Simplifying animal studies for risk assessment
Natural and man-made chemicals having the ability to mimic estrogens are considered hazardous when aquatic organisms are exposed to them as they may result to reproductive dysfunction. Until now, research has focused on the effects of single chemicals while in reality exposures are related to mixtures of estrogenic agents. Therefore, the ways that estrogenic chemicals act as mixtures and the additive manner when they combine along with their effects to aquatic wildlife (concentration addition) has to be further explored. The ACE project focused on analysing the combined effects of mixtures of estrogenic chemicals in aquatic wildlife. One of the key project results involved the concordances between estrogenic mixture effects in sub-cellular, cell-based and fish assays. Using a variety of estrogenic assays for both single substances as well as for mixtures were compared and analysed. It was found that for five chemicals (E2, EE2, BPA, OP and NP) in vitro assays for single substances could predict in vivo responses. Although certain abnormalities were found, these were either considered insignificant in the regulatory perspective or predictable. For the mixture effects, the analysed assays verified the concentration addition theory, that the components of estrogenic chemicals when combined contribute to the overall activity of the mixture. This proves that the additive effects are reflected at different levels of biological complexity displaying that extrapolated data in vitro has an increased potential to indicate effects in vivo. Therefore, future risk assessment studies could become less expensive and time consuming as in vivo assays in the analyses of mixture effects could be avoided.
