A groundbreaking study led by McGill University researchers has found that ultrafine particles (UFPs) in the air are linked to about 1,100 premature deaths each year in Montreal and Toronto, Canada’s two largest cities.
These tiny particles mainly come from vehicle emissions and industrial activities. Unlike larger fine particles known as PM2.5, UFPs are not regulated by Canada’s federal and provincial governments.
Ultrafine particles are extremely small, making it easy for them to penetrate deep into the lungs and enter the bloodstream.
Increasing evidence suggests that these pollutants may contribute to heart and lung diseases, as well as certain types of cancer, according to Scott Weichenthal, the principal investigator and an associate professor in McGill’s Department of Epidemiology, Biostatistics, and Occupational Health.
Until now, no studies had examined the impact of UFPs on mortality in Canada.
The research team tracked air pollution levels from 2001 to 2016 in neighborhoods in Montreal and Toronto, where 1.5 million adults live.
Using advanced models that combine machine learning methods with ground-level measurements, land use information, and aerial images, the researchers estimated the concentration of UFPs in the air over time.
They then used statistical methods to calculate the connection between exposure to UFPs and the risk of death.
The findings, published in the American Journal of Respiratory and Critical Care Medicine, showed that long-term exposure to UFPs is associated with a 7.3% increase in the risk of non-accidental death.
Respiratory deaths saw the highest increase at 17.4%, followed by a 9.4% rise in deaths from coronary artery disease.
Weichenthal emphasized the importance of particle size when assessing health impacts. “Previous studies that did not take particle size into account might have missed or underestimated the serious health risks associated with them,” he said.
The researchers noted that while environmental regulations have successfully reduced air pollution in North America, ultrafine particles are still slipping through the regulatory cracks. In New York, for example, UFP levels have risen even as PM2.5 levels dropped.
“Our research shows a clear link between long-term UFP exposures and increased mortality risk, underscoring the urgent need for regulatory actions targeting these particles,” Weichenthal said. “As urban areas continue to grow, addressing air pollution is increasingly crucial for the health and well-being of city dwellers.”
This study was a collaboration between McGill University, the University of Toronto, Carleton University, the University of Ottawa, Health Canada, and Statistics Canada. The researchers hope their findings will lead to new regulations and cleaner air for everyone.
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