governments, private and public groups, and educational institutions. Regional EPA offices develop, propose, and implement approved regional programs for comprehensive environmental protection activities. Data collected since the agency began its work show significant improvements in environmental quality; there has been a nationwide decline of virtually all air pollutants, for example. However, in 1990 many Americans believed that still greater efforts to combat air pollution were needed. Congress passed important amendments to the Clean Air Act, and they were signed into law by President George Bush (1989-1993). Among other things, the legislation incorporated an innovative market-based system designed to secure a substantial reduction in sulfur dioxide emissions, which produce what is known as acid rain. This type of pollution is believed to cause serious damage to forests and lakes, particularly in the eastern part of the United States and Canada.