Delhi's air quality dipped on Wednesday due to a drastic fall in wind speed, triggering rapid accumulation of pollutants and a grey haze, which affected visibility across the city.
The Central Pollution Control Board (CPCB) recorded an air quality index (AQI) of 359, marking the return of 'very poor' air after eight days. The AQI had turned 'moderate' on December 12 and since then had remained 'poor'. CPCB scientist Dipankar Saha said the situation is likely to improve soon as winds blowing from the north will bring down temperature resulting in precipitation of fog. "We are witnessing calm conditions but good news is that wind is likely to come from north and we can expect drop in temperature, and fog," Saha said.
Due to precipitation of fog (liquid droplets turning into vapour), the level of particulates also fall. Vivek Chattopadhyay, a researcher with the Centre for Science and Environment (CSE), said conditions are considered calm when wind speed hovers around 0.3 metres per second. "It makes the air more dense. Moreover, due to drop in temperature, the boundary layer, the layer where particulates and air mix, also comes near the surface," he said.
The concentration of PM10 was 408.8 ug/m3 at 8 pm after rising through the day. PM2.5, which are finer and deadlier particulates, was recorded at 256.2 ug/m3 as per the Central Control Room for Air Quality Management of the CPCB.
Concern over Kolkata's air quality
An air quality report by the US consulate here has shown that the PM 2.5 level at the city's Park Street area has surpassed Delhi's Chanakyapuri locality on Tuesday, with environmentalists and people here expressing concerns.
The particulate matter (PM) level -- an important index in measuring pollution -- in the Chanakyapuri area of Delhi had improved from 292 Acceptable Quality Limit (AQL) to 189 AQL between noon to 6 pm on Tuesday. In Park Street here, the count went up from 274 AQL to 288 AQL during that time, the consulate website report says. Expressing concern over the report, environmentalist S M Ghosh said diesel cars are the main contributing factor to the alarming level of pollution in the city.
The West Bengal Pollution Control Board is doing very little to reduce the fleet of diesel cars, he alleged. The situation, however, improved this morning with the PM 2.5 level at 171 AQL, far higher than the minimum alarming level of 151 AQL (acceptable quality limit), the website said. In New Delhi, the AQL count shot up to 389 at 1 pm today, it added. WBPCB Chairman Kalyan Rudra, however, said there was no reason to panic as the report covers just one area and does not give a complete picture.
The WBPCB is initiating a number of measures to ensure good ambient air quality for the people here, Rudra said. There are 14 WBPCB air pollution monitoring units in the city and their display boards have been put up across the thoroughfares here to give updates on Suspended Particulate Matter (SPM) and PM 2.5. Environmentalist Ghosh, however, said three pollution monitoring devices in the city are lying defunct for months now. "The WBPCB is sitting on a proposal by environmentalists to increase the monitoring devices across the city from 14 to 25. They (WBPCB) would not admit but three of their monitoring units are lying defunct for several months," he alleged.
Debmit Dutta, a 39-year-old telecom engineer who works at an MNC in the Salt Lake area of the city, said he has ordered special air filter masks online considering the situation.
"The situation is not very different here from that of Delhi, I feel. I have ordered masks online and hopefully it will protect us from the toxic air to an extent," he said. West Bengal Public Health Engineering Minister Subrata Mukherjee said the situation here is better than Delhi and necessary steps are being taken to curb air pollution. Echoing similar sentiments, West Bengal Environment minister Sovon Chatterjee said, "I am yet to go through the contents of the US consulate report. But the government is taking every measure to reduce pollution level.
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