Multi-Metal Leachate from Lithium Slag Induces Oxidative Stress, Circadian Disruption, and Neurobehavioural Toxicity in Zebrafish Larvae

The rising global demand for lithium has led to substantial accumulation of lithium slag, a by-product of lithium carbonate production and a potential environmental contaminant. Leachates from this material contain various metal elements and may pose risks to ecosystems and organismal health. However, research on its neurotoxicity and underlying mechanisms remains limited. In this study, zebrafish embryos at 6 h post-fertilisation were exposed to varying concentrations of lithium slag leachate for 7 days. The leachate contained multiple metal ions (Li, Fe, Mn, Ni, Zn, As, Cr, Cu, Hg, Cd, Pb, etc.). Following exposure, significant metal accumulation was observed in larvae, accompanied by developmental malformations (yolk sac oedema, cardiac haemorrhage, and uninflated swim bladders). Behavioural assessment revealed reduced swimming distance and velocity, along with disrupted circadian rhythms. Biochemical analyses showed elevated Reactive oxygen species (ROS), Superoxide dismutase (SOD), Catalase (CAT), and Malondialdehyde (MDA), alongside decreased Glutathione (GSH), indicating oxidative stress. Transcriptomic analysis confirmed downregulation of core circadian genes. Neurotransmitter assays revealed decreased acetylcholine (Ach), noradrenaline (NE), and dopamine (DA), with increased gamma-aminobutyric acid (GABA) and serotonin (5-HT). These findings demonstrate that lithium slag leachate induces oxidative stress, circadian disruption, and neurobehavioural toxicity in zebrafish, providing important evidence for environmental risk assessment.