Short-term wildfire smoke exposure linked to 440 deaths in Canada a year

Thick smoke fills the air and nearly blocks out the sun just before 3 p.m. as a motorist on Highway 97 travels past an area burned by the White Rock Lake wildfire in Monte Lake, east of Kamloops, B.C., on Saturday, August 14, 2021. THE CANADIAN PRESS/Darryl Dyck

Toronto -

An international team of researchers have calculated that short-term exposure to wildfire smoke is attributable to around 440 deaths in Canada and more than 33,000 deaths globally each year.

The study, which was published earlier this month in The Lancet, looked at the association between wildfire pollution and deaths in 749 cities across 43 countries.

Between 2000 and 2016, researchers measured daily concentrations of PM2.5, which are tiny particles smaller than 2.5 micrometres and are the primary pollutant in wildfire smoke. These numbers were compared against daily counts of death due to cardiovascular causes, respiratory causes and all causes.

Researchers calculated that approximately 0.33 per cent of all deaths in Canada were attributable to wildfires, occurring within the first three days of exposure. Similarly, short-term wildfire smoke was found to be attributable to 0.33 per cent of all cardiovascular deaths and 0.32 per cent of respiratory deaths in the country.

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In Canada, researchers also found that an increase of 10 micrograms per square metre in PM2.5 content was associated with a 2.3 per cent increased risk of respiratory mortality.

"We noticed that the effects were mainly higher for respiratory mortality, which was not surprising because we know that wildfires impact the respiratory system," Éric Lavigne, University of Ottawa Faculty of Medicine professor and one of the study’s authors, told CTVNews.ca in a telephone interview on Sunday.

The highest rates of wildfire mortality were found in Central America and Southeast Asia, where the percentages of deaths due to wildfire smoke exceeded 1.6 per cent.

The cities of Saskatoon and Regina had some of the highest daily concentrations of PM2.5, researchers also found.

Lavigne says this could be due to wildfire smoke from B.C. being blown through the wind, eastward towards Saskatchewan.

"I would say climatological or environmental factors may be into play, but in this study, we couldn't say why," Lavigne said.

For months, British Columbia has been grappling with out-of-control wildfires fuelled by heat and dry conditions that have destroyed towns and prompted widespread evacuations. As of Monday, over 860,000 hectares have burned in B.C. with 1,594 wildfire incidents having been recorded this year.

One limitation of the study is that it only looked at deaths due to short-term exposure to wildfire smoke, Lavigne noted.

"There's still some uncertainties with people who are repeatedly exposed every year, whether it increases their risk of dying from those causes in a long-term perspective. That's one limitation that we should keep in mind when interpreting the findings," he said.

Nonetheless, the authors say that the data underscores the need for policy makers to address wildfire smoke from a public health perspective.

"Policy makers and public health professionals should raise awareness of wildfire pollution to guide prompt public responses and take actions to reduce exposure," the authors wrote.