What is air pollution? How is it caused?

Air pollution means degradation of air quality due to the increase in the concentration of harmful contaminants that affects human, plant and animal lives.

Causes of air pollution are :

Natural Sources

1. Volcanoes — Volcanoes release large amounts of air pollutants such as carbon monoxide, sulphur dioxide, hydrogen sulphide, chlorine, hydrogen chloride, hydrocarbons and particulates.
2. Decaying vegetation — Microbial action on organic matter in soil releases a pollutant - nitrous oxide.
3. Forest fires release the poisonous gas - carbon monoxide.
4. Winds and dust storms carry particulate matter like sand and dust.

Man-made sources

1. Automobiles use diesel or petrol as fuel. Incomplete combustion of these fuels releases carbon monoxide, sulphur dioxide, hydrocarbons, nitrogen oxide and particulates like lead.
2. Factories release carbon dioxide, sulphur dioxide, nitrogen monoxide and particulates.
3. Industrial processes release different types of air pollutants, depending upon the type of process involved.
4. Decay of crop residue in rural areas is the main source of carbon monoxide and methane.
5. Burning of plastics releases carbon monoxide and other harmful gases.