Wildfires in Canada are becoming more frequent, more intense, and more destructive鈥攍argely due to climate change. We already know the wildfire smoke causes serious respiratory problems in children and adults. But new research published in the Lancet Planetary Health by MC3H Associate Director Scott Weichenthal has uncovered a lesser-known consequence: cancer.听 The followed over 2 million Canadians for nearly two decades. The researchers found that people living within 50 km of a wildfire in the past 10 years were more likely to develop certain cancers: a 5% higher risk of lung cancer and a 10% higher risk of brain tumors compared to those who had not lived near a wildfire.听听
As wildfires burn, they release a complex mix of pollutants into the air, including small particles (known as PM2.5), heavy metals, and toxic gases. Many of these are known or suspected carcinogens. These pollutants seep into the air in homes, contaminate water supplies, and settle into soil, creating prolonged exposure long after the fire has been extinguished.听听
According to Weichenthal, it鈥檚 no longer a question of if wildfires raise cancer risk, but how much. In a 2025 in Nature Reviews, he calls for urgent action to protect Canadians from long-term exposures to wildfires, especially as wildfire seasons grow longer and more dangerous.听
Wildfire risks are not distributed equally in Canada, noted Weichenthal. He emphasizes that rural and lower-income communities are often more exposed because they live closer to fire-prone areas and may lack access to air filters or clean water during and after fires.听
But, noted Weichenthal, there are public health measures that can be taken to reduce risk. First, public health agencies can provide clear, accessible guidance on how individuals and communities can protect indoor air quality and ensure safe drinking water during wildfire season, especially during heatwaves when it may be hard to keep windows and doors closed. Second, they can work with urban planners and emergency services to design communities in ways that reduce exposure to smoke and fire, especially in high-risk areas. Third, they can advocate for stronger environmental policies that limit pollution and ensure that vulnerable populations receive targeted support before, during, and after wildfire events.听
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