Endocrine Disruption
The ability of environmental contaminants to affect reproductive and developmental processes in fish and wildlife species has long been known. An increasingly persuasive body of evidence indicates that many of these chemicals may be causing such effects through interference and disruption of normal endocrine function. Field observations have correlated abnormal sex organ morphology, unusual sex hormone levels and ratios, and altered physiological and biochemical processes with exposure to environmental contaminants. These developmental end points are under the control of the endocrine system, lending support to the hypothesis that environmental contaminants may disrupt endocrine function.
The USGS Contaminant Biology Program investigates the exposure and effects of contaminants on fish and wildlife and focuses on Endocrine Disruption as a part of Toxicology component of the research. It closely collaborates with two other USGS programs - Toxic Substances Hydrology and the National Water Quality Assessment, which conduct research and monitoring (respectively) to determine the presence and chemical fate of contaminants in aquatic environments.
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What does the endocrine system do?
The cells, tissues, organs, and glands of the endocrine system secrete hormones that regulate development, reproduction, metabolism, behavior and homeostasis.
| Hormone |
Physiological function |
| insulin |
metabolism |
| estrogen |
reproduction |
| thyroid hormone |
growth |
| adrenaline |
stress response |
What do endocrine disrupter do?
Endocrine Disrupters interfere with the synthesis, secretion, transport, activity, or elimination of natural hormones. This interference can block or mimic hormone action, causing a wide range of effects.
| Endocrine-active chemical |
Physiological effect |
| DDT |
disrupts function of sex metabolites or hormones, causes eggshell thinning, and other problems |
| PBDEs (Polybriminated diphenyl ether flame retardants) |
disrupts thyroid function |
| Bisphenol A |
estrogenic |
How widespread is endocrine disruption?
This question continues to plague scientists and environmental managers. Though there are many examples of endocrine disruption in the environment, determining its prevalence is a much more difficult task. USGS continues to work on different approaches to solving this problem using models, land use information and nationwide reconnaissance efforts, but considerably more effort will be needed before a clear understanding emerges. |
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River otter baculi. USGS biologists in Corvallis, OR, studied river otters in the lower Columbia River and found a correlation between the size of the baculum, a bone found in the penises of certain mammal groups, and PCB concentrations.
Egg and sperm cells of fish. USGS biologists have found "intersex" fish (those with both eggs and sperm) in many aquatic environments throughout the country.
August 2006 testing at three tributaries emptying into the Potomac revealed that more than 80 percent of all male smallmouth bass found were growing eggs, according to Vicki S. Blazer, a fish pathologist within the U.S. Geological Survey.
Listen to USGS CoreCast "Endocrine Disruption: Sex-Changing Fish and More" to learn more about the effects humans are having on aquatic life by introducing chemicals and waste products into lakes and streams.
Featured Publications
Lead authors Dr. David Alvarez, Columbia Environmental Research Center, Columbia, MO, and Dr. Luke Iwanowicz, National Fish Health Research Laboratory, Kearneysville, WV, and their co-authors, detail the reproductive health of the bass and the seasonal occurrence of persistent and emerging organic contaminants. Further sampling is also being conducted in the mainstream upper Potomac River and the tidal area downriver of Washington, D.C. Partners in these studies include the U.S. Fish and Wildlife Service and the Maryland Department of Natural Resources Fisheries Service. (David Alvarez, Columbia, MO 573-441-2970)
 Iwanowicz, L.R., Blazer, V.S., Guy, C.P., Pinkney, A.E., Mullican, J.E. and Alvarez, D.A. 2009, Reproductive health of bass in the Potomac, USA, drainage: Part 1. Exploring the effects of proximity to wastewater treatment and plant discharge. Reproductive health of bass in the Potomac, USA, drainage: Part 1. Exploring the effects of proximity to wastewater treatment and plant discharge. Environmental Toxicology and Chemistry, 28(5): 1072-1083.
Alvarez, D.A., Cranor, W.L., Perkins, S.D., Schroeder, V.L., Iwanowicz, L.R., Clark, R.C., Guy, C.P., Pinkney, A.E., Blazer, V.S. and Mullican, J.E. 2009, Reproductive health of bass in the Potomac, USA, drainage: Part 2. Seasonal occurrence of persistent and emerging organic contaminants (91609)
Reproductive health of bass in the Potomac, USA, drainage: Part 2. Seasonal occurrence of persistent and emerging organic contaminants. Environmental Toxicology and Chemistry, 28(5): 1084-1095.
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U.S. Department of the Interior |
U.S. Geological Survey
