later, in Title IV of the CAA Amendments of 1990, Congress enacted specific legislation to mitigate the adverse effects of acid rain as well as to “encourage energy conservation, use of renewable and clean alternative technologies, and pollution prevention as a long-range strategy … for reducing air pollution and other adverse impacts of energy production and use.”

The legislation in Title IV represented a significant departure from the regulatory approaches prescribed by Congress for criteria pollutants and HAPs. Instead of directing the EPA administrator to set standards to protect human health and welfare, Congress imposed their own standards—standards that, as noted in Box 2-1, were influenced to some extent by scientific understanding of the effects of acid rain but also by nontechnical economic and political considerations. The standards prescribed by Congress were aimed at the emissions of SO2 and NOx from electric utilities and were designed to bring about significant reductions in these emissions nationwide. Electric utilities were targeted because they were estimated to contribute two-thirds of all SO2 emissions and one-third of NOx emissions (EPA 1999c).

Because the scientific evidence suggested that SO2 emissions made the largest contribution to acid rain (NAPAP 1991a), the most aggressive control program in Title IV was aimed at SO2 emissions. Specifically, SO2 emissions from electric utilities nationwide were capped at an amount that would require a decrease in total emissions by 2010 of 10 million tons (or about 50%) relative to emission levels of 1980. Instead of imposing a technological or emissions-based standard on power-generating facilities, Congress specified that the emission reductions were to be achieved through a market-based mechanism; specifically in this case, a cap-and-trade program. A smaller and more traditional program for reducing NOx emissions was also enacted. This program involved a two-phase strategy to reduce NOx emissions from coal-fired electric utility plants by over 400,000 tons per year between 1996 and 1999 (Phase I) and by approximately 1.17 million tons per year beginning in year 2000 (Phase II). To accomplish these reductions, Congress imposed emission standards on power plants; standards varied depending upon the type of facility. Language was also included to allow a state or group of states to petition the EPA administrator to use a cap-and-trade program instead of emission standards to meet Congress’s NOx reductions goals. A more detailed discussion of the SO2 and NOx acid-rain emission-control programs and their implementation can be found in Chapter 5.

Environmental Justice as an Air Quality Goal

Environmental justice has been defined by EPA as the “fair treatment for people of all races, cultures, and incomes, regarding development of

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