ARS | Publication request: Persistence and Fate of 17beta-estradiol and testosterone in agricultural soils

Submitted to: Chemosphere
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 23, 2006
Publication Date: March 1, 2007
Citation: Fan, Z., Casey, F.X., Hakk, H., Larsen, G.L. 2007. Persistence and Fate of 17beta-estradiol and testosterone in agricultural soils. Chemosphere 67(5):886-895.

Interpretive Summary: The two primary natural hormones estradiol (female hormone) and testosterone (male hormone) are constantly being released into the environment by excretion from man and animals in their urine and feces. The goal of this study was to examine the persistence and fate of these hormones in soils. Soil incubation experiments with native and sterilized soils in the presence or absence of air (oxygen) were conducted using estradiol and testosterone. The results indicated that 6% of the estradiol and 63% of testosterone could be mineralized to carbon dioxide in native soils in the presence of oxygen. When oxygen was excluded, 2.19% of testosterone and no estradiol were converted to methane in the soil incubations. Essentially, no mineralization of either testosterone or estradiol to carbon dioxide occurred in sterilized soils in the presence or absence of oxygen. Results also indicated that estradiol could be transformed to an unidentified compound through chemical processes not involving the soil bacteria; however, estradiol was only converted to estrone, a metabolite of estradiol, when the soil bacteria were present. Results also indicated that testosterone was degraded, but only in the presence of soil bacteria. These experiments also demonstrated that assumed risks of estrogenic hormones in the environment might be over-estimated because incorporation and/or binding to the soil's humic component (an organic fraction in soil), which was shown to immobilize the majority of the estrogenic hormones, and thereby reduce their bioavailability and toxicity.

Technical Abstract: Steroidal hormones are constantly released into the environment by man-made and natural sources. The goal of this study was to examine the persistence and fate of 17beta-estradiol and testosterone, the two primary natural hormones. Incubation experiments were conducted under aerobic and anaerobic conditions using [4-14C]-radiolabeled17beta-estradiol and testosterone. The results indicated that 6% of 17beta-estradiol and 63% of testosterone could be mineralized to 14CO2 in native soils under aerobic conditions. In native soils under anaerobic conditions, 2.19% of testosterone and no 17beta-estradiol was methanogenized to 14CH4. Essentially, no mineralization of either testosterone or 17beta-estradiol to 14CO2 occurred in autoclaved soils under aerobic or anaerobic condition. Results also indicated that 17beta-estradiol could be transformed to an unidentified polar compound through abiotic chemical processes; however, 17beta-estradiol was only oxidized to estrone via biological processes. The TLC results also indicated that testosterone was degraded, not by physical-chemical processes but, by biological processes. Results also indicated that the assumed risks of estrogenic hormones in the environment might be over-estimated due to incorporation and/or binding to the soil's humic substances, which can immobilize a majority of estrogenic hormones and, thereby, reduce their bioavailability and toxicity.