Increasingly severe wildfires threaten air quality and public health across North America

Marking World Environment Day on 5 June, Joanne Telfer of CAREX writes about how climate change is intensifying wildfire frequency and severity in Canada, posing significant health risks due to carcinogens in wildfire smoke.

Canada’s air quality is often ranked among the cleanest in the world. But climate change threatens to disrupt that. Wildfires are not a new phenomenon in Canada, though the frequency and severity of fires are on the rise as climate change continues to intensify weather conditions that increase the risk of wildfires.

CAREX Canada (CARcinogen EXposure), a multi-institution team of researchers and specialists that work to provide the largest and most comprehensive source of information on carcinogen exposures in the country, is paying particular attention to the emerging health concerns related to climate change and wildfire smoke. Wildfire smoke contains several carcinogens, including fine particulate matter (PM2.5), benzene, polycyclic aromatic hydrocarbons (PAHs), and formaldehyde. The International Agency for Research on Cancer (IARC) classifies outdoor air pollution and associated particulate matter as carcinogenic to humans and cites wildfire smoke as a contributing source.

Wildfires are not the only source of outdoor air pollution in Canada. Canadians are exposed to fine and ultrafine particles by breathing outdoor air containing emissions from any combustion source, including industrial processes, gasoline and diesel engine exhausts, fireplaces, furnaces, and prescribed burning for forestry and agricultural purposes. According to the Canadian Population Attributable Risk of Cancer (ComPARe) study, 6.9%, or 1,700 lung cancer cases were due to exposure to PM2.5 in outdoor air in 2015. As wildfire smoke becomes more common, it is important for us to understand how these changes contribute to our overall exposure to outdoor air pollution and how it impacts the health of those exposed.

Year after year, we hear news stories of longer, more severe wildfires across the country. We see and smell the smoke that these fires cause throughout the spring, summer, and fall months. We feel the short-term health impacts of exposure on smoky days - eye irritation, headaches, sore throat, coughing, and runny nose. And it’s not just those who live close to the fires that are impacted - wildfire smoke can travel hundreds and thousands of kilometres from the fire, moving into cities where millions of people live and crossing international borders.

Those who are at higher risk of adverse health effects - including seniors, people working outdoors, children, pregnant people, and those with existing health or respiratory conditions - are encouraged to do more to protect themselves during these events. Indigenous people in Canada are also disproportionately threatened by wildfires; while these communities represent 5% of the population, they experience 42% of wildland fire evacuation events. Wildfire smoke exposure can exacerbate existing heart and respiratory diseases and may increase the risk of death. But the long-term health effects from acute, recurring exposures to wildfire smoke are still unknown, and are a focus of new and emerging research as wildfire season in Canada continues to become longer and more extreme.

Our team at CAREX Canada has recently been awarded a grant from the Canadian Institutes of Health Research to investigate how extreme weather events related to climate change, including wildfires, impact workers across the country. This work will examine potential impacts to those who are particularly at risk due to their work duties, such as wildland firefighters, as well as other workers who may be incidentally exposed to wildfire smoke, such as outdoor workers that do not have the option to go inside on smoky days. We will also explore the indirect risks that these extreme weather events may have on workers, including mental health impacts and negative health outcomes due to physical, biological, chemical, and psychosocial exposures. This work will provide valuable insight into how we can better protect Canadian workers from the impacts of climate change.

By monitoring and investigating the emerging health issues related to wildfires and climate change, CAREX Canada is well positioned to help support efforts that prevent exposures to carcinogens and ultimately decrease the risk of cancer and chronic disease in Canada. The resources available on our website - including summary profiles on over 80 known or suspected carcinogens - offer valuable information to those wanting to learn more or take action to help reduce exposures.

As climate change and extreme weather events continue to threaten human health, we must focus our efforts on protecting those who are at the highest risk. CAREX Canada and our community partners are committed to better understanding the impacts of extreme weather events like wildfires and reducing the risk of adverse health outcomes.