Air pollution is the increase in the harmful substance in air like carbon-di-oxide, carbon mono oxide etc. it is caused due to,

1) Gaseous emissions from vehicles releases carbon-di-oxide and carbon mono oxide in the air which are highly toxic.

2) Smoke coming out from factories and industries also releases more toxic gases into the air making it highly toxic.

3) In villages and other backward areas, still wood and cow dung are burnt as a source of fuel which pollutes air.