Pollution is undesirable change in physical, chemical or biological characteristics of air, land and water that may or will harmfully affect human life or that of desirable species, our industrial process, living conditions and cultural assets; that may or will waste or deteriorate our raw material sources. Pollutants are residues of the think we make, use and throw away. In short, environmental pollution means a sort of imbalance of the natural ecosystem by the potentially harmful substances introduced into environment. Pollutants are thus unwanted substances that cause pollution. Pollution is often classified as point source or non-point source:

·         A point source of pollution is a single identifiable source of air, water, thermal, noise or light. A point source has negligible extent, distinguishing it from other pollution source geometries.

·         Nonpoint source pollution refers to both water and air pollution from diffuse sources. Non-point source water pollution affects a water body from sources such as polluted runoff from agricultural areas draining into river, or wind-borne debris blowing out to sea.

Classification of pollution:

Pollution can be classified on the basis of following criterion:
A. Based on environment
B. Based on pollutants