Ambient PM2.5, O3, and NO2 Exposures and Associations with Mortality over 16 Years of Follow-Up in the Canadian Census Health and Environment Cohort (CanCHEC)
Background: Few studies examining the associations between long-term exposure to ambient air pollution and mortality have considered multiple pollutants when assessing changes in exposure due to residential mobility during follow-up.
Objective: We investigated associations between cause-specific mortality and ambient concentrations of fine particulate matter (≤ 2.5 μm; PM2.5), ozone (O3), and nitrogen dioxide (NO2) in a national cohort of about 2.5 million Canadians.
Methods: We assigned estimates of annual concentrations of these pollutants to the residential postal codes of subjects for each year during 16 years of follow-up. Historical tax data allowed us to track subjects’ residential postal code annually. We estimated hazard ratios (HRs) for each pollutant separately and adjusted for the other pollutants. We also estimated the product of the three HRs as a measure of the cumulative association with mortality for several causes of death for an increment of the mean minus the 5th percentile of each pollutant: 5.0 μg/m3 for PM2.5, 9.5 ppb for O3, and 8.1 ppb for NO2.
Results: PM2.5, O3, and NO2 were associated with nonaccidental and cause-specific mortality in single-pollutant models. Exposure to PM2.5 alone was not sufficient to fully characterize the toxicity of the atmospheric mix or to fully explain the risk of mortality associated with exposure to ambient pollution. Assuming additive associations, the estimated HR for nonaccidental mortality corresponding to a change in exposure from the mean to the 5th percentile for all three pollutants together was 1.075 (95% CI: 1.067, 1.084). Accounting for residential mobility had only a limited impact on the association between mortality and PM2.5 and O3, but increased associations with NO2.
Conclusions: In this large, national-level cohort, we found positive associations between several common causes of death and exposure to PM2.5, O3, and NO2.
1Environmental Health Science and Research Bureau, Health Canada, Ottawa, Ontario, Canada; 2Department of Sociology, University of New Brunswick, Fredericton, New Brunswick, Canada; 3College of Public Health and Human Sciences, Oregon State University, Corvallis, Oregon, USA; 4Air Quality Research Division, Environment Canada, Downsview, Ontario, Canada; 5Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada; 6Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada; 7Institute of Health: Science, Technology and Policy, Carleton University, Ottawa, Ontario, Canada; 8School of Public Health, University of California, Berkeley, Berkeley, California, USA; 9Department of Medicine, McGill University, Montreal, Quebec, Canada; 10Division of Clinical Epidemiology, Research Institute of the McGill University Hospital Centre, Montreal, Quebec, Canada; 11Department of Economics, Brigham Young University, Provo, Utah, USA; 12School of Population and Public Health, University of British Columbia, Vancouver, British Columbia, Canada; 13Division of Cardiovascular Medicine, University of Michigan, Ann Arbor, Michigan, USA; 14Atmospheric Science and Technology Directorate, Environment Canada, Dorval, Quebec, Canada
Recommended Citation:
Dan L. Crouse,1,2 Paul A. Peters,et al. Ambient PM2.5, O3, and NO2 Exposures and Associations with Mortality over 16 Years of Follow-Up in the Canadian Census Health and Environment Cohort (CanCHEC)[J]. Environmental Health Perspectives,2015-01-01,Volume 123(Issue 11):1180