Firecrackers caused pollution to spike three-fold this Diwali: Report

Pollution levels spiked the most during late-night, between 10 PM to 1 AM

Across India, pollution levels spike during the time of Diwali, due to the widespread bursting of firecrackers. This can be termed a seasonal rise in air pollution. Delhi and its surrounding regions, especially, face one of the most significant surges in fine particulate matter (PM2.5) concentrations during this period, according to a new report by the Delhi-based Climate Trends. 2025 showed the highest recorded mean (488 μg/m3) and maximum concentration (675.1 μg/m3 post-Diwali), indicating severe pollution buildup.

The report found that PM 2.5 concentrations show a consistent and pronounced increase during the Diwali period for five years between 2021-2025. Pollution levels spiked the most during late-night, between 10 PM to  1 AM, inferencing high firecracker activity.

While meteorological factors like temperature influence the level of pollution in the air, the research specifically determined the short-term air quality deterioration picture during Diwali by evaluating hourly changes in PM2.5 and temperature patterns before, during, and after Diwali.

The data was collected for 24-hour periods before, during and after Diwali for all five years, from the Central Pollution Control Board (CPCB) online monitoring network, averaged across all Delhi monitoring stations. 

Unsustainable firecracker bursting

“It is most likely that the high concentration of PM 2.5 is due to local emission of firecrackers in the different parts of the city on this auspicious Diwali festival night. Wind speed was quite low, less than 1 m/s, hence no chance to transport the pollutants from one place to another in a short span of a few hours of firecrackers burning,” said Dr. S K Dhaka, professor at Rajdhani College, University of Delhi.

He also pointed out that green firecrackers enhanced the particulate matter at a rapid rate, suggesting checking the quality of the green firecrackers.

The fact that green crackers made no measurable difference to air pollution levels was reiterated by the report’s author Palak Balyan, research lead at Climate Trends.

The report found that PM2.5 values increased sharply during Diwali, peaking either late at night or early morning after the festival, throughout all five years.

“This year’s Diwali has proven to be even worse than before. The data clearly shows a sharp rise in pollution levels, with post-Diwali PM readings averaging around 488, compared to just 156.6 before the festival. That’s more than a threefold increase, making 2025 one of the most polluted Diwalis in recent years. The spike between the nights of the 19th and 20th directly corresponds to the widespread use of firecrackers across Delhi-NCR,” said Balyan, adding that allowing firecrackers during this time of year is simply not sustainable for the NCR region’s already critical air quality.

On the temperature scale, the average temperature remained within a narrow range (19–27°C) across all years, indicating relatively cooler nights. That also adds to the problem.

According to the report, emissions from fireworks and low nighttime temperatures jointly contribute to elevated PM2.5 concentrations. This pattern was consistent over all five years, and the sharp post-Diwali pollution spikes indicated both sustained emissions and poor atmospheric dispersion.

The report also pointed out that there is a slight downward trend in peak PM2.5 levels across the five years, suggesting incremental improvement, likely due to public awareness campaigns, restrictions on fireworks, and enforcement of pollution control measures.

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