Application of toxicokinetic–toxicodynamic models in the aquatic ecological risk assessment of metals: A review

The issue of toxic metal pollution is a considerable environmental concern owing to its complex nature, spatial and temporal variability, and susceptibility to environmental factors. Current water quality criteria and ecological risk assessments of metals are based on single-metal toxicity data from short-term, simplified indoor exposure conditions, ignoring the complexity of actual environmental conditions. This results in increased uncertainty in predicting toxic metal toxicity and risk assessment. Using appropriate bioavailability and effect modeling of metals is critical for establishing environmental quality standards and performing risk assessments for metals. Traditional dose-effect models are based on a static statistical relationship and fall short of revealing the bioavailability and effect processes of metals and do not effectively assess ecological impacts under complex exposure conditions. This paper summarizes the toxicokinetic–toxicodynamic (TK–TD) model, which is gaining interest in environmental and ecotoxicological research. The key concepts, and theories of its construction theories, are discussed and the application of the TK–TD model in toxicity prediction and risk assessment of different metals in the aquatic environment, and trends in the development of the TK–TD model are highlighted. The findings of our review prove that the TK–TD model can effectively predict toxic metal toxicity in real time and under complex exposure conditions in the future.