What is the difference between pollutant and contaminant?

Explanation

Pollutant is the substance produced by natural sources or by the human activities. When these substances are present in the environment in greater proportion, then these substances cause harmful effect to the living or non-living organisms. These are known as pollutants.
For example, carbon monoxide, sulphur dioxide, oxides of nitrogen, dust particles etc.
Contaminant : It is a substance which is not present in the nature, but is added to the environment by certain human activities. These may or may not be harmful to the human beings or the nonliving organisms. For example, methylisocyanate (MIC) is not present in the nature but is being introduced by human activities, which is very harmful.