Polluted air is contaminated with the substances like smoke, dust and other harmful substances called pollutants. These pollutants can come from natural sources or from human activities. Following are the main sources of air pollution:

● The natural sources of air pollution are smoke and dust arising from forest fires or volcanic eruptions.

● The pollutants can also be added from the human activities. These are from automobile exhausts, power plants, factories and burning of firewood and dung cakes.

● The pollutants like Sulphur dioxide and Nitrogen dioxide when present in polluted air causes acid rain.

● The gas called carbon monoxide enters the air by the incomplete burning of fuels such as petrol and diesel. It is a very poisonous gas which reduces the oxygen carrying capacity of blood.

● The Chlorofluorocarbons which are used in the refrigerators, air conditioners and aerosol sprays also act as air pollutants. They are responsible to deplete the ozone layer in the atmosphere.