Review of the Air Quality Criteria Document for Particulate Matter

coarse particle effects. The paragraph clearly comes across as there may besome PM coarse mode effects but they probably are specific in location andthey may even be due to biogenetically-derived particles. In addition, thestatements throughout the chapter reflect strong statements of PM 2.5 causingeffects and then the statements around the coarse mode, i.e., PM 10-25 usephraseology such as may also be important . This comes across to the reader asa bias of the authors relative to fine vs. coarse mode effects. This tone iscontinued on page 6-78, l. 2 4 where the statement is made that crustal particlesdo not appear overall to support associations with mortality in the sourceoriented evaluations. While clear recognition must be given that there are morestudies demonstrating the importance of PM 2.5 , the dismissal of coarseparticles in the presence of positive studies is disconcerting, particularly giventhat much of the western part of the United States has PM 10 dominated by thecoarse mode fraction.p. 6-84, Table 6-6 In the cardiopulmonary mortality column for the six cities original vs. the HEIreanalysis, a consistency of the point estimate is what one would expect.However, the much larger difference in the confidence limit bounds issurprising. It would be worth checking the entry in this table to ensure that atypographical error has not occurred.p. 6-105, l. 11 26 The actuarial and statistical calculations presented based upon Brunekreef arehard to believe. The implication that the life span of persons exposed to anddying from air pollution is a reduction of more than 10 years, if true, wouldsurely have been detected without the kind of sophisticated statistical analysesthat are currently being required. In addition, what exactly is meant by implyingthat up through age 25 a loss of 1.31 years occurs for the entire population? Isthis life span reduction? If so, actuarial numbers likely contradict thisconclusion.p. 6-107, l. 17 The conclusion from the Krewski et al. study that mortality may be associatedwith more than one component of the complex of ambient pollutants in urbanareas bears emphasis in the synthesis chapter and is appropriately highlighted invarious sections of the epidemiological discussions.p. 6-107, l. 30 The mortality log hazard ratio increasing to 15 mg/m 3 and then being flatbefore continuing to increase again, while being a statistical model that appearsto fit the data, has little biological motivation to support it (i.e., such a modelmakes little biological sense).p. 6-108, l.8 13 The Krewski et al. study looking at the relative risk and incorporating timedependentestimates is particularly important for the standard setting process.EPA must factor the temporal decline in PM that has been occurring in itsassessment of the need for revisions of or new standards for particulate matter.This is particularly important with the various implementation strategies thathave yet to take effect that are clearly leading to a reduction in overall pollutionlevels in this country.p. 6-205, l. 10 19 A number of studies on long term effects from PM are cited as having beenconducted in California but with inconsistent results. Yet the authors choose todescribe the McConnell study as the most notable because it showed an increasethat is similar to results reported by Dockery. Why is this study notable? Itappears the authors have considered it such because it found effects when othersdidn t. This does not appear to be a balanced representation and discussion ofthe newly available studies.p. 6-230, l.17 20 The nonlinear model for fine PM effects in the study by Smith et al. is ofpotential interest since a threshold between 20 25 mg/m 3 for PM 2.5 was seen inthis study. Has the type of model presented by Smith et al. been applied in otherdata sets?p. 6-247, l. 25 The summation of the Smith study relative to threshold selection andimportance of fine vs. coarse is phrased as these results, if they in fact reflectreality, make it difficult to evaluate the relative role of different PMcomponents One might interpret the authors use of the phrase if they in factreflect reality as a bias for wanting to attribute one of the two modes as beingmore important. Alternatively, the sentence is an excellent summary of why thePM issue is so entangled and difficult to separate on a causative basis for oneA - 5