A numerical model estimates the potential impact of environmental processes on contaminant fate of growth-promoting hormones used in beef production and leads the authors to believe they may persist in the environment at higher concentrations and for longer durations than previously thought - and they also believe their model illustrates potential weaknesses in the U.S. system of regulating hazardous substances, which focuses on individual compounds and but cannot always account for complex and sometimes surprising chemical reactions that occur in the environment
The ecologists focus on the environmental fate of trenbolone acetate, or TBA, a synthetic anabolic steroid sometimes used to promote weight gain or maintain weight during transport in beef cattle. There haven't been any studies showing that the trace amounts of trenbolone acetate can be harmful, they remain within naturally occurring limits, but there is some concern that over time it can make its way to streams and rivers via manure that washes from feedlots or is applied to land as fertilizer, even though it breaks down rapidly when exposed to sunlight.
The generic term 'endocrine disruptor' has been applied to it, and is by these authors, but the study did not test for endocrine disruption nor has it been shown in 30 years of testing. Still, one study in 2013 did claim that the breakdown products reverted back to 17-alpha-trenbolone in the dark so might remain in the shallow streambed where stream water mixes with groundwater, known as the hyporheic zone. And it is an endocrine disruptor at realistic levels (rather than 10,000 shots of Scotch levels) the model might lead to improvements in testing.
Until then, it is a rather tenuous daisy chain, since there have been 2 trillion cattle grown using TBA and no fish have been endocrinally disrupted by it, but Adam Ward, lead author of the study and assistant professor in the Indiana University Bloomington School of Public and Environmental Affairs, and collaborators wanted to estimate how much longer trenbolone may persist in the environment if this unique reactivity is real, and whether this added persistence matters for aquatic ecosystems.
Their mathematical model says that concentrations of TBA metabolites may be about 35 percent higher in streams than previously thought. And the compounds persist longer, resulting in 50 percent more biological exposure than anticipated.
If that is true, it might be a problem, at least in the volumes that beef cattle excrete. Nonetheless, rather than Ward takes their model and runs with the endocrine disruption conclusion. "These compounds have the potential to disrupt entire ecosystems by altering reproductive cycles in many species, including fish. We expect impacts that extend through the aquatic food web."
Yes, especially after a trillion steers. But one of the key papers claiming endocrine disruption in frogs was shown to have no data and was rejected by the EPA, it never went through peer review, but ever since there have been concerns about endocrine disruption, to an extent where to even imply it is environmental guilt, even if it is not science.
Citation: Adam S. Ward, David M. Cwiertny, Edward P. Kolodziej, Colleen C. Brehm, 'Coupled reversion and stream-hyporheic exchange processes increase environmental persistence of trenbolone metabolites', Nature Communications 6, Article number: 7067 08 May 2015 doi:10.1038/ncomms8067
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