Exposure to fine particulate matter air pollution in Canada.

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.