Male smallmouth and largemouth bass in the Potomac have recently started developing distinctly female characteristics, such as development of eggs inside their sex organs. The first discovery of the "intersex" fish was in 2003, and since then they have been found in waters hundreds of miles away from the original find in a West Virginia stream.
Scientists say they are unclear on an exact cause of the mutations, but many speculate that waterborne contaminants in the Potomac -- which millions of residents draw their tap water from -- are altering the animals' reproductive systems.
A study conducted last fall by Vicki S. Blazer, a fish pathologist with the U.S. Geological Survey, found that more than 80 percent of the male smallmouth bass collected from three sites -- the Shenandoah River in Virginia and the Monocacy River and Conococheague Creek in Maryland -- were growing eggs.
Blazer's research found that water tests of the upper Potomac revealed low levels of pollutants known to disrupt the endocrine system, which is responsible for natural chemical signals in the body. However, scientists cannot pinpoint the exact cause of the mutation, and speculate that it could be human estrogen from sewage or a combination of unknown contaminants in the water. Scientists are unsure if and how the polluted water will affect humans.
Critics of the U.S. Environmental Protection Agency (EPA) say the agency has been slow at identifying endocrine disruptors in public waters -- a requirement passed by Congress a decade ago. Ten years later, the EPA has not tested a single chemical, according to its officials, who say the testing program is "very difficult."
"The U.S. population is now taking part in a grand medical experiment involving chemical hormone disruptors," explains Mike Adams, a consumer health advocate. "And today's skyrocketing rates of hormone-related cancers such as prostate cancer and breast cancer are undoubtedly one side effect of this experiment," he said. "If the public is currently drinking from the same waters that make fish have two sets of sex organs, there are bound to be more health surprises to come."