SAN FRANCISCO, California -- Oral contraceptives often take the blame for estrogen pollution in rivers, lakes, and reservoirs, but a new meta-study from researchers at the University of California, San Francisco, reports that oral contraceptives are not the source of most of the estrogens found in waterways Environ. Sci. Technol., DOI: 10.1021/es1014482).
Estrogen in water has raised concerns because, in laboratory and field tests, the synthetic estrogen found in birth control pills disrupts reproduction in several fish species, such as the South European roach (Rutilus rutilus). The hormone can trigger 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.
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 postdoctoral fellow Amber Wise and her colleagues reviewed 82 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 for other estrogen sources that 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. 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 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 make up 15% of the estrogens in the water. The data suggest 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 probably contribute to feminizing 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 says 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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