RISK-BASED APPROACH IN THE REVISED EU DRINKING WATER LEGISLATION: OPPORTUNITIES FOR BIOANALYTICAL TOOLS.

A plethora of in vitro bioassays is developed in the context of chemical risk assessment and clinical diagnostics to test effects on different biological processes. Such assays can also be implemented in effect-based monitoring (EBM) of (drinking) water quality in parallel to chemical analyses. EBM can provide insight in the risks for environmental and human health associated with exposure to (unknown) complex low-level mixtures of micropollutants, which fits in the risk-based approach that was recently introduced in the European Drinking Water Directive. Some challenges remain, in particular related to selection and interpretation of bioassays. For water quality assessment, carcinogenesis, adverse effects on reproduction and development, effects on xenobiotic metabolism, modulation of hormone systems, DNA reactivity and adaptive stress responses are considered as the most relevant toxicological endpoints. An evaluation procedure of the applicability and performance of in vitro bioassays for water quality monitoring based on existing information has been developed, which can be expanded with guidelines for experimental evaluations. Besides, a methodology for the interpretation of in vitro monitoring data is required, since the sensitivity of specific in vitro bioassays in combination with sample concentration may lead to responses of chemicals (far) below exposure concentrations that are relevant for human health effects. Different approaches are proposed to derive effect-based trigger values (EBTs), including EBTs based on 1) relative ecotoxicity potency, 2) health-based threshold values for chronic exposure in humans and kinetics of reference chemicals, and 3) read-across from (drinking) water guideline values. EBTs need to be chosen carefully in order to be sufficiently but not over-conservative to indicate potential health effects. Consensus on the crucial steps in the selection and interpretation of in vitro bioassay data will facilitate implementation, as well as legal embedding in the context of water quality monitoring of such assays in EBM strategies. This article is protected by copyright. All rights reserved.