Particulate matter (PM) pollution, particularly of the PM 2.5 variety, went as high as 3,000 microgramme/cubic metre (ug/m³) around Delhi University in 2017 winter, says a year-long analysis of air-pollution trends by the CSIR-NISTADS, a research and policy wing of the Council of Scientific and Industrial Research. This, even as average concentrations of the pollutant ranged from 80-150 ug/m³ through the year.
The scientists measured PM 10 , PM 2.5 and PM 1 at 15-minute intervals between 7 a.m. and 9 p.m. for a year from January 2017 to January 2018 at four areas in Delhi — Pusa institute, Punjabi Bagh, Delhi University and Dheerpur.
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The recordings were made by sensors fitted on vans that plied in three locations within each of the four spots. “This was done to gauge the short-term exposure to pollution in a wide expanse of Delhi. Several studies have reported a link between such exposure and the impact on health,” said Naresh Kumar, a CSIR-NISTADS scientist, involved with the study.
“The bigger purpose of this exercise is to develop a traffic management system that can alert motorists if they are approaching a region of high pollution and then, if need be, decide on a diversion,” said CSIR-NISTADS director Prashant Goswami.
A scientist not involved with the study said that 15-minute measurements could be much higher than the 24-hour averages. While useful for traffic alerts, such measurements did not always mean a higher health risk as the actual exposure could be lower. “Globally, the standards are for 24 hours because its known particulate matter shows substantial variation through the day. The health effects of 24-hour concentrations are better studied and much better understood than the 15-minute interval measurements,” said S.K. Goyal, head of National Environmental Engineering Research Institute which also is a CSIR body. He was present at a workshop on Tuesday where the CSIR-NISTADS findings were discussed.
Previous studies by a range of institutions — from the Central Pollution Control Board to the SAFAR — have recorded average 24-hour PM 2.5 concentrations as high as 500 ug/m³.
Delhi’s pollution levels are known to spike in the winter months and the CSIR-NISTADS too showed an increase in pollution levels in January, February, October, November and December. Lancet Commission reveals air pollution was responsible for 2.5 million deaths in India in 2015. India’s National Ambient Air Quality Standards (NAAQS) specifies that PM2.5 not breach 40 ug/m³ annually and 60 ug/m³ over 24 hours. As Delhi braces for winter, State and Centre government are preparing to buffer against a spike in pollution levels — particularly around November — when wind speeds drop and road dust, vehicular emissions and biomass burning combine to generate a smoggy pall that, doctors say, also leads to a rise in respiratory illnesses in the city.
