Indiana Daily Student

Environmental exposure to hormones used in animal agriculture greater than expected

Research by an IU environmental scientist and colleagues at universities in Iowa and Washington found that potentially harmful growth-promoting hormones used in beef production are expected to persist in the environment at higher concentrations and for longer durations of time than previously thought, according to a press release.

“What we release into the environment is just the starting point for a complex series of chemical reactions that can occur, sometimes with unintended consequences,” Adam Ward, lead author of the study and assistant professor in the IU School of Public and Environmental Affairs, said in the release. “When compounds react in a way we don’t anticipate — when they convert between species, when they persist after we thought they were gone — this challenges our regulatory system.”

This study illustrates potential weaknesses in the United States’ system of regulating hazardous substances, which focuses on individual compounds and often fails to account for complex and sometimes surprising chemical reactions that occur in the environment, according to the release.

The published study “Coupled reversion and stream-hyporheic exchange processes increase environmental persistence of trenbolone metabolites,” focuses on the environmental fate of trenbolone acetate, or TBA, a potent synthetic analogue of testosterone, used to promote weight gain in beef cattle. The majority of beef cattle produced in the U.S. are treated with TBA or other growth hormones.

TBA and its byproducts are examples of increasingly concerning endocrine disrupter contaminants.

In the environment, they are capable of interfering with reproduction in fish and other aquatic life.

In regards to beef production, TBA is implanted in the ears of beef cattle. The cattle metabolize the compound to produce 17-alpha-trenbolone, an endocrine disrupter chemically similar to TBA. The metabolite makes its way to water sources via manure from feed lots or fertilizer.

Ward and his collaborators David Cwiertny, Colleen Brehm and Edward Kolodziej said they wanted to learn how much longer trenbolone might persist in the environment because of its unique reactivity and whether this added persistence matters for aquatic ecosystems.

Concentrations of TBA metabolites might be about 35 percent higher in streams than previously thought. The compounds persist longer, resulting in 50 percent more biological exposure than ?anticipated.

“These compounds have the potential to disrupt entire ecosystems by altering reproductive cycles in many species, including fish,” Ward said. “We expect impacts that extend through the aquatic food web.”

Studies by the U.S. Geological Survey and other agencies have found endocrine disrupters to be present in many streams, rivers and lakes, and several similar compounds have even been found in drinking water.

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