Acid rain

Acid rain, popular name for polluting rain or other precipitation caused by the combining of oxides of sulfur and nitrogen with atmospheric moisture. Although it is produced by naturally occurring combustion (volcanoes, forest fires), its serious increase is blamed on the burning of fossil fuels (oil, coal, natural gas) by automobiles and in industry. Acid rain may pollute water, kill vegetation, and erode buildings far from its point of origin and has thus become an international as well as a local issue.

See also: Air pollution; Environmental pollution.