In vitro toxicity of arsenic rich waters from an abandoned gold mine in northeast Portugal

This is a follow-up study of physicochemical water monitoring data from the abandoned Freixeda gold mine in Portugal, where arsenic (As) has remained above drinking water and irrigation limits over the years. The main objective of the current work was to investigate the toxicological potential of As-containing water on human cell line as an indicator of a potential health risk to humans. Six water samples collected in February 2018 were analysed for arsenic, major anions, cations and trace elements. Toxicity experiments were carried out on the human gastrointestinal cell line Caco-2 with five water samples containing As above 10 μg L−1. The results show that groundwater contains higher amounts of dissolved minerals than surface water, particularly with higher concentrations of SO42−, Fe and HCO3− and also higher As(III), reaching 336 μg L−1 (As(T) = 607 μg L−1). In surface waters As concentration decreased and reached 150 μg L−1, mainly as As(V). Metabolic activity was generally lower in Caco-2 cells exposed to As-containing water samples compared to pure As(III) solution, adapted to As concentrations, while production of reactive oxygen species (ROS) was higher. Short-term exposure to As-contaminated water samples also resulted in increased genotoxicity. This study suggests that mixture of As with various chemical elements in water may have a synergistic effect in promoting cytotoxicity. It is likely that prolonged exposure, as is common in areas with contaminated water, would have even more harmful effects. •Arsenic is a persistent water contaminant in an abandoned mining area in Portugal.•In vitro toxicity assessment in human cells as an indicator of human health risk.•Reduced metabolism in Caco-2 cells exposed to As-containing water.•Increased generation of reactive oxygen species and genotoxicity.•Other chemicals in the water composition may have a synergistic effect in toxicity.