With the help of this guideline, a harmonized detection of the assessment-relevant mechanisms of action genotoxicity, neurotoxicity and endocrine effects is possible on the basis of the test strategies shown. This allows the derivation of corresponding health orientation values for drinking water.

The present guideline deals with the assessment-relevant mechanisms of action genotoxicity, neurotoxicity and endocrine effects, which are used to derive health orientation values (GOWs; precautionary values for the protection of health) for anthropogenic trace substances in drinking water. The experimental recording of these priority mechanisms of action is a prerequisite for a prompt toxicological substance evaluation based on the GOW concept for the estimation of hazard potentials and for the resulting options for measures to be taken as well as for subsequent monitoring programs. For each of these mechanisms of action, their scientific background and the current status of regulation are explained, and the corresponding test strategy for their experimental detection is presented. The test protocols of the individual test procedures with corresponding result evaluation are also listed. Furthermore, the guide answers frequently asked questions about the health guidance value in chapter 5. Overall, this guideline transparently presents the decision-making basis of the Federal Environment Agency for the derivation of health orientation values and creates the prerequisite for experimentally recording the corresponding mechanisms of action according to a harmonized procedure.