Pollution made COVID-19 worse. Now, lockdowns are clearing the air.

Photograph by Francois HENRY, REA/Redux
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Smoke from the district heating plant rises above clouds near a 360-foot observation tower in Grenoble, France.


As the novel coronavirus tears around the world, it’s exploiting our biggest weaknesses, from creaking health care systems to extreme social inequality. Its relationship with one pervasive and neglected problem, however, is more tangled: Air pollution has intensified the pandemic, but the pandemic has—temporarily—cleaned the skies.

When new evidence emerged this week that dirty air makes COVID-19 more lethal, it surprised no one who has followed the science of air pollution—but the scale of the effect was striking. The study, which must still undergo peer review for publication, found that the tiny pollutant particles known as PM2.5, breathed over many years, sharply raise the chances of dying from the virus.

Researchers from Harvard University’s T.H. Chan School of Public Health analyzed data on PM2.5 levels and COVID-19 deaths from about 3,000 U.S. counties covering 98 percent of the U.S. population. Counties that averaged just one microgram per cubic meter more PM2.5 in the air had a COVID-19 death rate that was 15 percent higher.

“If you’re getting COVID, and you have been breathing polluted air, it’s really putting gasoline on a fire,” said Francesca Dominici, a Harvard biostatistics professor and the study’s senior author.

That’s because the fine particles penetrate deep into the body, promoting hypertension, heart disease, breathing trouble, and diabetes, all of which increase complications in coronavirus patients. The particles also weaken the immune system and fuel inflammation in the lungs and respiratory tract, adding to the risk both of getting COVID-19 and of having severe symptoms.


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