As Delhi chokes on polluted air, the Union government claimed on Saturday that the overall air quality of Delhi-NCR (National Capital Region) has been improving gradually over the last eight years, barring the Covid year which is considered an exception. In contrast, Center for Science and Environment (CSE), a Delhi-based research and advocacy organisation, released an analysis recently to stress that there has been no improvement in longer-term trends in Delhi air quality, particularly during winter when it assumes critical proportions.
The government also claimed that the annual average PM2.5 count in Delhi shows a decline over the last eight years, but CSE warned that PM2.5, which shows a plateauing in its analysis, is contributing to a more dangerous trend by combining with other pollutants creating a “toxic cocktail”. The report has found 13 pollution hotspots within Delhi- NCR with north and east Delhi localities recording the highest levels.
PM2.5 represents a cohort of ultrafine particulates, one of the most toxic pollutants, that can get into the deeper crevices of lungs and trigger a range of diseases including fatal ones.
Both the reports are based on government data accessed from the portal of the Central Pollution Control Board (CPCB).
PM2.5 lower in 2025: Govt
The government has claimed that from January-November in 2025, Delhi has registered its lowest ever average AQI (Air Quality Index), compared to the last eight years, from 2018-2025 (barring 2020 – the lockdown year). The AQI from January–November in 2025 was recorded as 187, as against 201 in 2024, 190 in 2023, 199 in 2022, 197 in 2021, 172 in 2020, 203 in 2019 and 213 in 2018, according to government figures.
The government further claimed that January– November, 2025 (up to November 27), has seen the lowest levels of PM2.5 concentration in Delhi since 2018 and the 2025 level is at par with the year 2020, the lockdown year. Delhi, according to the government release, has witnessed an average PM2.5 of 85 µg/m3 in the current year as against 98 in 2024. The figures for other years show a fluctuation, though an overall decline in PM2.5: 90 in 2023, 90 in 2022, 95 in 2021, 85 in 2020, 99 in 2019 and 103 in 2018 respectively.
The government release said that during January–November, 2025, there were just three days when the daily average AQI had shot more than 400 (‘Severe to Severe+’ categories). There were 11 such days in 2024, 12 in 2023, 4 days in 2022, 17 days in 2021, 11 days in 2020, 16 days in 2019 and 12 such days in 2018.
Moreover, 2025 has not recorded a daily average AQI of more than 450 (‘Severe+’) on any day so far, the government figures claimed. There were two such days in 2024, two in 2023, three in 2021, two in 2020, five in 2019 and no such days in 2022 and 2018.
Winter pollution deteriorating: CSE
The CSE figures clearly show that there has been a crucial increase of PM 2.5 in Delhi during winter; the most critical period when the exposure to the pollutant heightens due to atmospheric conditions. It was accompanied by increasing levels of nitrogen dioxide (NO2) and carbon monoxide (CO), which was highly toxic. The analysis looked at early winter trends (October-November 15) in Delhi and adjoining areas.
“What’s more worrying (than the average figures) 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,” says Anumita Roychowdhury, executive director, research and advocacy, CSE, who leads the study.
The data validates the claim. The CSE analysis finds that 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 rise 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,” says the CSE statement.
“The longer-term air quality trend in Delhi has also plateaued 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,” Roychoudhury adds.
The CSE analysis points at local sources and says that the situation calls for looking at the right pollution sources. “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 the new assessment by CSE.
Carbon monoxide surge
Carbon monoxide (CO), another toxic pollutant that curdles the blood and asphyxiates and is mostly emitted by vehicles, has shown sharp surges across Delhi this winter. Dwarka Sector 8 was the worst affected, with 55 exceedance days.
The pattern demonstrates that particulate pollution spikes are consistently reinforced by traffic-related emissions of both NO2 and CO, especially in winter. “This cocktail of pollutants also makes 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,” adds Roychowdhury.
Crop burning not to blame
Official data shows that crop burning was less in extent in Punjab and Haryana this year, partly because of the floods in Punjab.
The dip prevented sharp spikes in air pollution, but hardly improved 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,” says the CSE statement. This indicates the role played by Delhi’s local, year-round sources, it added.
“The October-November PM2.5 average is about 9 per cent lower than the previous year, and even the worst peaks appear slightly lower,” the statement says. “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 Sharanjeet Kaur, deputy programme manager, Urban Lab, Clean Air unit, CSE.