Many pollutants have a poisonous effect on the body. Carbon monoxide is an example of a substance which is damaging to humans. This compound is taken up in the body instead of oxygen. That makes the body and in severe cases may lead to death.
Some pollutants became dangerous by reaction with other naturally occurring compounds. The oxides of nitrogen and sulphur are released from impurities in fossil fuels when they are burnt. They react with water vapour in the atmosphere to become acid rain. Acid rain damages buildings and makes lakes unable to support marine life, which causes fish and water plants to die.
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