Delhi Chokes on ‘Very Poor’ Air After Cleanest October in Years

Thick smog cloaked Delhi Wednesday as the national capital’s winter pollution worsened a week ahead of the Diwali festival, when firecrackers typically intensify the haze.

(Bloomberg) -- Thick smog cloaked Delhi Wednesday as the national capital’s winter pollution worsened a week ahead of the Diwali festival, when firecrackers typically intensify the haze.

The citywide air quality index reached 379 at 10 a.m., near the top end of what India describes as “very poor,” according to the Central Pollution Control Board data. The average concentration of fine particulate matter that can penetrate lungs and enter the bloodstream reached 277, more than 18 times the 24-hour level recommended by the World Health Organization.

The deterioration marks a reversal from an AQI of 166 last month — the cleanest October in eight years — as unusually heavy rain washed away pollutants and favorable airflow helped disperse emissions. 

Every winter, falling temperatures and weak winds trap emissions from vehicles, industry, construction, waste burning and farm fires over Delhi, turning the capital’s air toxic for weeks. The recurring crisis forces schools and businesses to adjust operations, strains public health and erodes productivity across one of the world’s largest urban economies. 

Authorities tried to get ahead of the problem this year with a formal calendar of restrictions. The latest measures that took effect Nov. 1 bar older commercial vehicles and dust-emitting construction, limit people working from offices and double parking charges. The regional air-quality regulator also rolled out similar emergency restrictions.

“But having a plan alone doesn’t ensure clean air. The implementation is still not up to the mark,” said Sunil Dahiya, founder and lead analyst at climate research firm Envirocatalysts. The measures don’t cover the larger area around the capital that contributes to emissions, while crop burning is adding to an “already elevated pollution load,” he said.

Delhi’s microscopic pollutants that have been linked to cancer come from a mix of local and regional sources. Secondary particles — chemicals formed as emissions from all sources blend — account for the biggest 27% share every winter, according to India’s Environment Ministry. Transport is the next top source, followed by burning of biomass including crops in surrounding areas.

Crop fires in the nearby states of Punjab and Haryana have fallen by more than 90% since 2021, according to federal government data. Still, an Indian Institute of Tropical Meteorology model forecasts their contribution to pollution rising from less than 9% on Nov. 2 to more than 20% by Nov. 5. 

But environmentalists say the capital’s air remains relatively unhealthy for much of the year.

“Authorities are still treating Delhi’s pollution as an episodic event, and not a yearlong problem,” said Manoj Kumar, an analyst at the Centre for Research on Energy and Clean Air. “Concern spikes when air turns severe and visibility falls. But less attention is given to why Delhi has recorded only one ‘good’ air day in 2026.”