear average of a percentile (e.g., 98 th in this case) is reasonable and consistent with other pollutants. I may differ with othe rs in that I prefer a multiyear average of the 98 th %ile as opposed to the 98 th %ile of a multiyear distribution, both for consistency with other pollutant standards (par ticularly for PM2.5) and for stability for planning

purposes.

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 PM10 standard levels, in conjunction with a 98th percentile form, in cluding the weight placed on different

studies?

b. Staff’s conclusion that the evidence most strongly supports standard levels around 85

μ g/m3? c. The alternative approach to considering the ev idence that could suppor t standard levels as

low as 65 μ g/m3?

52 The approach used by staff in determining an appropr iate level is consistent with the approach used for other pollutants and PM 2.5, and is based on the relevant health studies. If the 24-hr PM2.5 standard is tightened, however, this would argue for tightening of the 24-hr PM10 standard beyond the “around 85” (or below 65 if one is persuaded th at the standard should be effectively tightened) currently proposed to maintain the appropriate level of PM 10-2.5 allowed. (That is, the approach

A-might be posed as taking the 24 hr PM2.5 and adding 50 (or 30, if y ou want to go with the tighter level). Their reasoning for considering a level as low as 65 is viable, and they note that while

studies tended to have a decrease in statistically significant positiv e results at the lower levels, a bulk of the studies (but not all) still found positive associations. A nother reason to explore levels

below 85 is that some ar eas that meet an 85 98 th %ile can have levels above the 150 current standard, so this would effec tively loosen the standard.

Chapter 4.

12. Nature of the Indicator (sect ion 4.3. 1): What are the Panel’s views on the following:

a. Staff’s consideration of th e three indicators identified in this section and our conclusions on the appropriateness of these in dicators for consideration in this review? b. The development and evaluation of a new approach that is based on using speciated PM2.5 mass and relative humidity to calculat e PM2.5 light extinction by means of the IMPROVE algorithm? c. The assessment approach and results comparing the PM compon ents that contribute to the hours selected in the top percentiles for PM2.5 mass and PM10 light extinction?

Staff has laid out three potential indicators:

1. PM2.5 mass

2. Directly measured PM2.5 light extinction

3. Mass-calculated light extinction

First, if the secondary effect of interest is PM impacts on visibility, the indicator should include all components of PM that impact visibility unless re asoned otherwise. If we are going to directly measure light extinction, there are good reasons to limit the measur ements to just those particles less than PM2.5, driven largely by instrumental concerns, and supported by the more widespread impacts of fine PM versus coarse. If there ar e no instrumental limitations, the inclusion of PMcoarse on visibility should be include d or argued away w ith sound reasoning.

Each of the three has potential benefits, strengt hs and weaknesses. The PM2.5 mass indicator is the easiest to implement, but as shown both here and the UVFA it is not necessarily a good indicator of light extinction. What is not shown is that the relati onships developed for each city will also vary with time, adding further uncer tainty in using PM2.5 mass as an indicator for visibility degradation. The use of a mass indicator would not necessarily lead to selecting strategies that are selected to improve visibility the desired amount. Given the problems with this indicator, and the advantages of the other two, it should be ruled out. EPA does not provide a strong argument for its consideration. Further, a reasoned argument for not including PM coarse impacts should be given. Appendix 4 provides some evaluation of the use of a PM2.5 mass indicator, but does not addr ess concerns about the extent of control that would be needed to provide the desired light extinction.

Measuring light extinction directly has the benefit that you are truly measuring the quantity of concern. Technologies exist currently, and othe rs are being tested and further developed, to provide such information, and such information can augment our understanding of atmospheric

A- 53dynamics of the pollutants that impact health a nd visibility. On the other hand, those instruments do not provide information, directly, on the speci es leading to visibility degradation.

A PM2.5 Speciated Ma ss Calculated Light Extinction Indicator has the advantage of giving results that are likely close to the actual light extinc tion due to PM2.5 aerosol and relies on current measurements. On the other hand, the performanc e of the proposed approach has not been tested against direct measurements (currently, it has been model-to-model evaluation) and there have been a variety of simplifications added to simplify the procedure. A particular concern is that

concentrations of constituents of PM2.5 correlate w ith RH and aerosol water content (e.g., nitrate, and components of organic carbon). At present, there are only 24-hour average measurements of those constituents, so the likely pe riods where visibility is most degraded (where RH is high), will also have higher nitrate and OC that would not be captured in a daily (or longer) average composition. Further, both those constituents can be lost in some continuous and/or integrated measurements, adding furt her uncertainty to correctly calcula ting the actual visibility reduction at the time of the peak hourly extinction. Un til continuous measurements of the components of PM2.5 are employed, this issue is going to plague this approach. Thus, while much better than just using PM2.5 mass, this approach can lead to incorrect estimates of visibility degradation, and we currently do not know the extent of this problem. One issu e that arises with choice of this indicator as other than a bridging approach (to bridge between now and the time direct measurements can be used) is that if this were to be the indicator of choi ce, it might as well include PM-coarse. A driving reason to just consider just PM2.5 impacts on visibility is instrumental if this is not being used to bridge the gap.

As an aside, the limit of 90% RH has an added benefit beyond in strumental considerations, that being f(RH) in the extinction calculation goes up dramatically with RH beyond 90%, and at 90% it is about 4. Above 3.3, it biases the controls to sulfate and nitrate and aw ay from EC on a per mass basis (my climate-related concerns).

As a note, Appendix 4 provides criti cal support for the arguments laid out in support of the three indicators. However, it is a very difficult read, and it would help if they could iden tify the major questions being addressed and provide more succinc t responses with the appropriate foundation. At present, they provide too many graphs and tables without targeted summary graphs and tables. Also, on 4b-22, there is an error in that a slope of 1.07 does not indicate a bias of 7% unless the intercept is zero. (Otherwise, LA and NY would have negative biases, which are impossible.) Further, you should not change scales in the gr aphs when asking for people to use them for comparison. Having a series of stacked, colored bar charts is not a very good way to provide a quantitative understanding of relationships. Other fi gures/tables can be more informative in this

case.

13. Alternative Levels and Form s (section 4.3.3): What are Pa nel views on the following: a. The performance assessment whic h focused on the Candidate Pr otection Levels of 64, 112, 191 Mm-1 for PM2.5 light extinction and specia ted PM2.5 mass-calculated light extinction, and alternative levels of 10, 20, and 30 μ g/m3 for PM2.5 mass concentration?

54 b. Use of three-year averaged 90t h and 95th percentiles in conj unction with a 1-hour daily maximum form and use of three-ye ar averaged 98th percentile in conjunction with the all daylight hours form?

A-c. Insights to be drawn by comparing the PM components for hours included among the 10% highest for a 1-hour daily maxi mum form with the hours includ ed among the 2% highest for an all daylight hours form, for the vari ous indicators considered (Appendix C)?

a) I might recommend not including three significant digits in the CPLs if the final direction chosen goes that way. In terms of level, gi ven my climate-concerns , I would tend towards the less stringent end of the spectrum unless th ere are some safeguards as to going after the warming components first.

Q14: Uncertainties and Areas for Future Research and Data Collection : They have captured some of the key research areas and uncertainties (e .g., visibility preference studies). However, as part of the light extinction measurement/monito ring program, instrument development should be added. Another key uncertainty in terms of setti ng a visibility standard is assessing the impact of such a standard on potential climate forcing. Th is would be a somewhat involved study looking at potential regional climate changes from reducing specific components of PM , and it is recognized that this would be pushing present modeling approach es. A general concern of mine is that the potential adverse consequences of reducing comp onents of PM2.5 that would lead to warming have not been adequately wrappe d in to the considerations of the current review . Warming will have both health and welfare implications. While I agree that there are significant uncertainties in the climate responses, the likely outcomes should in fluence the choice of a standard (thus my tendency to a less tight secondary standard unles s something is done to focus on the warming components).

A- 55Dr. Frank Speizer

General Comment: Staff should be congratulated on an ex cellent job of incorporating suggestions from CASAC as we ll as streamlining th e PA. The addition of an Executive summary and the format used with in the text should go a long w ay as a model fo r the future. Most of my comments below (in bold) represen t minor “tweeking” of the text and might be

considered alternative semantics. There are a few pla ces where they might bear discussion of emphasis.

Charge to the Panel in Reviewing th e Second Draft PM Policy Assessment 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 standard s and on alternative standards for consideration?

Section 2.1.3 provides a logical and thorough discussion of th e approach to be applied. Although I previously questioned the usefulness of imbedding rhetorical questions in the text (see beginning of section 2.2) I am now convinced that this is helpful since it better focuses the discussion within each section and provi des a logical sequence to the discussion. I applaud the staff for expanding the discussion on evidence of life stages of risk as well as specific susceptibility risk factors and the introd uction of the use of combined empirical data

and risk assessment. With regard to the adequacy of the current stan dard, it may only be a matter of semantics, but I would suggest that the stat ement at the bottom of page 2.3 0 is not quite strong enough. The data presented more than adequately indicate that that the current standard is not as protective with a margin of safety and thus to indicate that th e data “call into question” the adequacy could have be more forc efully indicated to say that the current standard is simply not protective. That is what the rest of the paragraph says. Ditto the consideration of the

risk assessment data and as i ndicated bottom of page 2.43.

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)?

Yes

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 sus ceptible populations, including low income groups and minorities associated with spatial averaging allowed by the current annual

standard?

Good job in raising the logic of the issue and why it would be inappropriate to continue to rely on spatial averaging

A- 56b. In light of these analyses, what are the Panel’s views on staff’s c onclusion that the form of the annual standard should be revised to eliminate spatial averaging?

Top of page 2.54: Although this is an attempt to correct a defi ciency with regard to identifying the problem of highes t values apparently being recorded in area of lowest social class and potentially minority popu lation, it is not clear that the wording solves the problem.

"...measurements made at the mo nitoring site that represents "community-wide air quality" recording the highest PM2.5 concentration". I think a footnote is need to define "community-wide air quality" For example, wh at if there is a pocket of folks living in a highly impacted area but they are small en ough that they would not be considered "community-wide" These might be the only blacks living in a 1 mile radius in a 10 mile

radius town and thus would not be considered "community wide".

3. Alternative Level s (section 2.3.4): What are the Panel’s views on the following: a. The insights that can be gained into potentia l alternative standard levels by considering: i. Confidence bounds on concen tration-response relationships?

It would appear that Staff is not confiden t enough in the existi ng data to use the widening of confidence bounds as a measure of where uncertainty becomes important. However, in their evaluation of the data it seems clear that until one reaches about 12ug/m3 for the annual average the conf idence bounds are relatively tight and thus, I would have thought that Staff could have used this numb er as a "benchmark" with which to assess other

alternatives with more conf idence than expressed.

ii. Different statistical metrics that charac terize air quality distributions from multicity epidemiological studies?

The arguments given for using the comp osite monitor and the maximum monitor distributions are well presented. The arbitrary selection of 1 SD below the max mean is logical and consistent with the data in terms of keeping uncert ainty at a minimum, however, it is clear that much of the uncertainty below th at level relates to lack of data rather than increased variability. Thus, the more conservative alternativ e of assessing between 25-10 percentile should not be off the table.

b. Potential alternative annual standard levels based on composite monitor distributions

versus maximum mon itor distributions?

The differences between these tw o alternative seem to me mi nimal and more semantic in interpretation than actually change the concluding numbers.

c. Use of risk information in informing staff conclusions on alternative annual and 24- hour standard levels, including approaches used to a ssess overall confidence and potential bias in the risk estimates?

Provides additional confidence that the conclusi on are not wildly diffe rent comparing risks.

A- 57d. Staff’s conclusion that a lternative annual standard level s in the range of 13 to 11 μ g/m3 are most strongly supported by the availa ble evidence and risk-based information?

Agreed.

e. Staff’s approach of focusi ng on peak-to-mean ratios to info rm the level of a 24-hour standard that would provide supplemental pr otection to a generally controlling annual

standard?

This appears to be an important consideration an d is appropriate. However, it is not clear that it is adequately dealt with in discussion , since the discussion se ems to focus on two not necessarily matched alternatives. (Eg. 13-11ug /m3 with a 24 hour of 35; and 11ug/m3 with a 24 hour of 30). There should be a whole range in between, an d figure 2-10 suggests that Northwest is truly out of bounds with either . Does this suggest that the peak-to- mean

doesn't work?

f. Staff’s conclusion that consideration shou ld be given to retaining the current 24-hour standard level of 35 μ g/m3 in conjunction with annual st andard levels in the range of 13

to 11 μ g/m3, and that consideration could also be given to an alternative 24-hour standard level of 30 μ g/m3 particularly in conjunction with an annual standard level of

11 μ g/m3?

See above.

4. Key Uncertainties and Area s 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?

The list of key areas of research is compre hensive and covers the main areas to be considered. Although me ntioned I would have lik e to have seen a more full discussion of potential for changes in effects as sociated with time over the life course of populations. With regard to relative priorities, I believe, wisely, Staff has avoided ranking the various research need. However, it may be worth a discussion by CASAC and Staff as to whether one or two of the categories might be emphasized. For example, have we reach the stage where the focus should be on components of PM and or co-pollutants over and above further data in other categories? By taking these two arenas on can we incorporate many of the other suggested areas both to reduce uncertainty and improve understanding?

Chapter 3 (Primary Standard for Coarse Particles) 5. Current Approach (s ections 3.1.4, 3.2, 3.3) : a. What are the Panel’s views on th e approach to translating the av ailable evidence and air quality information into the basis for revi ewing the coarse particle standard?

A- 58Unfortunately, the approach seems to indicate that studies of PM10-2.5 which are few in number and interpreted only as suggestive for cardiovascular a nd respiratory disease. At least a summary of how the PM10 studies are to be included, to bolster the logic of retaining PM10 as a surrogate for course particles, with all the appr opriate caveats, should be included. (To try to understand this better I went back to th e on-line version of the Final ISA (Dec 2009) and found that figure referred to as 6.2 on page 6.66 is not printed appropriately. This is unfortunate as it re presents the IHD data and should be more impressive than figure 6 .3 which is CHF).

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)?

In contrast to the above introduction, the PM10 data are presented, which would seem appropriate.

6. Adequacy of the Current PM 10 Standard (section 3.2): What are the Panel’s views on the alternative approaches presented for considering the evidence and its uncertainties as they relate to the adequacy of the current standard?

Although the conclusion seems to be right, not contained in this sectio n is the logic of why PM10 effects (since there are only suggestive effects for PM10- 2.5) translate to a range of potential concerns below the current standard for PM10. All of the disc ussion seems to focus on the few positive PM10-2.5 studies.

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 PM10 remains an appropri ate indicator in this

review?

From middle of page 3.27 to en d of section I think the logic is well presented and supported by the data.

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 c onclusion that revising the form to a 98th percentile form would be appropriate for a 24-hour PM10 standard meant to protect against exposures to thoracic coarse particles?

See below, as Staff seems to want to consider these two questions together.

9. Level (section 3.3.4): What are the Panel’s views on the following: a. The approach taken by staff to identify pot ential alternative PM10 standard levels, in conjunction with a 98th percen tile form, including the we ight placed on different

studies?

A- 59Appropriately, more weight is given to the mult i-city studies over the single city studies. Although it is not clear that th e impact of which studi es are chosen to co nsider in setting an upper bound of 85 ug/m3 is really any better supported than any other number. The 98 th
percentile value of 87 seems to keep all sites below the leve l where effects are seen with PM10-25, but there are so few studies I certainly do not have a lot of confidence in these

numbers. Table 3.2 offers some confidence but not much that there really are differences between 150 and 87, particularly at the higher sites. I think the specific level for

consideration will need to be discussed and be tter logic provided. b. Staff’s conclusion that the evidence most strongly supports st andard levels around 85

μ

g/m3?

See above. c. The alternative approach to considering the evidence that could support standard levels as low

as 65 μ g/m3?

See above.

10. Key Uncertainties and Areas for Future Re search and Data Colle ction (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? All of the usual suspects are me ntioned. The emphasis need to be simply pu t on more data,

with uniform or standardized measures of PM10-2.5.

A- 60Dr. Helen H. Suh

2. Form of the Annual Standard (section 2.3.3.1):

a. What are the Panel’s views on the additional an alyses conducted to characterize the potential for disproportionate impacts on susceptible p opulations, including lo w income groups and minorities associated with spatial averaging allowed by the current annual standard?

b. In light of these analyses, what are the Panel’s views on staff’s c onclusion that the form of the annual standard should be revised to eliminate spatial averaging?

The additional analyses and their explanation seem appropriate and provide additional justification in favor of the elimination of spatial averaging. The elimination of spa tial averaging makes sense and is appropriate.

9. Level (section 3.3.4): What are the Panel’s views on the following: a. The approach taken by staff to identify pot ential alternative PM10 standard levels, in conjunction with a 98th percentile form, including the weight placed on different studies?

b. Staff’s conclusion that the evidence most strongly supports st andard levels around 85 μ g/m3?

c. The alternative approach to considering the evidence that could support standard levels as low

as 65 μ g/m3?

The approach and considerations in identifying potentia l alternative PM 10 standard levels is appropriate. The discussion rega rding the weight on different st udies was clearly and cogently presented. However, even with the various st udy weighting options, it is not clear from the epidemiological study results that a PM 10 standard level of 85 ug/m 3 protects public health with a sufficient margin of safety from the impacts of coarse particle exposures. The case seems stronger in support of standard level of 65 ug/m 3

.

A- 61Dr. Sverre Vedal

3. Alternative Levels (section 2.3.4): What are the Panel’s views on the following:

a. The insights that can be gained into potentia l alternative standard levels by considering:

i. Confidence bounds on concen tration-response relationships? It was good to see progress made in attempting to use these bounds in focusing on levels of the standard. There are some issues, however. First, it appears that a comprehensive effort was made to identify relevant studies repor ting bounds on C-R relationships; this should be stated. Second, it seems that what is stated regarding what thes e bounds do not indicate (“these analyses do not provide evidence of a concentration below which the confidence interval becomes notably wider and uncertainty in a C-R relationship substantially increases” [p.2-57]) is exac tly what they in fact do indicate. It is important to understand not on ly that the widening of the confidence bounds at lower concentrations is partly due to there being less data at those concentrations (as acknowledged by staff), but that this is itself a source of unce rtainty about which we are interested. This does not make these bounds less useful, but in fact provide s the information that we want to glean from them. Third, I do not agree with the conclusion that these bounds cannot be used to inform us

about alternative levels of the PM NAAQS, even with the limite d C-R functions shown. Staff should be encouraged to integrate the informati on available on relevant C-R confidence bounds with that on study concentration distributions in arriving at a range of levels for consideration.

There are several ways in which one might use findi ngs from epidemiological studies to arrive at a suggested range of levels for consideration. Most ideal would be information on the

concentrations that were most in fluential in generating the health effect estimate in individual studies. Less ideal, but still useful , would be information on the di stribution of concentrations in the population sample employed in individual stud ies. For time series st udies, because of the similar number of events (e.g., deaths) per day, this is likely to be the same as the PM concentration distribution; this is probably not th e case for cohort studies. Least ideal is using PM concentration distribution metrics, such as those used by staff in arriving at a range of levels for consideration. An attempt should be made, as much as possible, to integrate this latter approach with aspects of the first two a pproaches, realizing that the repo rted study findings needed to accomplish this may not be readily available.

ii. Different statistical metrics that characte rize air quality distributions from multicity epidemiological studies?

62 Obviously there is a relationship between these di stributions and the confidence bounds on the C-R functions, but the relationship is comp lex. It must be realized that this approach (use of air quality distributions) is not the ideal one, but one that is utilized here because of pe rceived inadequacies in

the use of C-R bounds for this purpose. Selection of concentra tions “just somewhat below” the long-term mean concentrations in epidemiologica l studies is obviously arbitrary, as is use of concentrations “substantially below” these means. Selection of 1SD belo w the mean is also as arbitrary as any of the proposed percentiles (25 th or 10 th percentile, for example). Also, I don’t understand why 1 SD is “a more comparable statis tical measure across studies” (p.2-65, line 21) than are percentiles. Consider ation of alternative percentiles provides for intuitive sensitivity analyses.

A-b. Potential alternative annual standard levels based on composite monitor distributions versus

maximum monitor distributions?

This choice is intended to provide for some margin of safety in an indirect way, recognizing that

standards use metrics based on maximum concentration distri butions. Again, it would be preferable to use the C-R functi ons themselves for this purpose. I don’t understand why using the composite vs. maximum monitor dist ributions is more robust when all of these data should be available. I’m not sure that defending the use of composite vs. maximal on the basis that the

former were what were used in the epidemiology studies is much of an argument, as opposed to arguing in favor of the latter b ecause that corresponds more with the form of the standard.

c. Use of risk information in informing sta ff conclusions on alter native annual and 24hour standard levels, including approach es used to assess overall confidence and potential bias in the

risk estimates? No comments to make at this point.

d. Staff’s conclusion that alte rnative annual standard levels in the range of 13 to 11 μg/m 3 are most strongly supported by the available ev idence and risk-based information? The concentration distribution approach to lin king epidemiological findings and proposed revisions to the PM NAAQS has focused attention on concentrations as low as 11 and 10 mcg/m3, which are below those supported by the Panel earlier. Also, as I anticipated, endpoints characterized in the ISA as having a “suggestive” cau sal link with exposure, once incorporated into this analysis, end up influencing the concentrations of interest in considering the standard. I do not think this is appropriate.

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? The argument that 35 mcg/m3 is a reasonable 24-hr standard because it is at least 2.5 times greater than the suggested annual standards (13 to 11 mcg/ m3; p.2-73) does not seem to be relevant. The

24-hr standard should be based on health cons iderations, not observed concentrations. Arguing that considering an annual standa rd of 11 mcg/m3 (with a 24-hr st andard of 30) retains the annual standard as the controlling standa rd is no argument at all (p.2 -74). Obviously a lower annual standard, whatever it is, will retain its role as the controlling sta ndard. Again, the 24-hr standard should be based on health considerations, not obs erved concentrations or observed ratios.

f. Staff’s conclusion that consideration should be given to retaining th e 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 with an annual standard level of 11 μg/m 3 ? As noted above (section e.), the latter c onclusion is based on a strange argument.

g. Additional points : 1. The risk assessment only went down to an annual concentra tion of 12 mcg/m3. The Panel did not recommend doing a risk assess ment for lower concentrations.

A- 63A- 64 2. I believe (but could be wrong) that the Panel recommended the hybrid rollback approach to estimated risk reduction and remaining risk rather than the two extreme alte rnative approaches of proportional (used here) or locally-focused rollbacks.

4. Key Uncertainties and Areas for Future Rese arch 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? This section, as written, has more to do with future research prio rities than with uncertainties that influence decisions on revisions to the PM2.5 NAAQS. What is outlin ed here is a very broad and ambitious research agenda. It wo uld help to begin this section w ith a prioritized review of key uncertainties in order to help es tablish priorities among the suggeste d research topics. Obviously the key uncertainty is that regard ing the concentrations that are most responsible for the observed health effects in the epidemiologi cal studies, and the degree of cer tainty in effects at the lower concentrations along the C-R relationship. This un certainty has necessitated the less than ideal use

of the distributional measures of concentrations from the epidemiology st udies in attempting to make the link between the epidemiological findi ngs and PM NAAQS levels to consider. While this uncertainty is reflected in two (p.2-88 and 2- 90) of a long list of re commendations for future

research that C-R functions include confidence bounds, this uncertainty should be highlighted.

This further motivates the more general point that there should be some prioritizing of research

recommendations that are most critic al for future revisi ons to the PM NAAQS, rather than simply the itemization presented here.

With respect to the recommendations listed, th ese are reasonable and would provide useful

information for the NA AQS setting process.