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Severity of COVID symptoms linked to air pollution

In a new study, scientists have investigated whether a relationship exists between air pollution and COVID severity. The researchers examined the levels of common air pollutants in Ontario, Canada, and the incidence of more serious cases of COVID-19 in people who resided in those areas. 

The researchers analyzed data on all 151,105 people, aged 20 years and older, who tested positive for SARS-CoV-2 infection in 2020, and who did not live in a long-term care facility. They noted whether these people were hospitalized, admitted to an ICU or died as a consequence of developing COVID-19. 

To find out whether there was an association between long-term exposure to air pollution and disease severity, the researchers modeled each participant’s historical exposure to three common air pollutants present in the areas where they resided. The pollutants of interest were fine particulate matter (PM2.5), nitrogen dioxide (NO2) and ground-level ozone (O3). 

Before analyzing the data, the researchers adjusted for several potentially confounding factors, including date of diagnosis, sex and age, being part of an outbreak, having essential worker status, participants’ neighborhood socioeconomic status, health care access (including previous influenza vaccination history), and previous outpatient visits to hospital.

“We observed that people with SARS-CoV-2 infection who lived in areas of Ontario with higher levels of common air pollutants (PM2.5, NO2 and O3) were at elevated risk of being admitted to the ICU after we adjusted for individual and contextual confounding factors, even when the air pollution level was relatively low,” explained Dr. Hong Chen, Health Canada and ICES.

In particular, the results showed that people infected with SARS-CoV-2 had an elevated risk of being hospitalized when they had historical long-term exposure to PM2.5 and O3, and an increased risk of death from COVID-19 if they had chronic exposure to ground-level O3

These results add to the growing reports linking levels of ambient air pollution to COVID-19 severity from other countries, including Spain and Mexico.

“Given the ongoing pandemic, our findings that underscore the link between chronic exposure to air pollution and more severe COVID-19 could have important implications for public health and health systems,” wrote the study authors.

The researchers emphasize the need for more extensive research into the exact mechanisms through which long-term exposure to air pollution may influence the severity of COVID-19 symptoms.

The study is published in the Canadian Medical Association Journal.

By Alison Bosman, Staff Writer

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