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Biomarker-assisted evaluation of toxicity of co-exposure of emergent pollutants triclosan and microplastics in striped catfish, Pangasianodon hypophthalmus
Summary
A 45-day exposure study in striped catfish found that co-exposure to triclosan and polystyrene microplastics suppressed immune function, elevated oxidative stress markers, increased tissue accumulation of triclosan, and caused haematological abnormalities compared to either contaminant alone. The synergistic toxicity observed when microplastics act as vectors for antimicrobial chemicals has implications for aquatic ecosystem health and for the safety of farmed fish consumed by humans.
The present study investigates the single and mixture toxicity of triclosan (TCS), a widely used antimicrobial agent, and polystyrene microplastics (PS-MP) on innate immunity, bioconcentration, haematology, and oxidative stress in the striped catfish Pangasianodon hypophthalmus (P. hypophthalmus). The fish were exposed to graded concentrations of TCS in combination with a constant concentration of microplastics for 45 days. Following exposure, the fish were challenged with Edwardsiella tarda (E. tarda), and their immune response and survival were assessed using various haematological and enzymatic biomarkers. The bioconcentration factor (BCF) showed a dose-dependent accumulation of TCS in tissues, with the order: gills > liver > kidney > muscle > brain. A comparatively higher concentration was observed in the presence of PS-MP than in the control. Co-exposure reduced immune parameters, including myeloperoxidase (MPO) activity, total serum immunoglobulin, respiratory burst activity (RBA), and serum proteins. Elevated superoxide dismutase (SOD) and catalase (CAT) activities in the exposed groups indicated oxidative stress. Alterations in haematological parameters and erythrocyte abnormalities in co-exposed groups compared to controls further confirmed haematotoxicity. The findings demonstrate that co-exposure to these emerging pollutants enhances toxicity through metabolic disruption and oxidative stress. The highest Integrated (IBR) indices were observed for RBA in blood (10.15), SOD and CAT in the liver (14.06) and gills (9.70), and serum total protein. Overall, the study establishes that PS-MP potentiates the bioconcentration of TCS and increases oxidative stress and immunotoxicity in experimental fish.