New Delhi recently earned the dubious distinction of the world’s most polluted city, thanks to a smog that enveloped the capital in the early week of November. The smog, caused by burning of post-harvest paddy stalks in neighbouring states, smoke from firecrackers during Diwali and vehicular traffic, put the city’s Air Quality Index at 999, over and above the “hazardous” level of 500. The level of particulate matter, finer than 2.5 micrometers, in some areas crossed the 900 mark, almost 15 times over the safety limit. The situation was largely exacerbated by low wind speed and a drop in temperature, causing pollutants to stagnate in the air. In contrast, China’s most polluted city, Baoding, saw the highest AQI level of 298. Reduced visibility saw traffic slowing down and schools staying shut for three days. But savvy vendors are making the most of the crisis. Most shops selling anti-pollution masks, ranging from 90 to 2,200, saw brisk business as panicky customers sought protection from the toxic smog.