Plain English Summary

Existing regulatory frameworks for aquatic pollutants in the United States are idealized, often lacking mechanisms to account for contaminants characterized by (1) bioactivity of both the parent and transformation products and (2) reversible transformations (that is, metastable products) driven by chemical or physical heterogeneities. Here, we modelled a newly discovered product-to-parent reversion pathway for trenbolone acetate (TBA) metabolites. We show increased exposure to the primary metabolite, 17a-trenbolone (17a-TBOH), and elevated concentrations of the still-bioactive primary photoproduct hydroxylated 17a-TBOH, produced via phototransformation and then converted back to 17a-trenbolone in perpetually dark hyporheic zones that exchange continuously with surface water photic zones. The increased persistence equates to a greater potential hazard from parent-product joint bioactivity at locations and times when reversion is a dominant trenbolone fate pathway. Our study highlights uncertainties and vulnerabilities with current paradigms in risk characterization. DOI: 10.1038/ncomms80671

Abstract

Existing regulatory frameworks for aquatic pollutants in the United States are idealized, often
lacking mechanisms to account for contaminants characterized by (1) bioactivity of both the
parent and transformation products and (2) reversible transformations (that is, metastable
products) driven by chemical or physical heterogeneities. Here, we modelled a newly
discovered product-to-parent reversion pathway for trenbolone acetate (TBA) metabolites.
We show increased exposure to the primary metabolite, 17a-trenbolone (17a-TBOH), and
elevated concentrations of the still-bioactive primary photoproduct hydroxylated 17a-TBOH,
produced via phototransformation and then converted back to 17a-trenbolone in perpetually
dark hyporheic zones that exchange continuously with surface water photic zones. The
increased persistence equates to a greater potential hazard from parent-product joint
bioactivity at locations and times when reversion is a dominant trenbolone fate pathway.
Our study highlights uncertainties and vulnerabilities with current paradigms in risk
characterization.
DOI: 10.1038/ncomms8067
1

Citation

Ward, A.S., Cwiertny, D.M., Kolodziej, E.P., and Brehm, C.C. (2015): Coupled reversion and stream-hyporheic exchange processes increase environmental persistence of trenbolone metabolites. Nature Communications. DOI: 10.1038/ncomms8067

This Paper/Book acknowledges NSF CZO grant support.