Air pollution over Beijing
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Air pollution over Beijing. See more green science pictures.

AP Photo/Greg Baker

Air Pollution, the contamination of the air by impurities. These impurities, called pollutants, can occur naturally or they can be produced by human activities. Naturally occurring pollutants include dust, pollen, salt particles, smoke from forest fires, and gases from decaying organisms. Most pollution caused by human activities is directly or indirectly the result of burning of fuels in furnaces or engines. This article is primarily concerned with air pollution caused by human activities.

A serious consequence of air pollution is its impact on human health. Air pollution can contribute to respiratory diseases such as chronic bronchitis, asthma, emphysema, and lung cancer. Air pollution also harms or destroys plant and animal life, and damages property.