Long-Term Exposure to Fine Particle Elemental Components and Natural and Cause-Specific Mortality—a Pooled Analysis of Eight European Cohorts within the ELAPSE Project

Abstract

Background: Inconsistent associations between long-term exposure to particles with an aerodynamic diameter [fine particulate matter ( )] components and mortality have been reported, partly related to challenges in exposure assessment. Objectives: We investigated the associations between long-term exposure to elemental components and mortality in a large pooled European cohort; to compare health effects of components estimated with two exposure modeling approaches, namely, supervised linear regression (SLR) and random forest (RF) algorithms. Methods: We pooled data from eight European cohorts with 323,782 participants, average age 49 y at baseline (1985–2005). Residential exposure to 2010 annual average concentration of eight components [copper (Cu), iron (Fe), potassium (K), nickel (Ni), sulfur (S), silicon (Si), vanadium (V), and zinc (Zn)] was estimated with Europe-wide SLR and RF models at a scale. We applied Cox proportional hazards models to investigate the associations between components and natural and cause-specific mortality. In addition, two-pollutant analyses were conducted by adjusting each component for mass and nitrogen dioxide ( ) separately. Results: We observed 46,640 natural-cause deaths with 6,317,235 person-years and an average follow-up of 19.5 y. All SLR-modeled components were statistically significantly associated with natural-cause mortality in single-pollutant models with hazard ratios (HRs) from 1.05 to 1.27. Similar HRs were observed for RF-modeled Cu, Fe, K, S, V, and Zn with wider confidence intervals (CIs). HRs for SLR-modeled Ni, S, Si, V, and Zn remained above unity and (almost) significant after adjustment for both and . HRs only remained (almost) significant for RF-modeled K and V in two-pollutant models. The HRs for V were 1.03 (95% CI: 1.02, 1.05) and 1.06 (95% CI: 1.02, 1.10) for SLR- and RF-modeled exposures, respectively, per , adjusting for mass. Associations with cause-specific mortality were less consistent in two-pollutant models. Conclusion: Long-term exposure to V in was most consistently associated with increased mortality. Associations for the other components were weaker for exposure modeled with RF than SLR in two-pollutant models. https://doi.org/10.1289/EHP8368

Long-Term Residential Exposure to Particulate Matter and Its Components, Nitrogen Dioxide and Ozone—A Northern Sweden Cohort Study on Mortality

“…The ESCAPE study also reported an association between PM 2.5 sulfur and all-cause mortality independent of PM 2.5 mass exposure [52]. In a pooled analysis of eight of the European ESCAPE cohorts, residential exposure to the 2010 annual average concentration of eight PM 2.5 components (Cu, Fe, K, Ni, S, Si, V and Zn) was estimated with Europe-wide models at a 100 × 100 m scale, and all were found associated with all-cause mortality [20]. In two pollutant models, adjusting for PM 2.5 or NO 2 , Ni, S, Si, V and Zn remained associated with all-cause mortality.…”

“…The meta-analysis also found support for associations between Fe, nitrate, Zn, Si and CVD mortality, whereas there were not sufficient number of studies to conduct a meta-analysis for respiratory mortality. Cu, iron (Fe), potasium (K), nickel (Ni), sulfur (S), Si, vanadium (V) and Zn were associated with natural-cause mortality in a pooled analysis of eight European cohorts [20]. Within a recent study of the Danish Diet, Cancer and Health cohort all-cause mortality increased with NO 2 , O 3 , PM 2.5 , BC and secondary organic aerosols (SOA) [21,22].…”

Near-Source Risk Functions for Particulate Matter Are Critical When Assessing the Health Benefits of Local Abatement Strategies

“…These observations suggest strong effects from primary combustion-related particles, e.g., vehicle exhaust particles, per increase in mass concentration. However, the limited number of studies on PM 2.5 elemental components have produced rather inconclusive results regarding which components are most important for mortality, perhaps because elements such as Fe, Zn, and K may represent different sources in different places [ 7 ].…”

The Role of Fossil Fuel Combustion Metals in PM2.5 Air Pollution Health Associations

“…Overall, this study, similar to the Medicare population study, found that PM 2.5 mass that contained more sulfates demonstrated greater risk estimates, indicating the importance of PM 2.5 resulting from fossil fuel combustion. The ELAPSE Study subsequently examined this issue in Europe [105]. Pooled data from eight cohorts with 323,782 participants, average age 49 y at baseline .…”

“…Other potential toxic constituents including nitrate, sulfate, Zn, Si, Fe, Ni, V, and K were each associated with adverse cardiovascular health, while nitrate, sulfate and V were relevant for adverse respiratory health outcomes. However, the authors' choice to focus on model results simultaneously including particle mass with constituents would be expected to statistically weaken health associations for those that also comprise a significant percent of the mass (e.g., sulfates), as occurred in the Chen et al study [105]. In general, models including both constituents and mass simultaneously, such as conducted here, should be avoided, due to the intercorrelation bias introduced for some, but not all, constituents.…”