Dhaka, Bangladesh

With 22 million people compressed into an unplanned megacity, Dhaka’s year-round PM2.5 averages 97 µg/m³ — cheap diesel generators and brick kilns push it above 150 in dry months, making it the most consistently polluted city after #1 Lahore. This is 40% dirtier than the typical South Asian rival, yet the city lacks an enforceable emission standard.