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.

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.

India's capital region of Delhi has virtually shut down as air pollution hit "severe plus" levels, according to Indian government officials in its pollution control authority Delhi's Chief Minister Atishi Marlena said that all of northern India was in the middle of a "medical emergency.

Unhealthy

Pollution levels in Chandigarh - India's first planned city, located about 240km (150 miles) from capital Delhi - have been at more than 15 times the safe limit recommended by the World Health Organization (WHO) for more than a month.

Strong surface winds (at speeds of 15km/hr) that had helped disperse pollutants on Sunday, dropped to near-calm levels of 4-6km/hr by Monday morning, leading to a haze engulfing the city again. Delhi’s 24-hour average air quality index (AQI) was recorded at 285 (“poor”) at 9am on Monday,