A toxic start to winter: Delhi-NCR's pre-Diwali PM2.5 touches 3-year high, says CSE

A toxic start to winter: Delhi-NCR's pre-Diwali PM2.5 touches 3-year high, says CSE

New Delhi, Delhi-NCR's early-winter air pollution has worsened this year, with the average PM2.5 concentration in the week preceding Diwali touching a three-year high, while vehicular emissions and regional pollution inflow continued to drive the toxic air, according to a new analysis by the Centre for Science and Environment .

A toxic start to winter: Delhi-NCR's pre-Diwali PM2.5 touches 3-year high, says CSE

The analysis released on Wednesday said the average PM2.5 concentration during the week before Diwali stood at 236 micrograms per cubic metre, marking a 97 per cent increase from 120 micrograms per cubic metre in 2025 and a 32 per cent rise from 179 micrograms per cubic metre in 2024.

It said pollution levels were generally higher in the pre-winter period this year than in 2025, except for a brief decline in late September due to rainfall.

CSE said the findings highlighted the failure of year-round pollution control measures, with Diwali firecrackers aggravating an already deteriorating situation rather than being the sole cause of the pollution crisis.

"Baseline pollution is higher than in previous years," said Anumita Roychowdhury, executive director of research and advocacy at CSE, adding that inadequate emission control across major pollution sources had contributed to the worsening air quality.

The analysis, based on air quality data from the Central Pollution Control Board , pollution-source contribution estimates from the Indian Institute of Tropical Meteorology , crop fire data and traffic analytics from Tom Tom , said vehicular transport remained the largest contributor among Delhi's local pollution sources.

According to the IITM's Decision Support System data for November 1-8, pollution transported from neighbouring NCR districts accounted for 54.43 per cent of Delhi's PM2.5, while local sources contributed 33.06 per cent and stubble burning 14.29 per cent.

Among local sources, vehicular transport accounted for 52 per cent of pollution, followed by residential activities and peripheral industries . Construction contributed 7 per cent, while energy use and waste burning accounted for 5 per cent each.

The report also pointed out that severe pollution episodes continued even as the contribution of stubble burning declined.

Farm fire smoke contributed 3.9 per cent to Delhi's PM2.5 during GR Stage I restrictions. The share rose to 11.5 per cent on November 1 before declining to 8.6 per cent on November 2.

It peaked at 16.2 per cent on November 4 but dropped to around 8 per cent by November 6, when Delhi's air quality index deteriorated to 382, prompting the invocation of GR Stage III measures.

The analysis also flagged the emergence of new pollution hotspots across the national capital.

While 11 of Delhi's 13 officially designated pollution hotspots recorded lower PM2.5 concentrations between October 1 and November 8 compared to the corresponding period last year, several other locations reported high pollution levels.

Anand Vihar recorded a 49 per cent decline in PM2.5 levels, followed by Wazirpur , Ashok Vihar and Bawana .

However, Jahangirpuri and Punjabi Bagh recorded marginal increases of 2 per cent and 1 per cent, respectively. Jahangirpuri remained the most polluted designated hotspot, with an average PM2.5 concentration of 163 micrograms per cubic metre.

Among emerging hotspots, Vivek Vihar recorded an average PM2.5 concentration of 144 micrograms per cubic metre, followed by Sonia Vihar , ITO and Delhi Technological University .

The report also raised concerns over vehicular congestion, noting that emergency traffic restrictions under the Graded Response Action Plan had provided negligible relief to weekday traffic movement.

During the November 2-6 restriction period, Delhi recorded an average daily Travel Time Index of 2.40 and an evening peak of 3.49, almost unchanged from 2.38 and 3.48, respectively, on October 30, the day before the curbs took effect.

Commuters continued to take 13 per cent longer to complete their journeys compared to standard weekdays between January and April this year, it said.

The analysis further found that nitrogen dioxide , nearly 80 per cent of which is emitted by vehicles, rose sharply during evening rush hours and remained elevated until midnight.

Daily NO2 concentrations increased by around one-third from November 2, even as traffic congestion remained largely unchanged, it said.

"In effect, the evening rush loads the air and the still night air keeps it there," said Sharanjeet Kaur, deputy programme manager, Urban Lab, CSE.

The organisation said the rapid emergence of new pollution hotspots and the deterioration in air quality across Delhi-NCR pointed to persistently high baseline emissions.

Roychowdhury said short-term emergency measures could not substitute for sustained pollution control across the region.

The report called for year-round emission reduction measures targeting vehicular transport, industries, construction, waste burning and other urban sources.

It also recommended reducing the number of vehicles on roads through improved mass public transport, mandatory trip-reduction measures and stricter restrictions on private vehicles.

"Conventional traffic engineering and piecemeal emergency restrictions cannot absorb this overload," said Shubham Srivastava, deputy programme manager, clean air and sustainable mobility at CSE.

He said effective pollution control required strategies to actively reduce vehicular volumes on city roads.

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