In vitro assessment of toxicological profile of drugs present in wastewater obtained from Bozen water treatment plant

Background: A wide variety of substances, e.g. drugs, may be present in wastewater at low concentrations depending on the water treatment processes applied. Such complex of substances is difficult to characterize and represents a challenge for risk assessment. In fact, individual compounds can contribute to mixture effects, which may lead to an increase or a decrease of their biological activity or a modification of their toxicological profile. Cell-based bioassays that target health-relevant biological endpoints may therefore integrate chemical analysis for water quality assessment. Aim: The aim of this study was to assess efficacy of water treatment processes of wastewater treatment plant of Bozen (Italy), evaluating toxicological profile of two samples on HepG2 cells (Human hepatoma-derived cell line). The selected assays provide measures of primary nonspecific toxicity (cytotoxicity and ROS production), as well as markers of xenobiotic metabolism (liver enzymes modification). Results: Generally, exposure for 48–72 h to wastewater did not affect HepG2 cell proliferation. Even if concentration of drugs increased by 12 times that detected in wastewater samples, no toxic effects were observed. ROS production was assessed after 1, 2, 3 and 24 h exposure without obtaining appreciable differences from control. No genotoxic effect was observed in wastewater-treated cells using micronucleus assay. Interestingly, an increase of CYP3A4 protein expression after 48 h exposure, while a significant decrease after 72 h were observed. Conclusion: Wastewater collected from Bozen treatment plant shows a safe toxicological profile, even if it affects differently CYP3A4 expression in an exposure time-dependent manner.