The three reasons you mentioned are indeed the prevalent reasons but mostly in rural part of india.
In cities like Delhi and Mumbai, none of these is major reason. Pollution from vehicles (especially diesel vehicles), crop waste burning (esp in areas around Delhi) and industrial pollution are the major reasons. These cities are too densed and yet too big.
The sad thing is that there are hundreds of laws to prevent pollution but law enforcement is not a thing in India.
In cities like Delhi and Mumbai, none of these is major reason. Pollution from vehicles (especially diesel vehicles), crop waste burning (esp in areas around Delhi) and industrial pollution are the major reasons. These cities are too densed and yet too big.
The sad thing is that there are hundreds of laws to prevent pollution but law enforcement is not a thing in India.