(a) Pollution of air is caused by humans in the following ways :
1. Large amount of coal burnt in thermal plants throw out huge amounts of smoke and ash in the atmosphere.
2. Vehicles using petrol or diesel give out a lot of smoke and harmful gases like carbon dioxide, lead-carbon- monoxide.
3. Burning of garbage causes a lot of pollution due to the formation of carbon monoxide, sulphur dioxide and nitrogen dioxide.
4. Pesticides spread in the fields also cause air pollution.
(b) Pollution of air by humans can be minimised in the following manner :
1. In the thermal power plants, steel plants etc., electric precipitators should be used to reduce the smoke and ash entering the air.
2. Efficient internal combustion engines should be used in vehicles.
3. Improved chulha or stoves should be used to minimize the production of smoke and carbon monoxide.
4. We must grow more trees as they absorb harmful gases.
