Risk of non-accidental and cardiovascular mortality in relation to long-term exposure
to low concentrations of fine particulate matter: a Canadian national-level cohort study
http://ehp03.niehs.nih.gov/article/info ... hp.1104049
Dan L. Crouse, Paul A. Peters, Aaron van Donkelaar, Mark S. Goldberg, Paul J. Villeneuve, Orly Brion, Saeeda Khan, Dominic Odwa Atari, Michael Jerrett, C. Arden, III Pope, Michael Brauer, Jeffrey R. Brook, Randall V. Martin, David Stieb, Richard T. Burnett
Background. Few cohort studies have evaluated the risk of mortality associated with long-term exposure to fine particulate matter (particulate matter ≤ 2.5-µm in diameter (PM2.5)). This is the first national-level cohort study to investigate these risks in Canada.
Objective. We investigated the association between long-term exposure to ambient PM2.5 and cardiovascular mortality in non-immigrant Canadian adults.
Methods. We assigned estimates of exposure to ambient PM2.5 derived from satellite observations to a cohort of 2.1 million Canadian adults who in 1991 were among the 20% of the population mandated to provide detailed census data. We identified deaths occurring between 1991 and 2001 through record linkage. We calculated hazard ratios and 95% confidence intervals (CI) adjusted for available individual-level and contextual covariates using both standard Cox proportional survival models and nested, spatial random-effects survival models.
Results. Using standard Cox models we estimated increased risks of mortality of 15% (CI: 13-16%) from non-accidental causes and 31% (CI: 27-35%) from ischemic heart disease for each 10-µg/m3 increase in concentrations of PM2.5. Using spatial random-effects models controlling for the same variables, we estimated increased risks of 10% (CI: 5-15%) and 30% (CI: 18-43%), respectively. We found similar associations between non-accidental mortality and PM2.5 based on satellite-derived estimates and ground-based measurements in a sub-analysis of subjects in 11 cities.
Conclusions. In this large national cohort of non-immigrant Canadians, mortality was associated with long-term exposure to PM2.5. Associations were observed with exposures to PM2.5 at concentrations that were predominantly lower (i.e., mean 8.7-µg/m3, inter-quartile range 6.2-µg/m3) than those reported previously.