Cow Hormones in the Water

by Project Censored

A study published by the journal Environmental Science & Technology in May 2012 reported that large dairy farms are a “primary source” of estrogen contamination in the environment.

Lactating cows excrete estrogen in their waste, which is thrown into wastewater pools and later used as crop fertilizer. The study found that when the estrogen is exposed to low-oxygenated environments, as in the dairy wastewater pools, the hormones can survive for months or even years.  (By contrast, estrogen exposed to open air quickly breaks down to harmless byproducts.)  Researchers found three primary estrogens in the wastewater, and further analysis revealed that, because of the rapid conversion from one form estrogen to another, these hormones do not degrade, but persist in the environment.

The study’s leading research scientist, Wei Zheng, noted that they found “hormone concentrations in livestock wastes are 100 to 1,000 times higher than those emitted from the plants that treat human sewage.” Nonetheless, dairy farm hormone pollution is currently unregulated.   According to Zheng, strategies to “decrease the build up of these hormones in the environment” are urgently needed.

Minor levels of estrogen affect marine life, leading to mutations and potential population collapses.  In humans, increases in estrogen intake produce harmful, possibly deadly side effects including weight gain, migraines, poor sleep patterns, increased risk of blood clots, reduced oxygen levels in cells, and increased risk of cancer and trigger autoimmune diseases.[1]


Source: Lindsey Blomberg, “Cow Hormones in the Water,”  E-The Environmental Magazine, June 11, 2012,


Note: [1]


Student Researcher: Carissa Callas (Santa Rosa Junior College)

Faculty Evaluator: Susan Rahman (Santa Rosa Junior College)