United Nations Environment Programme

Acid Rain

Rain is a naturally mild acid that helps to dissolve minerals into the earth's crust and make them available to plant and animal life. However, the addition of sulphur dioxide (SO2) and nitrogen dioxide (NO2) from human sources disturbs the acid balance of rainwater, converting it into “acid rain”, which is much more acidic and has substantial environmental impacts.

Sources of Acid Rain:
Transport is responsible for a minor share of the pollution leading to acid rain – typically less than 5%. The main contributors of pollution are industry and power plants using sulphur-rich coal.

Acid rainfall may occur at a place far away – up to 1000 km – from pollution sources. For example, acid rain in Sweden and Canada has been traced to large SOx emissions from densely populated areas of the United Kingdom and United States, respectively.

Damage from Acid Rain:
Acid rain causes extensive damage to materials and ecosystems, including damage to buildings, structural materials, and ancient sculptures and heritage sites constructed with or carved from marble, limestone, sandstone and other natural substances. Acid rain also damages crops and forests, resulting in reduced productivity levels.

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