Oct. 26 (UPI) -- Up to 15% of all COVID-19 deaths globally, and 18% of fatalities caused by the virus in the United States, may be linked to long-term exposure to air pollution, an analysis published Monday by the journal Cardiovascular Research estimated.
This means that air pollution may have played a role in roughly 40,000 of the more than 220,000 deaths attributed to the coronavirus nationally, the researchers said.
"If both long-term exposure to air pollution and infection with the COVID-19 virus come together, then we have an additive adverse effect on health, particularly with respect to the heart and blood vessels, which leads to greater vulnerability and less resilience to COVID-19," study co-author Thomas Münzel said in a statement.
"If you already have heart disease, then air pollution and coronavirus infection will cause trouble that can lead to heart attacks, heart failure and stroke," sad Münzel, a professor at the University Medical Center of the Johannes Gutenberg University and the German Center for Cardiovascular Research.
The findings are based on an analysis of data from previous U.S. and Chinese studies of air pollution, as well as COVID-19 case and death totals globally through the end of June, according to the researchers.
They combined this with satellite images that show global exposure to polluting fine particles known as particulate matter, or PM, the researchers said.
Specifically, researchers focused on exposure to PM2.5, or particulate matter measuring 2.5 microns in diameter or less, they said.
These small particles are thought to have the most significant health effects and their presence is a widely used measure for air pollution.
Using information on atmospheric conditions and ground-based pollution monitoring networks, the researchers created a model to calculate the fraction of COVID-19 deaths that could be attributable to long-term exposure to PM2.5.
Estimates for individual countries show that air pollution contributed to 29% of coronavirus deaths in the Czech Republic; 27% in China; 26% in Germany; 18% in France; 16% in Sweden; 15% in Italy; 14% in Britain; 12% in Brazil; 8% in the Republic of Ireland; 6% in Israel; 3% in Australia; and 1% in New Zealand.
These percentages are estimates of "the fraction of COVID-19 deaths that could be avoided if the population were exposed to lower counterfactual air pollution levels without fossil fuel-related and other [humans-caused] emissions," according to the researchers.
However, the estimates don't "imply a direct cause-effect relationship between air pollution and COVID-19" death, only a possible relationship between two. A more comprehensive evaluation of the role of air pollution in COVID-19 needs to be performed after the pandemic has subsided, they said.
"When people inhale polluted air, the very small polluting particles, the PM2.5, migrate from the lungs to the blood and blood vessels, causing inflammation and severe oxidative stress, which is an imbalance between free radicals and oxidants in the body that normally repair damage to cells," Münzel said.
"This causes damage to the inner lining of arteries and leads to the narrowing and stiffening of the arteries," he said.