Submitted to: Journal of Hazardous Materials
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/16/2013
Publication Date: 9/15/2013
Publication URL: http://handle.nal.usda.gov/10113/59342
Citation: Bai, X., Casey, F.X.M., Hakk, H., Desutter, T.M., Oduor, P.G., Khan, E. 2013. Dissipation and transformation of 17B-estradiol-17-sulfate in soil-water systems. Journal of Hazardous Materials. 260:733-739. Interpretive Summary: Endocrine disrupting estrogens are constantly, and at high levels, being eliminated by production animals as non-toxic, water-soluble metabolites, known as conjugates. Unexpected is the widespread occurrence of non-water soluble, but biologically active, deconjugated estrogens in surface waters. We hypothesized that after application to agricultural soil, estrogen conjugates are transported by water through soil, and then deconjugated to parent estrogen by soil bacteria. If true, this hypothesis would provide a mechanism for estrogen transport into surface and ground waters. In laboratory studies, we added a conjugated estrogen to various agricultural soils saturated with water and studied the fate of the conjugate over time. Consistent with our hypothesis, partial degradation of the estrogen conjugates to free estrogens did occur. Depending on the type of soil, estrogen conjugates could persist in water much longer than the parent estrogens (the parent estrogens rapidly absorb to soils). Our findings suggest that the common practice of manure injection into soil might enhance the movement and entry of estrogens into water systems.
Technical Abstract: Estrogen conjugates are known to be precursors of endocrine-disrupting free estrogens, e.g. 17B-estradiol (E2) and estrone (E1), in the environment. This study investigated the fate of a sulfate conjugated estrogen, 17B-estradiol-17-sulfate (E2-17S), in agricultural soils using laboratory batch studies. 17B-Estradiol-17-sulfate has been found in animal manures and fields receiving manure applications. The batch experiments were designed to compare soils with different organic carbon (OC) content (1.29% for topsoil versus 0.26% for subsoil) under different initial concentrations of radiolabelled E2-17S (0.6, 2.9, 8.9, and 30 mg/L). The dissipation of E2-17S was more rapid from the aqueous layer of the topsoil, but E2-17S could be detected at 14 d in the aqueous layer for both soils. The dissipation half-lives (DT50) for E2-17S in the aqueous layer ranged from 4.9 to 26 h for the topsoil and 64 to 173 h for the subsoil at the various initial concentrations. The major transformation pathway in the aqueous phase was hydroxylation, yielding mono- and di-hydroxy-E2-17S (OH-E2-17S and diOH-E2-17S) metabolites. Free estrogens, E2 and E1, were observed at low concentrations (~1% of applied dose) on the sorbed phase, indicating that deconjugation/hydrolysis occurred. Although deconjugation was not a major pathway, E2-17S could be a precursor of free estrogens in the environment.