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Vehicular pollution, particularly from diesel cars and trucks, are primarily responsible for the worsening air quality in Kolkata, which is emerging as the pollution capital of India

A high percentage of vehicles on Kolkata’s roads are powered by diesel (Photo by Jayanta Basu)

Will Kolkata soon wrest the country’s pollution capital crown from Delhi? Delhi may be vying with Beijing for global topper status in air pollution and garnering all the attention for polluted air, but Kolkata has silently pushed Delhi behind on the air quality index and turned the toxic topper among metro cities in India during the first two months of 2018.

Experts warn that the actual air quality in Kolkata may be even poorer, and hence the difference of Kolkata and Delhi’s pollution levels are even wider, as air pollution in the eastern Indian city is measured manually, which tends to underestimate the pollution figures. Incidentally, while a slew of actions on prodded by Supreme Court and the National Green Tribunal have been taken to combat toxic air pollution in Delhi, Kolkata is yet to even devise a concrete road map for tackling foul air.

Kolkata tops pollution chart

An analysis of the official air quality index (AQI) data of different metro cities — West Bengal Pollution Control Board (WBPCB) for Kolkata and Central Pollution Control Board (CPCB) data for rest of the cities — for the months of January and February found that Kolkata’s average AQI at 295 parts per million during the period was higher than Delhi at 287 ppm.

The figure was just short of the ‘very poor’ AQI category — which starts at 300 ppm — that may trigger respiratory illnesses among people on prolonged exposure over and above exacerbating problems of those already affected. Out of 59 days in January and February, Kolkata’s pollution level was worse than Delhi on 32 days, and was more than double of Delhi’s pollution level on some days.

Kolkata’s air stood almost twice as polluted compared with other metros like Mumbai (AQI of 155), Chennai (127), Bangalore (88) and Hyderabad (130) during the period. The AQI has been calculated on basis of dominant pollutant, PM 2.5 in most cases, measured in automatic stations. In the case of Kolkata, the readings of four manual stations — Behala Chowrasta, Minto Park, Moulali and Shyambazar — were considered, as the city’s automatic stations have been non-functional for the past few months.

However, even before becoming non-functional, they were not used to measure PM 2.5, which is the most potent air pollutant, and can penetrate the innermost crevices of lungs and trigger a bevy of diseases. “The actual scenario may be even poorer as manual stations tend to under-calculate the pollution figures,” Dipankar Saha, a CPCB scientist, told

Considering the two months separately, Kolkata was found to be at par with Delhi on the pollution count during January. The average AQI values were 328 and 327 in Delhi and Kolkata, respectively. Kolkata’s air worsened in February with an average AQI score of 260 versus 243 in Delhi. Kolkata’s air quality was found to be comparable to Faridabad and Ghaziabad, two of the most highly polluted cities in country as per the CPCB list, which recorded AQI values of 298 and 349 between January 1 and February 28.

Data refutes official claim

The data refutes the claim of the West Bengal government that state capital’s air quality is much better than that of Delhi. Sometime back, state environment minister Sovan Chatterjee rubbished the notion that Kolkata’s air quality is poorer than Delhi, alleging that the media had been jumping to “false conclusions” by only comparing the single point data generated atop US Consulate in Kolkata and the US Embassy in Delhi, which is unscientific. “Kolkata’s air is much better than Delhi and one of the best in world,” the minister had told in an earlier interview.

“What will the minister say now that all the data being referred to are official data? I will try to raise the issue in appropriate legal forums,” said environmental activist and lawyer Subhas Datta, who has filed a number of petitions on the city’s air pollution in the Calcutta High Court and the National Green Tribunal.

WBPCB officials declined to comment on the data. “We have to analyse the data first,” a WBPCB official said, speaking on the condition of anonymity.

Diesel dominate, action absent

Experts are unanimous that Kolkata’s bane is vehicular emission, particularly from diesel vehicles. The city has a two million strong fleet of vehicles, out of which about 50% run on diesel. More important, the diesel fleet includes over 95% of the city’s commercial vehicles.

The diesel capital status of Kolkata is the biggest hurdle for the city to combat burgeoning air pollution, experts say. “Nearly two lakh (200,000) commercial vehicles, many of which are old and poorly maintained, are the worst offenders for ultrafine particulates, PM 2.5, pollution,” emissions expert Somendra Mohon Ghosh told

Anumita Roy Choudhury of Centre for Science and Environment, an environmental think tank, said the ordeal for the people of Kolkata would continue unless the city moves over to compressed natural gas (CNG) as an alternative to diesel. Although the Gas Authority of India Ltd (GAIL) has launched a project in 2008 to take CNG to Kolkata, it has remained a non-starter in the past one decade due to combined apathy of the state and central governments.

“With National Green Tribunal pushing in context to a petition filed by me, it is now expected that CNG may ultimately reach the city through tankers from the Asansol area, where CNG is manufactured from coal bed methane,” Datta said. “Pipeline supply will take a few more years.”

The AQI data showed that air quality in Kolkata was generally better on weekends, which also proves the role of vehicles in Kolkata’s air pollution, as the trips made by commercial vehicles are down by around 30% on weekends.

Green activists complained that successive state governments have done little to arrest the rise in pollution from transport, especially from commercial vehicles, despite several judicial verdicts. Biswajit Mukherjee, a former chief law officer of the state pollution control board, pointed out that though in 2008 the Calcutta High Court had imposed a ban on commercial vehicles 15 years or older in the Kolkata Metropolitan Area, a part of which is Kolkata Municipal Corporation area, many of the old polluting vehicles continue to ply on the fringes of the city due to the absence of proper monitoring.

“The state government is sitting on recommendations of an expert committee, which was set up by the National Green Tribunal through an order about one and a half years ago,” alleged Datta. The tribunal had on August 11, 2016, directed the state government to implement the recommendations of an expert committee appointed by the tribunal, but so far there has been little action on the ground.

“It’s very unfortunate. Kolkata should have prepared and start executing the graded response action plan like Delhi with emphasis on vehicular pollution, as such a plan is mainly instrumental for Delhi’s improvement on the air front,” Roy Choudhury told

“The government is unlikely to take strong measures against the polluting commercial vehicles because a lot of political stake is associated with it. It’s like the model of political rent-seeking — win-win for polluters and political parties, as polluters pay rent to politicians, who in turn give them administrative protection,” said Prabal De, an economist from City College of New York. “The people suffer as a result.”

Doctors declare emergency

A panel of doctors, from pulmonologists to cardiologists to oncologists, has declared a health emergency in the city on the face of rising air pollution. “It’s an emergency situation. I am really scared about the future of our children,” Arup Haldar, a pulmonologist, said during a meeting organised as part of the Kolkata Clean Air campaign.

Raja Dhar, another pulmonologist associated with the National Allergy Asthma Bronchitis Institute, stated that research shows 47% of the city’s population is affected by air pollution while 70% of people who are outdoors regularly for six hours or more in a day show unusual lung function test results. “The direct effect due to air pollution is confirmed when somebody retains a dry cough for three weeks or more and needs at least one dose of antibiotics to recover,” said Dhar.

Oncologists say the relationship between the city’s air pollution dominated by ultra-fine particulate matter and lung cancer has been found to be quite categorical. “Out of two major types of lung cancers, the dominant one in Kolkata is squamous cell cancer, which is not only directly linked to air pollution but also much more difficult to treat than any other,” said Chandrakanth M.V., an oncologist, while Suman Mullick, an onco-surgeon, said that on an average “50% cases” he treats are non-smokers, emphasising the role of killer air pollution in Kolkata.


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