Predicting cadmium and lead toxicities in zebrafish (Danio rerio) larvae by using a toxicokinetic–toxicodynamic model that considers the effects of cations

Protons and cations may affect metal accumulation in aquatic organisms and further influence metal toxicity . The effects of K + , Na + , Ca 2+ , Mg 2+ , and H + on the accumulation and toxicity of Cd and Pb in zebrafish larvae after 24 h exposure were examined. We found that Na + , Ca 2+ , Mg 2+ , and H + exerted significant effects on both the accumulation and toxicity of Cd, and Ca 2+ , Mg 2+ , and H + also affected both the accumulation and toxicity of Pb significantly. Subsequently, stability constants for the binding of Pb 2+ , Cd 2+ , K + , Ca 2+ , Mg 2+ , Na + , and H + to biotic ligand were estimated with the Langmuir model and biotic ligand model (BLM). Using the BLM-estimated binding constants calculated with toxicity data, a refined toxicokinetic-toxicodynamic (TK-TD) model considering cation competition effects was used to predict Cd and Pb accumulation and survival rates in zebrafish larvae with varying cation concentrations. Results showed that the developed TK-TD model could successfully predict Cd and Pb toxicity to zebrafish larvae as a function of major competitive cations. The TK-TD model incorporated cation competition effects is a promising tool to quantify and assess the metal risk in natural water.