Review of the Air Quality Criteria Document for Particulate Matter

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- Page 4-113, lines 13 through 19 focuses on CVM, but really is about stated preferencemethods, including CVM applications. Some of the past economic studies are more like SPchoice studies than conventional CVM applications. Consequently, it may be appropriate tomerge the paragraphs starting on lines 13 and 20.- Page 4-113, line 19 could use a citation, either NAPAP or Chestnut and Dennis, or Mitchelland Carson.- Does the Hanley and Spash reference discuss visibility applications in specific and in detail?- Page 4-113, line 31. “Davis” should be “Dennis”.Health Risk Assessment (Staff paper Chapter 4 and separate paper).- I support conducting the assessment in more than 2 locations, as discussed at the meeting.- Staff paper 4-13, lines 10-26 discusses assumptions about changes in ambient conditions tomeet standards, relying predominately on the rollback method. Using the rollback method isreasonable, but EPA should give careful attention to the proposed sensitivity analysis ofalternative adjustments (lines 24-26). With increasing costs of compliance, episodic andother control strategies that reduce the highest concentrations may receive increasedattention. Further, given that the population exposed is not uniform across concentrationlevels, and many concentration-response functions are non-linear, differences in theassumptions to reduce concentrations to achieve standards can have a significant impact onthe risk assessment.- Deck et al, 2001 is cited several times, starting in the first paragraph, but is not available. Itmay be useful to provide this paper for this review.Criteria Document Chapter 9This chapter is well done as a series of separate summaries, but it needs more integrationand needs to be reduced in length – not everything needs to be summarized. It appropriatelyfocuses on the larger questions of increasing consistency in the results of available health effectsliterature and extensions to this literature. In terms of the important question of retaining orrevising the existing PM 2.5 standard levels (15 ug/m3 annual average and 65 ug/m3 24 hours),little is presented in this chapter on the strength of the evidence, shapes of the estimated C-Rfunctions around these levels, or effect thresholds (although this is touched on in Section 6.4.6).Jonathan Samet, MDChapter 5 - General Comments:In general, this is a cohesive and thorough chapter that carefully sets out concepts of exposureassessment, measurement approaches, and findings. The literature review appears complete andfindings are well represented in tables and in the text. The chapter has a potentially key role insetting a framework for interpreting the epidemiological data presented in Chapter 6. Thechapter does address the implications of the exposure literature for interpreting theepidemiological evidence. Unfortunately, there is little linkage between the two chapters in thisregard; Chapter 6 almost reads as though Chapter 5 had not preceded it. There is a need forbetter integration, a burden which clearly lies with the authors of Chapter 6.This chapter also discusses issues related to confounding and measurement error that overlapwith Chapter 6. With regard to issues of confounding, it will be important to have a uniformview throughout the CD. My comments for Chapter 6 should be considered in this regard.A - 73
Specific Comments:Page 5-19, lines 15-18: Generalizability (external validity) is not dealt with well here. A“purposeful study” may give generalizable information; the extent of generalizability is a matterof judgment, based on study participant characteristics. The term statistical inference is usedinappropriately here.Page 5-41, lines 5-16: This paragraph is far too sweeping in its condemnation of the exposureassessment literature. What are the “important questions” that are so poorly answered.Chapter 6 - General Comments:This lengthy chapter provides an exhaustive, descriptive summary of the most recentepidemiological findings on particulate matter and morbidity and mortality. The literaturereview is comprehensive and the tables offer useful summaries of an extensive literature. Thereare, however, weaknesses that should be addressed; these weaknesses may reflect the multiauthorednature of the chapter which has resulted in an uneven approach in style, synthesis, andinterpretation. Key aspects of the chapter needing to be addressed include:1. The chapter is not adequately connected to the remainder of the CD. There is a lack ofintegration with Chapter 5, which should provide a foundation for exposure considerationsrelated to interpretation of the epidemiological literature. This foundation is not used, and farless strong and competent text is provided.2. The chapter fails to sharply set out key concepts—confounding, causal associations, andcausal pathways, in particular. Effect modification is also not handled well and the text relatedto these key aspects of interpretation is often murky. In the chapter’s introduction, it would beuseful to provide diagrams indicating the relationships that hold under confounding, direct causalpathways, and indirect causal pathways. I have attached one possible set of diagrams.Additionally considerations as to confounding, reflect biological understanding as to theindependent action of the confounder and not just patterns of association in data. Changes inestimates are not a particularly useful gauge as to the presence of confounding in the presence ofmeasurement error, possible effect modification, and correlations among the independentvariables. The text in places offers some clear thinking on these difficult topics, but much of it isnot clear.3. In interpreting data, there is excessive reliance on p values and attaining statisticalsignificance for effect estimates. This needs to be corrected; the p value should not be held as adecision-making tool for data interpretation, as in the present chapter (see Epidemiology for arecent set of perspectives on this issue. Emphasis should be placed instead on precision of effectestimates (i.e., width of confidence intervals..4. In fact, the chapter never clearly sets out how data will be interpreted. Summary judgmentsare offered but without reference to any common framework Judgments are often couchedsubjectively and there is a general failure to place the epidemiological evidence within thebroader context of toxicological and dosimetric understanding. The framework for interpretationis badly needed. Throughout the text, there is variably use of significance level, precision ofeffect estimates, and magnitude of effect, as the effects of PM are weighed against those of otherpollutants. The same problem is evident when the chapter interprets the literature on particlecharacteristics and components.Specific CommentsPage 6-2, lines 11-15: This proposed hierarchy of “inferential strength” is neither correct noruseful.Page 6-3, lines 19-21: This type of sweeping statement should be avoided. On close reading,the sentence offers only a garbled pejorative comment.A - 74
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Review of the Air Quality Criteria Document for Particulate Matter

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