Personal PM_2.5-Bound Metal Exposure Profiles and Their Associations with Inflammatory Biomarkers among Older Adults...

Metals are key toxic components of PM_2.5, but their personal exposure levels and health effects remain unclear, due to their high spatiotemporal heterogeneity and large differences in individual behaviors. This study proposed a "personal PM_2.5-bound metal exposome" framework to (1) systematically characterize personal metal exposure profiles and their variability, (2) comprehensively evaluate the health effects of multimetal exposures, and (3) explore interactions among metals. Using data from the SCOPE (Study Comparing the cardiO-metabolic and respiratory effects of air Pollution Exposure) panel study, we analyzed personal samples and data from 588 follow-up visits of 120 elders in Beijing, China. Personal 23.5-h PM_2.5 samples were collected using portable devices, and concentrations of 15 metals were quantified by micro-synchrotron radiation X-ray fluorescence (μ-SRXRF). Linear mixed-effects models were applied to assess the impacts of transportation modes and personal exposure sources on personal PM_2.5-bound metal exposure profiles. A Bayesian Kernel Machine Regression (BKMR) model was applied to examine the associations between metals and inflammatory biomarkers and evaluate interactions among metals. The results indicated that participants exposed to the subway microenvironment had elevated exposure levels of iron (Fe), manganese (Mn), and copper (Cu). This suggests that even when metal exposure is accumulated over only a short period in the subway, the enclosed environment may still lead to potentially pronounced health impacts. An interquartile range increase in arsenic (As) was associated with an increase of 6.2% in IFNγ (95% CI: 0.0-12.4%), 20.2% in sCD40L (95% CI: 7.1-33.3%), 2.9% in MCP-1 (95%CI: 1.0-5.5%), 1.8% in white blood cells (95% CI: 0.3-3.2%), and 3.3% in monocytes (95% CI: 1.0-5.4%). Suggestive evidence indicated that transition metals (Fe, Cu, Mn) may have synergistic pro-inflammatory effects. Based on a "personal PM_2.5-bound metal exposome" analytical framework, this study has improved scientific understanding of personal metal exposure profiles and their health effects.