Massive Emissions of Carcinogenic Benzenoids from Paddy Residue Burning in North India

Benzenoids are organic pollutants emitted mainly by traffic and industrial sources. Here, using a combination of on-line in situ PTR-MS measurements of several benzenoids and methyl cyanide (a biomassburning tracer), satellite remote sensing data of fire counts and back trajectory of air masses at a site in Mohali, we show that massive amounts of benzenoids are released from post-harvest paddy residue burning. Two periods, one that was not influenced by paddy residue burning (period 1, 18 : 00-03 : 30 IST; 5-6 October 2012) and another which was strongly influenced by paddy residue burning (period 2, 18 : 00- 03 : 30 IST; 3-4 November 2012) were chosen to assess normal and perturbed levels. Peak values of 3830 ppb CO, 100 ppb NO_x, 40 ppb toluene, 16 ppb benzene, 24 ppb for sum of all C-8 benzenoids and 13 ppb for sum of all C-9 benzenoids were observed during period 2 (number of measurements in period 2 = 570) with the average enhancements in benzenoid levels being more than 300%. The ozone formation potential of benzenoids matched that of CO, with both contributing 5 ppb/h each. Such high levels of benzenoids for 1-2 months in a year aggravate smog events and can enhance cancer risks in northwestern India.