New Study: Hormones in Dairy Wastewater Persist for Years

Dairy cows© Wei Zheng

A new study has found that wastewater from large dairy farms contains notable concentrations of estrogenic hormones that, instead of breaking down, can persist for years. The unusual behavior, unknown to scientists before, involves estrogens quickly converting from one form to another in the absence of oxygen – resulting in halted biodegradation, and as an extra bonus, making them much harder to detect.

The study, led by researchers at the Illinois Sustainable Technology Center (ISTC), appears in the journal Environmental Science & Technology.

The problem starts when lactating cows create estrogenic hormones that are excreted in their waste, said ISTC senior research scientist Wei Zheng, leader of the study. In large confined animal feeding operations (CAFOs) the hormones end up in wastewater, (euphemistically called lagoons). The water is used to fertilize crops, and although there are federal regulations limiting certain agricultural nutrients from polluting rivers, streams, lakes or groundwater, the regulations do not protect groundwater and surface waters from contamination by animal hormones and veterinary pharmaceuticals.

Animal hormone concentrations in agricultural waste are 100 to 1,000 times higher than those detected in human sewage - and large dairy farms are one of the major sources of estrogens in the environment, according to Zheng.

"These estrogens are present at levels that can affect the [reproductive functions of] aquatic animals," Zheng said. Even low levels of estrogens can "feminize" animals that spend their lives in the water, for example, causing male fish to have low sperm counts or to develop female characteristics, compromising their ability to reproduce.

"Hormones that end up in surface or groundwater can pollute sources of drinking water for humans," Zheng said. "The estrogens may also be taken up by plants – a potential new route into the food chain," he added. "We need to develop a strategy to prevent these hormones from building up in the environment."

What to do? Support small dairy farms, limit your dairy, experiment with alternative dairy products:

New Study: Hormones in Dairy Wastewater Persist for Years
Even low levels of estrogens in water can "feminize" aquatic animals, undermining their ability to reproduce.

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