Abstract

Background

Immigrants make up 20% of the Canadian population; however, little is known about the mortality impacts of fine particulate matter (PM_2.5) air pollution on immigrants compared with non-immigrants, or about how impacts may change with duration in Canada.

Methods

This study used the 2001 Canadian Census Health and Environment Cohort, a longitudinal cohort of 3.5 million individuals, of which 764,000 were classified as immigrants (foreign-born). Postal codes from annual income tax files were used to account for mobility among respondents and to assign annual PM_2.5 concentrations from 1998 to 2016. Exposures were estimated as a three-year moving average prior to the follow-up year. Cox survival models were used to determine hazard ratios (HRs) for cause-specific mortality, comparing the Canadian and foreign-born populations, with further stratification by year of immigration grouped into 10-year cohorts.

Results

Differences in urban–rural settlement patterns resulted in greater exposure to PM_2.5 for immigrants compared with non-immigrants (mean = 9.3 vs. 7.5 μg/m³), with higher exposures among more recent immigrants. In fully adjusted models, immigrants had higher HRs per 10 μg/m³ increase in PM_2.5 concentration compared with Canadian-born individuals for cardiovascular mortality (HR [95% confidence interval] = 1.22 [1.12 to 1.34] vs. 1.12 [1.07 to 1.18]) and cerebrovascular mortality (HR = 1.25 [1.03 to 1.52] vs. 1.03 [0.93 to 1.15]), respectively. However, tests for differences between the two groups were not significant when Cochran’s Q test was used. No significant associations were found for respiratory outcomes, except for lung cancer in non-immigrants (HR = 1.10 [1.02 to 1.18]). When stratified by year of immigration, differences in HRs across varied by cause of death.

Conclusions

In Canada, PM_2.5 is an equal-opportunity risk factor, with immigrants experiencing similar if not higher mortality risks compared with non-immigrants for cardiovascular-related causes of death. Some notable differences also existed with cerebrovascular and lung cancer deaths. Continued reductions in air pollution, particularly in urban areas, will improve the health of the Canadian population as a whole.

Keywords

immigrant, air pollution, mortality, immigrant health, demography, fine particulate matter

DOI: https://www.doi.org/10.25318/82-003-x202000300002-eng

Findings

Ambient fine particulate matter (PM_2.5) air pollution contributes to millions of deaths around the world each year and is a major contributor to the overall global burden of disease. Given that many immigrants to Canada arrive from countries with higher levels of ambient air pollution, they could experience an increased risk of chronic disease with exposure. While the mortality impacts of PM_2.5 have been demonstrated repeatedly in large cohorts representative of the Canadian-born population, immigrants have often been excluded from these analyses to some degree. The proportion of the foreign-born population living in Canada in 2011 was 21%, or 7.1 million individuals, and is projected to rise to between 25% and 30% over the next 25 years to meet demographic and labour needs. Therefore, it is important to understand the extent to which their risks from air pollution exposure may differ from those of the general population, particularly as the population ages and a larger proportion of Canadians become seniors. [Full article]

Authors

Anders C. Erickson (anders.erickson@ubc.ca) and Michael Brauer are with the School of Population and Public Health at the University of British Columbia in Vancouver, British Columbia. Tanya Christidis, Amanda Pappin, Lauren Pinault and Michael Tjepkema are with the Health Analysis Division at Statistics Canada in Ottawa, Ontario. Daniel L. Crouse is with the Department of Sociology at the University of New Brunswick in Fredericton, New Brunswick. Jeffrey R. Brook is with the Dalla Lana School of Public Health at the University of Toronto in Toronto, Ontario. Perry Hystad is with the College of Public Health and Human Sciences at Oregon State University in Corvallis, Oregon. Chi Li, Randall V. Martin, Jun Meng and Aaron von Donkelaar are with the Department of Physics and Atmospheric Science at Dalhousie University in Halifax, Nova Scotia. Randall V. Martin and Scott Weichenthal are with the Department of Epidemiology, Biostatistics and Occupational Health at McGill University in Montréal, Quebec. Richard T. Burnett is with the Population Studies Division at Health Canada in Ottawa, Ontario.

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