Pollution may be defined as an undesirable change in the physical, chemical or biological characteristics of air, water and land that may or will harmfully affect human lives or other organism. Pollution can be natural or man made. Natural pollution comes from volcanic eruptions, emission of natural gas, soil erosion, ultraviolet rays, etc. Most of the pollution is man-made. Contamination occurs due to the presence of harmful organisms or their products or undersirable products in a desirable product causing disease or discomfort, for the organism who consume it. Therefore pollution and contamination are two different things.