While air quality in the United States has steadily improved over the last few decades, more than a hundred million Americans continue to live in communities where pollution causes the air to be unhealthy at times, according to the Environmental Protection Agency (EPA). The Clean Air Act, first passed in 1963, was last reauthorized and amended in 1990, when new programs were created and changes were made to the ways in which air pollution is controlled. The 1990 amendments included hundreds of requirements for EPA, as well as other parties, to take steps that will ultimately reduce air pollution. The amendments also established deadlines for many of these requirements. Since the 1990 amendments, various actions have been proposed to either amend the Clean Air Act or implement its provisions in new ways. GAO was asked to report on the current status of EPA's implementation of requirements under Titles I, III, and IV of the 1990 amendments. These titles, which address national ambient air quality standards, hazardous air pollutants, and acid deposition control, respectively, are the most relevant to proposed legislation and recently finalized regulations addressing emissions of air pollutants by power plants.

As of April 2005, EPA had completed 404 of the 452 actions required to meet the objectives of Titles I, III, and IV of the Clean Air Act Amendments of 1990. Of the 338 requirements that had statutory deadlines prior to April 2005, EPA completed 256 late: many (162) 2 years or less after the required date, but others (94) more than 2 years after their deadlines. Consequently, improvements in air quality associated with some of these requirements may have been delayed. The numerous actions required to implement these titles varied in scope and complexity. For example, these actions included reviewing numerous state plans to comply with national health- and welfare-based air quality standards for six major pollutants, setting technology-based standards to reduce emissions from sources of hazardous air pollutants, and developing a new program to reduce acid rain. EPA officials cited several reasons for the missed deadlines, including the emphasis on stakeholders' involvement during regulatory development, which added to the time needed to issue regulations; the need to set priorities among the tremendous number of new responsibilities EPA assumed as a result of the 1990 amendments, which meant that some actions had to be delayed; and competing demands caused by the workload associated with EPA's response to lawsuits challenging some of its rules. Of the 48 requirements EPA had not met as of April 2005, 45 had associated deadlines, and 3 did not. The unmet requirements include 15 Title I requirements to promulgate regulations to limit the emissions of volatile organic compounds from a number of consumer and commercial products, such as household cleaners and pesticides. According to EPA officials, these rules were not completed because EPA shifted its priorities toward issuing standards related to the emissions of hazardous air pollutants regulated under Title III. However, the unmet requirements also include actions under Title III to periodically assess whether EPA's emissions standards for sources that emit significant amounts of hazardous air pollutants appropriately protect public health. These "residual risk" assessments are to be made within 8 years of the setting of each of the emissions standards, and 19 of these assessments are now past the 8-year mark. EPA completed the first of these residual risk assessments in March 2005. Any improvements in air quality that would result from EPA meeting these requirements remain unrealized. In commenting on a draft of this report, EPA generally agreed with our findings and provided supplemental information, primarily on the benefits of the Clean Air Act Amendments of 1990 and the reasons for implementation delays.

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