A cell-based testing strategy designed for targeted testing with sensitive bioassays for specific mechanisms of action and able to cover the largest possible group of PFAS would represent a very good option for a rapid initial toxicological assessment based on the precautionary principle. Based on the results in testing single substances (PFAS), effects can be measured for an interaction with the ER, antiAR and TTR-TRβ and the cytotoxicity parameters. A clear priorization can be made, favoring the mode of action regarding the thyroid hormone transport molecule TTR (TTR-TRβ).