A child looks out from the observation deck of the CN Tower as smoke from wildfires blankets the city of Toronto on 16 July 2026. (Cole Burston/The Canadian Press via AP)
This past week, a child stood on the observation deck of Toronto's CN Tower and looked out at a city skyline blurred by haze.Hundreds of miles away, National Guard troops patrolled a smoke-dimmed National Mall in Washington, and commuters pulled on masks.Smoke drifting south from Canada's wildfires has become an almost annual visitor to American skies. None of these scenes look that unusual these days.What's perhaps less familiar is how it's impacting our health beneath the surface – inside hearts, lungs, brains, and even developing fetuses.Wildfire smoke can deliver a cocktail of harmful air pollutants, including PM2.5, NO2, ozone, aromatic hydrocarbons, and lead.It is killing tens of thousands of people a year.The typical contents of wildfire smoke. (IQAir)Particulate matter in smoke can irritate eyes, noses, and throats, and it can travel deep into your lungs when you breathe. This can damage the lungs and make breathing difficult.Small particles in the lungs can travel from there into the bloodstream – and their effects can persist after the visible haze is gone.In a recent paper published in the European Heart Journal, scientists studying the effects of wildfire smoke on the brain and blood vessels found that "chronic exposure to wildfire smoke PM2.5 increases stroke risk in older adults"."Wildfire smoke is not only an immediate breathing hazard," says environmental health scientist Yang Liu from Emory University in the US.A commuter wears a face mask as smoke from wildfires blankets the sky in Washington on 17 July 2026. (AP photo/Miriam Zuhaib)Research shows more people experiencing heart attacks and other cardiovascular issues, alongside a surge in mental health crises."Your whole body is affected," Liu told Naomi Mihara at Deutsche Welle."Wildfire smoke causes oxidative stress to your system and exacerbates or accelerates the development of diseases." Part of the danger is what's actually inside the plume. When flames reach a built-up town or city, the smoke is no longer just from burnt vegetation. A 2024 smoke plume, seeding a cloud formation. (NASA Earth Observatory)"We sometimes see smoke in the air hundreds of miles away from a wildfire," said Aubrey Miller, an environmental disasters expert at the National Institutes of Health. "Think about what's burning: plastics, heavy metals, arsenic. These can cause a whole series of other hazards for the community."The acute effects are only the beginning.PM2.5 particles have been linked to chronic disease, including autoimmune disease. Smoke exposure during pregnancy raises the risk of premature birth and low-birth-weight babies, and longer-term exposure has been linked to some cancers."Our results also suggest that there is no apparent safe threshold for smoke exposure," says Liu. "That means even 'moderate' recurring smoke could matter, not just extreme events."
