Define the following terms :
(iii) air pollution.
i)the presence in or introduction into the environment of a substance which has harmful or poisonous effects
a substance that pollutes something, especially water or the atmosphere.
iii) Air Pollution - The air which pollute and contaminate the air inthe atmospehere. It is caused by using harmful gases in industries or factories. In addition, it is caused by smoke coming out from vehicles , etc.