progress toward attainment of satisfactory air quality in areas where current air quality violates the NAAQS.³

This interim report focuses on changes made to the NSR programs over the past few years that affect modifications to existing stationary sources of pollutants. In December 2002, the U.S. Environmental Protection Agency (EPA) made a number of revisions to the NSR programs, including revisions to methods used to determine whether particular physical changes to a facility would result in significant emission increases that would be subject to NSR. Regulatory revisions were also made in October 2003 concerning the extent of equipment replacements or other modifications for which an NSR permit would not be required, even if pollutant emissions increased significantly, so long as the source did not exceed its maximum level of allowable emissions.⁴ EPA and other supporters of the revisions say the changes will provide greater flexibility in operating the facilities, increase energy efficiency, and help to modernize American industry, all without damaging the environment. Opponents say that the EPA revisions will slow progress in cleaning the nation’s air, thus damaging human health, and that the NSR changes are not necessary to provide operating flexibility to industry.

Because of the controversy over EPA’s revisions, Congress requested that EPA arrange for an independent study by the National Research Council (NRC) to estimate the potential impacts of EPA’s final NSR rules of December 2002 and October 2003. Congress called for an assessment of changes in emissions of pollutants regulated under the NSR programs; impacts on human health; and changes in energy efficiency, pollution prevention, and pollution control activities at facilities