Under unprecedented: What Deepavali did to the ambient air quality

CHENNAI: The ambient air quality survey in Triplicane, Besant Nagar, Nungambakkam, Sowcarpet and T Nagar on Deepawali day show all the five places recorded hazardous concentration of particulate matter enough to make a healthy person fall sick. Sowcarpet recorded the highest with 777 µg/m3 followed by residential Triplicane 597, T Nagar 529 and Nungambakkam 541. The lowest was Besant Nagar at 387 µg/m3, which was still nearly four times higher than permissible limits.

TNPCB officials confessed that this Deepavali could be the ‘most polluting’ ever. A quick number crunching of previous years’ data reveals that the last two years were the best Deepavali days for Chennai in terms of pollution, as the PM10 value hadn’t breached 200. In 2016, Nungambakkam and Sowcarpet topped with 178 µg/m3 followed by Triplicane 177, T Nagar 113 and Besant Nagar 102. The best year was 2015, when Besant Nagar, Triplicane and Sowcarpet registered 88, 90 and 93 µg/m3, respectively, which were under permissible limits. Interestingly, the noise pollution levels remained uniform in all the three years.

Blame it on weather
TNPCB member secretary N Sundara Gopal told Express that the city suffered this time primarily because of unfavourable climatic conditions. “With cloudy skies, no rain and wind, all the pollutants stayed low. This led to smog-like condition,”he said.

Why PM2.5 not measured?
City activists and environmentalists are questioning why the TNPCB did not measure PM2.5, which is far more damaging to human health than PM10. PM2.5 is about 3% the diameter of a human hair. It can bypass the nose and throat and penetrate deep into the lungs and even circulatory system.
Social activist Nityanand Jayaraman said it has been more than a decade since PM10 was abandoned as a measure of dust pollution in favour of PM2.5, which represents respirable dust matter that is far more hazardous than larger dust particles. PM2.5 is a Class I carcinogen.

“Measuring PM2.5 is not an expensive affair. Some of the NGOs in the city are having air monitors that measure PM2.5. Besides, all TNPCB readings were averages. The noise levels were six-hour averages, and PM10 levels were 24-hour averages. They hide spikes and peaks in air pollution that would have sent the air pollution monitors into a tizzy. The TNPCB should report the peak hourly values. I suspect the PM10 values would have crossed 1000 ug/m3 and noise levels breached the 100 dB limit,”he said.
Reacting to the criticism, a top TNPCB official said that all these years only PM10 values were released during Deepavali. From next year, PM2.5 values will also be measured.
“We are having five continuous amient air monitoring stations, which measure PM2.5. But, the equipment that is used for Deepavali survey measures only PM10, SO2 and NO2 pollutants,”he said.

Private air monitors
Dharmesh Shah of Vettiver Collective, which maintains four air quality monitors in Ennore, Tondiarpet, Teynampet and Besant Nagar, has recorded pollution levels as high as 15 times during peak hours. Between 9 and 10 pm on October 18, the Air Quality Index (AQI) at Teynampet was 1,541. Tondiarpet recorded 1,139 and Adyar recorded 969. He said one air quality monitor has been moved to Vepery as north Indians celebrate Deepavali on Thursday.

23 flights delayed
A total of 23 flights, both international and domestic, were delayed between 10 pm and 2 am as thick smog resulted in poor visibility. Top airport sources said one flight was diverted to Hyderabad and other took off post 2 am.