The city’s air quality dropped from “good” to “very unhealthy” in the last three months of 2021, says a report released by the West Bengal Pollution Control Board on Sunday.
The city’s air quality index (AQI), an indicator of criticality of the pollution level in the air, has risen sharply since September 2021, the report says.
The report, published on the occasion of the World Environment Day, points out that till September 2021, Kolkata had the lowest average monthly air quality index value among four major metros in the country.
Kolkata’s air pollution shifted gear after that and the city had the second worst air quality among the four metros, after Delhi, pushing Mumbai and Chennai behind.
State environment minister Ratna De Nag and secretary Vivek Kumar released the report along with senior board officials.
Air quality index (AQI) is an indicator of the level of pollution in outdoor air, measured on the basis of the dominant air pollutant present. Its value indicates the kind of health impact on the people.
Kolkata's AQI in September 2021 was 49, considered “good”. Delhi topped the list scoring 78, followed by Chennai at 59 and Mumbai at 58.
However, in October, Kolkata’s AQI jumped almost 110 per cent to 103. Delhi’s was 173 and Mumbai and Chennai stood third and fourth with AQI 96 and 63.
The trend continued as the city’s AQI in November and December climbed up to 202 (very unhealthy).
People with respiratory ailments such as asthma, as well as others, should avoid all outdoor exertion when the AQI crosses 200, says experts.
Overall, the report shows, the average level of particulates PM10 (about 105 micrograms per cubic meter of air) rose marginally in 2021 compared with 2020 and was close to the 2019 level. However, it was way down compared with the 2018 level of around 145 microgram.
The average level of PM 2.5, finer than PM10 and so more toxic, in 2021 was marginally less (about 40 micrograms per cubic meter of air) compared with 2020.
“We have undertaken a very aggressive water sprinkling programme in the city and the surrounding area to minimise air pollution. About 50 per cent of the pollutants in the city’s air is from outside the city,” said Kalyan Rudra, chairman of the state pollution control board.
“The reduction in air pollution in the city air in 2020 and 2021 was by default, not by design, because of Covid-induced restrictions. The real test of the state PCB will be next winter, hoping Covid will no longer be an issue then,” said environment activist Subhas Datta.