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Environment

Hunting For Estrogen In Drinking Water

Water Pollution: The birth control pill is responsible for only a small fraction of the hormone found in waterways

by Sara Peach
September 30, 2010

THE PILL
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Credit: Wikimedia Commons
Researchers find that oral contraceptives are not the source of most of the estrogens in drinking water.
Credit: Wikimedia Commons
Researchers find that oral contraceptives are not the source of most of the estrogens in drinking water.

Oral contraceptives often take the blame for estrogen pollution in rivers, lakes and reservoirs. In laboratory and field tests, the synthetic estrogen found in birth control pills triggers male fish to develop female reproductive organs and to produce eggs. And researchers have connected estrogens in drinking water to human fertility problems and cancers.

But in a new meta-study, researchers at the University of California, San Francisco report that oral contraceptives are not the source of most of the estrogens found in waterways (Environ. Sci. Technol., DOI: 10.1021/xxxxxxx).

Nearly 11 million American women use oral contraceptives, according to the Guttmacher Institute, a nonprofit organization that researches sexual and reproductive issues. Most contraceptives contain a mixture of synthetic estrogen and progestin. These chemicals flow into wastewater treatment systems via urine and feces.

But estrogen-like chemicals also enter waterways from other sources, such as large-scale animal farms, landfills, and non-birth-control pharmaceuticals. Also, people of both sexes and all ages excrete natural estrogens.

To better understand the sources of estrogens in drinking water, UC San Francisco professor Amber Wise and her colleagues reviewed more than seven dozen studies. Using the data they gathered, the researchers estimated that ethinylestradiol, the most commonly used synthetic estrogen in the birth control pill, likely accounts for less than 1% of the total estrogens excreted by Americans. In addition, the researchers found evidence that other estrogen sources could play an important role in contaminating surface waters.

For example, according to the National Health and Nutrition Examination Survey, American health care providers wrote 43 million prescriptions for hormone-replacement therapy in 2007, about four times the number of prescriptions for oral contraceptives. Hormone-replacement therapies contain conjugated equine estrogens, which have been shown to induce estrogenic effects in fish at low concentrations. Some cancer treatments and veterinary medicines also contain estrogens.

Meanwhile, scientists have measured large quantities of estrogens produced by plants called phytoestrogens in wastewater streams near soy milk and biodiesel factories.

The UC San Francisco researchers also found that runoff from large animal farms could contribute to waterway contamination, in part because – unlike household waste – livestock effluents are untreated. A study conducted in the United Kingdom estimated that even if only 1% of the estrogens produced by farm animals reached waterways, they would be responsible for 15% of the measured estrogens in the water. The data suggests that animal farm runoff should be treated before being released into the environment, Wise says.

Karen Kidd, a biologist at the University of New Brunswick in Canada, says that in addition to estrogens, chemicals that interfere with testosterone are probably contributing to the feminization of male fish in some rivers.

"What happens in the fish will really depend on the total mixture that they are being exposed to," she says.

But Wise points out that there are still many suspected estrogenic chemicals that researchers do not check for in drinking water: "We don't even know exactly what chemicals to watch for, much less where they're all coming from."

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