The maximum air pollution level this Diwali night dropped by 20 to 60 per cent in various parts of the city compared with the previous Diwali, shows an analysis by the Central Pollution Control Board of the data recorded by various pollution measuring stations.
“I am happy with the development and would like to thank police and common people for this improvement,” state pollution control board chairman Kalyan Rudra told Metro on Sunday evening.
According to the central board, the city’s air quality index (AQI) was moderate on Diwali. The AQI is an indicator of the overall air pollution level.
The central board analysed the AQI data generated hourly by seven automatic air quality monitoring stations across the city on Diwali. The study shows the highest air quality index value from 7pm to midnight on Diwali was 398, recorded by the monitoring station on the Rabindra Bharati University campus on BT Road. It was followed by Fort William (326), Ballygunge (316), Jadavpur (283), Victoria Memorial (277), Rabindra Sarobar (236) and Bidhannagar (192).
Last year, the highest hourly AQI had reached 500 – the highest value measurable under the National Air Quality Index and considered severe – at all stations on Diwali evening.
However, the AQI index this Diwali, though much better compared with last Diwali, was still nearly 50 per cent worse compared with the evening before, vindicating the pollution-triggering role of fireworks, whatever little was burnt on November 14 evening and night.
The average hourly AQI between 7pm and midnight on November 14 was 197, compared with the value during the same period on November 13 (133). The data also suggests that the average AQI was worst at midnight – 289 – increasing consistently from 7pm, when it was 120. No such trend could be seen November 13 evening, which negates the possible involvement of meteorological and other factors.
On Diwali night, the state pollution control board received 33 complaints of bursting of firecrackers and Sabuj Mancha, an organisation that works for protection of the environment, received 52. “Thirty of those complaints were from Calcutta. The frequency of complaints increased as the night progressed,” said Naba Dutta, the secretary of Sabuj Mancha.
According to the organisation, stray complaints came from areas like Kalighat, Dover Place, Entally, Beleghata, Rabindra Sarobar, Lake Town and Thakurpukur. More frequent complaints came from areas like Kasba, Behala, Rajpur-Sonarpur and Tangra.
“However, most of the spots known for violations, like the area around BC Roy Children Hospital and Ramkrishna Mission Seva Pratisthan and major parts of north Calcutta, were quiet,” said a member of Sabuj Mancha.
"The high court order pushed the administration into action and also people at large cooperated, perhaps because of the Covid pandemic,” said Biswajit Mukherjee, a retired chief law officer of the state board.
According to a report of the state pollution control board, the level of the toxic PM2.5 pollutant, which can reach the deepest crevices of the lungs and trigger a range of respiratory diseases, dropped at least four times this Diwali compared with last year’s. The report says that while the maximum PM2.5 value recorded last year was 768.38 micrograms per cubic metre, it was 185.75 microgram this year. The national limit is 60 microgram.