Ecotoxicity of a representative urban mixture of rare earth elements to rainbow trout juveniles

Municipal wastewaters contain a peculiar mix of rare earth elements (REEs) dominated by gadolinium (Gd). The sublethal and lethal toxicity was examined in rainbow trout exposed to a representative REE mixture (municipal waswaters) composed of Gd (105 ng/L), Ce (9 ng/L), Nd (8 ng/L), Yb (6.2 ng/L) and Dy (4 ng/L) corresponding to total REEs loading of 137 ng/L. Juveniles were exposed to a mixture of REEs (Gd representing 80 % of the loading) at concentrations between 0.5 and 100X for 96 h at 15 °C. The data revealed that the 100X mixture was not acutely lethal but produced a range of sublethal effects at concentrations in the 1-10X range, which could be found in some municipal wastewaters. The sublethal effects involved changes in liver weight, heat stable metal binding proteins, protein aggregation, lipid peroxidation and DNA damage. Hence, these sublethal effects were observed in juvenile fish at environmentally relevant concentrations. This suggests that the REEs found in wastewaters could contribute to long-term negative impacts on fish populations.