“A lot of confusion seems to exist over what really contributes to air pollution, particularly PM2.5 (fine, respirable particles) from the transport sector or from vehicles in Delhi. A letter accessed by TOI written by IIT professor Dinesh Mohan to the transport ministry claims that people may be overestimating the “pollution load from traffic” and that there may be a huge difference in the actual number of vehicles on the road as compared to those registered officially.” The Times of India. Read it on delhiair.org