Bob Weber, The Canadian Press Published Tuesday, May 24, 2022, 7:33 AM EDT Last Updated: Tuesday, May 24, 2022, 7:33 AM EDT
An extensive study of thousands of patients with COVID-19 in Ontario hospitals found links between the severity of their infections and the levels of common air pollutants they experience.
“This complements 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 found how many of those patients were admitted to hospital because of the disease, how many were transferred to intensive care units and how many died.
Researchers then turned to pre-developed data that combined air surveillance records with other sources, such as satellite imagery, to model Ontario levels of three common pollutants – fine particles, nitrogen dioxide and ground-level ozone.
Nitrogen dioxide is released into the exhaust gases of the engine, which then decomposes into the atmosphere to ozone. All three pollutants together create smog.
The researchers then combined data on health and pollution, using statistical methods to eliminate the effects of more than 10 different “disruptive factors”, such as existing conditions and economic status.
Researchers have been able to show that more severe reactions to the virus are associated with higher levels of long-term exposure to air pollutants.
For every 25 percent increase in the fine particles to which the patient was exposed, the chance of being admitted to hospital after being infected with COVID-19 increased by six percent, and the chance of being admitted to the intensive care unit increased. increased by nine percent. The team found no link between mortality and particulate matter exposure.
The effects are smaller for nitrogen dioxide.
But for ground-level ozone, the study found that the correlations for every 25% increase in exposure were much higher.
The chances of admission to hospital have increased by 15%. Intensive care intake increased by 30 percent and mortality increased by 18 percent.
“Of those people who were already infected, we observed that some of them who were exposed to higher levels of air pollution before the infection were more likely to have worse results,” Chen said.
The study builds on previous studies that look at the direct links between levels of pollution and COVID-19 infections. Chen said the approach fails to capture the long-term effects of air pollutants.
“We looked at long-term levels of pollution and their impact on the severity of COVID.
Chen warned that the study did not find that the three pollutants actually caused the deterioration of COVID-19 results.
But it will not be a surprise. These contaminants are known to irritate the lungs and lung function, and COVID-19 is a lung disease.
“We know this virus is attacking our lung system,” she said. “It is possible to be exposed to more air pollution before the infection makes you more susceptible.”
Chen said the study opens the door to more detailed research on variations in COVID-19 results. What is the influence of age, for example, or economic status?
Furthermore, the study does not look at the mechanism of how air pollution can act to aggravate the disease.
“This study raises many questions,” Chen said.
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