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 .

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

A new report has shed light on the locations of the most polluted cities in the U.S. On Tuesday, IQAir, a Swiss tech company that tracks global air quality, released the report, which evaluated the state of global air quality based on fine particulate matter,