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2L (1) - Immunotoxicity - genotoxicity - ED (TH8/1) Combination effects of estrogenic substances at low concentrations. Meyer, Wiebke1, Backhaus, Thomas1, Faust, Michael2, Frische, Tobias1, Grimme, L. Horst1, 1 University of Bremen, Bremen, Germany, Germany2 F&B Environmental Consulting, Bremen, Germany, Germany ABSTRACT- Organisms in aquatic ecosystems are not only exposed towards single substances but to a multitude of chemicals that are able to mimic natural estrogens. Compared to the concentrations of the individual chemicals that are needed in laboratory biotests to produce estrogenic effects, the concentrations of many of these compounds found in aquatic ecosystems are rather low. Thus it is important to examine if there are combination effects of individual chemicals at low concentrations to be taken into account. Additionally, a clear conceptual link between the effects of the individual substances and the corresponding mixture would form a scientifically sound basis for the hazard assessment of estrogenic mixtures. Therefore, concentration-response relationships of a series of estrogens, synthetic estrogens, and different xenoestrogens were determined in a yeast estrogen screen (YES). Subsequently, multi-component mixtures of these substances with all mixture components present in environmentally relevant low concentrations were tested. Two concepts, Concentration Addition and Independent Action, were used to predict the overall effects of the mixture from the known concentration-effect relationships of the individual substances. The experimentally determined combination effects are compared to the predicted mixture effects and discussed in relation to environmental concentrations. Key words: low dose, mixture effects, endocrine disrupters, yeast estrogen screen |
