Environmental drivers and ecological risks of bisphenol A occurrence in Chao Phraya River, Thailand.

Bisphenol A (BPA) is a ubiquitous industrial chemical, yet its behavior in tropical river systems remains poorly understood. This study presents the first integrated assessment of BPA occurrence, controlling factors, and ecological risks in the Chao Phraya River, Thailand. Surface water samples collected in October 2023 were analyzed using ultra-performance liquid chromatography with a quadrupole time-of-flight mass spectrometer (UPLC-QTOF-MS). BPA was detected at all sites, with concentrations ranging from 21.61 to 113.07 ng/L (mean: 60.44 ng/L), exhibiting a clear downstream increase. Multivariate analyses revealed a dual-control mechanism governing BPA distribution: (1) an urban-industrial gradient representing source inputs and (2) a water quality axis, where dissolved oxygen (DO) was the strongest predictor (β = -22.90, p < 0.001), indicating that low-oxygen conditions enhance BPA persistence. Ecological risk assessment indicated negligible acute risk but widespread high chronic risk. Human health risk assessment showed negligible non-carcinogenic risk for adults and children, underscoring wastewater management, river oxygenation, and routine BPA monitoring programs.