Ultrafine particles linked to 1100 deaths per year in these two major cities

Scientists from McGill University conducted a groundbreaking study in Canada's two largest cities. They estimate that around 1100 premature deaths per year are linked to an unregulated air pollutant.

Ultrafine particles primarily emanate from vehicle emissions and industrial activities. In Canada, federal and provincial governments have not set a maximum allowable concentration for ultrafine particles, unlike larger fine particles (often referred to as PM2.5).


"Ultrafine particles are so tiny that they can penetrate deep into the lungs and enter the bloodstream. There is a growing body of evidence to suggest these pollutants may contribute to the development of heart and lung diseases, as well as certain types of cancer," explains Scott Weichenthal, lead researcher and Associate Professor in the Department of Epidemiology, Biostatistics, and Occupational Health at McGill University. "Yet, until now, no study has examined the impact of ultrafine particles on mortality in Canada."

Cutting-edge tools for detecting deadly pollution

The research team studied air pollution levels recorded between 2001 and 2016 in neighborhoods of Montreal and Toronto, encompassing 1.5 million adults. Using advanced models that combine machine learning methods with ground-based measurements, land use data, and aerial imagery, the researchers were able to estimate the amount of ultrafine particles present in the air at various times. They then employed statistical methods to establish a correlation between exposure levels and the risk of death.

According to the study's findings, published in the American Journal of Respiratory and Critical Care Medicine, long-term exposure to ultrafine particles would increase the risk of non-accidental death by 7.3%. Respiratory-related deaths saw the greatest increase at 17.4%, followed by deaths caused by coronary heart disease, which increased by 9.4%.

Scott Weichenthal emphasizes that the size of particles is crucial when assessing their health impacts.

"In previous studies that did not take particle size into account, it is possible that scientists may have missed or underestimated significant health risks," he adds.

A call for action to ensure clean air

The scientists note that environmental regulations have led to a reduction in air pollution in North America, but ultrafine particles are slipping through the cracks. As evidence, they found that in New York, ultrafine particle levels were rising even as PM2.5 concentrations were declining.

"Our work shows a clear link between long-term exposure to ultrafine particles and an increased risk of mortality, highlighting the urgent need for regulatory measures to target these particles," states Scott Weichenthal. "To ensure the health and well-being of urban dwellers, tackling air pollution is increasingly crucial, especially as urban areas continue to grow."

The study was a collaboration between McGill University, the University of Toronto, Carleton University, the University of Ottawa, Health Canada, and Statistics Canada, and was funded by the United States Health Effects Institute.