While the forest fire season is already well underway in Canadian Prairies, its effects are being felt several hundred, if not thousands, of kilometres away from where the fires originated. In early June, winds carried smoke from the fires currently raging in Saskatchewan and Manitoba to several regions of Quebec and even Europe, resulting in poor air quality and reduced visibility in many areas.   

Figure 1: Model of PM2.5 concentration in Quebec-Labrador, June 6, 2025 (from: Environment and Climate Change Canada, 2025). 

Although fires are allies in the regeneration and diversification of forests, they can affect forest ecosystems and the well-being of human populations when they’re too intense or too frequent.

With rising temperatures and dry conditions exacerbated by climate change, forest fire seasons are longer and more active. Fires are gaining in frequency and intensity. They threaten the health of various ecosystems, as well as the health, safety and well-being of people who are exposed to the risks and consequences of these events. 

Exposure to smoke from fires and deteriorating air quality: A dangerous cocktail for health 

While forest fires can have immediate, direct and obvious effects on human health, such as burns caused by flames, it is the indirect effects caused by their smoke that have the greatest impact on our health.  

This is because smoke from wildfires is a complex mix of harmful pollutants, including fine particulate matter (PM2.5), carbon monoxide and volatile organic compounds. These contribute to the deterioration of ambient air quality and affect people’s health, with fine particles being of particular concern due to their ability to penetrate deep into the lungs and even enter the bloodstream.  

In the short term, exposure to smoke can cause respiratory problems like asthma and chronic obstructive pulmonary disease (COPD) and, to a lesser extent, other lung conditions such as bronchitis or pneumonia. People with pre-existing respiratory diseases, children and the elderly are particularly vulnerable.  

Health problems can get worse   

Beyond the immediate effects, wildfire smoke can also have long-term health impacts. However, there is insufficient evidence to draw strong conclusions. This is due in part to the episodic nature of fires, the seasonal and geographic variability of the smoke, and the difficulty of distinguishing the sources of fine particles.

That said, the results of a study published in 2022 in the journal The Lancet Planetary Health, conducted over a 20-year period with 2 million Canadians, found that living near a forest that has burned can increase the risk of developing lung cancer by 5% and the risk of developing a brain tumour by 10% compared to someone living far from the burned areas.

In addition to the consequences of poor air quality, forest fires also release contaminants into the environment that can persist long after the flames have been extinguished. Ash, soot and erosion from burned soils can contaminate waterways and drinking water sources and can enter the food chain, exposing local populations to long-term health risks.  

And what about mental health?  

In addition to the physical health consequences, forest fires can have significant psychological impacts. The loss of property, forced evacuation, environmental destruction, and uncertainty about the future can cause high levels of stress and anxiety, and even depression. Children are particularly susceptible to long-lasting psychological trauma, especially when they are removed from their usual living environment.

Firefighters who battle the flames are also exposed to high levels of physical and psychological stress, which can lead to mental health issues like post-traumatic stress disorder.  

Indigenous communities, who are regularly exposed to evacuations due to the geographic locations of their communities, have also reported high stress due to the loss of their social structure and their relocation. When an environment is altered or destroyed, it can create a feeling of psychological distress that results in a decrease in the sense of belonging to a place or the comfort it brings. 

Stay informed and focus on preventive measures 

Faced with the plume of smoke currently covering several regions of most of Quebec, preventive measures are essential to limit its health effects. These include keeping an eye on the alerting and monitoring systems offered by the governments of Canada and Quebec.

Individuals can also take various measures before, during and after a fire, to limit the health impacts. By focusing on preventive measures and strengthening collaboration between different parties, we can face this challenge and protect our collective well-being.