Impact of natural organic matter in water on in vitro bioactivity assays

At non-cytotoxic concentrations both NA-FA and NR-NOM induced AhR activity, inhibited AR activity with and without the known inducer dihydrotestosterone, inhibited Nrf2 activity, and NR-NOM induced ER activity. The results indicate that the presence of NOM in water samples may lead to false positive results for AhR activity and false positive results for AR and Nrf2 activity, when assessing inhibition of induced bioactivities from anthropogenic substances. We have demonstrated that NA-FA and NR-NOM have an impact on in vitro bioactivities and conclude that the impact of NOM in water should be considered in the evaluation of results from bioactivity assays.