Air pollution is some form of contamination of the atmosphere which has adverse effects on humans and other living beings, or is harmful to crops, forests, materials, or the climate. There are both anthropogenic (human-made) pollutants and pollution causes by natural phenomena.
Air pollutants are effectively either specific gas-phase molecules, or small solid-phase particles suspended in the air. The latter are as a collective referred to as particulates. Liquid-phase aerosols can also be pollutants but are normally caught under the “particulates” label.
Small fractions…
Roughly speaking and as long as we stay at ground level, ambient air consists of gas phase nitrogen (N2, a volume share of 78 %) and oxygen (O2, 21 %). The noble gas argon (Ar) fills out most of the remaining 1 %. There’s a tiny remaining share of about 0.045 % of which most is carbon dioxide (CO2). Background levels of CO2 are slightly above 0.04 % (400 volumetric parts per million, ppm), although rising due to human activities. CO2 is therefore to some extent an air pollutant. Next in line of the pollutants is methane (CH4) with background concentrations in the range of 1-2 ppm. All other air pollutants are typically measured in even lower concentrations, often expressed in units of volumetric parts per billion, ppb.
…but Notable Effects
Despite that most air pollutants are just “fractions of fractions” of the air, they are still of major concern.
Air pollution can cause a number of diseases including respiratory infections, heart diseases, stroke, and lung cancer. It has been claimed to be the world’s largest single environmental health risk, causing millions of deaths worldwide each year. In terms of impaired quality of life and productivity losses, the impact on world economy is huge. Air pollution is therefore regulated in most parts of the world, often in terms of emissions limitations and monitoring of the air quality.
Sources of Air Pollution
There are many sources of air pollution. A large part is generated by one or other form of combustion, notably when turning fossil fuels into energy at power plants or in vehicles, but also by controlled burns of agricultural areas and forests. Industrial production processes as well as the finalized goods can also emit large amounts of pollutants. Among natural sources are volcano eruptions and leakage of methane from grounds where the permafrost gives way.
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About the Author
Bengt Löfstedt
Operative Support, OPSIS AB