Density of fine pollutants was nearly 1,665 in one part of the city – the safe limit is 25

Pollution in the Indian capital Delhi exceeded the safe limit by 66 times on Thursday, shrouding the city in toxic fumes the morning after millions of firecrackers were burst for the Hindu festival Diwali.

Delhi government monitors showed the density of fine pollutants — small enough to evade the body’s natural defences and breach the blood-brain barrier — reached 1,665 in Anand Vihar, a central neighbourhood. The World Health Organisation’s safe limit for pollutants that size is 25.

Images from across Delhi showed it blanketed in thick haze that slowed traffic and engulfed the city’s best-known monuments. Health officials warn the air can cause headaches and respiratory discomfort in the short term and has been linked to heart disease, chronic respiratory disease, lung cancer, cognitive decline and obesity in the long term.

Along with exchanging sweets and lighting traditional lamps, contending with poisonous fog has become an annual feature of the Diwali festival in Delhi and other major Indian cities — despite attempts by the Indian supreme court to limit the use of crackers during the season.

Facebook Twitter Pinterest A man cycles past a government building amid heavy smog in Delhi Photograph: Money Sharma/AFP/Getty Images

Last year the court banned the use of crackers in Delhi outright as a trial. This year it limited their use to a two-hour window, and said only “green” crackers – which supposedly emit less pollution and noise – would be permitted.

Both years, Delhi residents have flouted the restrictions, and crackers could still be heard going off in parts of the city on Thursday morning. One research group, Urban Emissions, estimated five million kilograms of fireworks had been burst, the same as in 2017.

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Delhi police said they had seized more than 600kg of firecrackers from across the city, registered 120 criminal cases and arrested 28 people in the past day.

“It’s a tradition,” said Gopal, 40, a fitness instructor based in Chatturpur, south of Delhi, who burst crackers with his children on Wednesday evening. “Lord Ram came home after 14 years so we celebrate it with crackers and sweets and many others things.”

He said people elsewhere used fireworks to celebrate events such as New Year’s Eve. “We only use it for one day and that can be allowed,” Gopal said. “It’s not good if we’re not going to celebrate our tradition, which is more than 4,000 years old.”

Talk shows in the country have debated whether the ban on firecrackers infringed Indians’ right to worship, with some making the point the firecrackers cause a short-term spike in an environment already dangerously polluted by vehicles, industrial fumes, construction sites and the seasonal burning of crop residue by farmers in neighbouring states.

Pollution levels in the week leading up to Wednesday reached more than 25 times the safe limit, mostly due to farm fires Haryana and Punjab states, which formed a cloud of smoke over north India that “hundreds, if not thousands of kilometres long and about 20 to 30 kilometres wide”, said Josh Apte, an assistant professor at the University of Texas who researches air quality.

Recognition is growing that poor air quality is a regional issue that afflicts other cities in north India to an even worse degree than Delhi; and that the capital’s pollution is exacerbated by unlucky geography.

“If the same amount of emissions were there in both Berlin and Delhi, Berlin would have better air quality simply because it’s a windy city,” said Siddharth Singh, author of The Great Smog of India, a new book on the crisis.

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He said overpopulation, leading to an increase in vehicles and construction, was the major culprit for the declining air quality, but that Delhi was also cursed by the combination of low wind speeds and surrounding mountains which trapped the air.

“Human activity leads to most of the emissions stock in the air, but the geographic reality is that the emissions emitted by human activity will have a far worse impact in Delhi than other cities.”

After several Sri Lankan cricketers vomited on the pitch at a Delhi stadium early this year, focus has grown on the impact of the air on athletes and the potential for sporting events to be shifted out of the city during the winter.

Atul Chauhan, a professional badminton player based in Delhi, said his squad had simply stopped training this week and were spending their time inside their air-purified homes.

“We have an upcoming tournament right now, we should be training like hell, but in this weather it’s better to stay home than practice,” Chauhan, 26, said.

“Playing now, I get tired within 20 minutes, even though I have the stamina of more than one hour. It’s like something is inside your eyes, you can’t see properly. And when the shuttlecock is coming at 300km/h, you can’t see it properly.”