80% Of Post-Diwali Pollution In Delhi Caused By Firecrackers: Study

Delhi's post-Diwali air pollution spike had a clear and unusually concentrated source: Firecrackers. Emissions from fireworks accounted for more than 80 per cent of the capital's pollution load on Monday, a day after Diwali, according to estimates by the Indian Institute of Tropical Meteorology (IITM). The high numbers maybe contested, but the toxic haze that covered the national capital and its neighbouring areas after Diwali highlighted how a few hours of fireworks can dramatically alter the composition of an already polluted atmosphere.

A separate IITM source-apportionment assessment estimated that firecrackers contributed 71.1 per cent of Delhi's PM2.5 concentration between 1 am and 9 am on November 9. 

IITM dashboard shows huge spike in PM2.5 level on Monday, a day after Diwali.
Photo Credit: ews.tropmet.res.in

The IITM assessment also reveals how dramatically the pollution mix changed around Diwali. Firecrackers accounted for 43.4 per cent of PM2.5 during the corresponding hours on November 8, compared to just 5.6 per cent on November 7. Their contribution had been 5.6 per cent on November 5 and 9.3 per cent on November 6.

The impact was visible in actual pollution measurements as well. PM2.5 concentrations at Jahangirpuri reached 4,985 micrograms per cubic metre at 3 am on November 9, while Nehru Nagar recorded 2,808 micrograms per cubic metre, according to a report in Times of India. However, the data was later revised to 776 micrograms per cubic metre by Delhi Pollution Control Committee (DPCC).

READ | Why Is Max AQI Capped At 500? Pollution Board Attempts To Clear The Air

Interestingly, vehicular emissions accounted for only 6.9 per cent of PM2.5 during the November 9 assessment window. Secondary inorganic aerosols contributed five per cent, while secondary organic aerosols accounted for 4.5 per cent.

With a value of 308, the AQI remained in the 'very poor' category on Wednesday morning. A further improvement in air quality is expected over the next few days as wind speeds are likely to increase.

Why Delhi's Pollution Spike Persisted

Weather conditions play a crucial role in determining how long pollutants remain suspended over a city. The India Meteorological Department (IMD) monitors wind speed, wind direction, temperature and humidity, all of which influence atmospheric dispersion. Favourable winds helped improve conditions after the Diwali pollution spike, although the accumulated pollutants did not disappear immediately.

A combination photo shows Vijay Chowk on October 31 (left) and on day after Diwali.
Photo Credit: PTI

Delhi's average Air Quality Index (AQI) stood at 376 on Diwali, November 8, placing it in the 'very poor' category. It improved to 299 at 4 pm on November 10, entering the 'poor' category, before rising to 302 by 6 pm.

READ | Data Blindspots, Weak Rules: Inside Delhi's Annual Battle For Clean Air

Following Diwali celebrations on November 8, India featured prominently in global pollution rankings, with 93 Indian cities among the world's 100 most polluted locations, according to AQI.in data published on November 9.

"Impact Temporary"

However, The IITM assessment was questioned by some people. Chamber of Trade and Industry (CTI) Chairman Brijesh Goyal said on Tuesday that firecrackers were being unfairly blamed for the national capital's pollution.

"While they (firecrackers) do cause some smoke, their impact is temporary. Pollution levels are already high between October and January, even before Diwali, so stubble burning and other sources must also be addressed," he said.

The trade body questioned why Delhi recorded high pollution levels even before Diwali, pointing out that the air quality index (AQI) was between 350 and 400 on November 5, 6 and 7, while firecrackers were burst on November 8.

Is Pollution Linked To Heart Attacks?

Pulmonologist Dr Arvind Kumar told NDTV that apart from coughing, wheezing, breathlessness and worsening asthma - among the most visible effects of pollution - extended periods of bad AQI can lead to a rise in cardiovascular emergencies, including heart attacks, strokes and dangerously elevated blood pressure.

"It was always thought that air pollution is a lung-centric problem. Now there is enough data to show that the lungs are the portal of entry and probably maximally affected. But there are three or four other areas where there is solid evidence available of serious damage being caused. First and foremost is the heart," said Dr Kumar.

"Every time there is a spike in these air pollution levels, a couple of days later, you will find a much higher percentage of people reporting to various casualties with heart attacks. There is a direct correlation," he added.

A 2025 study backs this observation. It analysed 41,436 hospital admissions, including 11,494 cardiovascular events in Delhi. Cardiovascular events in Delhi saw a surge during pollution months.