What's happening with air pollution

I live outside India and visit home every year. Almost everytime I uswd to be proud of the air quality here, compared to places like hyderabad and bangalore.Ee year horrible air pollution undhi ikkada. The visibility is so low. Currently aqi is worse than hyderabad (Hyd 153, Vizag 172). What is the reason for this? I see more and more apartment buildings every year. Is it because of construction materials left in the open or growing population and traffic. Is there anything we can do to help?