Nowhere to hide in city of poison air

June 21: Take a deep breath. Fringes of Calcutta that you thought had cleaner air than the city’s choked heart are even more polluted than the core, reveals a recently published document of the West Bengal Pollution Control Board.

The findings are based on an analysis of PM10 (fine particulate) and PM2.5 (ultrafine particulate) in the air at various places in Hooghly, Howrah and North 24-Parganas. These two forms of particulate matter are tiny enough to enter the deepest crevices of the lungs, triggering diseases ranging from respiratory and cardiac disorders to cancer.

Only South 24-Parganas had less pollutants in the air compared to Calcutta – 90 micrograms against 114 micrograms of PM10 per cubic metre of air – when the study was done in 2015.

The PM10 content of the air in Hooghly at the time was found to be far higher at 143 micrograms. Howrah’s reading was 124 micrograms per cubic metre and that of North 24-Parganas stood at 115 micrograms.

All these values are way above the national standard of 60 micrograms per cubic meter.

The PM2.5 values in both North 24-Parganas (76 micrograms) and Howrah (73 micrograms) during 2015 were also higher than Calcutta’s 61 micrograms. Hooghly and South 24-Parganas were not included in this part of the study. The national limit of PM2.5 in the air is 40 micrograms per cubic metre of air.

The report, a copy of which is with Metro, points out that the pollution levels in most of these areas have been on the rise. Hooghly’s PM10 value rose 23 per cent between 2013 and 2015. The rate of increase was 9 per cent in Howrah and 20 per cent in North 24-Parganas.

The number of non-compliant days in terms of the national limits for particulate pollution and the proportion of the affected population are rising too, states the pollution control board’s report.

Howrah and Hooghly top the non-compliance charts – toxic pollution levels in both places breach the national limits on three out of every four days (79 and 78 per cent respectively).

When it comes to “population affected by air quality”, Calcutta scores 100 per cent, followed by Howrah with 63 per cent and North 24-Parganas with 57 per cent. People living within the city are apparently more vulnerable to pollution because of greater population density compared to the fringe areas.

“The results show that there has been a semblance of control over air pollution within the core of the city because of the constant scan of environmentalists, judiciary and media. But pollution levels in the adjoining areas within what we call Greater Calcutta are spinning out of control,” said activist Subhas Datta.

According to emission expert S.M. Ghosh, what makes the difference is that around 30,000 illegal two-stroke autorickshaws and one lakh commercial vehicles older than 15 years are still in business on the fringes of Calcutta.

“In 2008, when Calcutta High Court ordered a blanket ban on commercial vehicles 15 years or older and two-stroke autos, it was meant for the entire Calcutta metropolitan area that includes the major portions of Howrah, Hooghly, North and South 24-Parganas. But the order was only implemented within the city proper,” said Biswajit Mukherjee, retired chief law officer in the state pollution control board and the environment department.

The impact of pollution on health is borne out by a surge in the number of people struck by respiratory and cardiac diseases. “The ravages of air pollution are visible in patients from the suburbs of Calcutta. Whenever we do a bronchoscopy, highly congested lungs with thick mucus can be seen. This is a tell-tale sign of exposure to high levels of air pollution,” said A.G. Ghoshal, head of the National Allergy Asthma Bronchitis Institute.