All but one of the 100 cities with the world’s worst air pollution last year were in Asia, according to a new report, with the climate crisis playing a pivotal role in bad air quality that is risking the health of billions of people worldwide.

The vast majority of these cities — 83 — were in India and all exceeded the World Health Organization’s air quality guidelines by more than 10 times, according to the report by IQAir, which tracks air quality worldwide.

The study looked specifically at fine particulate matter, or PM2.5, which is the tiniest pollutant but also the most dangerous. Only 9% of more than 7,800 cities analyzed globally recorded air quality that met WHO’s standard, which says average annual levels of PM2.5 should not exceed 5 micrograms per cubic meter.

“We see that in every part of our lives that air pollution has an impact,” said IQAir Global CEO Frank Hammes. “And it typically, in some of the most polluted countries, is likely shaving off anywhere between three to six years of people’s lives. And then before that will lead to many years of suffering that are entirely preventable if there’s better air quality.”