Delhi's post-Diwali air quality plunges to 5-year low, CPCB data shows

New Delhi: Delhi's air quality deteriorated sharply after Diwali, with fine particulate matter (PM2.5) levels surging to their highest in five years, according to an analysis of Central Pollution Control Board (CPCB) data.

The average PM2.5 concentration touched 488 micrograms per cubic metre in the 24 hours after Diwali, more than three times the pre-festival level of 156.6 micrograms per cubic metre.

The analysis, covering the period from 2021 to 2025, showed that PM2.5 values consistently spiked during Diwali night and early the next morning, with the 2025 post-Diwali reading of 488 micrograms per cubic metre being the most polluted period since 2021.

The data shows that in previous years, average PM2.5 levels rose from 163.1 to 454.5 in 2021, from 129.3 to 168 in 2022, from 92.9 to 319.7 in 2023 and from 204 to 220 in 2024.

The study by research and advisory group Climate Trends attributed the surge mainly to local emissions from firecrackers, stagnant winds of less than one metre per second and temperature inversion that traps pollutants close to the surface.

The high concentration of PM2.5 is due to local firecracker emissions across different parts of Delhi. Wind speed was extremely low, leaving no scope for dispersion, said S K Dhaka, professor at Rajdhani College, University of Delhi.

He added that even "so-called" green firecrackers contributed significantly to particulate buildup and there was a need to check their quality and composition.

Experts said the continuing rise in pollution levels despite restrictions shows both enforcement gaps and public disregard for health warnings.

It is disheartening that after years of witnessing the harmful effects of burning firecrackers, we still repeat the same mistake, said Aarti Khosla, founder and director of Climate Trends.

Palak Balyan, research lead at Climate Trends, said this year's Diwali was one of the most polluted in recent years.

The data clearly shows a threefold increase in PM2.5 levels from before to after the festival. It is now evident that allowing firecrackers at this time of year is unsustainable for the NCR's already critical air quality, she said.

While average temperatures remained between 19 degrees Celsius and 27 degrees Celsius during the period, a slight post-Diwali dip coincided with the highest PM2.5 spikes.

Unfavourable meteorological conditions, combined with vehicular emissions, paddy-straw burning, firecrackers, and other local pollution sources, contribute to hazardous air quality levels in Delhi-NCR during winters.

The capital's air quality has consistently fallen into the “severe” category (air quality index above 400) after Diwali for most of the past decade, despite court bans on firecrackers and repeated advisories from authorities.

Doctors say breathing Delhi's air during such episodes is equivalent to smoking about 10 cigarettes a day.

Prolonged exposure to such high levels of pollution can cause or worsen asthma, bronchitis, and chronic obstructive pulmonary disease and significantly raise the risk of heart disease.