Why India’s Delhi Has One of World’s Worst Air Pollution Problems

Hundreds of millions of Indians breathe some of the world’s most toxic air all year round. Air pollution in the capital area that’s home to about 30 million people is especially stubborn. In winter, the cold weather actually makes the smog even worse — and potent. This November, the capital saw some of the highest levels of pollution on record, and one measure of pollution in New Delhi frequently exceeds the World Health Organization’s daily recommended limits by a factor of more than 20. Studies show India’s dirty air has been killing about a million or more people a year, a massive figure authorities are still struggling to reduce.

Emissions from vehicles, factories and coal-fired power stations contribute to the dirty air. Construction plays a role, as do households lighting fires for cooking and heating. The burning of stalks and stubble from harvested fields in the states of Punjab, Uttar Pradesh, Haryana and Rajasthan that surround Delhi creates smoke so thick that it can be seen from space. In warmer periods, the smoke can more easily disperse, but cold air can trap toxic particles and cause them to linger close to the ground. It’s a condition known as temperature inversion. This is why air pollution, which is present in Delhi all year, becomes denser and more visible during winter.