Natural Cause Mortality and Long-Term Exposure to Particle Components: An Analysis of 19 European Cohorts within the Multi-Center ESCAPE Project

BACKGROUND: Studies have shown associations between mortality and long-term exposure to particulate matter air pollution. Few cohort studies have estimated the effects of the elemental composition of particulate matter on mortality.

OBJECTIVES: Our aim was to study the association between natural cause mortality and long-term exposure to elemental components of particulate matter.

METHODS: Mortality and confounder data from 19 European cohort studies were used. Residential exposure to eight a priori selected components of particulate matter (PM) was characterized following a strictly standardized protocol. Annual average concentrations of Copper (Cu), Iron (Fe), Potassium (K), Nickel (Ni), Sulfur (S), Silicon (Si), Vanadium (V) and Zinc (Zn) within PM size fractions <2.5 µm (PM_2.5) and <10 µm (PM₁₀) were estimated using land-use regression models. Cohort-specific statistical analyses of the associations between mortality and air pollution were conducted using Cox proportional hazards models using a common protocol followed by meta-analysis.

RESULTS: The total study population consisted of 291,816 participants, of which 25,466 died from a natural cause during follow-up (average time of follow-up 14.3 years). Hazard ratios were positive for almost all elements and statistically significant for PM_2.5 sulfur (1.14; 95% CI: 1.06, 1.23 per 200 ng/m³). In a two-pollutant model, the association with PM_2.5 sulfur was robust to adjustment for PM_2.5 mass, whereas the association with PM_2.5 mass was reduced.

CONCLUSIONS: Long-term exposure to PM_2.5 sulfur was associated with natural cause mortality. This association was robust to adjustment for other pollutants and PM_2.5.