A new study shows clean-air regulations have dramatically
reduced acid rain in the United States, Europe, Japan and South Korea over the
past 30 years, but the opposite is true in fast-growing East Asian megacities,
possibly due to lax antipollution rules or lack of enforcement.
The U.S. Clean Air Act began requiring regulatory controls
for vehicle emissions in the 1970s, and 1990 amendments addressed issues
including acid rain. Similar steps in the European Union, Japan and South Korea
over the past three decades have reduced nitrate and sulfate in rain -
components contributing to acid rain, said Suresh Rao, Lee A. Reith
Distinguished Professor of Civil Engineering and Agronomy at Purdue University.