EPA regulation effective in reducing acid rain in the U.S.

Sérgio Abranches

Emissions regulations effectively reduce acid rain says a new long-term study of acidic rainfall by researchers of the University of Illinois. The frequency and intensity of acid rain decreases as emissions fall.

The study was based on analysis for pollutants of weekly samples from more than 250 stations across the United States collected by the National Atmospheric Deposition Program, shows trends in acidic rainfall, widely known as acid rain, over 25 years, from 1984 to 2009. “This is the longest-term, widest-scale precipitation pollution study in the U.S.” said Christopher Lehmann, a researcher in the program, which is part of the Illinois State Water Survey at the U. of I. The study aimed at determining how trends in the pollution and the rain correlated back to emissions regulations. “We’re seeing regulations on emissions sources having direct and positive impact to reduce pollutants in rain.”

It is an important contribution to the appraisal of how effective the Environmental Protection Agency – EPA regulations have been. “You want to make sure that the regulations you put in place are effective, that they do what they were designed to do,” said David Gay, the coordinator of the deposition program. “That’s why we’re here. We spend a lot of money to promulgate regulations. There’s a lot of concern about their impact on industry. This study shows clear, significant evidence of the direct impact of regulation. The report attributes the decrease to the amendments to the Clean Air Act in 1990 regulating emissions of sulfur dioxide and nitrogen oxide, the gases that become sulfuric and nitric acid when mixed with rain water. Acidic precipitation – rain or snowfall with a pH value of 5.0 or less – decreased in both frequency and concentration over the 25-year span, says the report.

Acid rain has widespread effects not only on the ecosystem, but also on infrastructure and the economy. Polluted precipitation adversely affects forestry, fishing, agriculture and other industries. Acid also erodes structures, damaging buildings, roads and bridges.

“What goes up does come down. Rainfall chemistry directly correlates with air pollution. When we looked at the magnitude of the trend, we found it compared very well to the magnitude of the decrease in emissions reported by the EPA,” Lehmann said. “The trend is down, and we should celebrate that, but it’s still a problem. There is still progress to be made, and there are new regulations coming along to continue to reduce emissions of sulfur and nitrogen compounds,” he added.

Tags: acid rain, emissions, EPA, regulation, research, USA