Pollution air

The ATMOspHERE is an important resource for the survival of all species on the planet, as a source of fresh air for breathing and as a protective layer against direct solar radiation. The Earth's atmosphere is composed of 78.084 percent nitrogen, 20.948 percent oxygen, 0.934 percent argon, 0.031 percent carbon dioxide, and 0.003 percent trace gases such as water vapor and air pollutants. The analysis of air bubbles trapped in ice cores provides evidence that the contents of so-called greenhouse gases, such as carbon dioxide, methane, nitrous oxide, ozone, sulfate, and carbonaceous aerosols, have significantly increased over the past 200 years. This historic change of the atmospheric composition is not fully understood, but it has roots in natural processes and human activity. As a result, both roles of the atmosphere are affected. First, the increase of greenhouse gases contributes to the increase in the amount of solar radiative energy trapped at the Earth's boundaries, which directly affects the planetary climate. Second, the composition of atmospheric air, particularly the air pollutants, strongly affects the human and environmental health.

The air pollutants are defined as substances that adversely affect humans, animals, plants and/or damage property. The air pollutant substances are gases, liquids, or solids, which are suspended in the atmosphere and emitted from different stationary or mobile sources. The pollution sources can be located in outdoor or indoor environments, and as a result the pollution levels are location dependent. Typical outdoor pollutants are particulate matter resulting from different combustion processes, including transportation. The gaseous pollutants include nitrogen oxides (NOX), sulfur oxides (SOX), and carbon monoxide (CO), also resulting from combustion processes. These primary pollutants can have chemical reactions in the atmosphere and create secondary air pollutants such as chemical substances forming smog. An example of naturally occurring pollutant is radon (Ra), a radioactive gas, which is released from the soil, and can be dangerous when trapped in poorly ventilated building basements. Indoor air quality is also becoming important because symptoms called sick building syndrome were correlated to the high levels of indoor air pollutants such as volatile organic compounds emitted from common building materials.

Many countries have established their regulations and standards for air pollution. The so-called first class standards define the maximum concentration levels of target pollutants, which are then attained through regulations passed by environmental protection agencies. The second-class standards provide the scales that define risk levels associated with outdoor activity, which are provided as advisory information to the public.

sEE ALsO: Coal; Diseases; Industrialization; Nuclear Power; Oil, Consumption of; Oil, Production of; Pollution, Land; Pollution, Water.

bibliography. Jeremy Colls, David M. Farrell, Air Pollution. (Spons Architecture Price Book, 2002); F. Patania, C. A. Brebbia, eds., Air Pollution XI (WIT Press, 2003).

Jelena Srebric Pennsylvania State University

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