European River Basins Review Articles 30 © 2007 ecomed publishers (Verlagsgruppe Hüthig Jehle Rehm GmbH), D-86899 Landsberg and Tokyo • Mumbai • Seoul • Melbourne • Paris Env Sci Pollut Res 14 14 14 14 14 (1) 30 – 38 (2007) Review Articles Effect-Directed Analysis of Key Toxicants in European River Basins A Review Werner Brack 1 *, Hans J.C. Klamer 2 , Maria López de Alda 3 and Damià Barceló 3 1 UFZ Centre for Environmental Research, Department of Effect-Directed Analysis, Permoserstraße 15, 04318 Leipzig, Germany 2 National Institute for Coastal and Marine Management, RIKZ, PO Box 207, 9750 AE Haren, The Netherlands 3 IIQAB-CSIC, Barcelona, Department of Environmental Chemistry, Jordi Girona 18-26 08034 Barcelona, Spain * Corresponding author ( wer ner .brack@ufz.de) Conclusions. The development of tools and strategies for an identification of key toxicants on a broader scale are a challeng- ing task for the next years. Since investigations dealing with toxicant identification are too labor and cost-intensive for moni- toring purposes, they have to be focused on the key sites in a river basin. These should include hot spots of contamination, particularly if there is evidence that they might pose a risk for downstream areas, but may also involve accumulation zones in the lower reach of a river in order to get an integrated picture on the contamination of the basin. Recommendations and Perspectives. While EDA is almost ex- clusively based on measurable effects in in vitro and in vivo biotests to date, an increasing focus in the future should be on the integration of EDA into Ecological Risk Assessment and on the development of tools to confirm EDA-determined key toxi- cants as stressors in populations, communities and ecosystems. Considering these requirements and applied in a focused way, toxicant identification may significantly help to implement the Water Framework Directive by providing evidence on the main stressors and possible mitigation measures in order to improve the ecological status of a river ecosystem. Keywords: Aquatic ecosystems; chemical contamination; eco- toxicity; effect-based key toxicants; effect-directed analysis (EDA); European river basins; sediments; weight-of-evidence; Water Framework Directive (WFD) DOI: http://dx.doi.org/10.1065/espr2006.08.329 Abstract Background. Extensive monitoring programs on chemical con- tamination are run in many European river basins. With respect to the implementation of the European Union (EU) Water Framework Directive (WFD), these programs are increasingly accompanied by monitoring the ecological status of the river basins. Assuming an impact of chemical contamination on the ecological status, the assignment of effects in aquatic ecosys- tems to those stressors that cause the effects is a prerequisite for taking political or technical measures to achieve the goals of the WFD. Thus, one focus of present European research is on toxicant identification in European river basins in order to allow for a reduction of toxic pressure on aquatic ecosystems according to the WFD. Main Features. An overview is presented on studies that were performed to link chemical pollution in European river basins to measurable ecotoxic effects. This includes correlation-based approaches as well as investigations that apply effect-directed analysis (EDA) integrating toxicity testing, fractionation and non-target chemical analysis. Effect-based key toxicants that were identified in European surface waters are compiled and compared to EU priority pollutants. Further needs for research are identified. Results. Studies on the identification of effect-based key toxi- cants focused on mutagenicity, aryl hydrocarbon receptor-me- diated effects, endocrine disruption, green algae, and inverte- brates. The identified pollutants include priority pollutants and other well-known environmental pollutants such as polycyclic aromatic hydrocarbons, polychlorinated dibenzo-p-dioxins, furans, and biphenyls, nonylphenol, some pesticides and tribu- tyltin, but also other compounds that were neither considered as environmental pollutants before nor regulated such as substi- tuted phenols, natural or synthetic estrogens and androgens, dinaphthofurans, 2-(2-naphthalenyl)benzothiophene, and N-phe- nyl-2-naphthylamine. Discussion. Individual studies at specific sites in a European river basin demonstrated the power of combined biological and chemi- cal analytical approaches and, particularly, of effect-directed analysis. However, the available information on effect-based key toxicants is very limited with respect to the entirety of rivers possibly at risk due to chemical contamination and with respect to toxicological endpoints considered at a specific site. A rela- tively broad basis of information exists only for estrogenicity and aryl hydrocarbon Ah-receptor-mediated effects. Introduction The European Union (EU) Water Framework Directive (WFD) demands a good ecological status in European river basins by 2015. Together with river morphology and eutro- phication, toxic pollution is believed to be an important driv- ing force for the insufficient ecological status of many riv- ers. Thus, within the last decade, increasing attempts were made to analyze and monitor potentially hazardous com- pounds in many river basins and numerous individual com- pounds have been detected and quantified. As an example, polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) and the sulfur analogues of polychlorinated dibenzothio- phenes (PCDBTs), polychlorinated biphenyls (PCBs), chlo- robenzenes, polybrominated diphenylethers, dichloro-diphe- nyl-trichloroethane (DDT) and metabolites, hexachlorocyclo- hexanes, chlorostyrenes, polyaromatic hydrocarbons (PAHs), polycyclic aromatic sulfur hydrocarbons, naphthol, triaz-