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Summary:
On September 21, 2006, EPA Administrator Stephen Johnson signed a final revision to the National Ambient Air Quality Standards (NAAQS) for particulate matter (PM). EPA reviewed more than 2,000 scientific studies and found that the evidence continued to support associations between exposure to particulates in ambient air and numerous significant health problems, including aggravated asthma, chronic bronchitis, reduced lung function, heart attacks, and premature death in people with heart or lung disease. On the basis of various analytical approaches, the EPA estimates that compliance with the new NAAQS will prevent 1,200 to 13,000 premature deaths annually, as well as substantial numbers of hospital admissions and missed work or school days due to illness. The new PM NAAQS would strengthen the existing standard for "fine" particulate matter 2.5 micrometers or less in diameter (PM2.5). The existing PM2.5 standard promulgated in 1997 is only now beginning to be implemented. The new standard 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 (µg/m3) to 35 µ g/m3. Eighty-eight million people live in the 208 counties designated as "nonattainment" areas for the current PM2.5 NAAQS. EPA has not predicted the number of additional counties expected to exceed the new PM2.5 standard; however, the new areas will likely be expansions of existing areas and other urban populated areas. States are required to recommend nonattainment areas by December 2007, and EPA anticipates it will make final designations in December 2009. 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 annual standard is unchanged at 15 µg/m3 as proposed, which is counter to the recommendations of the Clean Air Scientific Advisory Committee (CASAC), an independent scientific body that advises the Administrator. CASAC had recommended that this standard be reduced to a range of 13 to 14 µg/m,3 a step that might have required more stringent controls in additional nonattainment areas. The new PM NAAQS also would retain the 24-hour standard and revoke the annual standard for slightly larger, but still inhalable, particles in the range of 10 to 2.5 micrometers (PM10). The EPA recommends that states focus this standard on urban, industrial, and construction sources, but the new standard does not exclude any mix of particles "dominated by rural windblown dust and soils and PM generated by agricultural and mining sources," as proposed. In addition to the divergence from the CASAC's recommendation, several elements of the new PM standard may prove controversial, including the decision not to exclude rural sources from the coarse particle standard. Some have also questioned EPA's strengthening of the standard for all fine particles, without distinguishing their source or chemical composition. The establishment of PM NAAQS in 1997 proved controversial and included extensive congressional oversight. Congress may conduct oversight of the new PM NAAQS, given its potential for public health and economic impacts. This report will be updated.
