Delhi’s official air quality index (AQI) hit 382 on Friday, the city’s worst since January 19, and may still be understating pollution levels after 13 new stations were added to the monitoring network in October, an HT analysis of Central Pollution Control Board (CPCB) data has found. Without the new stations, Friday’s 4pm bulletin would have read 393.
Most of the new monitors, set up by the Delhi Pollution Control Committee (DPCC), the city government’s pollution regulator, are on the city’s periphery, but older stations just as far out, in areas just as built-up, show much higher readings. Most stand on Delhi’s edge. Five are at government schools, three at Delhi Jal Board or Delhi Transco sites, and the rest at a hospital campus, a college, a stadium, an eco-park and an institute. The official added that the sites were chosen for their geographical spread, technical suitability, the availability of government land and the security of the equipment. Their air quality also needs to be measured.
HT’s analysis found the levels of PM2.5 — the biggest contributor to pollution during the winter smog spell — at the new stations are about 35% lower than those at their neighbouring stations. IIT Delhi and Rohini were the worst stations at 7am, at 474 each, according to the HT Pollution Dashboard. By 9pm, 26 of the 59 stations were severe. The Delhi Pollution Control Committee (DPCC), the city government’s pollution regulator, set up the 13 stations, which Union environment minister Bhupender Yadav and chief minister Rekha Gupta inaugurated on October 13. As a group, the new stations are a median 20 km from Connaught Place, against 10 km for the older ones, and their nearest main road is a median 2.2 km away, against 0.9 km. A senior Delhi government official, who asked not to be named, said the new stations were set up under the Commission for Air Quality Management’s regional plan, which prescribes one monitoring station for every 25 sq km in Delhi and adjoining NCR cities.
Because they may record lower pollution levels would itself result in an incomplete and potentially skewed assessment of the city’s air quality, excluding such areas merely.
They “have been placed primarily in previously uncovered areas, particularly in outer and peripheral parts of Delhi, to bridge the geographical gaps in the existing monitoring network,” the official said. Likening the city to a house, whose air could not be judged from the kitchen alone, the official said: “These areas are equally part of Delhi. The official said some of the new stations also read above the city average, and that “the purpose of installing additional monitoring stations is neither to increase nor to decrease the reported AQI”. Swagata Dey, a policy specialist on air quality at the Center for Study of Science, Technology and Policy (CSTEP), a Bengaluru-based think tank, said long-term data was not yet available. It was possible, she said, that the new stations were in cleaner areas than the older ones, which are typically at kerbside and commercial sites, and were pulling the average down. “At the same time, this is unlikely to make a significant difference to citizens’ exposure, given the prevailing meteorological conditions and very high background concentrations,” she said. Sunil Dahiya, founder of Envirocatalysts, an independent air-quality think tank, said the new stations may be pulling the city’s average down, though the evidence needed to be firmer before a final judgement. “But even without accounting for that, the air is already hazardous, at nearly four times the national standard,” he said.
