Hormones in Animal Agriculture May Persist in the Environment Far Longer Than Expected

Most people are aware that hormones are used in animal agriculture. Now, though, scientists have found that the environmental exposure to these hormones may be greater than anyone realized.

"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," said Adam Ward, lead author of the new study, in a news 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."

In this latest study, the researchers focused on the environmental fate of trenbolone acetate, or TBA. This highly potent synthetic analogue of testosterone is used to promote weight gain in beef cattle. In fact, a majority of beef cattle produced in the U.S. are treated with TBA or one of five other growth hormones approved for use in animal agriculture.

The compound actually breaks down rapidly when exposed to sunlight, which means that regulators believed that it had a low environmental risk. That said, scientists have found that the breakdown products revert back to 17-alpha-trenbolone in the dark, which means that the compound can persist in stream environments.

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

The findings reveal the importance of regulating these compounds in the environment. In fact, the study suggests that it may be time to update regulatory approaches to better include a wide range of findings from modern research.

"The next step is thinking about unexpected reactions that occur in the environment and how we can manage the diverse group of potential products and their joint effect on the environment and human health," said Ward.

The findings are published in the journal Nature Communications.

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