A new study by researchers from the Harvard University T.H. Chan School of Public Health suggests that people who live in areas where there is more air pollution are more at risk from the coronavirus than those who breathe cleaner air.
The researchers looked at pollution from PM2.5, which is fine particulate matter in the air that is 2.5 microns or less in width, or about 30 times smaller than the width of a single hair.
PM2.5 pollution is caused by, among other things, power plants, motor vehicles, burning wood or heating oil, wildfires, and some industrial processes. It can also be produced indoors by smoking, cooking, burning candles, and operating fireplaces. PM2.5 is one of the major components of air pollution.
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The researchers analyzed data on long-term exposure to PM2.5 and deaths in the United States from COVID-19, the disease caused by the coronavirus, and found “statistically significant evidence” that higher levels of PM2.5 led to higher COVID-19 deaths.
“The results of this paper suggest that long-term exposure to air pollution increases vulnerability to experiencing the most severe Covid-19 outcomes,” the authors wrote.
“Our results are adjusted for a large set of socioeconomic, demographic, weather, behavioral, and healthcare-related confounders and demonstrated robustness across a wide range of sensitivity analyses,” the authors wrote.
Exposure to PM2.5 is a known health risk, affecting people’s lungs and hearts. “Numerous scientific studies have linked particle pollution exposure to a variety of problems,” including premature death in people with heart or lung disease; nonfatal heart attacks; irregular heartbeat; aggravated asthma; decreased lung function; and increased respiratory symptoms, such as irritation of the airways, coughing or difficulty breathing, according to the US Environmental Protection Agency.
Researchers in their paper, which has been submitted to a journal, noted that PM2.5 pollution has been estimated to be responsible for 5.5 million premature deaths a year.
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At the same time, the CDC has said that people with certain pre-existing conditions, including chronic lung disease or moderate to severe asthma and people who have serious heart conditions, have been found to be more at risk for severe illness from COVID-19.
The researchers said that the “majority of the pre-existing conditions that increase the risk of death from COVID-19 are the same diseases that are affected by long-term exposure to air pollution.”
They set out to check out the hypothesis that “because long-term exposure to PM2.5 adversely affects the respiratory and cardiovascular system, it can also exacerbate the severity of the COVID-19 infection symptoms and may increase the risk of death in COVID-19 patients.”
The study found that an increase of only one microgram per cubic meter in long-term average PM2.5 exposure was associated with an increase of 15 percent in the COVID-19 death rate.
Francesca Dominici, a professor of biostatistics who led the study, said in a telephone interview that such a difference could be found in a city and an adjacent suburb.
The researchers found, for example, that the average reading over the period studied was 13.1 in Baltimore City and 11.5 in Baltimore County, she said.
“We found that people living in counties in the United States that have experienced a higher level of air pollution over the last 15 to 20 years have a substantially higher COVID-19 mortality rate," she said.
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Dr. John R. Balmes, a spokesman for the American Lung Association and a professor of medicine at University of California, San Francisco, told The New York Times that the findings were particularly important for hospitals in poor neighborhoods and communities of color, which tend to be exposed to higher levels of air pollution than affluent, white communities.
“We need to make sure that hospitals taking care of folks who are more vulnerable and with even greater air pollution exposure have the resources they need,” Balmes said.
Balmes noted that without studying individual characteristics of patients, the study could only suggest a causal connection between air pollution and Covid-19 deaths and would need to be confirmed by more research — a point with which Dominici agreed. But, Balmes said, “It’s still a valuable finding.”
The study comes at a time the Trump administration is working to push back clean-air regulations.
“The study results underscore the importance of continuing to enforce existing air pollution regulations to protect human health both during and after the Covid-19 crisis,” the study said.
The lead authors of the study were Xiao Wu and Rachel C. Nethery.
Material from Globe wire services was used in this report.
Martin finucane can be reached at martin.finucane@globe.com.