Air pollution from very small particles kills millions of people around the world each year and has been rising in the Trump era, leading to an annual increase of nearly 10,000 deaths in the US. Some of this has been due to wildfires, but some of it is related to ongoing deregulatory efforts by the Trump administration. President Trump has a number of initiatives in the works — from narrowing the range of science regulators are allowed to consider to making cars less fuel efficient — that are designed to exacerbate the problem. And while a growing body of literature links particulate pollution to a wide range of cognitive impairments, what we know about how air pollution kills people is largely through cardiovascular and respiratory distress.

Since these health problems are also thought to increase the risk that a coronavirus infection will lead to a fatal case of Covid-19, a team of researchers at Harvard’s T.H. Chan School of Public Health investigated whether places with more air pollution also see a greater lethality of Covid-19 cases.

Their preliminary finding, based on data through April 4, is that yes, air pollution makes Covid-19 much more deadly.

If that finding holds up as more data comes in, it could help us understand why death rates vary so widely among countries, and explain the stark racial disparities in Covid-19 lethality that appear to be emerging in the United States.

Counties with more air pollution see higher Covid-19 fatality rates

Danielle Braun, Francesca Dominici, Rachel Nethery, Ben Sabath, and Xiao Wu used a pretty standard research design looking at long-term air pollution levels as recorded in about 3,000 American counties that cover approximately 98 percent of the population.

They then looked at county-level Covid-19 deaths, adjusting for hospital beds available, smoking and obesity rates, and standard demographic factors. All else being equal, they found that an increase of one microgram of fine particulates per cubic meter is associated with a 15 percent increase in the Covid-19 death rate. That’s about 20 times the statistical association between fine particulate exposure and increases in the normal all-cause mortality rate, reflecting the commonsense view that coming down with Covid-19 greatly elevates the importance of your baseline respiratory and cardiovascular health.

It is well known among people who study air pollution that African American neighborhoods are much more likely to have high levels of contamination — the result of a multifaceted historical process. The link between air pollution and Covid-19 fatality could be a partial explanation for why African Americans seem to be dying at a disproportionate rate. It could also partially explain why things got so bad in Italy, which has about double the concentration of air pollution in the United States.

In policy terms, we cannot cope with the pandemic by going back in time to reduce background levels of air pollution. But we can use the data to spot and help the most vulnerable.

But right now, this is the type of study — based on statistical analysis rather than a controlled experiment — the Trump administration wants to exclude from regulatory analysis. It is also moving to suspend enforcement of clean air rules, allegedly as part of the response to the public health emergency. But this is exactly backwards. As the study’s authors write, their work “underscores the importance of continuing to enforce existing air pollution regulations to protect human health both during and after the Covid-19 crisis.”

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