Reflections on the Canadian CanCHEC Cohort: Where We've Been and Where We Are Going

Abstract

The Canadian Census Health and Environment Cohort (CanCHEC) was developed to advance the scientific knowledge about the impacts of prolonged exposure to low-levels of ambient air pollution. Initially, this large-scale cohort consisted of the 20% of Canadian households who were mandated to complete the more detailed long-form census in 1991. Dr. Burnett played a prominent role in the development of the cohort which has since been extended to include those who completed the long-form census in 1996, 2001, and 2006. Probabilistic record linkage of these cohorts were undertaken to link these individuals to Canadian income tax, mortality and cancer registry data. Linkages to the tax databases allowed for the determination of place of residence on an annual basis. Combined, these cohorts include nearly 13 million Canadians (37%) and approximately 1.7 million deaths identified during follow-up. Estimates of ambient air pollution concentrations have been assigned to cohort subjects based on their residential postal codes using a variety of methods including fixed-site monitoring, land use regression, and remote sensing techniques. Analyses of the CanCHEC have provided insights on how long term-exposure to low levels of ambient pollution is associated with cause-specific mortality. This presentation will highlight the contributions of Dr. Burnett with respect to the major research findings for air pollution that have been obtained from this cohort. These include estimates for associations between ambient air pollution concentration and mortality with respect to: (i) the shape of the exposure-response curve, (ii) oxidative burden of fine particulate matter, (iii) methods to indirectly adjust for the impacts of missing covariates, and (iv) methods to account for within- and between-city variations in risk. Lastly, this presentation will highlight ongoing and future research activities using the CanCHEC.