Traffic Emissions, Not Stubble Burning, Keep Delhi Air Quality in 'Severe' Category: CSE Report Analysis

On Monday, Delhi's Air Quality Index (AQI) registered at 303 by 3 pm, categorizing the capital's air as 'very poor.'

Despite farm fires reaching multi-year lows, Delhi-NCR continues to experience suffocating winter air quality. Throughout most of October and November, pollution levels remained dangerously high, fluctuating between 'very poor' and 'severe' categories. The primary culprit is a growing "toxic cocktail" of PM2.5, nitrogen dioxide (NO2), and carbon monoxide (CO) emissions, predominantly from vehicles and local pollution sources.

A comprehensive analysis by the Centre for Science and Environment (CSE) revealed that at least 22 air quality monitoring stations in Delhi exceeded permissible carbon monoxide limits on more than 30 of the 59 days studied. Dwarka Sector 8 recorded the highest number of violations at 55 days, while Jahangirpuri and Delhi University's North Campus both registered breaches on 50 days.

The study also highlights an alarming expansion of pollution hotspots across the capital. Compared to 2018, when only 13 locations were designated as pollution hotspots, numerous additional areas now consistently report pollution levels significantly above city averages.

Jahangirpuri emerged as Delhi's most polluted location, with an annual PM2.5 average of 119 micrograms per cubic metre. Bawana and Wazirpur followed closely at 113 micrograms per cubic metre, while Anand Vihar registered 111 micrograms per cubic metre. Mundka, Rohini, and Ashok Vihar recorded levels between 101-103 micrograms per cubic metre.

Several new pollution hotspots identified by CSE include Vivek Vihar, Alipur, Nehru Nagar, Siri Fort, Dwarka Sector 8, and Patparganj.

The pollution crisis has extended beyond Delhi's borders, with smaller NCR towns experiencing more intense and prolonged smog episodes this year. Bahadurgarh endured the longest continuous smog event, lasting 10 days from November 9 to 18. This indicates that the entire region increasingly functions as a single airshed with uniformly elevated pollution levels.

CSE's assessment concludes that early winter pollution has stabilized at unhealthy levels, primarily driven by local emissions, even as stubble burning contributions have decreased significantly.

Based on Central Pollution Control Board data, the analysis identifies a "toxic cocktail" of pollutants—PM2.5, nitrogen dioxide, and carbon monoxide—directly linked to vehicles and combustion sources, which have intensified health risks this season.

Researchers observed that PM2.5 and NO2 levels rose and fell almost simultaneously during peak traffic hours. Between 7-10 am and 6-9 pm, both pollutants increased sharply as vehicle emissions accumulated under shallow winter boundary layers.

While NO2 displayed rapid traffic-related peaks, PM2.5 showed broader, slower-developing spikes. Carbon monoxide levels also exceeded the eight-hour standard at numerous locations across Delhi.

"This synchronized pattern confirms that particulate pollution spikes are being fueled daily by traffic-related emissions of NO2 and CO, particularly under low-dispersion conditions," explained Anumita Roychowdhury, executive director of research and advocacy at CSE.

"However, winter control efforts continue to focus predominantly on dust measures, with inadequate action addressing vehicles, industry, waste burning, and solid fuel usage," she added.

The report notes that stubble burning in Punjab and Haryana was notably reduced this year, partly due to floods disrupting the agricultural cycle.

Throughout most of the early winter period, farm fires contributed less than 5 percent to Delhi's pollution, increasing to 5-15 percent on certain days and reaching a maximum of 22 percent on November 12-13.

Although the reduction in stubble burning prevented extreme pollution spikes, it did little to improve daily air quality. PM2.5 remained the dominant pollutant on 34 days, followed by PM10 on 25 days, ozone on 13 days, and CO on two days.

Throughout November, the AQI consistently remained in the 'very poor' to 'severe' range, highlighting the persistent impact of Delhi's local pollution sources—traffic, industry, waste burning, and domestic fuel use.

While peak pollution levels this year were lower compared to the previous three winters due to reduced firecracker use and farm fire impact, average pollution levels showed minimal improvement.

PM2.5 levels for October-November were approximately 9 percent lower than last year, but when compared to the three-year baseline, no significant progress was observed.

Between 2018 and 2020, PM2.5 levels showed a consistent decline, partly attributed to the pandemic. Since 2021-22, however, annual averages have plateaued at elevated levels.

In 2024, the annual average increased sharply to 104.7 micrograms per cubic metre, reversing previous improvements.

The report recommends comprehensive structural measures to address emissions across sectors—including time-bound electrification targets, retirement of older vehicles, expanded public transportation with improved last-mile connectivity, and enhanced walking and cycling infrastructure.

It also advocates for parking limitations, congestion taxes, cleaner industrial fuels, reduced gas taxes, elimination of waste burning, improved waste segregation, and remediation of legacy waste dumps.

According to the CPCB's latest air quality bulletin, Delhi's 3 pm AQI on Monday registered at 303, placing it firmly in the 'very poor' category.