Air Pollution

Earth is surrounded by a gaseous envelope called the atmosphere, which acts as a thermal insulator: it regulates the planet's temperature by selectively absorbing incoming ultraviolet solar radiation. Air pollution is defined as any alteration in the composition of the earth's atmosphere caused by natural processes or, increasingly, by anthropogenic (human) activities. Pollutants may be present as solids, liquids, or gases, and the severity of their effect depends on the nature and concentration of the pollutant as well as on atmospheric conditions such as humidity, precipitation, wind, air currents, and altitude prevailing at the time and place. Two of the most serious adverse effects singled out in this section are the depletion of stratospheric ozone by chlorofluorocarbons (CFCs, once widely used as refrigerants) and global warming driven by elevated carbon dioxide from industry, deforestation, and incomplete combustion. Common air pollutants include particulate matter (fine solid/liquid particles, categorized by size as PM2.5 and PM10) and gases such as sulphur dioxide, nitrogen dioxide, carbon monoxide, and carbon dioxide. Carbon monoxide, produced mainly by incomplete combustion of fossil fuels in automobiles, is especially dangerous because haemoglobin has a much greater affinity for it than for oxygen, so it interferes directly with the body's oxygen transport, causing headache and bl …