Exposure to air pollution from childhood increases the risk of poor health and can cause strokes and lead to cancer. Yet some governments in Asia are still failing to meet clean-air targets.

Whatever the causes of the smog, by one ranking Delhi was not just the most polluted city in the world, but “nearly five times as bad as the second most polluted city, Dhaka,” in Bangladesh next door, as Shashi Tharoor, a leader of the opposition in Parliament and best-selling author, posted on X.