RESUMO
Triclosan (TCS, 5chloro2(2,4dichlorophenoxy) phenol) is becoming a major surface waters pollutant worldwide at concentrations ranging from ngâ¯L-1 to µgâ¯L-1. Up to now, the adverse effects on aquatic organisms have been investigated at concentrations higher than the environmental ones, and the pathways underlying the observed toxicity are still not completely understood. Therefore, the aim of this study was to investigate the toxic effects of TCS at environmental concentrations on zebrafish embryos up to 120â¯hours post fertilization (hpf). The experimental design was planned considering both the quantity and the exposure time for the effects on the embryos, exposing them to two different concentrations (0.1⯵gâ¯L-1, 1⯵gâ¯L-1) of TCS, for 24â¯h (from 96 to 120â¯hpf) and for 120â¯h (from 0 to 120â¯hpf). A suite of biomarkers was applied to measure the induction of embryos defence system, the possible increase of oxidative stress and the DNA damage. We measured the activity of glutathioneStransferase (GST), Pglycoprotein efflux and ethoxyresorufinodeethylase (EROD), the level of ROS, the oxidative damage through the Protein Carbonyl Content (PCC) and the activity of antioxidant enzymes. The genetic damage was evaluated through DNA Diffusion Assay, Micronucleus test (MN test), and Comet test. The results showed a clear response of embryos defence mechanism, through the induction of P-gp efflux functionality and the activity of detoxifying/antioxidant enzymes, preventing the onset of oxidative damage. Moreover, the significant increase of cell necrosis highlighted a strong cytotoxic potential for TCS. The overall results obtained with environmental concentrations and both exposure time, underline the critical risk associated to the presence of TCS in the aquatic environment.