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Comments on the PM OAQPS Staff Paper
First Draft

The technical team of scientists associated with A.S.L. & Associates completed its review of the EPA Report: A Review of the Ambient Air Quality Standards for Particulate Matter: Policy Assessment of Scientific and Technical Information - OAQPS Staff Paper - First Draft. The comments were submitted to EPA in October 2003.

The draft of the OAQPS Staff Paper summarizes the fourth draft of the EPA PM Criteria Document. The Staff Paper has attempted to translate the CD and associated research on the health effects of PM into recommendations for new regulatory limits for ambient PM. The Staff Paper, like the CD, justifies its conclusions based on what it perceives to be a certain coherence among recent epidemiologic studies pertaining to PM. While identifying assorted deficiencies and limitations of these studies and substantial unresolved uncertainties, the EPA is apparently not concerned with these limitations and uncertainties. In addition to drawing attention not only to the limitations described in the Staff Paper and to other fundamental unresolved problems associated with the corpus of PM epidemiology, the technical team's comments question the logic of the EPA's methodology for establishing the form and level of the PM2.5 standards.

In using time-series data for proposing a form and level of the PM standard, the Staff Paper mainly focused on the PM concentrations for selected cities where statistically significant effects were observed in the epidemiological studies. The minimum of these selected values was considered for the proposed annual and short-term regulatory standards. The EPA assumed that the city with the minimum annual PM average that showed a statistically significant PM effect would presumably reduce this effect if that city reduced its PM concentrations. Applying this methodology for defining a regulatory limit ignores the (1) implications of the actual magnitudes of the PM effect estimates, (2) implications of no-threshold modeling, and (3) implications of city-to-city heterogeneity of effect estimates.

In illustrating the problems in applying the Agency's methodology for proposing the form and level of the PM-2.5 standards based on the time-series data, the technical team integrated the data from Appendix A of the Staff Paper with air characterization information on PM-2.5 concentrations from the Ross (2003) memo. Using the data provided for Total (nonaccidental) Mortality and Total Cardiovascular Mortality, no relationship was evident between the concentrations as listed in Ross (2003) and human health endpoint data as provided in Appendix A.

In order to establish a scientifically defensible set of standards for PM-2.5, the Agency should have first established dose-response relationships upon which the proposal for the form and level of the two PM-2.5 standards would have been based. Unfortunately, the Agency has chosen to utilize a methodology that has no biological connection to the epidemiology studies. Therefore, serious questions exist concerning the methodology utilized by the Agency to define the form and level of the PM-2.5 annual mean and 24-hour standards.

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