Ozone: Environmental Effects

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Ozone at ground level is a health hazard, causing respiratory ailments such as bronchitis and asthma. It also damages vegetation and causes rubber and some plastics to deteriorate. Nitrogen oxides and volatile organic gases emitted by automobiles and industrial sources combine to form ozone. In 1998, the United States Environmental Protection Agency (EPA) implemented a new air rule designed to curb nitrogen oxides released by coal-fired electric power plants. Many cities issue public air quality warnings when ozone levels rise to dangerous levels. See also Pollution.

Ozone in the upper atmosphere, however, is vital to life. This ozone forms by the action of ultraviolet light from the Sun on molecules of ordinary oxygen. The ozone layer absorbs ultraviolet radiation so that much of it never reaches the ground. Certain industrial compounds cause ozone to break down, opening holes in the ozone layer and exposing life on the ground to dangerous levels of ultraviolet radiation. A single atom of chlorine, for example, floating about in the upper atmosphere, can destroy hundreds of thousands of molecules of ozone because the chlorine acts as a catalyst and is not itself altered in the process. See also Chlorofluorocarbons; Ozone Layer.

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