Place-based screening of mixtures of dominant emerging contaminants measured in Lake Michigan using zebrafish embryo gene expression assay.

Determining impacts of emerging contaminants is difficult due to the different concentrations of mix- tures of these chemicals over a landscape. Assessment approaches need to account for absorption, dis- tribution, metabolism and excretion of the chemicals in an organism, and potential crosstalk between molecular pathways. The goal of this study was to assess the utility of employing a modified zebrafish embryo toxicity (ZFET) assay that assesses morphological alterations and measurements of estrogen- associated mRNA transcripts, to exposure of a mixtures of chemicals at concentrations measured in several locations in Lake Michigan. The 5 pharmaceuticals in this study were carbamazepine, diltiazem, fluoxetine, gemfibrozil and metformin. Exposures consisted of 4 concentrations of each individual chemical, mixture concentrations measured at seven locations in Lake Michigan, or 17b-estradiol. The relative expression of Estrogen Receptor-alpha, brain aromatase (CYP19A2), and gonadotropin