Question

What is air pollution ?

Answer 1

Air pollution is a gas (or a liquid or solid dispersed through ordinary air) released in a big enough quantity to harm the health of people or other animals, kill plants or stop them growing properly, damage or disrupt some other aspect of the environment (such as making buildings crumble), or cause some other kind of nuisance (reduced visibility, perhaps, or an unpleasant odour.

Answer 2

the presence in or introduction into the air of a substance which has harmful or poisonous effects.