1 Anybody who argues stubble burning is not a major pollutant is lying

Because there are multiple source-apportionment studies – they estimate contribution of various pollutants – some sections cite numbers to argue that stubble burning is not a major pollutant as far as Delhi’s air pollution problem is concerned. This is a disingenuous argument. The real impact of stubble burning on Delhi’s air matters not just on the intensity of the activity (satellite data gives us number of farm fires) but also metrological conditions, especially wind direction and speed. To put things simply, if the wind is blowing from east to west rather than west to east, stubble burning in Punjab will increase pollution in Pakistan rather than Delhi. Similarly, a high wind speed leads to faster dispersal of pollutants from farm fires. When these metrological factors turn adverse from Delhi’s perspective, the pollution problem becomes worse even for a lower intensity of stubble burning. For example, they were responsible for half (48%) of Delhi’s PM2.5 on November 7 last year, although the number of fires that day (4,997) was lesser than two days earlier (6,531), when they contributed 36% to Delhi’s PM2.5. In the peak stubble-burning season, farm fires have a significant contribution to Delhi’s air pollution.