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

Abstract

Protons and cations may affect metal accumulation in aquatic organisms and further influence metal toxicity. The effects of K⁺, Na⁺, Ca²⁺, Mg²⁺, and H⁺ on the accumulation and toxicity of Cd and Pb in zebrafish larvae after 24 h exposure were examined. We found that Na⁺, Ca²⁺, Mg²⁺, and H⁺ exerted significant effects on both the accumulation and toxicity of Cd, and Ca²⁺, Mg²⁺, and H⁺ also affected both the accumulation and toxicity of Pb significantly. Subsequently, stability constants for the binding of Pb²⁺, Cd²⁺, K⁺, Ca²⁺, Mg²⁺, 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.

Keywords: Accumulation; Competitive cations; Toxicity; Toxicokinetic-toxicodynamic (TK-TD) model; Zebrafish larvae.