WASHINGTON, D.C.--A controversial air pollution law substantially reduced acid rain in the United States in 1995, researchers reported  Tuesday. The success story could spur the wider adoption of market-based pollution controls, which allow businesses to buy and sell pollution permits.
The main cause of acid rain is sulfur dioxide released by burning fossil fuels. After reacting with sunlight and other chemicals in the atmosphere, sulfur compounds rain into lakes, streams, and soils. The hike in acidity can kill plants and wildlife: Over the last 2 decades, scientists have documented harm to thousands of lakes and rivers and millions of hectares of high-altitude forests. To combat the problem, Congress in 1990 adopted a permit-trading scheme that encouraged the owners of coal-burning electric power plants--the major source of sulfur pollution--to reduce emissions. Many observers were skeptical that the program would work.
But the plan appears to be succeeding, according to a report released by the federal National Acid Precipitation Assessment Program (NAPAP). In 1995, the first year of the new rules, sulfur emissions from power plants dropped by 19% to 11.9 million tons, more than 3 million tons below allowable limits. Acid precipitation also dropped as much as 25% in the eastern United States. But it is too early to tell if emissions continued to decline after 1995--or how soon damaged lakes and forests will recover. "Things are looking good, but we've only got 1 year of data," says NAPAP's Michael Uhart.
The new report represents "quite a reversal in position from studies issued by NAPAP in the past," notes David Hawkins of the Natural Resources Defense Council in Washington, D.C. In the late 1980s, he recalls, NAPAP officials "pooh-poohed the acid rain problem and emissions controls. ... Now they conclude that they are indeed effective."