Kolkata has second worst air among India’s metros. What it needs to do to breathe better
Telegraph | 19 March 2025
Kolkata recorded a marginal decrease in air pollution level during 2024 compared to 2023, but still stands as the second most polluted metro city in the country after Delhi and within the 2 per cent most polluted cities of the world, a recent global report has confirmed.
The city has already spent Rs 792 crore under the country's flagship National Clean Air Programme (NCAP) in the last five years within a total released fund of Rs 960 crore.
The study was carried out by IQAIR, a Swiss air quality technology company, based on PM 2.5 data collected from more than 40,000 air-quality monitoring stations across 8,954 locations in 138 countries, territories and regions.
PM 2.5 is one of the most potent air pollutants that can penetrate the deep crevices of lungs and trigger a bevy of respiratory diseases including the fatal ones.
Kolkata, with an annual average PM 2.5 level of 45.6 micrograms per cubic metre in 2024, exceeded the World Health Organization-set guideline limit of 5 micrograms by nearly nine times. The city’s level is also above the national limit of 40 micrograms.
The city, with a global rank of 184, is behind Delhi – which is the second most polluted city in the world with an average annual PM 2.5 level of 107 – but way ahead of Mumbai, Chennai, Hyderabad and Bengaluru in the pollution ladder.
Environmentalists pointed to a combination of topographical disadvantage – Kolkata is at the fringe of the Indo-Gangetic plain and hence a recipient of north-westerly transboundary pollution – and inadequate policy implementation as being responsible for Kolkata’s air remaining toxic despite the city having fewer industries and cars compared to several other metros.
Marginal improvement but winter was toxic
According to the IQAir report, Kolkata’s average annual PM 2.5 level last year – 45.6 micrograms – was marginally better than 2023 when it was 47.8 micrograms. But the city’s PM 2.5 level during the winter months of January, November and December in 2024 remained two to three times above the permissible limit.
The global result broadly tallies with national data. The Central Pollution Control Board data show that the PM 10 level in the city was 94 micrograms in 2023-24; just below the 97 micrograms recorded a year before. The national limit of PM 10 is 60 micrograms per cubic metre; hence Kolkata’s annual level was 1.5 times above the limit.
PM 10 are respirable particulates up to the diameter of 10 micrograms and PM 2.5 constitute a part of its concentration.
“We could control Kolkata’s pollution to an extent using a range of actions particularly sprinkling of water and reducing roadside emission by providing gas connection to several roadside eateries and cloth presser units,” said Kalyan Rudra, chairman of the West Bengal Pollution Control Board.
“However, it will be difficult to reduce the city's pollution beyond a point, as World Bank experts have pointed out, unless the pollution within regional air-shade can be countered,” he added.
Air pollution in Kolkata may have improved marginally, but most Bengal cities slipped during the same period.
According to the report, Durgapur, Asansol, Howrah recorded poorer pollution status in 2024 compared to a year before and recorded PM 2.5 levels more than 10 times compared to WHO guideline values.
Durgapur was the 24th most polluted global city, worst in West Bengal, while its twin city Asansol occupied the next global ranking; 25th.
Poor planning plays a key role
Kolkata has long been holding the tag of second most polluted metro in India despite having fewer industries and vehicles compared to several metro cities.
“It is a fact that climatic and meteorological factors play a key role in worsening Kolkata’s air pollution status as the city is in the tip of the Indo-Gangetic plains and gets affected by the pollution generated in the zone, like Delhi; but the inadequate policy implementation also contributes to the problem,” said Anumita Roychoudhury, an air pollution expert from the environmental think tank Centre for Science and Environment (CSE).
Roychoudhury said 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 level it needs to act as well to counter pollution from transport, waste burning and likewise,” she said.
Abhijit Chatterjee, a scientist associated with the Union government research organisation Bose Institute, said: “As observed through in-depth chemical characterisation, solid waste and biomass burning are the dominant sources over Kolkata. Such emissions are enhancing ammonia in 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.”
Chatterjee pointed out that increased surveillance to control waste and biomass burning, including domestic emissions, is required.