Say what is pollution and why it can be dangerous.

Millions of animals die every year because man has polluted their natural homes. The country air, once clear and fresh, now may be polluted by power stations and factories. Some of our rivers are now empty of fish. All over the world the forests are dissapearing. People cut over the trees down because they need wood and paper or new places for farms and houses ... Pollushion is very dangerous for people, wildlife and the environment. We live among litter and wastes which we were created ourselves.