Fumes from landscape fires are responsible for an estimated 1.5 million deaths annually, surpassing the combined death toll from floods, flames, storms, and heat, a 2024 Lancet study found. Scientists are working to understand the complex links between exposure to wildfire smoke and mortality.
The smoke contains toxic gases that can inflame airways and tiny particulates that can enter the lungs and bloodstream, affecting various organs. A 2023 Nature study reported that plumes from Canadian wildfires in 2023 led to 82,000 early deaths, with a quarter of these deaths occurring in Europe due to wind patterns. Researchers also found in March that approximately 10% of the UK's fine particulate pollution (PM2.5) comes from biomass burned in other countries.
Erin O’Connor, who manages the emergency department at University Health Network, observed an increase in patients with allergies and shortness of breath in Toronto during a period of severe smoke. She described the sky as an "almost post-apocalyptic" orange and noted a strong burning smell, even indoors. Toronto experienced some of the worst air quality globally last month, a situation O'Connor said she had not seen before with such sudden onset and prolonged duration.
Preliminary analysis for the Guardian indicates that on 16 July, at least 36 million people across North America were exposed to "very unhealthy" concentrations of PM2.5, exceeding 125.5μg/m³. At least 10 million people were exposed to levels above 250μg/m³.