Peak Diwali pollution in Delhi 13% higher than last year: CSE report
PM2.5 levels spiked 13% higher on Diwali 2024 compared to previous years, revealing increased firecracker use and environmental impact, per CSE report.
The peak concentration level of particulate matter (PM) 2.5 was 13% higher at midnight on Diwali this year compared to 2022 and 2023, according to a report released by the Centre for Science and Environment (CSE) on Saturday. It also found that PM2.5 levels were 34% higher on Diwali this year than on the night of the festival in 2022, which was also an end-of-October celebration.
Diwali 2022 was observed on October 24 and the festival in 2023 was on November 12.
The report’s findings corroborate the anecdotal evidence that suggests that the ban on firecrackers was violated in equal, if not larger, measures this year compared to the recent past, taking a heavy environmental toll on the city’s residents. In fact, evidence also suggests that the ensuing public health crisis would have turned far more toxic had it not been for the providential strengthening of winds on the morning after Diwali that helped blow the smoke away.
Data analysed by CSE showed that this year PM2.5 levels hit a peak of 603 microgramme per cubic metre (µg/m³) around midnight, which was 13% higher than Diwali peaks observed in both 2022 and 2023.
The overall PM2.5 levels, though, were about 22% lower this year compared to the Diwali last year. In absolute numbers, the average PM2.5 across the city on Diwali night was 289 µg/m³in 2022, 497 µg/m³in 2023 and 386 µg/m³in 2024.
The report added that air pollution between 6am to 4pm on Diwali was also higher than previous years. The average PM2.5 concentration during the day was 92% higher than last year’s Diwali daytime average, as per the report. This, the report said, reflects high local and regional pollution aided by the sharp increase in the share of farm fires.
In real time, PM2.5 levels in the city shot up by a staggering 15 times the permissible limits in some parts of the city on Thursday night, reaching as high as over 1,800 µg/m³ in certain residential areas, highlighting the impact firecrackers had on Delhi’s air.
The World Health Organization sets the safe limit of PM2.5 exposure at 15µg/m³, while India’s National Ambient Air Quality Standards sets it at 60µg/m³.
Anumita Roychowdhury, an air pollution expert and executive director at CSE, said, “There was sudden and sharp escalation in farm fire count on the day of Diwali and that combined with the change of wind direction to north westerly. This increased the share of its contribution to Delhi’s air quality by 27%.”
Moreover, the CSE report mentions that higher levels of NO2 were also observed on Diwali night compared to previous years. The average NO2 on Diwali night has been consistently high in the last three years from 42 µg/m³ in 2022 to 37 µg/m³ in 2023 and 53 µg/m³ in 2024.
“NO2 level in last three years have been higher on Diwali night and also the nights preceding it, which is indicative of congestion and high traffic conditions in the city leading to the festival night,” it said.
The data shows that ITO had the highest NO2 levels in the city with night-time average of 182 µg/m³, JLN Stadium and Patparganj had 104 µg/m³and 101 µg/m³ respectively. Lodhi Road with just 2 µg/m³of NO2 was the least affected area in the city.
However, a unique feature observed this year, according to the report, was a sudden sharp rise of pollution at night due to bursting of firecrackers, but also a quick dissipation of the pollutants on the same day and the day after due to high wind speed on 12-16 kmph till 6pm on Thursday and an average of 10 kmph on Friday.
“The PM 2.5 was in the poor category during the afternoon of October 31. But the evening build-up peaked at severe levels at midnight and stayed elevated until early morning the next day. This time, the dissipation occurred quicker compared to previous years – not lasting as a smog episode (that is remaining elevated at severe level for at least three consecutive days). It came down to more moderate levels of 97 µg/m³ by noon,” Roychowdhury said.
The CSE report attributed this late buildup and early dissipation of pollution on Diwali day to warm atmospheric conditions with relatively more efficient natural ventilation and adequate wind in the city.
“The 12-hour (from 8pm to 8am) of PM 2.5 concentration on Diwali night in 2024 was 34 per cent higher than Diwali night in October 2022, going from 289 µg/m³ to 386 µg/m³. Moreover, PM2.5 levels this year were more than twice as high as the average night-time pollution recorded over the seven nights before Diwali,” the report mentioned.
The report also shed light on the pollution hotspots on Diwali night.
“This year, 9 out of 38 air quality monitoring stations recorded PM2.5 concentrations exceeding the critical threshold of 900 µg/m³ on Diwali night,” it mentioned.
The highest levels were observed at Nehru Nagar, reaching 994 µg/m³, followed closely by Anand Vihar at 992 µg/m³, Pusa IMD at 985 µg/m³, Wazirpur at 980 µg/m³, and JLN Stadium at 963 µg/m³. Other affected areas were Okhla, CRRI-Mathura Road, Karni Singh Stadium, Lodi Road, Siri Fort, according to the CSE report.
“The favourable atmospheric conditions during the warm October of 2024 has contributed towards quicker dissipation of the nighttime pollution peak and also prevented a more durable smog episode from building up. But further intensification of air pollution is expected to happen with the anticipated worsening of inversion conditions that lead to cold and calm weather conditions during winter that traps and thickens pollution,” Roychowdhury said.