Exposure to fine particulate matter promotes platelet activation and thrombosis via obesity-related inflammation

Short-term exposure to fine particulate matter (PM2.5) increases thrombotic risk particularly in obese individuals, but the underlying mechanisms remain unclear. This study aims to compare the effects of PM2.5 on inflammation and platelet activation in obese versus normal-weight adults, and investigate potential causal pathways. We conducted a panel study measuring blood markers in 44 obese and 53 normal-weight adults on 3 separate occasions in 2017-2018. Associations between PM2.5/black carbon (BC) and biomarkers were estimated using mixed-effect models. An interaction analysis compared PM2.5/BC-related effects between subgroups. Biomarker combinations and mediation analysis were performed to elucidate the biological pathways. There was a significant "low-high-low" trend of PM2.5 levels across the 3 study periods. Increases in pro-inflammatory cytokines and changes of platelet activation and aggregation markers were associated with PM2.5/BC in obese subgroup only. Among obese subjects, the combination of pro-inflammatory cytokines and that of platelet markers increased 26.8% (95% CI: 16.0%, 37.9%) and 14.7% (95% CI: 1.9%, 27.0%) per IQR increase in PM2.5 over 5-day and 7-day averages. Inflammation mediated 24.5% of the pathways through which PM2.5 promoted platelet activation. This study suggested obese people are susceptible to pro-thrombotic impacts of PM2.5 exposures. PM2.5 may aggravate thrombosis through obesity-related inflammation.