title: Development of a Canadian socioeconomic status index for the study of health outcomes related to environmental pollution.
abstract: BACKGROUND
  Socioeconomic status (SES) is an important determinant of health and potential modifier of the effects of environmental contaminants. There has been a lack of comprehensive indices for measuring overall SES in Canada. Here, a more comprehensive SES index is developed aiming to support future studies exploring health outcomes related to environmental pollution in Canada.
  
  
  METHODS
  SES variables (n = 22, Census Canada 2006) were selected based on: cultural identities, housing characteristics, variables identified in Canadian environmental injustice studies and a previous deprivation index (Pampalon index). Principal component analysis with a single varimax rotation (factor loadings ≥ │60│) was performed on SES variables for 52974 census dissemination areas (DA). The final index was created by averaging the factor scores per DA according to the three components retained. The index was validated by examining its association with preterm birth (gestational age < 37 weeks), term low birth weight (LBW, <2500 g), small for gestational age (SGA, <10 percentile of birth weight for gestational age) and PM2.5 (particulate matter ≤ 2.5 μm) exposures in Edmonton, Alberta (1999-2008).
  
  
  RESULTS
  Index values exhibited a relatively normal distribution (median = 0.11, mean = 0.0, SD = 0.58) across Canada. Values in Alberta tended to be higher than in Newfoundland and Labrador, Northwest Territories and Nunavut (Pearson chi-square p < 0.001 across provinces). Lower quintiles of our index and the Pampalon's index confirmed know associations with a higher prevalence of LBW, SGA, preterm birth and PM2.5 exposure. Results with our index exhibited greater statistical significance and a more consistent gradient of PM2.5 levels and prevalence of pregnancy outcomes.
  
  
  CONCLUSIONS
  Our index reflects more dimensions of SES than an earlier index and it performed superiorly in capturing gradients in prevalence of pregnancy outcomes. It can be used for future research involving environmental pollution and health in Canada.
authors.affiliation: Department of Pediatrics, University of Alberta, Edmonton, Canada. ec9@ualberta.ca.
authors.forename: Emily
authors.initials: E
authors.lastname: Chan
authors.affiliation: School of Public Health, University of Alberta, Edmonton, Canada. jaserran@ualberta.ca.
authors.forename: Jesus
authors.initials: J
authors.lastname: Serrano
authors.affiliation: Population Studies Division, Health Canada, Ottawa, Canada. li.chen@hc-sc.gc.ca.
authors.forename: Li
authors.initials: L
authors.lastname: Chen
authors.affiliation: Population Studies Division, Health Canada, Vancouver, Canada. Dave.Stieb@hc-sc.gc.ca.
authors.forename: David M
authors.initials: DM
authors.lastname: Stieb
authors.affiliation: School of Public Health, University of California, Berkeley, USA. Jerrett@berkeley.edu.
authors.forename: Michael
authors.initials: M
authors.lastname: Jerrett
authors.affiliation: Department of Pediatrics, University of Alberta, Edmonton, Canada. osornio@ualberta.ca.
authors.forename: Alvaro
authors.initials: A
authors.lastname: Osornio-Vargas
mesh_terms: D000393:Air Pollutants / Q000009:adverse effects; D000397:Air Pollution / Q000706:statistics & numerical data*; D002170:Canada / Q000453:epidemiology; D004781:Environmental Exposure / Q000706:statistics & numerical data*; D004784:Environmental Monitoring / Q000706:statistics & numerical data*; D004787:Environmental Pollution / Q000706:statistics & numerical data*; D005260:Female; D054624:Health Status Disparities; D006801:Humans; D007231:Infant, Newborn; D011247:Pregnancy; D011256:Pregnancy Outcome / Q000453:epidemiology*; D047928:Premature Birth / Q000453:epidemiology; D018570:Risk Assessment; D012959:Socioeconomic Factors
chemical_list: D000393:Air Pollutants