PM2.5 in parts of Delhi exceeds 30 times WHO guideline before Diwali

Air quality worsens sharply

The haze over India's capital thickened on Wednesday, 4 November. A citywide reading of 379 at 10 a.m. sat near the top of the 301 to 400 band that India's pollution watchdog calls 'very poor', while an earlier Wednesday-morning figure stood at 377. Readings above 400 fall into the 'severe' category. The air-quality firm IQAir reported PM2.5 levels above 461 micrograms per cubic metre in some districts, more than 30 times the value the WHO recommends for these fine particles. PM2.5 particles are small enough to pass into the bloodstream, and the metropolitan area around the capital is home to more than 30 million people.

Measures so far have had little effect

Authorities have restricted traffic and construction work. The most polluting vehicles are barred from entering the city, and building activity is suspended, measures that took effect in early November. Authorities have also triggered the second tier of the Graded Response Action Plan (GRAP), a set of steps against dust and vehicle emissions. So far those steps have done little to lift the haze, which settles over the city from November to January as cooler temperatures keep pollutants near the ground.

What drives the haze

The environment ministry says vehicle exhaust produces 23% of winter pollution in Delhi, biomass burning such as crop-stubble fires accounts for 20%, and industry including coal-fired power plants for about 9%. The largest share, 27%, comes from pollutants formed when emissions from those sources react in the air. Jacob Koshy, a science journalist and author, says fertiliser spread on fields around Delhi also contributes, because escaping ammonia reacts with other pollutants to form secondary fine particles. Experts have blamed falling temperatures, slow winds and more crop-residue burning in neighbouring Punjab and Haryana. Before that, a storm had brought rain and stronger winds that cleared the air, but once the weather settled, north-westerly winds returned and carried smoke from burning fields toward the capital.

Vehicle exhaust23%

Biomass burning20%

Industry and coal power plants9%

Vehicle exhaust

23 %

Biomass burning

20 %

Industry and coal power plants

9 %

Data from the article text

Diwali and the health toll

Diwali falls on Sunday, 8 November, and fireworks are expected to push pollution higher. The Supreme Court has permitted 'green' firecrackers, designed to emit less, for a few hours on the eve of the festival and on the day itself. Such limits are often ignored, and firecracker blasts were already audible across the capital. Last year the city woke to smog the morning after the festival, even though a court had instructed people to use less polluting fireworks. A 2024 study in The Lancet Planetary Health estimated that 3.8 million people in India died between 2009 and 2019 in connection with air pollution.