Natural and cause-specific mortality and long-term exposure to particle components in a pooled cohort of 323,782 participants in Europe: the ELAPSE project

Abstract

Background/Aim Inconsistent associations between long-term exposure to components of particulate matter (PM) air pollution and adverse health outcomes have been reported. The aim of this study was to investigate the associations between long-term exposure to elemental components of PM and mortality in a pooled European cohort.Methods We pooled data from nine ongoing European cohorts with 323,782 participants. Residential exposure to annual 2010 mean concentrations of eight a priori-selected components of PM (copper, iron, potassium, nickel, sulfur, silicon, vanadium, and zinc) were assessed based on Europe-wide land use regression models at 100 m spatial scale. After harmonizing individual and area-level variables between cohorts, we applied Cox proportional hazard models with increasing adjustment for potential confounders to investigate the association between long-term air pollution exposure and natural and cause-specific mortality. Two-pollutant models were conducted for each element by adjusting for PM2.5 and NO2.Results The total study population contributed 6,317,234 person-year at risk (average follow-up 19.5 years). For natural-cause mortality, the hazard ratios were significantly positive for all components, and were strongly attenuated in two-pollutant models with adjustment for PM2.5 or NO2. Hazard ratios (HRs) in two-pollutant models for PM2.5 nickel, PM2.5 sulfur, PM2.5vanadium and PM2.5 zinc remained (borderline) significant [HRs adjusted for PM2.5: PM2.5 nickel: 1.04 (95% CI: 1.02, 1.07) per 1 ng/m3; PM2.5 sulfur: 1.05 (95% CI: 1.01, 1.09) per 200 ng/m3; PM2.5 vanadium: 1.0 (95% CI: 1.00, 1.03) per 2 ng/m3; PM2.5 zinc: 1.03 (95% CI: 1.02, 1.05) per 10 ng/m3; HRs adjusted for NO2 were similar]. The effect estimates for the more traffic-related pollutants copper and iron were especially reduced after adjustment for NO2. For cardiovascular and respiratory mortality, no consistent associations were found in two-pollutant models.Conclusions Long-term exposure to nickel, sulfur, vanadium and zinc in PM2.5 were associated with natural-cause mortality.