Air pollution occurs when the air contains gases, dusts, fumes in harmful amount. It is one of the most serious types of pollution. There are some causes that people make the air polluted. They use too much fossil fuel. They spray pesticides when doing farming and factories produce much smoke. Air pollution can have dramatic effects. It damages humans and animals' heath as well as food crop. It keeps breathing problems and lung cancer increasing. It also causes the global warming and acid rain. Because of these bad effects, we should reduce air pollution by using less fossil fuel, cutting down the amount of pesticides for farming and smoke from factories.