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Particulate Matter (PM2.5): Implementation of the 1997 National Ambient Air Quality Standards (NAAQS)

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Particulate matter (PM), including fine particulate matter (PM2.5), is one of the six principal pollutants for which the U.S. Environmental Protection Agency (EPA) has set National Ambient Air Quality Standards (NAAQS) under the Clean Air Act (CAA). NAAQS are designed to protect human health, with an adequate margin of safety. After years of litigation and other delays, the EPA is moving to implement the NAAQS for PM2.5 promulgated in 1997. Several key implementation milestones are scheduled to be completed in 2007. This report provides information on the designation process for PM2.5 "attainment" and "nonattainment" areas and describes the issues that have been raised as the EPA and states develop implementation strategies.

The EPA's final designation of 39 areas, consisting of 208 counties in 20 states and the District of Columbia, as nonattainment areas for the 1997 PM2.5 NAAQS became effective April 2005. States with PM2.5 nonattainment areas are required to develop comprehensive implementation plans, referred to as State Implementation Plans (SIPs), demonstrating how attainment will be reached by a designated deadline. SIPs include pollution control measures that rely on models of the impact on air quality of projected emission reductions to demonstrate attainment. States are required to submit SIPs for how they will meet the 1997 PM2.5 NAAQS by April 2008 (three years after the effective date for the final geographic designations), and states must be in compliance by 2010, unless they are granted a five-year extension. The EPA published a proposed "PM2.5 implementation" rule on November 1, 2005, but has yet to publish the final rule that would provide guidance and procedures for establishing controls to achieve and maintain attainment. Lack of final guidance has caused concern among state air pollution control agencies and some Members of Congress given that state SIPs are due to EPA by April 2008.

A number of issues will continue to be debated as the implementation of the 1997 PM2.5 NAAQS progresses. Questions and concerns include the following: what criteria were used to determine nonattainment; whether special provisions can be made for meeting attainment deadlines, particularly for areas affected by upwind pollution; what grants or other funding might be available to help areas reach attainment; and how nonattainment designation might affect economic development and transportation planning in an area.

The EPA rulemakings promulgated and proposed during FY2006 that affect various aspects of regulating air quality could influence the PM2.5 NAAQS implementation process. The EPA's completion of its periodic review of the particulates NAAQS, as required under the CAA, could also affect implementation of the 1997 PM2.5 NAAQS. As part of this CAA review process, on October 17, 2006, the EPA promulgated the final revisions to NAAQS for particulates, both PM2.5 and PM10, that included a strengthening of the 1997 PM2.5 standard. In late December 2006, several states and industry, agriculture, business, and public advocacy groups petitioned the court to review the new 2006 particulates NAAQS.