Ballygunge in south Kolkata was the most polluted part of the city last winter followed by Fort William area and Salt Lake; found a pan-India study covering metro cities. The study was carried out by a Delhi-based environment think-tank, based on the data generated by Central Pollution Control Board.
Winter months are considered most toxic as the pollution levels surge at this time due to a combination of increased emissions, stagnant atmospheric conditions, and reduced pollutant dispersion.
Ultrafine particulate PM 2.5, considered an extremely toxic pollutant having the ability to penetrate deep into the lungs and trigger range of diseases including fatal ones, has been considered as the benchmark in the study carried out by the Urban Lab at the Centre for Science and Environment (CSE) and released on Tuesday; a copy of which is with the correspondent.
The study, led by air pollution expert and CSE executive director (research and advocacy) Anumita Roychowdhury, and covering all metro cities of the country pointed out that Kolkata, overall, recorded improvement in its PM 2.5 level this winter (October 2024 to January 2025), compared to last year. However, pockets of the city showed pollution surges much above the national permissible limit this time. Kolkata was second, right behind Delhi, in winter pollution among the metro cities, as per the study.
Ballygunge had 54 very poor and poor air days in three months, Victoria recorded highest nitrogen oxide pollution rise
Victoria Memorial enveloped in smog in November 2024 My Kolkata
“Despite seasonal improvements, winter pollution levels in Kolkata surged well above annual averages across monitoring locations. Ballygunge remained the most polluted area, with a winter average PM 2.5 level of 80 micrograms per cubic meter, followed by Fort William (71 micrograms) and Bidhannagar (67 micrograms). Even Rabindra Sarobar, the least polluted location (based on data from seven continuous ambient air quality monitoring stations across Kolkata), saw a 29 per cent increase in winter PM 2.5 levels compared to its annual average” reads the report underlining the high pollution trend in winter. The national limit of PM 2.5 is 60 micrograms.
Overall, the city recorded “its lowest winter average PM 2.5 level in four years, with a seasonal average of 65 micrograms per cubic meter — a 19 per cent decline compared to the previous three winters”, but remains above national limit.
“The growing challenge of particulate pollution in Kolkata remains a concern despite improvements in winter air quality. While the overall seasonal average has improved, pollution spikes continue to be a challenge,” Roychowdhury told this correspondent on Tuesday morning.
The study shows that Ballygunge is clearly the most polluted part of the city with highest day reading during last winter with the highest spike of 195 micrograms — more than three times above normal. Incidentally Ballygunge also recorded the highest annual average of PM 2.5 in city during 2024 with a value of 51 micrograms followed by Fort William (49 micrograms). Rabindra Sarobar recorded the lowest with 39 micrograms. The annual national permissible limit of PM 2.5 is 40 micrograms. The report also has found that, during last winter Ballygunge had 54 very poor and poor air quality days out of 123; much above the city average.
The study also pointed out that the city faces a “multi-pollutant challenge” with levels of nitrogen dioxide (NO2) — another major pollutant mainly triggered by the vehicles — rising sharply between November and January. “Victoria witnessed the steepest increase, with NO2 levels surging 6.4 times from October to January,” read the study.
“These findings underscore the urgent need for a focused strategy to control pollution from key sources and mitigate the winter air quality crisis in Kolkata,” observed the report.
Needs stronger policy; air shade pollution control model
State pollution board chairman Kalyan Rudra pointed out that the government has been trying a string of measures to combat city pollution but that it would be difficult to cut significantly more pollution unless the regional air shade pollution control model is pursued.
“As the World Bank has been pointing out, we need to pursue the regional air shade pollution control mechanism since much of our pollution comes from outside the city; both across state and international borders,” said Rudra.
“The city, being at the tip of the Indo- Gangetic plains, gets affected by the pollution generated in the zone, like Delhi; but inadequate policy implementation also contributes to the problem,” explained Roychoudhury to this correspondent.
The expert stressed that Kolkata needs to focus on multisectoral action to counter air pollution. “Like the rest of the country, Kolkata has also been focusing on dust control, which is important, but to substantially reduce pollution levels it needs to act as well to counter pollution from transport, waste burning and likewise,” added the expert.
“As observed through in-depth chemical characterisation, solid waste and biomass burning are the dominant sources over Kolkata. Such emissions are enhancing ammonia in the air, which in turn helps form a huge amount of particulate matter. We need to target ammonia emission that is producing ultrafine particulate matter through a secondary process,” explained Abhijit Chatterjee, a scientist associated with the union government research organisation Bose Institute and also an advisor to the union government’s flagship National Clean Air Programme.