In this study a method was implemented for the determination of total As and its inorganic species in human urine by HPLC-HG-AFS. The method was applied to workers occupationally exposed to mining and thermoelectric operations. Results shows high levels of As in urine up to 188±4 μg L-1 and As(III) up to 10.7±0.6 μg L-1. Toxic effects of As(III) at the concentration levels founded in human urine were evaluated over the morphology and fibrosis of renal epithelial collecting duct cells in vitro. Our results suggest that urinary tract epithelial renal tubular cells exposed to this concentration of As(III) result in epithelial-mesenchymal transition.