After the lights, the haze: Delhi chokes on toxic smog after Diwali

Thick smoke hung over New Delhi this week as millions of Indians lit firecrackers to mark the Diwali festival, but calls for a boycott highlighted growing concerns over air quality in one of the world’s most polluted cities. Pollution in the Indian capital reached “severe” levels on Friday, the day after Diwali, according to a new air quality index launched earlier this month as part of Prime Minister Narendra Modi’s “Clean India” mission. Indian authorities regularly appeal to the public to restrict their use of firecrackers, which every year cause injuries as well as letting off the acrid smoke that chokes the capital. But this year the calls had particular resonance after a WHO study of 1,600 cities across 91 countries in May found the Indian capital had the dirtiest atmosphere in the world - a claim Indian authorities fiercely denied.

A majority of the time, Delhi air is quite bad, but it is still better than Beijing.

Gufran Beig, chief scientist at India’s state-run System of Air Quality Weather Forecasting and Research (SAFAR)

New Delhi’s air quality has steadily worsened over the years, a consequence of rapid urbanisation that brings pollution from diesel engines, coal-fired power plants and industrial emissions. The Indian capital also suffers from atmospheric dust blown in from the deserts of the western state of Rajasthan, as well as pollution from open fires lit by the urban poor to keep warm in winter or to cook food. The WHO study showed Delhi had the world’s highest annual average concentration of PM2.5, at 153. Experts says these extremely fine particles of less than 2.5 micrometres in diameter are linked with high rates of respiratory and cardiac disease. In the long run they can cause cancer as they settle deep into the lungs and pass into the bloodstream.

Modi can ask but nobody listens on Diwali. When you find your car with a layer of grime the next day, you know you’re inhaling poison.

29-year-old Delhi resident Riddhima Gill, saying even the prime minister is powerless to stop the noxious Diwali celebrations

Asia-Pacific