title: Trenbolone acetate metabolite transport in rangelands and irrigated pasture: observations and conceptual approaches for agro-ecosystems.
abstract: To assess the relative ecological risks of trenbolone acetate (TBA) use in agro-ecosystems, we evaluated the spatiotemporal dynamics of TBA metabolite transport during irrigation and rainfall events. Within a pasture, TBA-implanted heifers (40 mg TBA, 8 mg estradiol) were briefly penned (24 h) at high stocking densities (500 animal units (AU)/ha), prior to irrigation. Irrigation runoff concentrations of 17α-trenbolone (17α-TBOH) 0.3 m downslope were 11 ng/L in the wetting front, but quickly decreased to ∼0.5 ng/L, suggesting mass transfer limitations to transport. At 3 and 30 m downslope, efficient attenuation of 17α-TBOH concentrations is best explained by infiltration and surface partitioning. At plot scales, transport through vegetated filter strips resulted in <0.5-7 ng/L 17α-TBOH concentrations in rainfall-induced runoff with partial subsequent attenuation. Thus, even under intense grazing scenarios, TBA-metabolite transport potential is expected to be low in rangelands, with ecological risks primarily arising from uncontrolled animal access to receiving waters. However, 17α-TBOH concentrations in initial runoff were predicted to exceed threshold levels (i.e., no observed adverse effect levels [NOAELs]) for manure concentrations exceeding 2.0 ng/g-dw, which occurs throughout most of the implant life. For comparison, estrone and 17β-estradiol were modeled and are likely capable of exceeding NOAELs by a factor of ∼2-5 in irrigation runoff, suggesting that both endogenous and exogenous steroids contribute to endocrine disruption potential in agro-ecosystems.
authors.affiliation: Department of Civil and Environmental Engineering, University of Nevada-Reno , MS 0258, Reno, Nevada 89557, United States.
authors.forename: Gerrad D
authors.initials: GD
authors.lastname: Jones
authors.forename: Peter V
authors.initials: PV
authors.lastname: Benchetler
authors.forename: Kenneth W
authors.initials: KW
authors.lastname: Tate
authors.forename: Edward P
authors.initials: EP
authors.lastname: Kolodziej
mesh_terms: D000383:Agriculture / Q000379:methods; D045930:Anabolic Agents / Q000032:analysis / Q000493:pharmacokinetics; D000818:Animals; D002417:Cattle; D004958:Estradiol / Q000032:analysis* / Q000493:pharmacokinetics; D004967:Estrogens / Q000032:analysis* / Q000493:pharmacokinetics; D004970:Estrone / Q000032:analysis*; D005260:Female; D008372:Manure / Q000032:analysis; D008962:Models, Theoretical; D011891:Rain; D012989:Soil Pollutants / Q000032:analysis*; D014204:Trenbolone Acetate / Q000031:analogs & derivatives* / Q000032:analysis* / Q000493:pharmacokinetics
chemical_list: D045930:Anabolic Agents; D004967:Estrogens; D008372:Manure; D012989:Soil Pollutants; D004970:Estrone; D004958:Estradiol; D014204:Trenbolone Acetate