Pollution

Pollution occurs when humans contaminate the natural environmental; which brings about changes that affect our normal lifestyles. Humans are the key elements or components of pollution which are generally waste materials of different forms. Pollution disturbs our ecosystem and the balance in the environment. With modernization and development in our lives pollution has reached its peak; giving rise to global warming and human illness.
In the world there are many kinds of pollution, like the pollution in the air, in the land and in the water.

http://www.worldwildlife.org/threats/pollution