New UBC study reveals health dangers when extreme heat and smoke collide

CTV News

23-06-2025

As wildfires burn across the country and temperatures continue to climb, many Canadians are likely to face a mix of smoky skies and intense heat this summer.
New research from the University of British Columbia suggests that combination may pose a particularly serious threat to human health.
The study—led by Dr. Sarah Henderson, professor at UBC's School of Population and Public Health and scientific director at the B.C. Centre for Disease Control—looked at how simultaneous exposure to wildfire smoke and high temperatures can impact illness and death rates.
Henderson and her team looked at more than 21,000 deaths that occurred outside hospitals and care facilities in the greater Vancouver area over 13 wildfire seasons, from 2010 to 2022.
'There was a higher risk on those days that were both hot and smoky,' said Henderson.
However, she says the relationship between heat and smoke isn't straightforward. While smoke-related health risks climb quickly at moderate exposure and then tend to level off, she says the dangers linked to extreme heat keep rising sharply.
Henderson says the data suggests that high temperatures by themselves are more harmful to health than smoke exposure during milder conditions.
However, Henderson says the threat smoke poses cannot be taken lightly.
'There's often a lot of focus on wildfire smoke on those days when the sky turns orange and everything smells like a campfire,' she said. 'But we found that there was risk on days when people might not even realize that it's a little bit smoky.'
Henderson says their research showed that during the 2021 heat dome that killed more than 600 British Columbians, people with schizophrenia were the most at risk, because they often have a hard time realizing that they are unwell.
People living in poverty and older adults with underlying health conditions were also high-risk, according to Henderson.
She says keeping the air in your home as cool and clean as possible will give you the best chance to stay healthy.
Henderson suggests air conditioners, indoor air cleaners and sealing up potential openings to keep the smoke out.
Though she acknowledges that not everyone may have the ability to do that.
'If you can keep one room of your home cool and smoke free as possible, and spend time there when you need to, you will be protecting your health,' she said.