Long-Term Exposure to Low-Level PM2.5 and Mortality: Investigation of Heterogeneity by Harmonizing Analyses in Large Cohort Studies in Canada, United States, and Europe

Studies across the globe generally reported increased mortality risks associated with particulate matter with aerodynamic diameter ≤2.5μm (PM2.5) exposure with large heterogeneity in the magnitude of reported associations and the shape of concentration-response functions (CRFs). We aimed to evaluate the impact of key study design factors (including confounders, applied exposure model, population age, and outcome definition) on PM2.5 effect estimates by harmonizing analyses on three previously published large studies in Canada [Mortality-Air Pollution Associations in Low Exposure Environments (MAPLE), 1991–2016], the United States (Medicare, 2000–2016), and Europe [Effects of Low-Level Air Pollution: A Study in Europe (ELAPSE), 2000–2016] as much as possible.