air pollution

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Contamination of the atmosphere caused by the discharge, accidental or deliberate, of a wide range of toxic airborne substances. Often the amount of the released substance is relatively high in a certain locality, so the harmful effects become more noticeable. The cost of preventing any discharge of pollutants into the air is prohibitive, so attempts are more usually made to reduce the amount of discharge gradually and to disperse it as quickly as possible by using a very tall chimney, or by intermittent release.

One major air pollutant is sulphur dioxide (SO₂), produced from the burning of fossil fuels. It dissolves in atmospheric moisture to produce sulphurous acid (acid rain):

SO₂ + H₂O = H₂SO₃

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