Impact of co-exposure to titanium dioxide nanoparticles (TiO NPs) and lead (Pb) on African catfish Clarias gariepinus (Burchell, 1922) fed contaminated copepods (Eucyclop sp.).

The fast-growing discharge of effluents of engineered nanomaterials (ENM) and heavy metals in freshwater ecosystems raises concern in recent times. This study investigated the effects of the co-exposure between nanoparticles (TiO NPs) and lead (Pb) in a simplified freshwater food web model, including zooplankton (copepods sp.) and Clarias gariepinus on bioaccumulation and antioxidant activity. We carried out a chronic (28 days) semi-static bioassay by feeding individually fish with zooplankton exposed to TiO NPs (0.09 and 0.20 μM), Pb (0.01 and 0.04 μM), and their binary mixtures. The binary mixtures caused a significant (p < 0.05) decrease in malondialdehyde (1.64-2.01-fold), catalase (3.18-3.89-fold), glutathione reductase (1.37-1.46-fold), and glutathione peroxidase (1.19-1.89-fold) levels. Lead accumulated in the tissues had bioaccumulation factor between 0.40 and 1.42 in binary mixture. These results indicate that chronic exposure of TiO NPs could influence the BAF of Pb, neurotoxicity, changes of antioxidant enzymes, and retardation of food uptake. These findings raise concerns regarding the fate of higher trophic levels in polluted freshwater ecosystems with a binary mixture of engineer nanomaterials and heavy metals.