Air pollution is one of the major man made problem. When undesirable substances that are harmful for living beings are mixed with air, it is said to be polluted. Human activities are the main reason for air pollution. Air pollution is also caused by emission of harmful gases from vehicles and use of chemicals like fertilizers, insecticides and pesticides in agricultural activities. Beside human activities some natural processes like volcanic eruption, crop pollination etc. are also pollute air. Air pollutants are the harmful substances present in the air. Smoke, dust, soot, CFCs, oxides of carbon, sulphur and nitrogen are some common pollutants present in air. Particles of lead oxide present in the automobile exhaust can damage the brains of children. Incomplete combustion of fossil fuels produces highly poisonous carbon monoxide gas. Excess of carbon dioxide in atmosphere adds to global warming. Gases like sulphur dioxide, sulphur trioxide, hydrogen sulphide, nitrogen dioxide are highly poisonous and cause serious respiratory problems. Acid rain is a rain which is acidic in nature. Gases like sulphur dioxide, nitrogen dioxide, etc. react with water present in the air form sulphurous acid, sulphuric acid, nitrous acid and nitric acid respectively. We should keep our surroundings clean and also advise your friends and neighbours to do the same.