A Canadian study has found links between air pollution and the severity of COVID-19

A Canadian study has found links between air pollution and the severity of COVID-19

An extensive study of thousands of COVID-19 patients in Ontario hospitals has found links between the severity of their infection and levels of common air pollutants to which they are exposed.

An extensive study of thousands of COVID-19 patients in Ontario hospitals has found links between the severity of their infection and levels of common air pollutants to which they are exposed.

“This adds to the existing evidence that air pollution is a silent killer,” said Chen Chen, an environmental epidemiologist at the University of California and lead author of the study published in the Canadian Medical Association Journal.

The study looked at more than 150,000 cases of COVID-19 in Ontario patients in 2020. It revealed how many of those patients were hospitalized with the disease, how many were transferred to intensive care units and how many died.

The researchers then turned to previously developed data that combined air monitoring records and other sources, such as satellite imagery, to model levels of three common pollutants across Ontario — fine particulate matter, nitrogen dioxide and ground-level ozone.

Nitrogen dioxide is emitted in the engine exhaust, and then decomposes in the atmosphere to the ozone layer. All three pollutants together create smog.

The scientists then combined the health and pollution data, using statistical methods to eliminate the effects of more than 10 different “confounding factors,” such as pre-existing conditions and economic status.

The researchers were able to show that more severe reactions to the virus were associated with higher levels of long-term exposure to air pollutants.

For every 25 percent increase in fine particles a patient was exposed to, the chance of hospitalization after contracting COVID-19 increased by six percent, and the odds of being admitted to an intensive care unit increased by 9 percent. The team found no links between mortality rates and exposure to particulate matter.

Effects were lower for nitrogen dioxide.

But for ground-level ozone, the study found that the associations between each 25 percent increase in exposure were much higher.

Chances of hospitalization increased by 15 percent. Intensive care admissions increased 30 percent and death rates increased 18 percent.

“Of those people who were already infected, we observed that some of them who were exposed to higher levels of air pollution prior to infection had a higher likelihood of worse outcomes,” Chen said.

The study builds on previous research that looked at the immediate links between pollution levels and COVID-19 infection. This approach fails to recognize the long-term effects of air pollutants, Chen said.

“We were looking at long-term pollution levels and their impact on the severity of COVID.”

Chen cautioned that the study does not prove that the three pollutants actually worsened COVID-19 outcomes.

But it wouldn’t be a surprise. All of these pollutants are known to irritate the lungs and lung function, and COVID-19 is a lung disease.

“We know that this virus attacks our lung system,” she said. “It is possible that exposure to more air pollution prior to infection makes you more susceptible.”

Chen said the study opens the door to more detailed research on the difference in COVID-19 outcomes. What is the effect of age, for example, or economic status?

Also, the study does not look for the mechanism of how air pollution works to exacerbate disease.

“This research raises a lot of questions,” Chen said.

This report was first published by The Canadian Press on May 24, 2022.

Follow Bob Weber on Twitter at @row1960

Bob Weber, The Canadian Press



2022-05-24 04:43:59

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