Since humans populated the earth, they have caused a devastating effect on the natural environment. In the past, the earth's air has been polluted, many forests have been destroyed and thousands of animals have become extinct.
Air pollution has become a major problem since the first machines were made. Each year industrial developed countries generate billions of tones of pollutants. The major pollutants are: carbon monoxide, sulfur dioxide, nitrogen dioxide, ozone, lead, particles and volatile organic compounds. However most of the air pollution comes from the burning of fossil fuels.
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