The electricity-generation sector is a major contributor to air pollutionproblems in the United States. Emissions from electricity generators thatburn fossil fuels contribute substantially to urban ozone and other pollution problems in U.S. cities, to acid rain in the Northeast, to regional haze and visibility problems in some rural areas, and to the buildup of greenhouse gases in the earth’s atmosphere that has ignited concerns about global warming. Although virtually all electricity generators face some regulatory limits on their emissions of different

pollutants, the environmental regulator’s job is far from complete. Many U.S. cities are still not meeting their air quality goals for ozone and other local air pollutants identified as candidates for controls under the National Ambient Air Quality Standards in the Clean Air Act. In addition, the United States does not yet have a comprehensive plan to reduce greenhouse gas emissions to 1990 levels, the voluntary goal espoused in the U.N. Framework Convention on Climate Change that was signed and ratified by the United States in 1992.