Calcutta tops the Very Poor Air list- Air apparent takes pollution crown

JAYANTA BASU AND SUBHAJOY ROY, TT, 10 Nov 2018, Calcutta: The National Air Quality Index has dropped a Diwali bomb on Calcutta -- air quality in the city over two festive nights was the worst among the metros.

According to a report of the Central Pollution Control Board, Calcutta's average AQI (air quality index) from 4pm on Tuesday till 4pm on Wednesday was 326. In the next 24 hours, including Diwali night, the AQI crept up to 354.

On November 5 and 6, prior to Kali Puja and Diwali, the AQI reading was 73 and 57 respectively. In the national index, both readings fall in the "satisfactory" range. Any reading between 301 and 400 is "very poor" and can cause "respiratory illness on prolonged exposure".

A pocket of Howrah fared even worse than Calcutta. In Padmapukur, the AQI at 11pm on Diwali was 381. The prominent pollutant was PM2.5, the tiniest of particulate matter that can invade the deepest recesses of the lungs and cause various illnesses, including cancer.

Delhi, the usual chart-topper in any pollution comparison, had a "poor" AQI of 281 on Chhoti Diwali that coincided with Kali Puja in Bengal. But it was still a shade better than Calcutta's reading that night. On Diwali, it reclaimed the top spot with an average AQI of 390.

According to an air pollution researcher, the sustained high AQI of Calcutta over two days would have had a more adverse impact on health than the spike in Delhi on Diwali night.

Bangalore's emission record on those two nights was "satisfactory" while Chennai's was "moderate". Mumbai's average AQI was in the "moderate" range on Tuesday and "poor" on Diwali.

The index, calculated by taking data from automatic pollution-measuring machines, is a measure of the presence of all dominant pollutants in the air. It also shows how polluted the air is over a particular period.

After Wednesday night's fireworks spree, the city woke up to what looked like a wintry morning with a haze hanging in the air. "The readings show how the Supreme Court's order was flouted in the city on Di- wali," said Biswajit Mukherjee, retired chief law officer of the state pollution control board.

The court had fixed a window of 8-10pm for bursting firecrackers.

At 8pm, the reading at the Rabindra Bharati station was 362. An hour later, it was 359. At midnight, the AQI was 355. The station at Victoria showed a reading of 351 at 8pm and 353 at 9pm. At midnight, the reading was 347 at Victoria..