Fireworks after 8 pm led to major changes in PM10 and PM2.5 concentrations in Delhi on the Diwali night, the Delhi Pollution Control Committee said in a report on Friday.
The sudden deterioration in Delhi's air quality this year can be attributed to extremely calm conditions, change in wind direction and low ventilation coefficient, and use of firecrackers, according to the DPCC's Diwali day air pollution analysis.
This year, the 24-hour city average concentration of PM10 on the day of Diwali is 748 and PM2.5 is 607, the report read.
Though the increase in the concentration of pollutants was observed since Wednesday evening, the major changes were observed after 8 pm on Diwali when the fireworks started, the DPCC said.
A gradual increase in the concentration of particulate matter was observed on the day of Diwali and the highest value was observed at midnight and then slowly started decreasing, the report said.
A thick layer of acrid smog hung over Delhi-NCR on Friday after residents flouted the firecracker ban and emissions from farm fires in the region peaked at 36 per cent, pushing the capital's 24-hour average air quality index for the day after Diwali to 462, the highest in five years.
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In neighbouring Noida, the 24-hour AQI was 475, the highest in the country. The neighbouring cities of Faridabad (469), Greater Noida (464), Ghaziabad (470), Gurgaon (472) also recorded 'severe' air pollution levels.
As smog partially blotted out the sun in Delhi and residents complained of itchy throat and watery eyes, the city's Environment Minister Gopal Rai accused the BJP of instigating people to burn crackers by linking it to religion.
Ahead of the festive season, the Delhi government had announced a complete ban on firecrackers till January 1, 2022, and ran a campaign against their sale and use.