Delhi’s Diwali pollution started before the fireworks. What five years of action have achieved

Delhi's pollution problem was already worsening before the first firecracker was lit this Diwali. The average level of fine particles in the air (PM2.5) the week before the festival was 236 micrograms per cubic metre, nearly double the level recording during the same period in 2025, according to a Centre for Science and Environment (CSE) analysis.

The finding complicates the usual explanation for Delhi’s winter pollution, that the air quality crisis is mainly the result of Diwali fireworks and stubble burning around October/November. The capital city enters winter with pollution from vehicles, construction, industries, waste burning and neighbouring NCR districts already trapped in the air.

“Diwali pollution is an annual tipping point, but elevated particulate levels before the festival this year show that baseline pollution is higher than in previous years,” CSE executive director Anumita Roychowdhury said.

The smoke was already building

CSE compared air quality data, pollution source estimates and traffic conditions during October and November 2026. It found that the average PM2.5 level in the week before Diwali was 236 micrograms per cubic metre, compared with 120 in 2025 and 179 in 2024.

PM2.5 refers to fine particles in the air that are 2.5 micrometres or smaller. They can come from vehicle exhaust, industrial emissions, smoke from fires and burning, and can travel deep into the lungs.

The analysis also found that pollution remained severe even when farm fires contributed less. On November 6, Delhi's AQI reached 382, while the contribution of stubble burning had fallen to around 8%.

According to the World Health Organization’s 2021 air quality guidelines, PM2.5 should ideally remain below 5 micrograms per cubic metre as an annual average and below 15 micrograms per cubic metre over 24 hours. These are health-based recommendations, not legally binding limits.

India’s National Ambient Air Quality Standards, notified by the Central Pollution Control Board, set the PM2.5 limit at 40 micrograms per cubic metre as an annual average and 60 micrograms per cubic metre over 24 hours.

Pollution from neighbouring NCR districts accounted for 54.43% of Delhi's PM2.5 between November 1 and 8, according to CSE's analysis of data from the Indian Institute of Tropical Meteorology.

Among Delhi's local sources, vehicles were the biggest contributor to poor air quality, accounting for 52%. Residential activity contributed 13%, industries 11%, construction 7%, and energy use and waste burning 5% each.

Firecrackers still make it worse

Firecrackers caused a clear spike on Diwali night. CSE found that nitrogen dioxide, a key marker of vehicle pollution, rose sharply during the evening and remained high until midnight. But roads were at their least congested on Diwali even as pollution rose, suggesting that fireworks added significantly to the night time pollution independently of traffic.

The larger point is that firecrackers are a short term trigger. The wider pollution problem is created by emissions that continue throughout the year.

Have five years of action helped?

There has been some improvement in annual pollution levels. Delhi's average PM2.5 level fell from 105 micrgrams per cubic metre in 2021 to 97 in 2025. Average PM10 levels fell from 211 to 197 during the same period.

PM10 refers to larger airborne particles measuring 10 micrometres or smaller. They are commonly produced by road dust, construction activity, soil and other outdoor sources. Because they are larger, they generally do not travel as deeply into the lungs as PM2.5, but can still affect respiratory health.

The government said 2025 recorded the lowest annual PM2.5 and PM10 levels since 2018, excluding the Covid year of 2020. It also recorded 79 days in the “good” or “satisfactory” air quality categories. But the improvement has not been steady. Pollution rose again in 2024, and Delhi’s annual PM2.5 level remains well above India’s national standard.

What has been done over the past five years?

The Commission for Air Quality Management (CAQM), set up in 2021, has introduced measures across Delhi-NCR. Industries have been pushed towards cleaner fuels such as PNG, with more than 96% of industries in the national capital region reportedly shifting to approved fuels by 2025.

Construction sites now face registration, inspections and dust control rules. Authorities have also tightened restrictions on diesel generators and older commercial vehicles. Delhi has expanded its electric bus fleet, while buses entering from neighbouring states have been directed to use electric, CNG or BSVI diesel vehicles.

Authorities have also increased action against crop burning, landfill fires and open waste burning. Farm fire incidents in Punjab and Haryana fell in 2025 compared with the previous year, according to CAQM.

Emergency measures have limits

A study published in Discover Atmosphere in April 2026 analysed the Graded Response Action Plan, or GRAP, across nine Delhi-NCR pollution hotspots. It found that GRAP could provide short term relief, but its impact depended heavily on weather. Pollution remained high even after stricter restrictions were imposed because low wind speeds and stagnant air kept pollutants trapped over the region.

The researchers said GRAP could not solve the problem of fine particles already formed in the atmosphere. They recommended earlier action, better forecasting and stronger coordination across the NCR.

Reports point to a wider failure

A Parliamentary Standing Committee report in December 2025 said Delhi’s pollution response remained fragmented. It called for updated studies, better monitoring and a common plan covering Delhi, Haryana, Uttar Pradesh and Rajasthan.

The committee also flagged vehicle emissions, road dust, construction, waste burning and crop residue burning as continuing problems. It recommended phasing out end-of-life and diesel vehicles, expanding electric and CNG public transport, strengthening dust control measures and enforcing zero tolerance for open waste burning.

A 2026 report by the Centre for Research on Energy and Clean Air found that most clean air funding was being spent on road dust. It said transport, industry, waste burning and pollution monitoring needed greater attention.

A separate CAQM expert review found that winter pollution came from a combination of vehicles, biomass burning, dust, industry and particles formed from gases released by these sources.

Delhi’s air has improved slightly over five years, but not enough to make the city safe during winter. Firecrackers can turn a bad pollution day into a dangerous one, but the latest studies show that Delhi’s real problem begins much earlier, with vehicles, dust, industries, waste burning and pollution moving across the NCR.

The city may be able to control one Diwali night. It has yet to control the rest of the year.