The U.S. Clean Air Act in the 1970s and similar steps in the European Union, Japan and South Korea over the past three decades have reduced components contributing to acid rain, researchers at Purdue University said, but burgeoning cities in East Asia that lack regulations or enforcement show a dramatic rise in acid rain.
The researchers used publicly accessible data collected from 1980 to 2010 to track "wet deposition" of nitrates and sulfates --components contributing to acid rain as they wash down in precipitation -- near several U.S. and East Asian cities.
"Our analysis of wet deposition [acid rain] data provides compelling evidence that clean-air policies and enforcement of environmental regulations are profoundly important," civil engineering and agronomy Professor Suresh Rao said.
In several large fast-growing cities in East Asia, however, high wet deposition rates match high, unregulated emissions, he said.
"This is the same thing that transpired in the United States in the period leading up to the 1970s," Rao said. "We had rapid urban growth, rising emissions and rising wet deposition, which is analogous to what's happening now in places like Beijing and New Delhi."