In brief

• Thick smog covered New Delhi on Monday after Diwali celebrations, reducing visibility across the city.
• Fine particle readings in some areas reached about 60 times the WHO daily guideline.
• Many people reportedly ignored limits on conventional firecrackers despite court-backed restrictions.
• Seasonal weather and crop burning in neighbouring states worsen the air during winter.

Smog blankets the capital after overnight celebrations

A dense haze covered New Delhi on Monday morning, reducing visibility on roads and obscuring high-rise buildings, according to reports from the Associated Press and other outlets (Thick smog shrouds New Delhi after Diwali firecrackers add to seasonal pollution – KSAT) (Indické Naí Dillí po oslavách sviatku zahalil smog, koncentrácia látok je až 60-násobná – HNonline.sk). Residents described irritation in the throat and itchy eyes as the grey haze hung over the city. Local air quality readings on Monday were rated "severe" in several reports (India news: Delhi air quality level 'severe' after Diwali – DW).

Readings far above the health guideline

In some parts of the city, concentrations of PM2.5, the finest and most harmful particles, reached 879 micrograms per cubic metre, close to 60 times the daily maximum set by the World Health Organization, according to data from the Swiss group IQAir. Measurements from several monitoring stations pointed to a similar scale of exceedance (Nach Diwali-Fest - Trotz Feuerwerks-Regeln: Feinstaubbelastung in Neu Delhi übersteigt Grenzwert um ein Vielfaches – Deutschlandfunk). One locality was reported to have readings above 58 times the WHO daily limit.

Restrictions on firecrackers were widely ignored

India's Supreme Court had moved in October to limit pollution during the festival, banning conventional firecrackers on the Saturday and Sunday and allowing only approved low-emission versions within three-hour windows. Authorities had also imposed traffic curbs in recent weeks. Many people, however, appear to have ignored the rules, officials and media reports suggest. Even the approved eco-friendly crackers still release particles and other pollutants, so they add to an already dangerous air quality level.

Seasonal conditions compound the problem

Delhi's air normally deteriorates as winter approaches, when cold temperatures and weak winds keep pollutants close to the ground. Crop residue burning in neighbouring states, along with vehicle and industrial emissions, adds to the load (Homes and temples glow across India as Diwali celebrations begin – BBC News). Before the festival, the city's air quality index had already reached 391, in the "very poor" category.

Health risks and what happens next

Fine particles can enter the lungs and bloodstream, and experts link long-term exposure to asthma and lung cancer. A Lancet study cited by reporters estimated 3.8 million deaths linked to air pollution in India between 2009 and 2019. Authorities previously ordered some schools to move classes online during spikes in pollution (India: Delhi chokes on most polluted Diwali eve in 10 years – DW). Further restrictions and monitoring are expected as the post-festival smog persists, though reports did not detail new measures beyond the existing ones.