Estrogenic potential artifacts & toxic confounders
Reproductive dysfunction in European aquatic systems has been associated with chemicals with high estrogenic potency. Even though risk assessments on individual chemicals have been underway for many years, little is known on the combined action of toxic and estrogenic substances. With the aim to unveil the effect of multiple estrogenic chemicals and other toxicants on aquatic organisms, an integrated approach has been employed. The latest advances in both equipment and methodology have been utilized to perform chemical detection and quantification, high throughput bioassays and statistical analyses. One of the primary objectives in the frame of the research programme ACE was to evaluate apparent estrogenicity of a chemical or chemical mixture in the presence of a non-estrogenic toxicant. A modified yeast estrogen screen (YES) specifically developed by ACE researchers to study the aforementioned interactions, was employed along with the well known E-screen assay. Results showed that experiments involving assessment of estrogenic potential of single substance and the mixture chemicals should take into account toxic confounders. These findings clearly indicate that "true" estrogenicity of environmental samples needs to be properly evaluated to avoid artifacts induced by the variation of a toxic confounder. The way to successful application of the Concentration Addition concept in terms of predictability of apparent estrogenicity of the mixture components has already been paved. However, models that could quantitatively predict the impact of a given concentration of confounder require toxicity markers and are yet to be established.
