Air pollution is a broad term applied to all chemical and biological agents that modify the natural characteristics of the atmosphere.
Some definitions also consider physical perturbations such as noise pollution, heat, radiation or light pollution as air pollution. Some definitions include the term harmful as a requisite to consider a change to the atmosphere as pollution.
Air Pollutants are classified as either Primary or Secondary. A primary air pollutant is one that’s added directly to the air from a given source. An example of a primary air pollutant would be carbon monoxide because it is added to the air as a byproduct of combustion.
A secondary air pollutant is formed in the atmosphere through chemical reactions. An example of a secondary air pollutant would be the formation of ozone in photochemical smog.
3 million people die of air pollution each year worldwide. 2.8 million of the 3 million die from indoor air pollution. 90% of the 3 million are deaths in developing nations. 70,000 die each year in the U.S. (Some estimates are as low as 50,000 or as high as 100,000). Deaths from air pollution are compared to deaths from second hand smoke and chemical weapons. In the U.S, more people die from air pollution than from car accidents. They die specifically from agitated asthma, bronchitis, emphysema, lung and heart diseases, and other respiratory allergies. The EPA estimates that a proposed set of changes in diesel fuel technology (Tier 2) could result in 12,000 fewer premature mortalities, 15,000 fewer heart attacks, 6,000 fewer emergency room visits by children with asthma, and 8,900 fewer respiratory-related hospital admissions each year in the US.
The worst short-term civilian event from pollution in India was the 1984 Bhopal Disaster. Leaked industrial vapors killed more than 2,000 people outright and injured anywhere from 150,000 to 600,000 others, some 6,000 of whom would later die from their injuries. The worst single incident of air pollution to occur in the United States of America occurred in Donora, Pennsylvania in late October, 1948, when 20 people died and over 7,000 were injured. The United Kingdom suffered its worst air pollution event when the December 4th Great Smog of 1952 formed over London. In six days more than 4,000 died, and 8,000 more died within the following months. An accidental leak of anthrax spores from a biological warfare laboratory in the former USSR in 1979 near Sverdlovsk is believed to have been the cause of hundreds of civilian deaths.
Intentional air pollution in combat is called chemical warfare. Poison gas as a chemical weapon was principally used during World War I, and resulted in an estimated 91,198 deaths and 1,205,655 injuries. Various treaties have sought to ban its further use. Non-lethal chemical weapons, such as tear gas and pepper spray, are widely used.
The sources of air pollution are divided in two groups: anthropogenic (generated by human activity) and natural.
Natural sources include:
Anthropogenic sources are mostly related to burning different kinds of fuel. They include:
Sources not directly related to burning fuel include:
Industrial activity in general.
- Oil refining.
Waste deposition in landfills, which generate methane.
- Fumes from paint, varnish, and other solvents.
Aerosols and refrigeration, which once depended on Freon and other chlorofluorocarbons.
Arsenic and chlorine found in drinking water and inhaled in bathroom showers.
- Dust and chemicals from farming, especially of erodible land, see Dust Bowl.
- Military actions, including the use and testing of nuclear bombs, poison gases, and germ warfare.
Rocketry, which produces many tons of exotic emissions quickly and which deposits some of them directly into the tenuous upper atmosphere.
Contaminants of air can be divided in particulates and gases.
Particulates are small, solid particles, classified by their sizes. A usual division is in PM10 and PM2.5. PM10 are particles whose size is less than 10 micrometres; they are dangerous to humans because they can be breathed and reach the lungs. PM2.5 are particles whose size is less than 2.5 micrometres, and they are even more dangerous because they can pass through the upper airway filtering and down into the alveoli where they can cross the lung/blood stream barrier and transport into the blood. Smaller particles also tend to be more toxic than larger particles and tend to stay airborne longer than larger particles which settle out more quickly.
Important pollutant gases include:
Indoor air pollution
The lack of ventilation indoors concentrates air pollution where people are most exposed to them. Background pollution comes from such mundane sources as shower water mist containing arsenic, which is damaging to inhale. The arsenic can be trapped with a shower nozzle filter. Radon gas, a carcinogen, is exuded from the earth and trapped inside houses. Researchers have found that radon gas is responsible for over 1,800 deaths annually in the United Kingdom. These natural radon emissions can be blocked by a layer of aluminum foil under the carpet (according to the U.S. Department of Air Quality Management). Building materials including carpeting and plywood emit formaldehyde gas. Paint and solvents give off volatile organic compounds (VOCs) as they dry. Lead paint can degenerate into dust and be inhaled. Asbestos insulation was commonly used in many application and can be carcinogenic in the lungs. Intentional air pollution is introduced with the use of air fresheners, incense, and other scented items. Controlled wood fires in stoves and fireplaces can add significant amounts of smoke particulates into the air, inside and out. Clothing emits perchloroethylene for days after dry cleaning.
Deaths are often caused by using pesticides and other chemical sprays indoors without proper ventilation, and many homes have been destroyed by accidental pesticide explosions. Second-hand tobacco smoke is now recognized as an indoor air pollutant which accounts for an estimated 3,000 lung cancer deaths annually in the US. Carbon monoxide poisoning is a quick and silent killer, often caused by faulty vents and chimneys, or by the burning charcoal indoors. 56,000 Americans died from CO in the period 1979-1988. Chronic carbon monoxide poisoning can result even from poorly adjusted pilot lights . Smoke inhalation is a common cause of death in victims of house fires. Traps are built into all domestic plumbing to keep deadly sewer gas, hydrogen sulfide, out of interiors.
Biological sources of air pollution can also be found indoors, and include gases, particulates, allergens, and microbes. Pets produce dander, bed mites deposit shells and microscopic droppings, roommates can emit methane, mold can form in walls and generate spores, air conditioning systems can incubate Legionnaires disease, toilets can emit feces-tainted mists, and houseplants and surrounding gardens can produce pollen, dust, and mold spores.
- Davis, Devra, When Smoke Ran Like Water: Tales of Environmental Deception and the Battle Against Pollution, Basic Books, 2002, hardcover, 316 pages, ISBN 0-465-01521-2