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Study Says Trees’ Contribution To Ozone Has Been Ignored

September 16, 1988

ATLANTA (AP) _ Scientists trying to get to the root of America’s ozone pollution should reconsider the role trees play, researchers say.

Trees contribute such a high amount of hydrocarbons to the atmosphere, pollution-control efforts would be more effective if they sought to limit nitrogen oxide instead, according to research by Georgia Tech faculty members.

Aware of Ronald Reagan’s ″killer trees″ theories of 1980, Georgia Tech geophysicist W.L. Chameides hastens to say that trees don’t cause ozone pollution any more than the sun does.

Chameides concedes the conclusions place him and his colleagues out on a scientific limb, but said Thursday, ″I think there are other scientists that are coming along with us.″

He said he expected that the conclusions would be accepted, despite what he called ″institutional inertia.″

Ozone is produced by the combination of sunlight, hydrocarbons and nitrogen oxides. It protects the Earth from harmful radiation at high atmospheric levels, but can harm humans and crops at low levels.

All three ingredients must exist before ozone can be formed, and ″no one has inferred from that that the sun was a polluter or that we should put a big screen over the United States to protect it,″ Chameides said.

During the 1980 presidential campaign, Reagan angered environmentalists by suggesting that trees and other parts of nature were the chief culprits of air pollution. The idea led to jokes about ″killer trees″ and the appearance of protesters who dressed themselves as trees and carried signs saying, ″Chop Us Down Before We Kill Again.″

Chameides stressed that the researchers do not suggest cutting down trees, but instead believe pollution control efforts should center on nitrogen oxides, which are produced by many of the same processes that emit hydrocarbons.

Chameides led a team of Georgia Tech researchers who studied the production of hydrocarbons, or hydrogen-carbon compounds, in Atlanta, a heavily wooded city that frequently fails to meet federal air-quality standards.

The study found that vegetation, principally trees, emit as many hydrocarbons as cars and factories, and on a hot day can provide enough hydrocarbons on their own to form illegal levels of ozone.

Published in today’s edition of Science magazine, the study says the Environmental Protection Agency’s decision to attack ozone through limiting hydrocarbons is therefore doomed to failure.

The Clean Air Act has sought to limit ozone through devices on cars and in factories that reduce the emission of hydrocarbons, paying little attention to nitrogen oxide, Chameides said.

″We’ve pursued the hydrocarbon strategy for about 10 years or so, and I think it’s pretty clear that for some reason we have not been successful,″ Chameides said. ″We need to re-evaluate what we’re doing instead of continuing down the same garden path.″

EPA spokesman Chris Rice agreed that air-quality rules have not succeeded in reducing ozone levels significantly. But he said, ″We estimate that in the absence of control programs, (hydrocarbon levels) would be close to 80 percent higher than they actually are. We’ve basically treaded water in the ’80s.″

During the creation of ozone, natural hydrocarbons are used up faster than man-made hydrocarbons ″and thus can have a significant effect in spite of their low concentrations,″ the study says.

Chameides said his findings ″should be viewed cautiously,″ but he added, ″Just because there are some uncertainties, you don’t ignore a source of 50 percent of hydrocarbons. We’ve got to include all of the scientific evidence that’s available.″

He said he is anxious for other scientists to check his work and for research to be conducted in other cities.