A recent study reveals that the combination of wildfire smoke and extreme heat significantly raises the risk of mortality in British Columbia. Researchers from the BC Centre for Disease Control and University of British Columbia led the study. In doing so, it points to the everyday risks created by PM2.5 levels—microscopic, hazardous soot that can be inhaled deep into the lungs. Between 2010 and 2022, the study followed more than 21,000 deaths. At the same time, the region was experiencing an increase in hot and smoky days, making the findings around worsening health outcomes all the more alarming.
The research borrowed from climate science, utilizing temperature records to understand their effects. It looked at PM2.5 concentrations both through models and direct measurements through satellite imaging and ground-based sensors. These research findings point to a deeply concerning trajectory. The combination of increasing high temperatures and smoky skies are adding 7.9 percent more deaths in the area.
Health Impacts of PM2.5 Concentrations
PM2.5 is particulate matter with a diameter of 2.5 micrometers or less, which is hazardous to human health when inhaled. Sarah Henderson, senior author and scientific director of the BC Centre for Disease Control’s Environmental Health Services, emphasized the detrimental effects of exposure to moderate levels of PM2.5.
“But what this study is telling us is we actually see a significant amount of risk at the concentrations that people might not even notice.” – Sarah Henderson
Henderson explained that in past research there was a marginal negative association with mortality when very extreme levels of wildfire smoke occurred. It’s important to understand that even moderate levels can lead to some of the most severe health impacts. These types of insights are extremely timely, especially as British Columbia faces increasingly frequent days with smoky skies and record-breaking heat.
Increasing Frequency of Hot and Smoky Days
The study highlights a troubling trend: British Columbia has witnessed an increase in hot and smoky days over the past two decades, a pattern expected to accelerate with climate change. In her remarks, Henderson stated,
“We’re going to have more hot and smoky days.”
…at a time when extreme weather events are increasing. One way climate change affects our health is through increasing heat and the dangerous effects of wildfire smoke. The threats to forests that bubbled to the surface dramatically during the summer of 2021 are very real. A historic heat dome settled over the province, leading to as many as 619 people dying in a heat emergency that was largely preventable.
Michael Brauer, a professor at the University of British Columbia’s School of Population and Public Health, stressed the importance of addressing air pollution exposure alongside extreme heat management in a warming climate.
“This paper provides evidence that all of those things carry risk, and when we combine them, they carry sort of a multiplicative risk.” – Michael Brauer
Urgent Need for Policy Changes
As the authors point out, this leaves a major hole in Canada’s public health regulatory framework—the absence of indoor air quality standards for PM2.5. As it stands, landlords are not even mandated to maintain acceptable indoor temperatures below 26 degrees Celsius. This is an important public health threshold—once exceeded, the chances of harmful health effects significantly rise.
Henderson pointed out that as the situation deteriorates, it is more important than ever for policymakers to truly understand these challenges and how to solve them. She explained how individuals often become aware of the risks associated with smoke only during severe episodes when air quality deteriorates visibly.
“People start paying a lot of attention to smoke and its health risks when it’s very, very smoky outside, when we see those orange skies and those extreme air quality impacts,” – Sarah Henderson
The picture painted with evidence provided in this study indicates that even levels of smoke typically thought to be moderate can still be highly dangerous.
