On October 17, 2006, the EPA published its revisions to the NAAQS for particulates to provide protection against potential health effects associated with short- and long-term exposure to particulate matter (including chronic respiratory disease and premature mortality). While the new 2006 particulates NAAQS generally tightened the air quality standards for particulate matter, the action has caused considerable controversy, including concerns that the standards are outside the range recommended by both EPA staff and by the scientific advisory panel (Clean Air Scientific Advisory Committee, or CASAC ) established by the Clean Air Act (CAA). In December 2006, 13 states and the District of Columbia petitioned the U.S. Court of Appeals for the District of Columbia (D.C.) Circuit to review the new 2006 particulates NAAQS. Circuit challenging the new 2006 NAAQS. The EPA's most recent review found that the scientific evidence since 1997 reinforced the associations between exposure to particulates and numerous cardiovascular and respiratory health problems, including aggravated asthma, chronic bronchitis, reduced lung function, irregular heartbeat, nonfatal heart attacks, and premature death. In addition, the nonattainment counties tend to have larger populations than those in attainment: nearly 90 million people (about 30% of the U.S. population) live in the 208 counties designated nonattainment for the current standard. It is the CASAC ' s consensus scientific opinion that the decision to retain without change the annual PM 2.5 standard does not provid e an adequate margin of safety … requisite to protect the public health ' (as required by the Clean Air Act) ... . "

			Potential Health Benefits of a More Stringent PM2.5 Standard

In its RIA, the EPA estimated the nationwide monetized human health and welfare benefits of attaining two suites of PM 2.5 NAAQS: (1) the newly revised PM 2.5 NAAQS, which include the new 35 µg/m 3 daily (24-hour) standard and the unchanged 15 µg/m 3 annual standard, and (2) an alternative standard similar to the least stringent of the CASAC recommendations that includes a tighter annual standard of 14 µg/m 3 and the same 35 µg/m 3 daily (24-hour) standard. The EPA's proposal to exclude any ambient mix of PM 10-2.5 that is dominated by rural windblown dust and soils and particulates generated by agricultural and mining sources, and how the EPA would distinguish the sources during its implementation, raised a number of questions and resulted in numerous comments. Critics of more stringent particulates standards contend that
more stringent standards (and in some cases even the 1997 standards) are not justified by the scientific evidence; the proposal did not take into account hundreds of studies completed since the 2002 cut-off; requiring the same level of stringency for all fine particles without distinguishing sources is unfounded; costs and adverse impacts on regions and sectors of the economy are excessive; some commenters identified as "urban" sources contend exemption of rural particles may result in a disproportional compliance burden; those identified as "rural" sources contend exemption of rural particles is warranted by the lack of evidence regarding adverse effects associated with emission sources in these areas, and that not excluding these areas and sources creates an unnecessary burden; revising the standards could impede implementation of the existing particulates NAAQS and the process of bringing areas into compliance, given the current status of this process; revisions could also impede efforts to meet air quality regulations promulgated in 2004 and 2005, such as the Clean Air Interstate Rule (CAIR) and Clean Air Nonroad Diesel Rule; and the benefits (and costs) associated with implementation of the 1997 PM 2.5 NAAQS, as well as compliance with recent EPA air quality regulations, have not yet been realized. Circuit challenging the new 2006 NAAQS. Briefs from petitioners, EPA, and supporters were filed with the court by March 7, 2008, but the date for oral argument had not yet been scheduled at the time this report was updated. EPA anticipates a decision in late 2008. In December 2006, several states and industry, agriculture, business, environmental, and public health groups petitioned the Court of Appeals for the D.C. Circuit to review the new 2006 particulates NAAQS.
On October 17, 2006, the EPA published its final revisions to the National Ambient Air Quality Standards (NAAQS) for particulate matter (particulates, or PM). The 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. Based on several analytical approaches, the EPA estimated 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. Although a tightening of the standards, the new 2006 particulates NAAQS are not as stringent as recommended by EPA staff or the independent scientific advisory committee (Clean Air Scientific Advisory Committee, or CASAC) mandated under the Clean Air Act.
The new 2006 particulates NAAQS strengthen the pre-existing (1997) standard for "fine" particulate matter 2.5 micrometers or less in diameter (PM2.5) by lowering the allowable daily concentration of PM2.5 in the air. The new daily standard averaged over 24-hour periods is reduced from 65 micrograms per cubic meter (µg/m3) to 35 µg/m3. However, the annual PM2.5 standard, which is set in addition to the daily standard to address human health effects from chronic exposures to the pollutants, is unchanged from the 1997 standard of 15 µg/m3, although the CASAC had recommended a tighter annual standard in the range of 13 to 14 µg/m3. Nearly 90 million people live in the 208 counties designated as "nonattainment" areas for the 1997 PM2.5 NAAQS.
The 2006 particulates NAAQS also retain the 24-hour standard and revoke the annual standard for slightly larger, but still inhalable, particles less than or equal to 10 micrometers (PM10). The EPA abandoned its proposal to replace the particle size indicator of PM10 with a range of 10 to 2.5 micrometers (PM10-2.5), and did not follow through on its proposal to exclude any mix of particles "dominated by rural windblown dust and soils and PM generated by agricultural and mining sources."
The divergence from the CASAC's recommendation has proved controversial, as have several other elements of the 2006 particulates NAAQS, including the decision not to exclude rural sources from the coarse particle standard. Some have also questioned the EPA's strengthening of the standard for all fine particles, without distinguishing their source or chemical composition. In December 2006, several states and industry, agriculture, business, and public advocacy groups petitioned the U.S. Court of Appeals for the District of Columbia (D.C.) Circuit to review the new 2006 particulates NAAQS. All briefs from petitioners, EPA, and supporters were filed with the court by March 7, 2008, but the date for oral argument has not yet been scheduled. EPA anticipates a decision in late 2008. Congress may conduct oversight of the new 2006 particulates NAAQS, given the potential public health and economic impacts, and concerns regarding the role of CASAC in NAAQS reviews.