Air Pollution - Each year industrially developed countries generate billions of tons of pollutants. Many pollutants come from directly identifiable sources; sulphur dioxide, for example, comes from electric power plants burning coal or oil. Others are formed through the action of sunlight on previously emitted reactive materials (called precursors). For example, ozone, a dangerous pollutant in smog, is produced by the interaction of hydrocarbons and nitrogen oxides under the influence of sunlight. Ozone has also caused serious crop damage. The increasing number of vehicles have also lead to an increase in Air Pollution, due to the harmful gases like Carbon Monoxide emitted from these vehicles. Gases generated in the Chemical plants also cause air pollution. People suffer because of smoke and bad smell from the industrial units particularly from chemical plants.