Walking down Fort York Boulevard on a fresh, breezy afternoon, scientist Elisabeth Galarneau has no issue pointing out possible sources of air pollution.
The manicured lawns and flower beds? A potential source of airborne pesticides.
The nearby high-rise apartment buildings? A source of pollutants from both heating and cooling, not to mention the cleaners and personal care products being used inside — remnants of which could be circulating down at street level.
Charcoal barbecues, restaurant stoves, fire pits, squealing tires, nearby highways? They all contribute to the air Torontonians breathe.
Now, the first glimpse at an in-depth study conducted by Galarneau and over 100 other scientists looking at winter air quality in Toronto is shedding light on rarely-measured air pollutants across the city, such as microplastics, brake wear chemicals, and metals.
“We’ve done this study to kind of look at the whole mixture of what people are exposed to in cities, as well as how that varies from neighbourhood to neighbourhood,” said Garlarneau, who works for Environment and Climate Change Canada.
Researchers ‘didn’t expect’ to see AQHI exceeded
As the principal investigator on the Study of Winter Air Pollution in Toronto, known by the acronym SWAPIT, Galarneau led a group, that included contributors from 11 universities, that collected air samples from across the city over six weeks from January to March 2024.
Winter is a “typically understudied part of the year” that’s known for having cleaner air than the smoggy summers, Galarneau said — making the early results of their work all the more surprising.
“We thought we would see low concentrations” of pollutants, said Galarneau. Instead, they clocked a number of instances of pollutants heading into moderate or high risk levels on the Air Quality Health Index (AQHI).
“That air quality health index, I didn’t expect to see it exceeded in the winter,” she said.
Another surprise? The degree of variation in air pollution depending on neighbourhood.
Monitoring sites were placed across Toronto, from Pearson Airport in the west, York University to the north, and University of Toronto Scarborough in the east. One site was even perched on the CN Tower, 275 metres in the air.
“Some pollutants are quite uniform across the city,” Galarneau said. “But other ones are sometimes 40 times higher than the average depending where you’re looking.”
The specifics of where air pollution is worse — and by what degree — will be revealed in the next year or so, when the study’s peer-reviewed results are published in full.
Looking for patterns
To prepare for that publication, Galarneau and her colleagues will now begin a large-scale piece of detective work: determining where the pollutants are coming from, the health impacts for the people breathing them in, and the ways in which factors like income affect exposure.
“The data set that we’re producing here is going to help us to maybe see some patterns here in Toronto, and then expand that to other cities in Canada,” she said.
That forthcoming analysis on health impacts has drawn the attention of Jeffrey Brook, an assistant professor at the University of Toronto’s Dalla Lana School of Public Health, whose work on air pollution is cited by SWAPIT researchers.
“How can it be that in places like Canada where generally our [transportation emission] levels are considered some of the lowest in the world, we can continue to see health effects?” he said. “That’s a big mystery, not just for Canada, but for the world.”
Over in Mississauga, environmental activist Rahul Mehta also looks forward to seeing SWAPIT’s results laid out in full.
Mehta, who heads up an organization called Sustainable Mississauga, says poor air quality impacts him both at work, where he encourages newcomers to try active transportation, and personally, as he deals with allergies and mild asthma.
“Knowing these risks … I think that’s going to help us, it’s going to protect us and it’s going to then maybe empower us to demand some better regulations from government,” he said.
Toronto Public Health, which is a partner on the SWAPIT study, said that its results promise to be useful for exactly that reason, telling CBC Toronto in an email that the study outcomes will “provide valuable evidence to guide local policies and actions.”
