A study released by Swiss air-quality watchdog group IQAir on Tuesday found New Delhi, India, was the world’s most polluted capital city for the third year running, and South Asia overall had some of the worst air quality ever recorded.

Reuters dourly noted New Delhi’s particulate matter concentrations were “more than double the level of Beijing,” which is currently the 14th most polluted city on Earth. India’s pollution declined by 11 percent due to the coronavirus lockdowns, but it was still the third most-polluted country, right behind Bangladesh and Pakistan.

“Air pollution caused an estimated 54,000 premature deaths in New Delhi in 2020, according to a recent study by Greenpeace Southeast Asia Analysis and IQAir,” Reuters added.

Not all of this pollution was due to industrial byproducts, as IQAir noted a good deal of Delhi’s pollution this winter came from massive farm fires in Punjab. 

In a similar vein, China still has the world’s most polluted city, Hotan, but the report blamed “sandstorms exacerbated by climate change” for the high particle concentrations in Hotan’s air. Climate change was also blamed for “high pollution levels in California, South America, Siberia, and Australia.”

Most of the 20 cities with the worst air pollution, as ranked by IQAir, are located in south Asia, with a few notable exceptions like Bishkek, Kyrgyzstan, and Tehran, Iran. 

Bishkek, the Kyrgyz capital, is one of the great horror stories of air pollution, generating fantastic amounts of smog despite having a smaller population than most other high-pollution cities. Rapid industrialization, poor urban planning, and over-reliance on aging, dirty machinery are cited by analysts as the primary causes. Somehow Bishkek ended up with a thicket of high-rise buildings that block the refreshing mountain air, even though city ordinances supposedly forbid constructing anything taller than seven stories.

Denver, Colorado, is the only American city currently in IQAir’s list of the 20 most polluted cities worldwide.

According to IQAir’s report, 84 percent of the countries it monitors “observed air quality improvements” due to pandemic slowdowns, lockdowns, and recessions but, even so, only 24 of the monitored nations were able to meet the World Health Organization’s (W.H.O.) standards for particles in the atmosphere. 

“The year 2020 brought an unexpected dip in air pollution. In 2021, we will likely see an increase in air pollution due to human activity, again,” said IQAir CEO Frank Hammes. 

A study published by Science Advances in January found that pandemic lockdowns produced “major reductions in air pollutant emissions,” but the declines were “not as large as expected,” and were virtually negligible in some regions. The report struggled to come up with a solid explanation for why the reductions were often half, or less, as large as the reductions anticipated for the cessation of most travel and commercial activity in the monitored cities.