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Air pollution could increase COVID-19 cases, severity outcomes: Swedish study

By Erin Hitchcock, Air Aware Educator

A Swedish observational study suggests there is a correlation between air pollution and an increased risk of positive COVID-19 cases and more severe outcomes among young adults.

The study, published in April by Jama Network Open and led by researchers from the Karolinska Instituet in Stockholm, included a total of 425 participants, with the median age of 25.6, who were diagnosed with COVID-19.

“The findings of this case-crossover study of Swedish young adults with air pollution exposure and SARS-CoV-2 infection suggest that residential short-term exposure to air pollution was associated with increased risk of having positive PCR test results for SARS-CoV-2 infection,” the study said. “These findings support the broad public health benefits of reducing ambient air pollution levels.

Further, the study adds that “short-term exposure to air pollution can affect airway inflammation and oxidative stress, whereas absorbed air pollutants may cause deep lung irritation and immunomodulation of the host response to infection, possibly worsening the severity of existing infection.”

Interior Health’s Medical Health Officer Dr. Carol Fenton said there are strengths and drawbacks to the study, however.

She said because it uses a case-crossover method where each person has their
own controls, it eliminates, for example, the likelihood of the cases all being
in a specific socioeconomic status or geographic area that can also play a role
in the transmission of the virus.

“What they don’t talk about is whether or not the pollution actually changes
behaviour, because we know a lot of human behaviours can increase or decrease
the likelihood of infection. … For example, when it’s smoky here in the Interior, people tend to spend more time indoors in closed spaces, so you’re more likely to be infected,” she said, noting that exposure to pollution does increase the likelihood of adverse health effects. “I do think air quality is very important for health from a chronic health perspective, which is well
established, but also from an infectious disease perspective.”

To view the study, visit

Erin Hitchcock is an Air Aware educator with Scout Island Nature Centre.
Visit our newly updated website at and follow us on Facebook at
Air Aware Williams Lake. We gratefully acknowledge the financial support of the Province of BC through the Ministry of Environment and Climate Change Strategy.

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