Study: Canadians have the highest risk of respiratory mortality from wildfire pollution

Reviewed by Emily Henderson, B.Sc.Sep 10 2021

An international study has found Canadians have the highest relative risk of respiratory mortality resulting from wildfire pollution, with Regina and Saskatoon among the worst hit.

Published in The Lancet Planetary Health, this unprecedented multi-city, multi-country collaboration analyzed the impact of short term exposure to air pollution on mortality and assessed the impact of forest fire smoke on mortality by pooling data from 749 individual cities in 43 countries over a 17-year period.

Éric Lavigne, Adjunct Professor in the School of Epidemiology and Public Health at the University of Ottawa's Faculty of Medicine, is one of the international authors behind the study. He provided some insight into the findings.

How was the study conducted?
We used a chemical transport model to estimate daily wildfire derived fine particulate matter (PM_2.5) exposure, and a time series model was used to examine the association between exposure and mortality in each city.

What did you find?
In the first three days of exposure there were significant increases in the risks of all causes, cardiovascular and respiratory mortality. Overall, about 0.4 percent of total mortality is attributable to wildfire smoke. Saskatoon and Regina were among the cities with the highest levels of PM_2.5 while Canada was identified as one of the countries that had the highest relative risk for respiratory mortality. It's important to note that the relative risk for Canada is comparable to the one observed in the United States.

Were you surprised by the findings?
It's not surprising to see the risk of wildfire particle pollution is higher for respiratory mortality than for cardiovascular mortality or all-cause mortality. It's important to note that 0.32 percent of all annual respiratory mortality events in Canada are due to wildfires.

Why are rates so high in Saskatchewan?
It's unclear, this was a surprising finding which needs further validation through additional studies. However, this is information public health officials should be aware of.

What kind of urgent action can be taken to reduce health risks from the increasing wildfires?
The results are directly relevant to Canada and strengthens evidence for the need for public health measures to address wildfire smoke, especially in the context of climate change. Additional research is needed to evaluate wildfire pollutants and to identify vulnerable populations and prompt public responses to wildfire related air pollution and action to avoid exposure.