Effects of realistic concentrations of TiO sub(2) and ZnO nanoparticles in Prochilodus lineatus juvenile fish

The impact of nanoparticles on fish health is still a matter of debate, since nanotechnology is quite recent. In this study, freshwater benthonic juvenile fish Prochilodus lineatus were exposed through water to three concentrations of TiO sub(2) (0.1, 1, and 10 mu g l super(-1)) and ZnO (7, 70, and 700 mu g l super(-1)) nanoparticles, as well as to a mixture of both (TiO sub(2) 1 mu g l super(-1)+ZnO 70 mu g l super(-1)) for 5 and 30 days. Nanoparticle characterization revealed an increase of aggregate size in the function of concentration, but suspensions were generally stable. Fish mortality was high at subchronic exposure to 70 and 700 mu g l super(-1) of ZnO. Nanoparticle exposure led to decreased acetylcholinesterase activity either in the muscle or in the brain, depending on particle composition (muscle-TiO sub(2) 10 mu g l super(-1); brain-ZnO 7 and 700 mu g l super(-1)), and protein oxidative damage increased in the brain (ZnO 70 mu g l super(-1)) and gills (ZnO 70 mu g l super(-1) and mixture) but not in the liver. Exposed fish had more frequent alterations in the liver (necrosis, vascular congestion, leukocyte infiltration, and basophilic foci) and gills (hyperplasia and epithelial damages, e.g., epithelial disorganization and epithelial loss) than the control fish. Thus, predicted concentrations of TiO sub(2) and ZnO nanoparticles caused detectable effects on P. lineatus that may have important consequences to fish health. But, these effects are much more subtle than those usually reported in the scientific literature for high concentrations or doses of metal nanoparticles.