What is Air Pollution ? 

Air pollution occurs when the air contains gases, dust, fumes or odour in harmful amounts. This can affect humans , animals , plants etc. in many different ways. An example is Asthma for humans. Asthma is often caused by air pollution, and creates many problems, like trouble breathing, lung ailments and other related diseases. 

The substances that cause air pollution are called pollutants. Pollutants that are pumped into our atmosphere and that affect our air directly are called primary pollutants. Primary pollutant examples include carbon monoxide from car exhausts and sulfur dioxide from the combustion of coal.

Further, pollution can arise if primary pollutants in the atmosphere undergo chemical reactions. This is called secondary pollutants. Photochemical smog is an example of this.