Abstract
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Background
Exposure to ambient fine particulate matter (PM2.5) has been associated with a greater risk of non-accidental, cardiovascular and respiratory mortality in Canada. Research based on Canadian cohorts suggests that exposure to PM2.5 varies by demographic and socioeconomic characteristics. Studies of NO2, another pollutant, indicate that persons of lower socioeconomic status and some visible minority groups have greater exposure in urban centres.
Data and methods
National residential PM2.5 was estimated from a ~1 km2 spatial layer for respondents to the 2006 Census long-form questionnaire. Weighted PM2.5 estimates from personal-level estimates were determined for white, Aboriginal, visible minority and immigrant populations, as well as for socioeconomic groups (household income, educational attainment) and stratified by urban core, urban fringe and rural residence. Descriptive statistics were provided for selected comparisons.
Results
In Canada, PM2.5 exposure was 1.61 μg/m3 higher for visible minority (versus white) populations, and 1.55 μg/m3 higher for immigrants (versus non-immigrants). When the relatively high percentages of these groups in large cities were taken into account, exposure differences in urban cores were much smaller. Exposure among urban immigrants did not decrease substantially with time since immigration (< 0.5 μg/m3 between any two years). In urban cores, residents of low-income households had marginally higher exposure (0.56 μg/m3) than did people who were not in low-income households.
Interpretation
Differences between specific population groups in exposure to PM2.5 are due, at least in part, to higher percentages of these groups living in urban cores where air pollution levels are elevated.
Keywords
Environmental exposure, environmental monitoring, immigrants, rural health, socioeconomic factors, urban health, visible minority
Findings
Fine particulate matter (PM2.5) is one of the primary components of air pollution. It refers to a mixture of particles less than 2.5 microns in diameter, including aerosols, smoke and dust. According to the Global Burden of Disease Study, PM2.5 air pollution is responsible for an estimated 2.9 million deaths worldwide each year and is associated with increased risk of non-accidental, circulatory and respiratory disease mortality. In a study using the 1991 Canadian Census Health and Environment Cohort (CanCHEC), this association was observed in Canada, a country where the level of ambient air pollution is relatively low. A subsequent study using the Canadian Community Health Survey (CCHS) and mortality cohort adjusted for behavioural covariates (for example, smoking) found an excess mortality risk at a lower concentration threshold. The CCHS analysis used a fine-scale (1 km2) national model of PM2.5 , which provided more accurate exposure estimates than did previous models. [Full Text]
Authors
Lauren Pinault (lauren.pinault@canada.ca) is with the Health Analysis Division at Statistics Canada, Ottawa, Ontario. Aaron van Donkelaar and Randall V. Martin are with the Department of Physics and Atmospheric Science at Dalhousie University, Halifax, Nova Scotia. Randall V. Martin is also with the Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts.
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What is already known on this subject?
- Studies of individual Canadian cities and a national American study find greater exposure to nitrogen dioxide (NO2) among some visible minority populations and people of lower socioeconomic status.
- Another pollutant, fine particulate matter (PM2.5), is associated with an elevated risk of mortality, but population-level differences in exposure are relatively unknown.
What does this study add?
- PM2.5 exposure was 1.61 μg/m3 higher for members of visible minorities than for white people and 1.55 μg/m3 higher for immigrants than for non-immigrants; these differences were less pronounced in urban cores, where a large percentage of visible minorities and immigrants reside.
- Nationally, substantial differences in PM2.5 exposure by socioeconomic status were not observed, but in urban cores, residents of low-income households had marginally higher exposure than did people who did not live in low-income households.
- Toronto has a large influence on disparities, because it has a very high level of PM2.5 (9.08 μg/m3), and is home to 42% of visible minorities and 36% of immigrants.
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