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A UNB researcher played a leading role in the largest and most comprehensive Canadian study examining links between air pollution and risk of mortality ever conducted.

The study, published in Health Effects Institute report, reveals that even at the very low levels of pollution seen across most of Canada, including the Maritimes, exposure produces small but significant increased risks of dying.

Dr. Dan Crouse is a researcher with UNB’s department of sociology and the New Brunswick Institute for Research, Data, and Training; in partnership with Statistics Canada, and along with researchers from McGill University, the University of British Columbia, Dalhousie University and Oregon State University, he followed almost 9 million Canadian adults from across the country for up to 25 years. The group used varying methods of estimating exposure to pollution, including in relatively small buffers around people’s homes, in larger buffers covering their neighborhoods, and by looking at exposures in the recent short-term (e.g. the past year) versus exposures averaged over eight years, all while considering different mixtures of pollutants.

Dr. Crouse was involved in developing the methods for estimating individuals’ exposures to ambient air pollution and for running some of the statistical models and interpreting the results. “In the past,” he says, “most air pollution research had been based in large cities or heavily polluted areas, and so we had limited knowledge of the potential effects on health in areas with low levels of exposure.”

“We didn’t know if there was a threshold level below which we might see no effects of air pollution on health. So, a takeaway message from this study, is that we found no real threshold; we observed increased risks of dying associated even with very, very low exposures to concentrations of fine particulate matter.”

The study found there is at least a five per cent increase in the risk of deaths of Canadians when comparing between high- and low-pollution areas. A concerning figure considering millions of Canadians live in high-pollution areas.

Despite Canada being one of the few countries that meets World Health Organization air quality guidelines as well as national guidelines like Canadian Air Quality Standards, the study suggests air pollution at any concentration is hurting Canadians and the world population. The findings also suggest health benefits from continued improvements in air quality in Canada.

For the study, researchers combined satellite data with a model of pollutant transport and chemistry, and ground-level air quality measurements. They applied the data to, and produced a pollution map to estimate Canadian air pollution levels by the square-kilometre. They cross-referenced the air pollution data with anonymous Statistics Canada census information of approximately nine million Canadians, their addresses and the death registry.

Among the researchers’ other discoveries is that new immigrants to Canada are equally or more sensitive to the health impacts of air pollution. Because of mandatory health screenings that are required prior to moving to Canada, new immigrants are considered as being healthier in general than those living in Canada. These findings suggest that air pollution affects everyone, even those in good health.

Dr. Crouse and his fellow researchers say air pollution is the fourth highest risk factor for death globally and by far the leading environmental risk factor for disease. Reducing air pollution is an efficient way to improve the health of a population.

The group is now working on a follow-up analysis to look at the relationship between air pollution and specific causes of death, as well as evaluate whether moving from an area of poor air quality to an area of cleaner air quality reduces the risk of dying. In addition, the researchers are developing a tool for policy makers to assess how reducing air pollution will increase health benefits and decrease mortality rates in Canada.

Media contact: Hilary Creamer Robinson

Photo: UNB researcher Dan Crouse is one of the lead researchers on the largest ever study examining links between air pollution and risk of mortality. Credit: Rob Blanchard/Photo UNB