Recital (23)

The conventional chemical analytical methods used for monitoring substances under Directives 2000/60/EC, 2006/118/EC and 2008/105/EC cannot, in general, determine the cumulative risk from mixtures of substances. Considering the growing awareness of the relevance of mixtures and therefore of effect-based monitoring for determining chemical status, and considering that sufficiently robust effect-based monitoring methods already exist for estrogenic substances, Member States should apply such effect-based monitoring methods to assess the cumulative effects of estrogenic substances in surface waters over a period of at least two years. This will allow the comparison of effect-based results with the results obtained using the conventional methods for monitoring the three estrogenic pharmaceutical substances listed in Annex I to Directive 2008/105/EC. For that purpose, the Commission should adopt an implementing act setting out the technical specifications for the monitoring of estrogenic substances using effect-based monitoring methods. The Commission should also publish a report on the comparison of effect-based results with the results obtained using the conventional methods, and an analysis of it should be used to assess whether effect-based monitoring methods deliver data that are robust and accurate enough to allow those methods to be used as reliable screening methods. Using such screening methods would have the advantage of allowing the effects of all estrogenic substances having similar effects to be covered, not only those listed in Annex I to Directive 2008/105/EC, and could also replace substance-by-substance monitoring at many locations. The concept of effect-based trigger values should be defined. The definition of good surface water chemical status in Directive 2000/60/EC should be modified to ensure that it could, in the future, also cover trigger values that might be set for assessing the results of effect-based monitoring.