Air pollution exposure increases risk of COVID hospitalization, study suggests

Exposure to air pollution increases the risk of COVID-19 hospitalization, according to a new study.

Published this month in the American Journal of Respiratory and Critical Care Medicine, the peer-reviewed study found that exposure to common air pollutants increased the risk of hospitalization by up to 30 per cent for fully-vaccinated patients.

“Among vaccinated people, the detrimental effect of air pollution exposure is a little smaller, compared to people who were not vaccinated,” co-author Zhanghua Chen, an assistant professor of population and public health sciences at the University of Southern California, explained in a news release. “But that difference is not statistically significant.”

The study analyzed data from more than 50,000 COVID-19 patients in Southern California. Estimated air pollution exposure was calculated for every residential address using publicly-available data on fine particle (PM2.5), nitrogen dioxide (NO2) and ozone (O3) levels in the one month and year prior to each patients’ diagnosis.

“We investigated both long-term and short-term air pollution exposure, which may influence COVID-19 severity through different mechanisms,” Chen said.

Long-term exposure to air pollution is linked to an increased risk of cardiovascular and lung disease, both of which can lead to more severe COVID-19 symptoms, the researchers noted, while short-term air pollution exposure may intensify lung inflammation, and even affect patients’ immune responses. Since COVID-19 is a respiratory illness, it was no surprise to find that air quality impacted patient outcomes.

For the unvaccinated COVID-19 patients, short-term exposure to nitrogen dioxide and fine particles increased the risk of hospitalization by 13 to 14 per cent, while long-term exposure increased the risk by 22 to 24 per cent. For the partially and fully-vaccinated, the risks were slightly lower, but not statistically significant, according to the study. Ozone levels did not impact hospitalization rates.

The study was also able to further establish that COVID-19 vaccination leads to fewer hospitalizations.

“Fully vaccinated people had almost 90 per cent reduced risk of COVID hospitalization, and even partially vaccinated people had about 50 per cent less risk,” Chen said.

“These findings are important because they show that, while COVID-19 vaccines are successful at reducing the risk of hospitalization, people who are vaccinated and exposed to polluted air are still at increased risk for worse outcomes than vaccinated people not exposed to air pollution,” added co-author Anny Xiang, a senior research scientist at Kaiser Permanente, an American healthcare consortium, in the news release.

Since the findings suggest improving air quality could reduce severe cases of COVID-19, the researchers are now studying the impacts of indoor air purifiers on patients.

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