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Recently, EPA announced the release of its interim electric utility study report, which was prepared pursuant to Section 112(n)(1)(A) of the Clean Air Act (the Act), as amended in 1990. The Act directs EPA "... perform a study of the hazards to public health reasonably anticipated to occur as a result of emissions by electric utility steam generating units of ... [hazardous air pollutants] ... after imposition of the requirements of this Act." EPA submitted a copy of the full report to docket A-92-55; the report also should be available from the National Technical Information Service (NTIS). The Executive Summary section of the interim report has been posted to EPA's Technology Transfer Network (TTN). EPA states that its report is not final because its assessment of impacts to public health is not yet complete. Moreover, neither EPA's conclusions regarding the significance of the risks, nor the Agency's decision with respect to the appropriateness and necessity of additional regulations for the utility industry are presented in the interim report. The interim report does present EPA's inhalation risk estimates for several carcinogens. According to the report, the overwhelming majority of coal-fired plants (424 of 426) pose lifetime cancer risks to the most exposed individual (MEI) of less than one chance in 1 million (1 x 10-6). Arsenic and chromium are the hazardous air pollutants (HAPs) contributing most to inhalation cancer risks. According to the report, the majority of oil-fired plants (114 of 137) also pose lifetime cancer risks to the MEI of less 1 x 10-6. Nickel is the primary risk contributor, but there is much uncertainty in EPA's estimate because of a continuing debate over the carcinogenicity of the various forms (e.g., oxides, sulfides, metallic, etc.) of nickel in the flue gas. The above-cited results are from EPA's "local impact" analysis. The Agency also conducted a long-range transport analysis using its Regional Lagrangian Model of Air Pollution (RELMAP), which estimates air concentration far downwind from each point source. EPA's long-range transport modeling of arsenic suggests that the local analysis does not account for substantial percentage of the population exposures. Because EPA's estimated population exposure for long-range transport of arsenic was about seven times the exposure from local impact analysis alone, the Agency decided to multiply all of the population exposures for all of the HAPs by a factor of 7. RMB finds the presentation of EPA's long-range transport to be somewhat disingenuous. While EPA's local impact analysis could be characterized as a careful, methodical, plant-by-plant risk assessment, EPA's long-range transport analysis would more appropriately be termed a "back of the envelope" calculation. RMB's criticism is that EPA tabulates and presents the results in its Executive Summary as if both analyses are of equal quality and creditability. RMB intends to continue to review EPA's Interim Study Report and to provide the Agency with constructive review comments. .
Agora Environmental Consulting |