Beyond Degradation Efficiency: Toxicological Profile of Bisphenol Transformation Products in Nanomaterial-Based Advanced Oxidation Processes

Bisphenols are a family of synthetic endocrine-disrupting compounds commonly found in water systems, where they persist because of the limitations of conventional wastewater treatment. Nanomaterial-based Advanced Oxidation Processes (AOPs) have been widely studied as promising approaches for bisphenol degradation, achieving high removal efficiencies by generating reactive oxygen species (ROS). However, incomplete mineralization frequently leads to the formation of transformation products, which may have toxicological characteristics that differ significantly from those of the parent compounds. This review focuses on the toxicity of the degradation products generated during the nanomaterial-based AOP treatment of bisphenol A (BPA), bisphenol S (BPS), bisphenol F (BPF), and bisphenol AF (BPAF). Evidence from ecotoxicological, phytotoxicological, cytotoxic, genotoxic, neuroactive, and endocrine disruption studies shows that some intermediates may display toxicity equal to or exceeding that of the parent compounds, particularly during intermediate treatment stages. The influence of operational parameters such as catalyst type, ROS composition, irradiation conditions, and treatment duration on transformation product (TP) formation and toxicity evolution was further investigated. These findings suggest that removing the parent compound is not enough to guarantee the environmental safety of treated effluents and stress the importance of including a comprehensive toxicological assessment when evaluating advanced water treatment technologies.