Persistence and pathways of testosterone dissipation in agricultural soil

The persistence and pathways of dissipation of testosterone in three agricultural soils were examined in laboratory microcosm incubations at different soil moistures (1.7-39%) and temperatures (4-30 degrees C) using (14)C- and (3)H-labeled and unlabeled testosterone. Sterilized loam was also examined to assess possible abiotic pathways. Extractable (14)C decreased rapidly for all three soils at 30 degrees C with times to dissipate 50% of material (DT(50)) ranging from 8.5 to 21 h. Respired (14)CO(2) accounted for approximately 50% of the applied (14)C after 120 h. Androgenic activity of soil extracts declined faster than the extractable (14)C levels demonstrating that testosterone was not being converted to compounds with greater activity. Dissipation rates of nonvolatile, extractable (3)H in loam at 7, 15, and 39% moisture were similar, but the rate in air-dried loam (1.7% moisture) was significantly reduced. High performance liquid chromatography (HPLC) analysis of extracts of (14)C-testosterone-treated loam incubated at 30 degrees C for 6 h revealed that the (14)C was distributed among the remaining testosterone and three major metabolites (4-androstene-3,17-dione, 5alpha-androstane-3,17-dione, and 1,4-androstadiene-3,17-dione), which accounted for 48.7, 23.7, and 9.6% of the remaining (14)C, respectively. Periodic analysis of soil incubated at 23, 12, and 4 degrees C showed that the rates of testosterone dissipation and metabolite appearance and subsequent dissipation were temperature dependent with rates decreasing with decreasing temperature. In sterilized loam, 4-androstene-3,17-dione was the only metabolite detected. We conclude that testosterone is rapidly and thoroughly biodegraded in agricultural soils under a range of conditions typical of a temperate growing season and thus is unlikely to pose a long-term risk to adjacent aquatic environments.