Evidence of Reduced Estrogenic Activity with Binary Mixtures of Endocrine Disrupting Compounds measured with a Chemi-luminescent Assay

The concern about the impacts of endocrine disrupting compounds (EDCs) in the environment has increased recently with their high occurrence in surface waters and sex changes in various aquatic organisms. EDCs include ubiquitously used pharmaceuticals and personal care products, such as soap, detergents, contraceptives, and other medicines, which are released constantly into the environment in waste water treatment plant effluent. Though toxicological effects of these individual EDCs have been studied, knowledge on how these chemicals interact together in the environment is very limited. The objective of this project is to study the multi-residue effect of EDCs using a chemi-luminescent yeast assay with Saccharomyces cerevisiae. The dose response curve for 17β-Estradiol (E2, a natural hormone) ranging from 10pM to 500nM alone and with varying concentrations of the Bisphenol A (BPA, a monomer used in many chemical products) and Nonylphenol (NP a surfactant) were created. Results indicate reduced estrogenic activity in all the binomial mixtures of E2 and BPA or NP compared to E2 alone. The EC₅₀ for all the experimental treatments was more estrogenic than the individual BPA and NP EC₅₀. These results lessen the gap in our knowledge about EDC interactions in surface waters, and provide new information for future toxicological data on aquatic environmental health.