Cattle chemical can return in the night

Compounds that help cows build bulk are supposed to breakdown in the environment. And they do, just not as permanently as scientists had thought.

Farmers use the steroid trenbolone acetate to beef up their cattle, which metabolize it into 17α-trenbolone, a chemical that disrupts the system that sends hormone signals in animals. Scientists thought the chemical and other digestive by-products of trenbolone acetate broke down more completely — and were therefore less of a risk — when exposed to sunlight.

But after cycling 17α-trenbolone and other related chemicals through simulated days and nights, a team of researchers found that the chemicals reassemble in dark, moderate temperatures. Higher temperatures the chemicals can reconverge even faster.

The results, published September 26 in Science, suggest that the hormone-system disruptors may be more abundant than thought in the environment, especially in lakes and rivers from agriculture run-off.

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