Effect-based methods and effect-based trigger values for estrogenicity monitoring in surface water: an interlaboratory study

Effect-based methods (EBMs) may be included in the European Water Framework Directive (WFD) to evaluate estrogenic substances. The European Commission's Joint Research Centre conducted an interlaboratory study to assess estrogenic EBMs and effect-based trigger (EBTs) values derived using three options: (1) linking the EBT value to environmental quality standards (EQS), (2) correlating in vitro and in vivo data, and (3) averaging bioassay-specific EBT values. Surface water samples from eight Northern-Italian sites containing estrogenic hormones and endocrine-disrupting chemicals (EDCs) were analysed by fourteen laboratories employing EBMs, while four laboratories performed chemical analysis. Chemical data indicated cumulative risk in several samples, with estrone and bisphenol A identified as main drivers. All EBMs detected estrogenic activity, but specificity differed: some bioassays responded mainly to hormones, whereas others also responded to non-hormonal EDCs. EBMs flagged estrogenic risk in a sample that showed no individual exceedances of EQS. Applying EBT option 1 yielded the highest concordance with chemical results, achieving full compliance in eight bioassays and proven to be the most protective. Indeed, option 2 reduced the risk quotient (RQ) by > 30%, leading to two bioassays in full compliance, while Option 3 resulted in RQ changes (<20%) for most EBMs, with seven bioassays in full compliance with chemical analysis. The study underscores the need to harmonise EBMs - including data evaluation - to address chemical mixtures and provides recommendations for Member States on their application in the WFD. Integrating EBMs with conventional monitoring enhances protection against cumulative estrogenic risks from both hormones and EDCs.