Hong Kong (CNN) India accounts for seven of the world's 10 cities with the worst air pollution, according to a new report, but previously smogbound Chinese cities have seen a marked improvement.

Gurugram, a suburb of the Indian capital New Delhi, is the world's most polluted city, according to Greenpeace and AirVisual, which found it had an average air quality index of 135.8 in 2018 -- almost three times the level which the US Environmental Protection Agency regards as healthy

In two months of last year, the AQI in Gurugram -- as measured by levels of fine particulate matter known as PM 2.5 -- was above 200. The EPA regards this as "very unhealthy" and warns that "everyone may experience more serious health effects" if exposed.

According to the report, air pollution will cause around 7 million premature deaths globally next year and have a major economic impact.

"Air pollution steals our livelihoods and our futures," said Yeb Sano, executive director of Greenpeace Southeast Asia. "In addition to human lives lost, there's an estimated global cost of 225 billion dollars in lost labor, and trillions in medical costs. This has enormous impacts, on our health and on our wallets."

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