Access the full CSE study report here: https://www.cseindia.org/toxic-cocktail-of-pollution-during-early-winter-in-delhi-ncr-12957
New Delhi, December 1, 2025: “Delhi-NCR cannot hide behind the smokescreen of farm fires any more. While farm fires have contributed much less to local air quality this winter, the state of the air we breathe has been ranging from ‘very poor’ to ‘severe’ – this exposes the huge impact that local sources are having,” says a new assessment by Centre for Science and Environment (CSE) of early winter trends (October-November 15) in the capital and its adjoining areas.
Anumita Roychowdhury, executive director-research and advocacy, CSE elaborates: “What’s more worrying is the daily synchronised rise of PM2.5 and other toxic gases such as nitrogen dioxide (NO2) and carbon monoxide (CO), largely from vehicles and combustion sources, creating a toxic cocktail that has gone unnoticed. The longer term air quality trend in Delhi has also plateaeued without showing improvement. This signals urgent need for deep rooted shifts in infrastructure and systems to upscale action to cut emissions from vehicles, industry, power plants, waste, construction and household energy.”
Adds Sharanjeet Kaur, deputy programme manager, Urban Lab, Clean Air unit, CSE: “What further stands out is the stubborn stability and the vast spread of the pollution levels across the NCR region, as well as the worsening and proliferation of more pollution hotspots in the city. The smaller towns in the region display more intense and longer smog build-up. Even though the peak pollution spikes are lower this winter due to lesser contribution of farm fires, the airshed is getting increasingly more saturated.”
This CSE analysis is based on the air quality data accessed from the portal of the Central Pollution Control Board (CPCB).
The highlights
Toxic cocktail of particulates and gases during early winter: NO2 and CO spike
While all eyes in Delhi-NCR are fixed on the daily peaks of PM2.5 during early winter, the parallel trends in toxic and extremely harmful gases – nitrogen dioxide (NO2) and carbon monoxide (CO) -- have gone unnoticed.
PM2.5 has risen and fallen almost in tandem with NO2 during morning (7-10 AM) and evening (6-9 PM) hours, as both pollutants surge with traffic emissions and get trapped under shallow winter boundary layers. While NO2 shows sharper, more immediate peaks linked to vehicular plumes, PM2.5 displays broader peaks as fine particles accumulate and disperse more slowly.
Carbon monoxide (CO), yet another highly toxic pollutant that curdles the blood and asphyxiates and is predominantly emitted by vehicles, has shown widespread exceedances across Delhi this winter. Nearly 22 monitoring stations recorded CO levels above the eight-hour standard on more than 30 of the 59 days, indicating persistent traffic-linked emissions. Dwarka Sector 8 was the worst affected, with 55 exceedance days, followed by Jahangirpuri and North Campus (Delhi University), each reporting 50 days of violations.
This synchronised pattern clearly demonstrates that daily particulate pollution spikes are closely reinforced by traffic-related emissions of both NO2 and CO, especially under low-dispersion winter conditions. “This cocktail of pollutants also make the air more toxic to breathe. Yet, every winter, pollution control efforts are dominated by dust control measures with feeble action on vehicles, industry, waste and solid fuel burning,” says Roychowdhury.
Lesser contribution of farmfires expose high impacts of local sources
The crop burning season is now nearly over. Official data shows crop burning incidence has reduced substatially in Punjab and Haryana this year, partly due to the disrupton caused by the floods in Punjab during monsoon. For most part of the early winter, the daily contribution of farm fires to the day’s pollution levels has remained below 5 per cent, between 5 to 15 per cent on a few days, and has peaked to 22 per cent only on Novembr 12-13.
The dip in fires has prevented extreme spikes, but it did nothing to clean the daily average air quality. In October-November, PM2.5 remained the dominant driver of AQI, emerging as the prominent pollutant on 34 days, followed by PM10 on 25 days, ozone on 13 days and CO on two days. AQI stayed in the ‘very poor’ to ‘severe’ range for almost the entire month of November. This indicates the role played by Delhi’s local, year-round sources.
Even though the overall pollution levels have remained elevated at dangerous levels, the peak pollution during this early winter has reduced due to the lesser impacts of farm fires. Both the average and the peak levels are less compared to the previous three winters. The October-November PM2.5 average is about 9 per cent lower than the previous year, and even the worst peaks appear slightly lower.
“But when compared to the three-year baseline for early winter, the average hasn’t changed at all, it has plateaued at the same unhealthy level. Winter looks better only when compared to last year’s extreme; in real terms, pollution remains consistently high,” says Kaur.
Proliferation of more hotspots
In 2018, about 13 hotspots were officially identified based on their pollution levels – these not only exceeded the standards, but also the city average levels. These hotspots have continued to remain extremely problematic, with North and East Delhi recording the highest concentrations. Jahangirpuri is the most polluted hotspot with an annual (January-November) PM2.5 average of 119 microgramme per cubic metre (µg/m³), followed by Bawana and Wazirpur at 113 µg/m³, Anand Vihar at 111 µg/m³, and Mundka, Rohini and Ashok Vihar ranging between 101-103 µg/m³.
However, over the years, several more hotspots have emerged based on the same criteria. Vivek Vihar recorded 101 µg/m³, similar to Ashok Vihar. Other emerging locations are Nehru Nagar, Alipur, Sirifort, Dwarka Sector 8 and Patparganj which have crossed 90 µg/m³; Vivek Vihar and Nehru Nagar have remained persistent hotspots for four consecutive years, while Dwarka Sector 8 and Sirifort are featuring among the city’s most polluted locations for the second year in a row.
Even smaller towns in NCR have experienced more intense smog
Several NCR cities remained just as polluted as Delhi, and often worse, with towns like Bahadurgarh recording significantly higher smog intensities during this period. A region-wide smog episode affected NCR towns, but it was Bahadurgarh that endured the most persistent conditions, with the episode lasting a full 10 days, from 9 to 18 November. This clearly demonstrates that the entire region now behaves as a single air-shed, where smaller towns are no longer cleaner gaps but hotspots facing equal or even greater pollution pressure.
Is Delhi on the verge of losing its air quality gains?
Since 2022, the annual trend in PM2.5 levels has plateaued; it even took an upward turn showing plateauing of pollution at an elevated level. Between 2018 and 2020 (which was also the pandemic year), there was a steady decline in year-on-year PM2.5 levels in Delhi. But since 2021-22, the levels have remained largely elevated and stable with a slight variation. In fact, the annual average level took a sharp upward curve, touching 104.7 µg/m³ in 2024. Delhi continues to breathe extremely polluted air throughout the year, with no sustained downward trend.
What should be Delhi’s action agenda?
Says Roychowdhury: “Small incremental steps cannot help meet the clean air benchmarks. Pollution levels in the region have plateaued at dangerously high points. This is the inflexion point. Either a leapfrog strategy across the key sectors of pollution can bend the curve again, or the pollution trend can take a dangerous upward curve once again.”
CSE has proposed the following key action points:
For more details, interviews etc, please contact Sukanya Nair of The CSE Media Resource Centre: sukanya.nair@cseindia.org, 8816818864
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