Air pollution has become as much a part of North Indian winters as weddings and festivals. The average levels of particulate air pollution over November 2024 in India’s capital city of Delhi crossed 250 µg/m³, a number so high as to be almost uninformative. The World Health Organization’s standard for safe air is set at 5 µg/m³, and India’s own air quality standard sits at 40 µg/m³. Regulators like using adjectives to communicate air quality, but with pollution growing so bad, the government has found itself having to augment the Air Quality Index, whose highest level was “Severe”, with a new “Severe Plus” designation. We are running out of words to describe the problem.

India’s so-called “pollution season” attracts a lot of attention, but the problem is not restricted to a few cities and the winter months. The country has grown steadily more polluted over the last two decades. Satellite-derived measures of pollution in 2021 were around 51 µg/m³, about 10 times the WHO safe standard.

Researchers at the University of Chicago estimate that air pollution is now the single greatest threat to life expectancy in the country, lowering lifespans by about 3.6 years relative to aspirational WHO goals. These observations lead to...