Non-Negligible Bioaccumulation and Risks of Tetrabromobisphenol-A/S and Their Analogs in the World’s Largest Population of Indo-Pacific Humpback Dolphins

Despite increasing concerns regarding the bioaccumulation and toxicity of tetrabromobisphenol A/S (TBBPA/S) and their analogs, their environmental behavior and risks in marine ecosystems remain poorly understood. Here, we conducted the first quantitative assessment of TBBPA/S and eight of their analogs in Indo-Pacific humpback dolphins ( n = 102) and 14 prey species ( n = 105) from the Pearl River Estuary (PRE), China, characterizing their tissue distribution, maternal transfer, spatiotemporal trends, and potential health risks. All ten analytes (2.5–109.1 ng/g ww) were detected in both dolphins and their prey, demonstrating widespread contamination throughout the PRE ecosystem. TBBPA/S and their analogs exhibited distinct accumulation patterns in dolphin liver and brain tissues, likely influenced by differences in lipophilicity and molecular weight. The presence of most analytes in fetuses indicates their ability to cross the maternal-fetal barrier. While TBBPA levels in dolphins showed no significant trend from 2004 to 2023, the TBBPA:TBBPS concentration ratio declined markedly, potentially reflecting the increasing substitution of TBBPA with TBBPS in industrial applications. Notably, our findings suggest that, without dietary correction, the biomagnification potential and dietary exposure risks of TBBPA/S and their analogs from prey to dolphins may be substantially underestimated.