Why India has repeated air pollution problems

New Delhi struggles with pollution year-round, but the problem becomes acute during fall and winter months. On Wednesday, the concentration of tiny pollution particles was nearly 30 times above the level deemed safe over a 24-hour period by the World Health Organization.

Around the world, researchers closely track levels of airborne particulate matter less than 2.5 microns in diameter — known as PM 2.5 — because it can lodge in the lungs and other organs, causing long-term health damage. In 2020, 13 of the 15 cities with the most polluted air were in India.