Pollution

                                                                                                                                                                                                                                                                              

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Air pollution is the presence of any chemical, physical (e.g. particulate matter), or biological agent that modifies the natural characteristics of the atmosphere. The atmosphere is a complex, dynamic natural gaseous system that is essential to support life on planet earth.

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Enforced air quality standards, like the Clean Air Act in the United States, have reduced the presence of some pollutants. While major stationary sources are often identified with air pollution, the greatest sources of emissions are actually mobile sources, primarily cars. There are many available air pollution control technologies and urban planning strategies available to reduce air pollution; however, worldwide costs of addressing the issue are high.

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Sources

                                                                                                                                                                                                                                                                              

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Air pollutants are classified as either directly released or formed by subsequent chemical reactions. A direct release air pollutant is one that is emitted directly from a given source, such as the carbon monoxide or sulfur dioxide, all of which are byproducts of combustion; whereas, a subsequent air pollutant is formed in the atmosphere through chemical reactions involving direct release pollutants. The formation of ozone in photochemical smog is the most important example of a subsequent air pollutant.

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• Anthropogenic sources (human activity) related to burning different kinds of fuel

• Combustion-fired power plants

• Controlled burn practices used in agriculture and forestry management

• Motor vehicles generating air pollution emissions

• Marine vessels, such as container ships or cruise ships, and related port air emissions

• Burning fossil fuels

• Burning wood, fireplaces, stoves, furnaces and incinerators

• Other anthropogenic sources

• Oil refining, power plant operation and industrial activity in general

• Chemicals, dust and crop waste burning in farming

• Fumes from paint, varnish, aerosol sprays and other solvents

• Waste deposition in landfills, which generate methane

• Natural Sources

• Dust from natural sources, usually large areas of land with little or no vegetation

• Methane, emitted by the digestion of food by animals, for example cattle

• Pine trees, which emit volatile organic compounds (VOCs)

• Radon gas from radioactive decay within the Earth's crust

• Smoke and carbon monoxide from wildfires

• Volcanic activity, which produce sulfur, chlorine, and ash particulates