Ambient Particulate Matter Exposure and Risk of Venous Thromboembolism: An Updated Systematic Review and Meta-Analysis

BACKGROUND: Ambient air pollution is associated with cardiovascular morbidity and mortality, but its relationship with venous thromboembolism (VTE) remains uncertain. We performed an updated systematic review and meta-analysis evaluating particulate matter exposure and VTE risk. METHODS: PubMed, Embase, Web of Science, and the Cochrane Library were searched for observational studies evaluating PM2.5 or PM10 exposure and venous thrombotic outcomes. Studies were stratified by pollutants, exposure duration, and effect measure. Estimates were harmonized to 10 μg/m³, and random-effects models using restricted maximum-likelihood estimation and Hartung-Knapp adjustment were applied. RESULTS: Nineteen studies representing >4.5 million participants met the inclusion criteria. Overall long-term analyses showed no significant association for PM2.5 (HR 1.42, 95% CI 0.88-2.28; I²=97.0%) or PM10 (HR 1.18, 95% CI 0.85-1.64; I²=96.2%). However, sensitivity analyses restricted to studies natively reporting effects per 10 μg/m³ showed an association between PM2.5 and VTE (HR 1.070, 95% CI 1.010-1.135; I²=0%), while PM10 showed a borderline association (HR 1.023, 95% CI 1.000-1.047; I²=0%). Short-term PM2.5 and PM10 exposures were not significantly associated with venous thrombotic risk. CONCLUSIONS: Evidence suggests a possible modest association between long-term PM2.5 exposure and VTE; however, considerable between-study variability and sensitivity to exposure harmonization limit definitive conclusions. Standardized exposure metrics and consistent VTE definitions are needed to clarify this association.