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NCCOS Project

Determining the Cause of Endocrine Disruption in the Tributaries of the Shenandoah River

This project began in March 2010 and was completed in September 2013

Along with colleagues from the U.S. Geological Survey and Virginia Polytechnic Institute, we placed passive water samplers in the Shenandoah River in Virginia to determine which chemicals may be associated with the widespread endocrine disruption seen in fish, particularly smallmouth bass.

Why We Care
Fish in the Shenandoah are exposed to inputs from a variety of land-use activities, ranging from wastewater treatment to agricultural operations. Investigations prompted by fish kills revealed that many of the male smallmouth bass were feminized, an indicator of endocrine disruption. There are many kinds of endocrine disruptors, ranging from some types of detergent additives to pesticides to industrial chemicals and even natural hormones that are discharged, for example, from wastewater treatment facilities.

The endocrine disruption in male smallmouth bass in the Shenandoah was indicated by the appearance of immature eggs embedded in the reproductive tissues of males. (Similar endocrine disruptions have been detected in smallmouth bass in the upper Potomac River.) While the presence of a few immature eggs may not have much of an impact, higher numbers of eggs could prevent reproductive ability.

Moreover, endocrine disruption in fish could point to larger risks for humans, as both the Shenandoah and the upper Potomac Rivers are sources of drinking water locally and further downstream in the Washington, DC, area. It is possible that whatever chemicals are affecting the fish could also affect humans.

What We Are Doing
To begin to understand the chemicals that may be associated with the observed endocrine disruption, we placed a series of passive water samplers (or POCIS) in tributaries to the Shenandoah River in 2010, in areas where endocrine disruption had been observed and where fish had been collected. In addition, we are conducting laboratory tests to measure the estrogenicity—the ability to mimic the female hormone estrogen—of the waters in these areas.

What We Are Finding
We are currently analyzing the data from the passive water samplers to assess chemicals present in the water column that may be contributing to the observed endocrine disruption in fish. The results from this and follow up work will be used to better understand the causes of the endocrine disruption in the fish and may lead to modifications in land-use activities in these and other areas to reduce the input and effects of endocrine disruptors.

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