(a) >What is air? Write the names of various constituents of air.
(b) What is air pollution? What are the main sources of air pollution?

(a) Air is a mixture of several gases that are invisible and odorless.

It consists about 78% nitrogen, 21% is oxygen and less than 1% of Carbon dioxide and other gases like argon, methane and ozone and a varying amount of water vapors.

(b) 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:

1. The natural sources of air pollution are smoke and dust arising from forest fires or volcanic eruptions.
2. The pollutants can also be added from human activities. These are from automobile exhausts, power plants, factories and the burning of firewood and dung cakes.
3. The pollutants like Sulphur dioxide and Nitrogen dioxide when present in polluted air causes acid rain.