The earth's environment has been composed in a way which sustains life on this planet. Through on process, the different constituents of the atmosphere are consumed and through the other, these constituents are released into the atmosphere.

But due to industrial revolution, and speedy exploitation of natural resources, the composition of the atmosphere has been changed undesirably. In other words we have polluted the atmosphere.

Pollution is defined as undesirable change in physical, chemical or biological characteristic of are, land and water which is causing harmful effects on our life or that of other living organism and cultural assets. The undesirable or unwanted foreign species or matter causing pollution air, water soil or any segment of environment are called pollutants.