Degradation and metabolite formation of 17ß-estradiol-3-glucuronide and 17ß-estradiol-3-sulphate in river water and sediment17

Authors: MA, LI - University Of California; Yates, Scott

Submitted to: Water Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/27/2018
Publication Date: 4/3/2018
Citation: Ma, L., Yates, S.R. 2018. Degradation and metabolite formation of 17ß-estradiol-3-glucuronide and 17ß-estradiol-3-sulphate in river water and sediment17. Water Research. 139:1-9. https://doi.org/10.1016/j.watres.2018.03.071.
DOI: https://doi.org/10.1016/j.watres.2018.03.071

Interpretive Summary: There is increasing concern over the presence of steroidal hormones in environment and agricultural systems. There can be many adverse effects from exposure to hormones, which include intersexuality, masculinization, and reproductive and behavioral problems. The movement of hormones from urban and agricultural systems to surface water poses potential risks to wildlife and humans. Also, hormonal chemicals moving through environment/agricultural systems may enter the food chain impacting public health. Therefore, highly accurate and reliable information is needed on transformation of hormones in soil and water at environmentally-relevant concentrations to better understand its environmental fate. Experiments were conducted to determine the degradation rate of conjugated hormones. The study revealed that estrogen conjugates, together with their degradation products, could persist in water for two weeks or more. However, the degradation was much faster in river sediment where a near complete transformation (> 99.9%) was observed within one to two days at low initial concentration (0.01µg/g). Degradation was found to be very rapid in sediments due to relatively high population densities of microorganisms. This study also showed, for the first time, the existence of new, and important, intermediates. Some of the metabolites appeared to be labile since they existed in a transitional manner, but their role in the biodegradation of estrogen conjugates remains to be elucidated. This study provides useful information on the behavior of hormones in the environment and can be used in an effort to develop new strategies to mitigate hormone contamination. The new degradation rates and information on transformation should be of interest to researchers, regulators, commodity groups, farmers, and the public.

Technical Abstract: Laboratory degradation tests with two model estrogen conjugates, 17ß-estradiol-3-glucuronide (E2-3G) and 17ß-estradiol-3-sulphate (E2-3S), using river water and sediment as inoculum under aerobic conditions were investigated. Throughout the 14-day incubation, degradation of E2-3G in river water, at environmentally-relevant level (25'ng/L), obeyed first-order kinetics with the formation of 17-ß estradiol and estrone; in contrast, E2-3S was slowly converted to estrone-3-sulphate stoichiometrically. Degradation of the two conjugates across the spiking concentrations (0.01–1'µg/g) was much faster in sediment than in river water where 25'ng/L of conjugate standards were spiked, possibly due to relatively high population densities of microorganisms in sediment. De-conjugation of the thio-ester bond at C-3 position and oxidation at C-17 position were the predominant degradation mechanisms for E2-3G and E2-3S, respectively, with negligible presence of metabolites estrone-3-glucuronide for E2-3G and 17ß-estradiol for E2-3S. In addition, delta-9(11)-dehydroestrone and 6-ketoestrone were determined as new metabolites of the two conjugates. Also, a lactone compound, hydroxylated estrone and a few sulfate conjugates were tentatively identified. With the observation of new metabolites, biodegradation pathways of E2-3G and E2-3S were proposed. The formation of new metabolites may pose unknown risks to aquatic biota.