Air pollution refers to the presence of solid particles and gases in the air. Pollutants may be natural or manmade. These pollutants cause discomfort, disease, or death to humans. Other living organisms are also affected. The atmosphere is a dynamic complex mixture of gases that is vital for sustaining life on Earth. Emissions from vehicles, factories, dust, pollen and mould spores may be suspended as particles.
Some air pollutants are poisonous; inhalation of polluted air causes respiratory diseases such as asthma, heart diseases, changes in lung function, and also death. Long term exposure to polluted air can compromise the growth (especially lung development) in children. Air pollution is not restricted to the external environment: indoor pollution is also hazardous to health.Air pollutants may be solid particles, liquid droplets, or gases; they may be natural or man-made. Primary pollutants are produced directly through a process, for example carbon monoxide gas expelled by vehicles. Secondary pollutants are produced as a result of the interaction or reaction of primary air pollutants. For instance ground level ozone gas is a secondary pollutant.
- Smog: "Smog" is a portmanteau of smoke and fog. Photochemical smog is the result of chemical reaction of sunlight, nitrogen oxides, and volatile organic compounds in the atmosphere. Smog is a serious threat to human health and is regarded as a problem of modern industrialization.
- Ground level ozone (O3) becomes toxic at high amounts. Human activities including combustion of fossil fuels contribute to high levels of ozone in the air. Ozone is a normal component of the atmosphere and serves as a protective layer (ozone layer). Pollutants such as CFCs deplete the ozone layer.
- Peroxyacetyl nitrate (PAN) is produced from nitrous oxides and volatile organic compounds (VOCs).
- "Stationary Sources": These include power plants, factories, waste incinerators, furnaces and other fuel-burning heating devices. Burning of traditional biomass (wood, crop waste and dung) is a major source of air pollution in developing and poor countries.
- "Mobile Sources": Motor vehicles, marine vessels and aircraft are all mobile sources of air pollution
- The practice of burning in agriculture and forestry management
- Paint, hair spray, varnish, aerosol sprays generate fumes
- Waste deposition in landfills generate methane
- Military: nuclear weapons, toxic gases, germ warfare, rocketry
- Methane: digestion of food by animals is a source of methane
- Radioactive decay generates Radon gas
- Wildfires emit smoke and carbon monoxide
- VOCs come from vegetation, especially on warm days
- Volcanoes are sources of pollutants such as sulphur, chlorine, and ash particulatesThe World Health Organization (WHO) estimates that nearly 2.4 million deaths every year are attributable to air pollution. Nearly 1.5 million people die each year due to indoor pollution. Multiple systems of the human body are affected by polluted air.
- Air pollution is regarded as a risk factor for stroke
- Smoke, emissions from automobiles, tobacco smoke and improper use of indoor heating devices compromise lung function leading to several pulmonary complications. Especially people suffering from cystic fibrosis appear to be affected the most owing to their already compromised lung functions.
- Exposure to polluted air increases the risk of suffering from asthma and Chronic Obstructive Pulmonary Disease (COPD). Several data link air pollution to cancer. Studies have detected increased risk of lung cancer in people who live in areas with high nitrogen oxide concentration in the air.
- Children are at increased risk of developing asthma, pneumonia and other lower respiratory infections.
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