CFC Replacements Prove No Panacea

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Chemicals designed to replace ozone-destroying chlorofluorocarbons (CFCs) may end up doing environmental harm of their own. That possibility is raised in a research paper in the current issue of the journal Nature.

CFCs have been widely used as coolants for refrigerators and air conditioners, as well as in fire suppressants. When released into the atmosphere, the gas rises and, through a series of chemical reactions, breaks down ozone in the stratosphere. This ozone layer helps block harmful ultraviolet light from the sun. By international agreement, CFC production and use is being phased out over the next two decades.

Yet several replacements for CFCs, including the most common, known as HFC-134a, react with oxygen and hydrogen to form trifluoroacetic acid, which can return to the Earth's surface as another form of acid rain. According to the paper, written by four scientists at Atmospheric and Environmental Research Inc., in Cambridge, Mass., the average global concentrations of the acid aren't likely to be harmful. But their calculations suggest that concentrations could build to harmful levels in seasonal wetlands or tundra, which remain moist for part of the year and then lose their moisture to evaporation.

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