Chemical toxicity distributions in aquatic toxicology : relative sensitivities of estrogenicity assays and ecotoxicity of parabens in model freshwater organisms.

A probabilistic ecological hazard assessment technique, chemical toxicity distributions, was used to examine the relative sensitivities of in vitro and in vivo assays for detecting estrogenicity, and to assess the hazards associated with parabens to model aquatic organisms, Pimephales promelas and Daphnia magna. Parabens represent a class of understudied personal care products with estrogenic activity that have been detected in surface waters. MCF-7 and rainbow trout vitellogenin induction were found to be the most sensitive in vitro and in vivo assays of estrogenicity, respectively. Parabens were determined to not pose a hazard to aquatic organisms at levels that are environmentally relevant, based on the bioassay endpoints evaluated. A screening level assessment further identified estrogenic activity of select parabens to adult male P. promelas. This thesis demonstrated the utility of chemical toxicity distributions for determining sensitivities among toxicological models and for assessing those compounds for which environmental exposure data are limited.