When extreme heat and wildfire smoke converge, they create a particularly dangerous threat to public health that exceeds the impact of either condition alone, according to groundbreaking research from the University of British Columbia. The study, which examined hospital admission data during British Columbia’s unprecedented 2021 heat dome, reveals alarming evidence that should reshape our approach to climate-related health emergencies.
“What we discovered was genuinely concerning,” explains Dr. Sarah Henderson, lead researcher and professor of environmental health at UBC. “When temperatures soared above 35 degrees Celsius and smoke pollution reached hazardous levels simultaneously, hospital admissions increased by nearly 21 percent compared to normal conditions. This wasn’t simply an additive effect—it was synergistic.”
The research team analyzed more than 45,000 hospital records across British Columbia during the summer of 2021, when the province experienced both record-breaking temperatures and severe wildfire smoke. Their findings showed that respiratory-related admissions nearly doubled during combined heat-smoke events, while cardiovascular emergencies increased by 37 percent.
Most vulnerable were adults over 65 and those with pre-existing conditions such as asthma, COPD, or heart disease. Particularly troubling was the discovery that these combined events disproportionately affected lower-income communities, where access to air conditioning and air filtration systems is often limited.
“The physiological stress created by this combination is profound,” notes Dr. Henderson. “Heat already strains the cardiovascular system as the body works to cool itself, while smoke particles irritate the lungs and can enter the bloodstream. Together, they create a perfect storm that overwhelms the body’s defense mechanisms.”
Provincial health authorities are taking note. The BC Centre for Disease Control has begun integrating these findings into their emergency response protocols, acknowledging that traditional heat warnings may be insufficient when wildfires are also active.
“We need to fundamentally rethink our public health approaches,” says Dr. Michael Schwandt, a public health physician with Vancouver Coastal Health. “Cooling centers must now also address air quality, and we need better systems to identify and support those most at risk during these increasingly common events.”
Climate scientists warn that such convergent extreme weather events will likely become more frequent across Canada. Models predict that by 2050, the combination of heat waves and wildfire smoke could affect major population centers for up to three weeks annually—a dramatic increase from historical averages.
The study offers several recommendations, including the creation of centralized “clean air cooling stations” in urban areas, enhanced monitoring systems that track both heat and air quality simultaneously, and targeted outreach programs for vulnerable populations.
As Canadians continue to face increasingly volatile climate conditions, these findings raise critical questions about our preparedness. How will our healthcare systems adapt to this emerging threat, and what responsibility do governments bear in protecting those most vulnerable to our changing climate?
