Air pollution costs Indian businesses $95bn, or roughly 3% of its gross domestic product every year, according to UK-based non-profit Clean Air Fund and the Confederation of Indian Industry. 
Millions of Indians are breathing the world’s most toxic air. 
After a brief respite during the pandemic, smog returned this year to envelop the capital New Delhi and numerous other cities across the densely populated North Indian plains. 
Air pollution in the capital that’s home to 20mn people has proved especially stubborn, and potent: One measure of pollution frequently exceeds the World Health Organisation’s daily recommended limits by a factor of more than 20. 
The air quality index, or AQI, for Delhi was over 450 most days in the second week of November, with readings below 50 considered safe and anything above 300 as hazardous.
India’s alarmingly higher levels of pollution are brought about by confluence of supporting factors.
Vehicles and emissions from factories and coal-fired power stations contribute year-round, as do road and construction dust and domestic fires lit by the poor. For Delhi, a dark addition comes late in the year from the burning of crop stubble (farmers lighting fires to clear fields in preparation for the winter sowing season) in the surrounding states, even though the practice is banned. 
The Lancet medical journal has estimated that almost 18% of India’s deaths in 2019 were caused by bad air. The direst threat to humans is from PM 2.5, the fine, inhalable particles that lodge deep in the lungs where they can enter the bloodstream. 
WHO guidelines allow a daily average exposure to PM 2.5 of up to 15 micrograms per cubic metre. Delhi’s reading around noon on November 18 topped 500 in some places. 
India is still home to nine of the top 10 most-polluted cities in the world, as measured by PM 2.5, in a study by IQAir AirVisual. Six of the top 10 — Delhi, Ghaziabad, Bisrakh Jalalpur, Noida, Greater Noida and Bhiwadi — are part of the National Capital Region. 
As an election issue, air pollution tends to take a back seat to unemployment, food and electricity prices, and national security. Candidates are reluctant to tackle stubble burning because farmers are a strong electoral constituency. 
For sure, New Delhi has taken some action against polluting coal plants and vehicles, banned the use of dirtier fuels and curbed construction activity. 
But some of the biggest polluters are being let off, with the government twice extending a deadline for coal power plants to install pollution-control equipment.
In 2021, New Delhi residents breathed less than a week of air deemed “good” under US Environmental Protection Agency guidelines, according to US embassy data through November 5. 
While India earlier this month pledged to reach net-zero emissions by 2070, the country fails to tackle toxic smog that covers several of its cities every winter.
Air pollution accounted for 11.5% of India’s disease burden in 2019. It translates into $11.9bn of the country’s total healthcare cost of $103.7bn, based on National Health Accounts data, according to a Times of India report.
By World Bank calculations, diseases, medical conditions and premature deaths linked to pollution cost China and India about 7.5-8% of their annual GDP.
As for India, the worsening financial hit resulting from the enduring pollution could also strangle the country’s strategy to be a $5tn economy by 2025.