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Associations Between Socioeconomic Status and Air Pollution Exposure in Canadian Cities: Implications for Environmental Justice and Epidemiological Research

Hystad, Perry1,2; Ross, Nancy3; Demers, Paul2,4; Setton, Eleanor2,5; Cervantes-Larios, Alejandro2,6; Brauer, Michael4; Poplawski, Karla2,4; Deschenes, Steeve2,5; Crouse, Dan7; Allen, Ryan8; Goldberg, Mark9

doi: 10.1097/01.ede.0000392388.28666.a4
Abstracts: ISEE 22nd Annual Conference, Seoul, Korea, 28 August–1 September 2010: Air Pollution - Exposure Characterization and Health Effects

1School of Population and Public Health, University of British Columbia, Vancouver, British Columbia, Canada; 2Carex Canada, Vancouver, British Columbia, Canada; 3Department of Geography, McGill University, Montreal, Quebec, Canada; 4School of Environmental Health, University of British Columbia, Vancouver, British Columbia, Canada; 5Department of Geography, University of Victoria, Victoria, British Columbia, Canada; 6Department of Geography, University of British Columbia, Vancouver, British Columbia, Canada; 7Health Canada, Ottawa, Ontario, Canada; 8Simon Fraser University, Vancouver, British Columbia, Canada; and 9Department of Epidemiology, Biostatistics and Occupational Health, McGill University, Montreal, Quebec, Canada.

Abstracts published in Epidemiology have been reviewed by the societies at whose meetings the abstracts have been accepted for presentation. These abstracts have not undergone review by the Editorial Board of Epidemiology.


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Research examining the association between socioeconomic status (SES) and exposure to air pollution across multiple cities will improve our understanding of the variability in, and potential determinants of, environmental inequities. Here we report a national study that explores the association between SES and proximity to air pollution sources in 144 Canadian metropolitan areas, as well as between SES and concentrations of nitrogen dioxide (NO2) levels derived from land use regression models developed previously for a subset of 7 cities.

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SES variables were compiled from census data for 41,485 dissemination areas (DAs), representing 400–700 individuals per DA. Air pollution exposures were calculated for block points within each DA, representing approximately 123 individuals per block. SES surrogates included 8 census variables broadly covering social and material deprivation. Air pollution indicators included proximity to major roads, industrial land use, and point source emission sources. Concentrations of NO2 were extracted from land use regression models available for 7 cities (Victoria, Vancouver, Edmonton, Winnipeg, Toronto, Sarnia, and Montreal). Analyses included Spearman/Pearson correlations, loess plots, and multiple logistic regression with a smoothing function to account for spatial autocorrelation.

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Significant associations were found between SES and air pollution indicators across all 144 Canadian metropolitan areas, but large between-city variations exist. Similar results were found using NO2 estimates for 7 large cities. For example, the likelihood of a DA being in the bottom 10th percentile of median household income in Vancouver and Montreal increased by 1.81 (95% CI: 1.72–1.90) and 2.78 (95% CI: 2.44–3.19) times, respectively, with each 5 ppb increase in NO2. Current analyses are examining potential city and neighborhood level determinants of these environmental inequities.

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SES is associated with higher exposures to air pollution in several Canadian cities; however, the magnitude of these associations vary. Documenting and explaining this variation has important implications from both an environmental injustice and epidemiological perspective.

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