U.S. Geological Survey Identifies Intersex Fish Nationwide

(Beyond Pesticides, September 18, 2009)

Previously documented in the Potomac River, which flows through downtown Washington, DC, the occurrence of “intersex” fish is now found to be nationwide. U.S. Geological Survey (USGS) researchers published their study, “Widespread occurrence of intersex in black basses from U.S. rivers” in the online edition of Aquatic Toxicology.

USGS researchers examined 16 different species of fish across the U.S. between 1995 and 2004. The condition of intersex fish, male fish producing eggs, is most commonly found in smallmouth and largemouth bass. One third of male smallmouth bass and one fifth of the male largemouth bass are intersex.

Scientists tested sites in the Apalachicola, Colorado, Columbia, Mobile, Mississippi, Pee Dee, Rio Grande, Savannah, and Yukon River basins. Research shows intersex fish in approximately one-third of all examined sites. The only site where researchers found no intersex fish is the Yukon River basin.

While the study did not look for the causes for intersex fish, scientists believe endocrine disruptors, chemicals that interfere with the body’s hormonal systems, are certainly to blame.

“We know that endocrine-active compounds have been associated with intersex in fish, but we lack information on which fish species are most sensitive to such compounds, the way that these compounds interact to cause intersex, and the importance of environmental factors,” said Jo Ellen Hinck, the lead author of the paper and a biologist at the USGS Columbia Environmental Research Center. “Proper diagnosis of this condition in wild fish is essential because if the primary causes are compounds that disrupt the endocrine system, then the widespread occurrence of intersex in fish would be a critical environmental concern.”

While the government knows something is going wrong, it has yet to take any action to stop the contamination of water with endocrine disrupting chemicals. Environmentalists believe that given the severity of the situation, the Environmental Protection Agency (EPA), in consultation with USGS, should take a precautionary approach and begin phasing out suspected endocrine disruptors that contaminate the U.S. water supply while research continues. EPA announced in April 2009 that it is finally moving forward with the process, which experts call flawed, for screening endocrine disrupting chemicals, nearly 11 years after its deadline mandated by the Food Quality Protection Act of 1996. Beyond Pesticides believes the time for action is now.

Most scientists have suspected endocrine disruptors and synthetic estrogens, such as pesticides and birth control pills, from the beginning. Endocrine disruptors are a diverse group of several thousands of chemicals that are used in everything from pesticides and flame retardants to cosmetics and pharmaceuticals. Endocrine disruptors may be mistaken for hormones by the body and thus their presence may alter the function of hormones, either blocking their normal action or interfering with how they are made in the body. Since hormones regulate things like growth and body development, there is great potential for damage. In particular, some endocrine disruptors are mistaken for the female hormone estrogen. These estrogen mimics interfere with the reproductive system, causing infertility, malformed sexual organs, and cancer of sensitive organs.

When intersex fish were first discovered in the Potomac River, the USGS identified: atrazine, a common herbicide used in agriculture and on lawns that is already linked to sexual abnormalities in frogs; insecticides chlorpyrifos and endosulfan; the herbicide metolachlor; and two chemicals used to add fragrance to perfumes, soaps and other products, tonalide and galaxolide.

Disturbingly, there are many commonly used pesticides that are known or suspected endocrine disruptors, such as atrazine, 2,4-D, lindane, and permethrin. A recent study found that the commonly used lawn pesticide formulation Round-up, with the active ingredient glyphosate, causes damaging endocrine effects in fetuses. EPA does not currently evaluate or consider the endocrine disrupting properties of pesticides during registration or reregistration.

The environmental effects of these chemicals has been well-established: pseudo-hermaphrodite polar bears with penis-like stumps, panthers with atrophied testicles, hermaphroditic deformities in frogs, and male trout with eggs growing in their testes have all been documented as the probable result of endocrine-disrupting chemicals in the environment. Many scientists believe that wildlife provides early warnings of effects produced by endocrine disruptors, which may as yet be unobserved in humans.

Source: USGS Press Release News Room