FOLLOWING THE EVIDENCE AND USING THE APPROPRIATE REGULATORY TOOLS: A EUROPEAN-WIDE RISK ASSESSMENT OF COPPER IN FRESHWATERS.

The ecological risks of copper (Cu) in freshwaters have been the focus of regulatory assessments for several decades. Recently, it has been suggested by the European Commission that Cu represents a continent-wide risk to freshwaters. We assessed to what extent this suggestion is supported by the available evidence if copper bioavailability is considered in the assessment of risk. We used several evidence driven metrics to assess the continental-wide risks from Cu to European freshwaters. Such an approach is recommended and readily applicable where comprehensive datasets are available. We confirmed the validity of a bioavailability-based Environmental Quality Standard of 1 µg L -1 , and we used this to characterize the Cu risks in 286,185 regulatory monitoring samples from 17,307 sites across 19 European countries between 2006 to 2021. These data show that risks, based on site averages and accounting for bioavailability, were identified in only two countries (Spain and Portugal). Investigation of these risks showed them to be highly localised to single region for Spain, and not reflective of the country-wide risks for either country. The 95 th percentile of all the risk quotients, for the continent-wide dataset is 0.35. The relatively low levels of risk associated with Cu are supported by long-term trend data from sites on two large European rivers (Rhine and Meuse), where highly significant (p<0.001) decreases in Cu concentrations over the last 40 years can be observed. We conclude that it is critical to consider metal bioavailability in both effects and exposures in assessments of potential risk to ensure ecological relevance. This article is protected by copyright. All rights reserved. Integr Environ Assess Manag 2023;00:0-0. © 2023 SETAC.