On the traffic-choked streets of Canada’s largest cities, a silent killer lurks in the air. While the health impacts of air pollution are well-established, emerging evidence is linking tiny, largely unregulated ultrafine particles (UFPs) to prematures deaths.
A new study from McGill University shows UFPs — primarily from vehicle emissions and industrial activities — are linked to approximately 1,100 premature deaths each year in Toronto and Montreal. About 600 of those fatalities occur in Toronto alone.
The study found that UFPs heighten the risk of respiratory and cardiovascular diseases and can lead to tissue damage, DNA modification, and disruption of cell growth.
The nanometer-scale particles are produced by all combustion processes, according to Scott Weichenthal, an associate professor at McGill University. Any industry that burns fossil fuels, as well as brake and tire wear, contributes to UFPs emissions, Weichenthal said.
The study tracked air pollution levels over 15 years and found long-term exposure to the tiny pollutants is associated with a 7.3 percent increase in the risk of non-accidental deaths. Respiratory-related deaths increased the most: a 17.4 per cent jump.
Scientists began with a year of mobile air monitoring in each city. The data enabled researchers to develop models predicting where UFPs would be concentrated. Next, they used address data to estimate their annual average concentrations for a large cohort of residents.
Researchers looked at overall rates of non-accidental death, as well as respiratory, cardiovascular, and lung cancer deaths in the two cities.
The team also looked backwards, estimating past UFP emissions using historical traffic data to assess health outcomes in areas with higher versus lower exposure to UFPs.
Air pollution from fossil fuels is linked to one in seven premature deaths in Canada. And Canada has regulations governing concentration limits for larger fine particles such as PM2.5. However, governments haven’t focused on ultrafine particles yet because the evidence really hasn’t been there, he added. “I would say it’s only been over the past ten years or so that health evidence has started to emerge,” Weichenthal added.
In the absence of government intervention, individuals can take steps to protect themselves from the health impacts of UFP exposure.
“A lot of the same advice for protecting yourself from various forms of air pollution also applies to ultrafines,” Weichenthal advised. “For example, if you're biking around the city, try to avoid high-traffic areas.” However, he acknowledged that some exposure is unavoidable, especially for those living near highways, busy rail yards, or airports.
On a larger scale, though, reducing the amount of these particles in the air will take more work.
“One thing we can do is reduce emissions,” Weichenthal said, pointing to fossil fuel combustion and biomass burning as significant contributors to UFP levels. He also called for more routine measurements to help regulators better understand where UFP hotspots are located and identify their significant sources.
Joe Vipond, an emergency physician in Calgary and co-founder of the Calgary Climate Hub, noted the new research reinforces the significant impact these pollutants have on public health.
He said coming out of the COVID-19 pandemic, there is an increasing recognition of the impact of air quality.
A century ago, significant efforts were made to clean water to prevent illnesses like cholera and salmonella.
“Now we're entering a new era where air is the thing we should be cleaning in order to keep ourselves well,” said Vipond, “I'm hoping that as we gain more information, like from this study, it will provide the impetus to clean our air for our schools, homes, and places of work.”
Vipond noted that approximately a third of Canadians live within 250 metres of major roads, putting many at greater risk for elevated exposure to transportation-related air pollution and the associated health risks from ultrafine particles. Vipond said that the ongoing shift to electric vehicles will significantly reduce some air pollutants. “This lights another fire under us to transition from gasoline-fed cars to electric vehicles, which do not burn fossil fuels,” said Vipond.
He acknowledged, though, that electric vehicles still contribute to another major source of air and water pollution: microplastics and air pollutants released from tires ultimately, he said, increased public transit is the best way to improve air quality.
Canada's record-breaking 2023 wildfire season severely impacted air quality, raising particulate matter levels to two to three times above WHO recommendations. An IQAir report shows that some Canadian cities now rank among North America's most polluted, causing Canada’s air quality to drop below that of the U.S. for the first time.
Weichenthal said more evidence is needed to build a case for regulating ultrafine particles, noting that it took a long time to start regulating PM2.5 too, and required a substantial evidence base indicating harmful health effects. He believes that a similar process is beginning for ultrafine particles.
Quebec's Ministry of the Environment, the Fight Against Climate Change, Wildlife, and Parks stated that UFPs are monitored at the Quebec-Henri IV station, part of the Quebec Air Quality Monitoring Network. The ministry also mentioned that UFPs were assessed at the Collège St-Charles-Garnier station in 2021 to evaluate concentrations in Quebec City. However, it has so far not funded research projects focused on UFPs.
Canada’s National Observer reached out to both the federal and Ontario ministries of the Environment but did not receive comments in time for publication.
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