A major study of Toronto’s winter air reveals unexpected levels of pollutants including tire dust, metals, and perfumes, raising concerns about urban exposure.
Major Study Measures Toronto’s Winter Air Quality
In a groundbreaking winter air pollution study, over 100 scientists from 11 Canadian universities collaborated to examine what Torontonians are really breathing. The Study of Winter Air Pollution in Toronto (SWAPIT), led by Dr. Elisabeth Galarneau of Environment and Climate Change Canada, collected air samples from January to March 2024.
Their focus: rarely studied pollutants such as microplastics, tire particles, and airborne metals—many previously unmeasured during the colder months.
Surprising Pollution Levels During Colder Months
Despite winter traditionally being viewed as a “cleaner” season for air quality, the study revealed unexpected spikes in pollution. Some areas even recorded moderate to high risk levels on the Air Quality Health Index (AQHI), surprising researchers.
“We didn’t expect to see AQHI levels exceeded in winter,” said Dr. Galarneau. The data suggest indoor emissions and traffic-related pollutants like brake dust and tire wear may play a bigger role than previously thought.
Air Quality Varies Sharply by Neighbourhood
Air monitoring stations were strategically placed across Toronto—from Pearson Airport in the west to Scarborough in the east, including a high-altitude site atop the CN Tower. Results showed wide variation: some pollutants were 40 times higher in certain neighbourhoods compared to city averages.
“This kind of difference can have real implications for residents’ health,” Galarneau explained, noting that both location and local activities—from barbecues to household products—contribute to the air’s chemical makeup.
Health Impacts and Equity Under the Microscope
Researchers will now analyze the data for patterns in exposure and health impact, including how socioeconomic status affects air pollution risk.
Jeffrey Brook, a University of Toronto public health expert, noted that even in a country like Canada—with relatively low transportation emissions—health effects persist. “That’s a big mystery for us globally,” he said.
Public Awareness and Policy Potential
Activists and public health officials see the findings as a powerful tool. Rahul Mehta of Sustainable Mississauga, who suffers from asthma, says the data can fuel stronger environmental policies and promote public health.
Toronto Public Health, a SWAPIT partner, confirmed the study will “provide valuable evidence to guide local policies and actions.”
What Comes Next
Full peer-reviewed results are expected within the year, offering deeper insight into Toronto’s neighbourhood-level pollution and its sources. Researchers hope this blueprint will extend to other Canadian cities, prompting smarter urban planning and healthier air.
As Dr. Galarneau puts it: “Understanding what’s in the air is the first step to protecting the people who breathe it.”
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