Data from more than 40,000 air quality monitoring stations in 138 countries, territories and regions were analyzed for the report, IQAir said.

All but one of the world’s top 20 most polluted cities last year were in Asia, a new study shows. The majority of these cities – 13 – are in the world’s most populous country, India, where booming economic growth is fired largely by coal and where hundreds of millions live in traffic-clogged and congested megacities .

IQAir latest study shows 19 of 20 cities with worst air pollution are in India, Pakistan, Bangladesh, China, and Kazakhstan