In vitro bioassays are sensitive, effect-based tools used to quantitatively screen for chemicals with nuclear receptor activity in environmental samples. We measured in vitro estrogen (ER), androgen (AR), and glucocorticoid receptor (GR) activity, along with a broad suite of chemical analytes, in streamwater from 35 well-characterized sites (3 reference and 32 impacted) across 24 states and Puerto Rico. ER agonism was the most frequently detected with nearly all sites (34/35) displaying activity (range, 0.054-116 ng E2Eq L). There was a strong linear relationship (r = 0.917) between in vitro ER activity and concentrations of steroidal estrogens after correcting for the in vitro potency of each compound. AR agonism was detected in 5/35 samples (range, 1.6-4.8 ng DHTEq L) but concentrations of androgenic compounds were largely unable to account for the in vitro activity. Similarly, GR agonism was detected in 9/35 samples (range, 6.0-43 ng DexEq L); however, none of the recognized GR-active compounds on the target-chemical analyte list were detected. The utility of in vitro assays in water quality monitoring was evident from both the quantitative agreement between ER activity and estrogen concentrations, as well as the detection of AR and GR activity for which there were limited or no corresponding target-chemical detections to explain the bioactivity. Incorporation of in vitro bioassays as complements to chemical analyses in standard water quality monitoring efforts would allow for more complete assessment of the chemical mixtures present in many surface waters.
For all experiments, the concentrations of ethanol in the feed liquid, bottoms liquid, and permeate vapor condensate were determined using a gas chromatograph (GC, Agilent 6890) equipped with a Flame Ionization Detector (FID) with DI water dilution, as necessary, for the concentration to be in the calibrated range. Ethanol and water were quantitated in the feed vapor and retentate vapor condensates using a thermal conductivity detector (TCD) on the same GC using anhydrous 1-propanol (Sigma Aldrich) as a diluent. For experiments with the fermentation broth, all five samples were subjected to an additional set of analytical procedures to measure the concentration of the target analytes. Based on earlier scoping experiments and analyses with a
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