Ethynyl estradiol 3-β-D-glucuronide is a metabolite of ethynyl estradiol that can be detected in urine.1,2It is used as a marker of estrogen contamination in fresh and saltwater.2 1.Hadd, H.E., Slikker, W., Jr., and Helton, E.D.The synthesis and characterization of the glucopyranosiduronic acids of 17a-ethynylestradiol-17bJ. Steroid Biochem.13(9)1107-1114(1980) 2.Griffith, D.R., Soule, M.C.K., Eglinton, T.I., et al.Steroidal estrogen sources in a sewage-impacted coastal oceanEnviron. Sci.: Processes Impacts18(8)931-1106(2016)