Assessing the estrogenic contamination of the aquatic environment
Although it is generally acknowledged that endocrine-disrupting contaminants can cause a variety of adverse health effects, assessing the associated risks is considerably more complex methodologically and computationally than current practices. Existing environmental risk assessment procedures are limited in their ability to evaluate the combined effects of chemicals mixtures. In view of investigating the implications of such shortcomings, scientists at the University of Brunel analysed the combined effects of multicomponent mixtures of estrogens in aquatic organisms. The study focused on establishing the concentrations of chemicals required to induce vitellogenesis production in juvenile sea bass and male fathead minnows. Chemicals were combined at equipotent concentrations and the effects of the mixture were compared with those predicted by the model of Concentration Addition (CA) using biomathematical methods. The observed and predicted effects of chemical mixtures, emanating from both freshwater and marine species studies, indicated that estrogenic chemicals have the capacity to act additively at environmental relevant concentrations. Moreover, these findings highlighted the potential for their combined effects to be accurately predicted from information about the potency of individual components and the mixture's composition. Therefore, risk assessment procedures, which are currently based on single substance exposure studies, may underestimate the hazards posed by mixtures of similarly acting chemicals and thus lead to erroneous conclusions. This knowledge means that environmental standards can in the future be set with more confidence that they will be adequately protective.
