Ultrafine particles are responsible for 1,100 premature deaths each year in Montreal and Toronto, concludes a study carried out at McGill University.
These particles are so tiny that they can lodge deep in the lungs and even enter the bloodstream. Research into their impact on health is ongoing, but it is believed that they may contribute to lung disease, heart disease and cancer.
“I was somewhat surprised by the consistency of our results across the different outcomes,” said Professor Scott Weichenthal of McGill University’s Department of Epidemiology, Biostatistics and Occupational Health.
“We saw an increase in non-accidental mortality, respiratory and cardiovascular mortality, and lung cancer. So I think this is a very consistent kind of signal of how these particles are actually contributing to adverse health outcomes.”
Ultrafine particles come mainly from vehicle emissions and industrial activities. No level of government in Canada has imposed a maximum concentration for these particles, unlike the larger fine particles, PM2.5, with which the public may be more familiar.
Ultrafine particles are typically less than a micrometer in size, and are therefore significantly smaller than PM2.5, Weichenthal explained. In fact, they are so tiny that they cannot be measured in the same way that PM2.5 is measured, he added: if you measure the mass of PM2.5 in a cubic meter of air, you would instead measure the number of ultrafine particles in a cubic centimeter.
“If we only measure mass, we will not really measure exposure to ultrafine particles,” he said.
With PM2.5, he added, “you can put a small number of monitors around the city and get a pretty good idea of what the population is exposed to, because these particles don’t vary much in space.”
On the other hand, “ultrafine particles vary a lot in space, even from one street corner to another, and so you can’t put a single monitor in a city and claim that it represents the exposure of everyone in that city,” he continued.
“We really need these kinds of high-resolution exposure models to capture the fine-scale variations between cities,” Weichenthal said.
Professor Weichenthal and his colleagues studied air pollution levels recorded between 2001 and 2016 in neighbourhoods in Montreal and Toronto with 1.5 million adults.
Using sophisticated analytical methods, the scientists were able to estimate the amount of ultrafine particles present in the air at various times. They then used statistical methods to establish a correlation between the level of exposure and the risk of death.
Long-term consequences
Evidence of the health effects of ultrafine particles is still developing. Still, researchers determined that long-term exposure appears to increase the risk of non-accidental death by 7.3%. Deaths from respiratory diseases increased by 17.4%, followed by deaths from coronary heart disease, which increased by 9.4%.
Air pollution alters fundamental mechanisms related to inflammation and oxidative stress, which are central to many pathological processes, ranging from cardiovascular disease to cancer to respiratory diseases, explained Professor Weichenthal.
Today, he added, “we’re even seeing studies emerging that look at the neurological consequences, because we know that these particles are getting into people’s brains.”
“I think we’ve done a very good job of regulating PM 2.5 and reducing exposures,” he said in conclusion. “But if we’re really serious about reducing the health impacts of environmental exposures like air pollution on the population, ultrafine particles probably need to be on that list.”
The study is a collaboration between McGill University, the University of Toronto, Carleton University, the University of Ottawa, Health Canada and Statistics Canada. It was funded by the United States Health Effects Institute.
His findings were published by theAmerican Journal of Respiratory and Critical Care Medicine.