Considering the prevalence of emerging nanotechnology, predicting the environmental impact of nanomaterials has great importance. The aim of this study was to investigate the possible accumulation and histological damage resulting from the exposure of fish to silver nanoparticles (AgNPs). Hence, rainbow trout (Oncorhynchus mykiss) were exposed for 21 days to sublethal concentrations of either colloidal or powdered forms of silver nanoparticles (cAgNPs or pAgNPs, respectively); the resulting histological changes (in gills, intestines, liver, and kidneys) and bioaccumulation (in gills, intestines, liver, and white muscles) were examined on days 11 and 21. In the case of cAgNPs, the highest concentrations of silver were observed in the liver, gills, and intestines. Meanwhile, in the case of pAgNPs, the highest concentrations of silver were observed in the intestines, liver, gills, and muscles. The greatest histopathological impacts were observed in the gills (mostly proliferation and inflammation), intestines (mostly necrosis and inflammation), and liver (mostly pigmentation). Thus, when taken together, the current findings indicate that both forms of AgNPs had a chronic effect on the rainbow trout (as a model aquatic organism); therefore, preventing the entry of these nanomaterials into the aquatic environment would seem to be essential.
