Fireworks explode during Deepavali celebrations in Amritsar on October 31, 2024. | Photo credit: AFP

Ninety-nine of the 265 cities for which air quality index (AQI) data were available on the Central Pollution Control Board website reported “poor” air quality as of Friday, November 1, 2024 (data for 24 hours before 4 p.m. that day ). ).

An AQI value of 200 or more corresponded to “poor” quality.

Thirteen cities, including Delhi, Gurugram and Ghaziabad in the National Capital Territory region, recorded “very poor” air quality – AQI of 300 or more.

Ambala in Haryana recorded the highest AQI at 367, followed by Amritsar in Punjab (350), while Delhi's average AQI was 339.

That 24 hours corresponded to the time when Deepavali revelers burned crackers, defying a ban in places like Delhi. Also on Thursday (October 31, 2024) people burned crackers before 4 p.m.

On Thursday (October 31, 2024), the number of cities with “very poor” and “poor” air quality were comparatively lower – six, including Delhi (second highest AQI of 328), and 43, respectively. On Wednesday (October 30, 2024), a day before Deepavali celebrations, only Delhi recorded “very poor” air quality with an AQI of 307. The number of cities with “poor” AQI was even lower – 24, almost all of them in northern India.

Major cities like Mumbai, Chennai, Bengaluru, Hyderabad and Kolkata recorded “moderate” AQI on Friday, but even there, AQI levels had jumped compared to the levels recorded on October 30.

Data from 2023, corresponding to Deepavali celebrations, shows that Delhi's AQI was high at 358 on November 12, representing “very poor” air quality, up from 218 (“poor”) the previous day. A similar pattern was also observed last year. Similar to this year, on November 12 and 13, 53 and 85 cities had “very poor” and “poor” AQI, respectively, compared to eight and 42 cities, respectively, the previous day.

Pollution in winter

In cities like Delhi and others in north India, pollutant emissions peak during the winter season due to emissions from vehicles, industry, waste incineration and construction, besides stubble burning after the rice season in neighboring states, trapping particles in the cold air.

Unfavorable winds in the early winter months that do not flush out the pollutants also lead to faster formation. The setting off of fireworks also contributed to the deterioration in air quality during this time.

On Friday, Delhi's Anand Vihar station recorded the 10th highest PM2.5 concentration this year (273.04 micrograms per cubic meter), considering 24-hour levels. All nine others took place in January, when the city's winter was at its peak.