Question

what are causes of air pollution in big cities?

Answer 1

The major causes of air pollution are:
Burning of Fossil Fuels like coal etc.. in big industries.
Smoke from factories and industries which releases huge amounts of carbon monoxide.
 Mining operations.
Household emissions of smoke etc..
And due to traffic jam in peak house where mostly bad smoke is emitted.
And so on...
Hope this helps!!

Answer 2

the causes of air pollution in big cities are, factories,vehicles,dumping garbage,loud speakers, vehicle's horns etc.