What’s causing poor air quality?

NEW DELHI: DEC. 3 – India’s capital Delhi has experienced some of its worst levels of pollution in many years this winter.

It’s been blamed on various factors including the burning of farm stubble, on factory emissions, on traffic fumes, on general weather patterns, as well as fireworks that light up the night sky during the Diwali festival. But how much do each of these factors contribute to the problem?