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Summary:
On December 20, 2005, EPA Administrator Stephen Johnson signed a proposed revision to the National Ambient Air Quality Standards (NAAQS) for particulate matter (PM). In developing the revision, EPA reviewed 2,000 scientific studies and found associations between particulates in ambient air and numerous significant health problems, including aggravated asthma, chronic bronchitis, reduced lung function, irregular heart beat, heart attacks, and premature death in people with heart or lung disease. In the nine cities EPA analyzed, particulates would cause an estimated 4,729 premature deaths unless current standards are strengthened, according to agency data. The proposal would strengthen the existing standard for "fine" particulate matter 2.5 micrometers or less in diameter (PM2.5) and for larger, but still inhalable, coarse particles (PM10-2.5). The existing PM standard promulgated in 1997 is only now beginning to be implemented. The proposal would cut almost in half the allowable concentration of PM2.5 in the air, averaged over 24-hour periods, from 65 micrograms per cubic meter (?g/m3) to 35 ?g/m3. Eighty-eight million people live in the 208 counties designated as "nonattainment" areas for the current PM2.5 NAAQS. The proposal is expected to nearly double the number of counties where monitored PM pollution exceeds the standard. The proposal would eliminate some, but not most, of the premature mortality. Data compiled by the American Lung Association from EPA risk assessments indicate the proposed standard would eliminate only 22% of estimated PM2.5-related premature deaths in the nine cities studied. In addition to the 24-hour standard for PM2.5, an annual PM2.5 NAAQS addresses human health effects from chronic exposures to the pollutants. The Administrator proposed to leave the annual standard unchanged at 15 ?g/m3, counter to the recommendations of the Clean Air Scientific Advisory Committee (CASAC), an independent scientific body that advises the Administrator. CASAC recommended that this standard be reduced to a range of 13 to 14 ?g/m,3 a step that might have required more stringent controls in additional nonattainment areas. The December 20 proposal also would set a 24-hour standard for slightly larger, but still inhalable, particles in the range of 10 to 2.5 micrometers (PM10-2.5). The Administrator proposes to focus this standard on urban, industrial, and construction sources, excluding any mix of particles "dominated by rural windblown dust and soils and PM generated by agricultural and mining sources." In addition to the divergence from the CASAC's recommendation, several elements of the proposed PM standard may prove controversial, including the exclusion of rural sources from the coarse particle standard. Some may also question the EPA's strengthening of the standard for all fine particles, without distinguishing their source or chemical composition. Establishment of PM NAAQS in 1997 proved controversial and included extensive Congressional oversight. Congress may conduct oversight of the December 2005 proposal, given its potential for public health and economic impacts. Under a consent agreement, the Administrator is to promulgate final revisions to the standard by September 27, 2006. This report will be updated.
