Pursuant to a congressional request, GAO reviewed the Environmental Protection Agency's (EPA) and states' implementation of the Clean Air Act's provisions concerning copper, zinc, and lead smelters' sulphur dioxide emissions, including: (1) EPA measures to determine smelter compliance with the act and actions it took to enforce such compliance; and (2) factors EPA considered in exempting smelters from certain requirements of the act.

GAO found that EPA and states have been effective in getting smelters to reduce emissions and national ambient air quality standard violations. The 1984 levels for both sulphur dioxide emissions and standards violations have been reduced at least 75 percent from the levels in the mid-1970's, even though 50 percent of the reductions were attributable to decreased production. Although EPA and the states have used different enforcement strategies, each has been successful in achieving compliance. EPA has issued consent decrees with compliance schedules and fixed fines for violations, while states have taken enforcement actions without imposing fines. Congress gave smelters the opportunity to defer compliance with emission limitations and installation of expensive constant controls through nonferrous smelter orders, whereby smelters could continue to operate emission dispersion techniques, but were still expected to maintain air quality standards. Although some smelters operating under first-period orders have violated air quality standards, EPA allows those smelters the opportunity to improve their intermittent control systems while deciding whether to award second-period orders. EPA is evaluating whether the smelters have provided an adequate basis to ensure that the national standards will not be violated during the second period.