Assessing alkaline battery waste toxicity in Nile tilapia (Oreochromis niloticus): integrating physiological...

The widespread disposal of alkaline battery waste (ABW) poses significant environmental risks, particularly in aquatic ecosystems where heavy metals can accumulate and disrupt biological functions. This study evaluates the acute toxicity and sub-lethal effects of ABW exposure on Nile tilapia (Oreochromis niloticus), a key species in aquaculture and freshwater food chains. The 96-h LC₅₀ of ABW for Nile tilapia was determined to be 25.64 mg/L. Experimental fish were exposed to sub-lethal concentrations (10 and 40% LC₅₀) of ABW for 30 days, and multiple physiological and biochemical biomarkers were assessed. Growth performance parameters, including weight gain (WG) and specific growth rate (SGR), were significantly reduced in exposed groups. Elevated cortisol and blood glucose levels indicated heightened physiological stress, while liver function enzymes (alanine amino transferase (ALT) and aspartate aminotransferase (AST)) activity exhibited significant increases, reflecting hepatic impairment. Histopathological analyses of liver, gill, and muscle tissues revealed necrosis, hemorrhage, and myolysis, indicative of tissue damage due to ABW exposure. Molecular docking studies further demonstrated potential interactions of ZnO and MnO₂ with antioxidant enzymes (Superoxide dismutase (SOD), glutathione S-transferase (GST), and catalase (CAT)), suggesting oxidative stress as a contributing factor to observed toxic effects. These findings highlight the potential environmental hazards of ABW and emphasize the urgent need for proper waste management strategies to mitigate aquatic ecosystem contamination.