Pandemic closures led to a rare decline in air pollution around the world during 2020, except in cities affected by smoke from large wildfires, including much of the western United States.
With fewer people traveling amid shutdowns and quarantines, most major cities saw double-digit declines in average particle levels compared to 2019, according to an annual air quality report released Tuesday by IQAir Group, a Swiss-based air quality technology company. Air pollution readings fell 38% in Singapore, 23% in Beijing, 17% in Paris, 15% in New Delhi and the surrounding region and 12% in Johannesburg.
Los Angeles was on track to join that list with one of its cleanest years in decades through the first half of 2020. Then wildfires burned a record 4.3 million acres in California as of last summer, including three that they were unleashed at the same time around the second most populous city. Los Angeles ended up with a 15% increase in particulate air pollution, according to IQAir.
Similarly, air pollution increased 35% in San Francisco, 38% in Portland, Oregon, 53% in Phoenix, and 18% in Salt Lake City.
Dirty west
Smoke from the wildfires caused air pollution to rise in major cities in the western US, while declining in most of the east.
Habitable fine particles (PM2.5), commonly produced by wildfires and dangerous to humans at high densities
WHO guideline level
for safe air quality
Health for
sensitive groups
Habitable fine particles (PM2.5), commonly produced by wildfires and dangerous to humans at high densities
WHO guideline level
for safe air quality
Health for
sensitive groups
Habitable fine particles (PM2.5), commonly produced by wildfires and dangerous to humans at high densities
WHO guideline level
for safe air quality
Health for
sensitive groups
Habitable fine particles (PM2.5), commonly produced by wildfires and dangerous to humans at high densities
WHO guideline level
for safe air quality
Health for
sensitive groups
Smoke from wildfires also fueled increased pollution in Melbourne, Australia, where readings soared 27% and in Buenos Aires, where it increased 15%.
“This really shows the alarming scale of wildfires,” said Meghan Thurlow, vice president of detection systems and applied science at Aclima, a San Francisco company that measures air pollution.
Cities across the US reflected global declines. Air pollution fell 13% last year in Chicago, 9.5% in Philadelphia and 7% in New York.
The worst overall air quality was recorded in Asia last year. India’s New Delhi and the surrounding region had the dirtiest air of all the world’s capitals measured, according to IQAir, and 49 of the 50 most polluted cities measured worldwide were in Bangladesh, China, India and Pakistan.
Global satellite data indicates that wildfires are getting bigger and more intense. WSJ talks to NASA’s Doug Morton to understand the science behind what makes the planet more flammable and makes fires harder to control. Noah Berger / Associated Press
Air pollution is responsible for seven million premature deaths a year, the World Health Organization has estimated. With life returning to normal around the world, levels of air pollution related to human activity will likely rise again, IQAir officials say.
Even before Covid-19, the world’s largest economies were already trying to reduce air pollution amid pressure to cut carbon emissions.
In China, where the Covid-19 pandemic began, 86% of the country’s cities reported cleaner air in 2020 than in the previous year. Half of that improvement was attributed to lockdowns early last year, while the other half was due to China’s long-term anti-pollution measures, said Lauri Myllyvirta, senior analyst at the Center for Research on Energy and Clean Air.
A sandstorm hit northern China on Monday, erasing skyscrapers and turning the sky in Beijing yellow. WSJ’s Jonathan Cheng explains what the country’s economic recovery has to do with this. Photo: Getty Images
China’s air quality has steadily improved since 2013, when the government began, among other measures, to switch from coal-to-gas heating.
The reduction in emissions around the world was “an unplanned scientific experiment” that showed how quickly air pollution levels can be reduced, said Glory Dolphin Hammes, CEO of IQAir North America, a subsidiary of IQAir. . “What we’ve been able to determine is that we can do it,” Hammes said.
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But when fires start in California, Australia and elsewhere, they grow faster than in the past and create an unprecedented public health threat, according to the researchers. The fine particles they generate are the most concerning, because they often contain incinerated pipes, plastic and other household materials, said Lisa Miller, a professor at the University of California Davis School of Veterinary Medicine.
“We think that perhaps the particulate matter from these fires may be more dangerous than the particulate matter from a car,” said Dr. Miller.
Write to Jim Carlton at [email protected] and Sha Hua at [email protected]
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