Endocrine Disrupters Found in Fish, Water In Potomac River Tributaries

Pesticides, flame retardants and personal-care products containing known or suspected endocrine-disrupting chemicals have been found in several tributaries to the Potomac River and in the smallmouth bass that inhabit them, the U.S. Geological Survey (USGS) announced on Jan. 17.

The discovery of a high incidence of intersex (male fish exhibiting female characteristics) in smallmouth bass of the Potomac River Basin led to the USGS investigation of water quality and wastewater discharge into the upper Potomac, and blood-plasma studies on this fish species. Data from the study will help focus further research of the occurrence of emerging contaminants, endocrine-disrupting compounds and intersex characteristics in smallmouth bass in the Potomac River tributaries.

In an organism, the endocrine system excretes hormones that govern many functions, including sexual and reproductive characteristics. Endocrine disrupters in the environment include pharmaceuticals in untreated wastewater and agricultural runoff. Agricultural, industrial and household products often contain compounds that mimic estrogen when ingested. Endocrine disrupters of this type may contribute to the high percentage of male smallmouth bass found in the Potomac that exhibit female characteristics.

"We analyzed samples of 30 smallmouth bass from six sites, including male and female fish without intersex and male fish with intersex," said Douglas Chambers, USGS scientist and lead investigator. "All samples contained detectable levels of at least one known endocrine-disrupting compound, including samples from fish without intersex."

Known or suspected endocrine-disrupting chemicals from pesticides, flame retardants and personal-care products also were present in water samples taken from all eight sites, including those where fish did not exhibit intersex. Wastewater from several sites that discharge municipal effluent or from sites contributing runoff was examined to identify point sources of these compounds. Antibiotics were found in wastewater samples, with municipal effluent having at least seven such compounds, but were not detected in water from other sites.

The reproductive anomalies in the Potomac's smallmouth bass population were discovered by accident. In 2003, scientists investigating massive fish kills and widespread lesions found oocytes, precursors of egg cells that females normally produce, while looking at tissues from the testes of male fish under the microscope.

High intersex occurrence in aquatic species has been documented at other locations in the United States and in Europe. It is not unique to the Potomac Basin, and not unique to smallmouth bass. Previous studies have found that known or suspected endocrine disrupters are widespread in the environment.

Research is under way to further define the occurrence of endocrine-disrupting compounds in the South Branch of the Potomac basin and to determine the potential for environmental mixtures of these compounds to interfere with normal endocrine function.

Additional information on the report, "A Reconnaissance for Emerging Contaminants in the South Branch Potomac River, Cacapon River, and Williams River Basins, West Virginia, April-October 2004," is available at http://pubs.usgs.gov/of/2006/1393.

This article originally appeared in the 01/01/2007 issue of Environmental Protection.

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