we all know that clean air is important to good health. wherever you go and whatever you do, you are always surrounded by a sea of gases that we call air. if there are impurities in the air, they may be absorbed by our bodies and make us ill. we need clean air, but unfortunately , air pollution is globally present , especially in cities.
many large cities are anything but pollution-free. our cities have many factories, which we need to make food, clothing and other things. every year these factories pour millions upon millions of tons of smog into air. power plants and houses that burn coal add greatly to air pollution. besides , there are more cars in cities now. once out on the streets, they will take in fresh air and replace it with poisonous gases.