Causes of air pollution: Air pollution can be either natural or man-made. Natural sources include forest fires, dust storms and pollens. Man-made causes are burning of fossil fuels in industries, vehicles and thermos electric plants, emission of gases from industries, mining, processing and stone crushing.

Particulate air pollutants are also known as suspended particulate matter (SPM).

SPM consists of smog, soot, fly ash and dust. Gases such as sulphur dioxide, nitrogen oxide, carbon monoxide, hydrogen sulphide, hydrogen cyanides, hydrogen fluorides, chlorine, methane and ammonia also cause air pollution. Unburnt hydrocarbons act as pollutant vapours.

Following are the effects of air pollution:

(i) Suspended particulate matter in air causes asthma, bronchitis and allergic cold.

(ii) Air pollutants cause irritation in the eyes, throat and lungs.

(iii) Hydrocarbon vapours cause internal organ damage and cancer.

(iv) SO₂ reacts with water in the atmosphere to form sulphuric acid, which causes acid rain that washes down the soil and water bodies and deteriorates the growth of plants and certain fishes.

(v) Increase in atmospheric CO₂ levels intensifies the greenhouse effect and leads to global warming.