Factories like this are a major source of air pollution.
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Air Pollution Sources
Air pollution comes from many different sources. Natural processes that affect air quality include volcanic activity, which produce sulfur, chlorine, and ash particulates, and wildfires, which produce smoke and carbon monoxide. Cattle and other animals emit methane as part of their digestive process. Even pine trees emit volatile organic compounds (VOCs).
There are many forms of air pollution that are human-made. Industrial plants, combustion-fired power plants and vehicles with internal combustion engines generate nitrogen oxides, VOCs, carbon monoxide, carbon dioxide, sulfur dioxide and particulates. In most megacities, such as Mexico City and Los Angeles, cars are the primary source of these pollutants. Stoves and incinerators, especially ones that are coal or wood-fired, and farmers burning their crop waste produce carbon monoxide, carbon dioxide, as well as particulates. Other human-made sources include aerosol sprays and gases leaking from refrigeration systems, as well as fumes from paint, varnish, and other solvents. Additional pollutants, like ozone and acids, are made in the atmosphere when human-made gases combine chemically.
One important thing to remember about air pollution is that it doesn’t stay in one place. Winds and weather play an important part in transport of pollution locally, regionally, and even around the world, where it affects everything it comes in contact with.
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