The environmental fate of anabolic steroid trenbolone acetate
Abstract
17β-trenbolone Acetate (TBA) is a synthetic anabolic hormone widely used in beef cattle across the U.S. TBA is administered as a subcutaneous implant and often in combination with 17β-estradiol (E2) for growth promotion in beef cattle. Implanted cattle excrete primarily 17α-trenbolone along with small amounts of 17β-trenbolone and trendione. Quantifying the fate of these hormones after being land-applied is important in assessing the potential risk to aquatic species. Therefore, sorption and degradation of 17α-trenbolone, 17β-trenbolone and trendione were measured for several agricultural soils and hormone concentrations were quantified in manure and manure-receiving lagoon effluents from TBA:E2-implanted beef cattle for 9 weeks after implants. Sorption correlates well to soil organic carbon (OC) content and is isomer dependent with average log OC-normalized distribution coefficients ( Koc, L/kg) of 2.77 ± 0.12 for 17α-trenbolone, 3.08 ± 0.1 for 17β-trenbolone and 3.38 ± 0.19 for trendione. Pseudo first-order aerobic degradation rates were determined for several temperature (5 to 35°C) and water availability (-0.03 to -1 MPa) combinations representing the range of environmental conditions expected in tile-drained agricultural fields. Under optimal conditions both isomers degraded to trendione in a similar manner with half lives (t½) in the order of a few hours to 0.5 d at applied concentrations from 0.05 to 1 mg/kg. Trenbolone degradation rates decreased with increasing applied concentrations. Trendione persisted longer than trenbolone. A small amount (≤ 1.5%) of trendione and 17α–isomer converted back to 17β-trenbolone. Microbial degradation rates decreased with decreasing water availability (i.e., more negative soil matric potential) and decreasing temperature. In manure from TBA:E2-implanted cattle, 17α-trenbolone was the most abundant androgen with the highest concentration observed of 3.6 mg/kg dry manure. For the estrogens, the highest concentrations were observed for estrone (3 mg/kg) and estriol (2.2 mg/kg). In lagoon water, 17α-trenbolone and estrone were detected in highest concentrations (1500 and 1700 ng/L respectively). Assuming even a 1 to 2 order dilution during transport to surface water, these hormone levels from land-applied effluents and manures could lead to concentrations in receiving waters that exceed some of the lowest observable effect levels reported for hormones (e.g., 10-30 ng/L).
Degree
Ph.D.
Advisors
Lee, Purdue University.
Subject Area
Animal sciences|Soil sciences|Organic chemistry
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