Discounting the threat of acid rain.

Discounting the threat of acid rain

There is little evidence that acid rain has had a significant impact on lakes and streams in the United States, says a controversial report issued last week by a Reagan administration study group. Even in regions such as New York's Adirondack Mountains, where lake acidification has occurred, it says only a small percentage of lakes have been affected. The report also concludes that most watersheds in the Northeast have reached a steady state, meaning that further acidic deposition is unlikely to increase the number of acidified lakes.

These conclusions are contained in an interim assessment of the causes and effects of acid rain, issued by the National Acid Precipitation Assessment Program (NAPAP), the umbrella organization coordinating federal acid rain research. Originally scheduled to appear in 1985, the report summarizes the current state of scientific knowledge about acid rain after more than five years of study (SN: 7/18/87, p.36).

This document, says NAPAP's Charles N. Herrick, focuses on "what we found out, how we found that out, what we still need to find out, and what we need to do to find it out.'

The interim assessment was greeted with strong protests by the Canadian government, several environmental groups and a number of scientists whose work had contributed to the NAPAP report. Canada's Environment Minister Tom McMillan complained that the report is "voodoo science,' designed to prove that the situation isn't serious enough to warrant immediate action. The report, for instance, ignores the potential impact of U.S. emissions on Canadian lakes, a large number of which lie on granite beds, making them more sensitive to acid rain than most U.S. lakes.

Scientists, including James N. Galloway of the University of Virginia in Charlottesville and Michael Oppenheimer of the Environmental Defense Fund in New York City, argue that the NAPAP assessment uses data selectively, ignoring new evidence that doesn't seem to support its conclusions. For example, one recent study shows that some lakes may continue to become more acidic even when the deposition rate of strong acids is reduced. Some researchers also argue that the criteria used by NAPAP to define an acid lake are inadequate. The assessment, they say, excludes a number of lakes where damage has occurred and doesn't take into account the strong pulse of acidity associated with spring snow melts.