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 .

India, the fifth most polluted country in the world, is home to 13 of the top 20 most polluted cities in the world, according to the latest report by IQAir.

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