Health Risk Assessmentof Dietary Arsenic Exposureand Selenium Deficiency in Tibet Based on In Vitro GastrointestinalSimulation

Abstract The Tibetan Plateau has a distinctive high-As and low-Se geochemical background. This geochemical characteristic can be transferred to the human body via food intake, thereby posing potential health risks. Conventional assessments based only on total elemental concentrations may not reflect the fraction released during gastrointestinal digestion. In this study, the Unified Bioaccessibility Method (UBM) was combined with Monte Carlo simulation to evaluate dietary As exposure and Se intake from typical Tibetan foods. The results showed a low dietary Se/As ratio of 0.80, far below the national average of 4.35. Bioaccessibility-adjusted modeling reduced estimated As exposure, but carcinogenic risk remained above 10–4 in all age groups, with the highest mean risk in children. Estimated Se intake was also below the recommended level. After simulated gastrointestinal digestion, the As–Se correlation increased from r = 0.40 to 0.58, indicating a stronger postdigestion association. These findings highlight the need to incorporate bioaccessibility into dietary exposure assessment and suggest that Tibetan populations may face both elevated As-related risk and insufficient Se intake.