Vehicular emissions are now the biggest contributors to Delhi’s worsening winter air quality, according to a new analysis released by the Centre for Science and Environment (CSE). The national capital-based think tank found that traffic-related pollution is rising sharply while the level of fine particulate matter has shown no improvement since 2022, raising serious concerns over the effectiveness of current pollution control measures.
The report shows a consistent pattern of PM2.5 levels rising and falling in tandem with nitrogen dioxide during morning and evening rush hours. This synchronised movement, the CSE says, underscores the dominant role of daily traffic in driving air pollution. Nitrogen dioxide, a gas produced immediately from tailpipe emissions, peaks sharply at busy times, while PM2.5 accumulates more slowly and remains trapped under shallow winter boundary layers. The study also highlights a worrying increase in carbon monoxide, another hazardous pollutant largely emitted by vehicles.
“What is more alarming is the daily synchronised rise of PM2.5, nitrogen dioxide and carbon monoxide, mainly from vehicles and combustion sources, creating a toxic cocktail that has gone unnoticed,” CSE executive director of research and advocacy Anumita Roychowdhury said. She added that the trend points to an urgent need for long-term solutions, including deep changes in infrastructure, waste systems, transport networks, industrial emissions, and household energy.
The problem is widespread across the city. Twenty-two monitoring stations in Delhi recorded carbon monoxide levels above the safe eight-hour limit on more than 30 out of the first 59 days of this winter season. Dwarka Sector 8 recorded the highest number of unsafe days at 55, followed by Jahangirpuri and Delhi University’s North Campus with 50 days each.
The report describes the combination of PM2.5, nitrogen oxides and carbon monoxide as a “toxic cocktail” because these pollutants come from everyday combustion sources, including household fuels, waste burning and vehicles. Each winter, authorities tend to focus on construction dust and roadside cleaning, while the core issue of combustion receives less urgent attention, the study said.
Contrary to popular belief, stubble burning was a relatively minor factor this season. According to the CSE, the contribution of farm fires stayed under 5 percent during most of the early winter period, rising briefly to 22 percent on November 12 and 13, and reaching between 5 and 15 percent on a few scattered days. The drop in agricultural fires this year was linked in part to heavy monsoon flooding in Punjab.
Even with this decline, Delhi’s air quality did not improve significantly. Throughout November, overall air quality remained in the “very poor” to “severe” categories, and PM2.5 remained the most alarming pollutant. The reduction in smoke prevented extreme one-day spikes but failed to clean the average daily air, proving that local emissions now drive the baseline pollution level.
One of the most important findings in the report is that Delhi’s PM2.5 levels have plateaued since 2022. Between 2018 and 2022, levels dropped slightly, aided in part by the slowdown during the pandemic. But beginning in 2021 and 2022, PM2.5 levels stabilised at high concentrations, showing no sign of improvement. The city’s annual average jumped to 104.7 micrograms per cubic metre in 2024. Early-winter averages this year are slightly lower than last year, but when compared to a three-year baseline, they show no progress at all. According to the report, this means Delhi is consistently breathing toxic air throughout the year with no downward trend in sight.
The CSE also found that pollution hotspots in Delhi have expanded. Established hotspots such as Jahangirpuri, Bawana, Wazirpur and Anand Vihar continue to report extremely high PM2.5 levels, but emerging hotspots now include Vivek Vihar, Nehru Nagar, Alipur, Sirifort, Dwarka Sector 8 and Patparganj. Even smaller towns in the National Capital Region, which earlier had cleaner air, are now experiencing prolonged smog. Bahadurgarh recorded a ten-day smog period with average pollution levels higher than Delhi’s, indicating that the entire region now behaves as a single polluted airshed with very little natural dispersion.
The report concludes that Delhi has reached a critical point. Short-term measures and seasonal curbs will no longer be sufficient. Without major structural changes in transport policy, waste management, industrial controls, power generation and household fuel use, the city risks losing whatever limited gains it made in earlier years.