Feminised Fish: a Mystery Inside an Enigma

Since 2004, scientists from the U.S. Fish and Wildlife Service and the U.S. Geological Survey have been trying to solve the mystery of why the Potomac’s fish exhibit biological characteristics of both males and females, writes Alan S. Kolok. Aquatic Toxicology Laboratory, University of Nebraska at Omaha. According to his article, published by Environmental Health News, since it has been well documented in laboratory studies that exposure to water pollutants can create intersex animals, the attempt to link a chemical contaminant to it is certainly prudent. However, an update published in the Washington Post on April 22 highlights the fact that relationships between organic pollutants and intersex creatures can be very difficult to establish.

One of the first places that the scientists looked for the cause was downstream from wastewater treatment plants. These results have led to the speculation that the abnormal fish could be due to exposure to a pharmaceutical or an agricultural compound or something else entirely. Furthermore, the scientists have speculated that the problem may be caused by a mixture of pollutants arising from human sewage, farm manure and pesticide runoff.

So why is it that a clear cause-and-effect relationship is not forthcoming in the studies on the Potomac? Simply put, the reason is that the water quality issues that we are struggling with today are much more difficult to solve. The issue is no longer one solely related to toxicity, but may also include endocrine disruption, organizational effects, and the hijacking of cell signaling pathways. This signal mimicry can lead to bizarre changes in development, such as ovarian follicles within the testes of male fish.

In addition, the sources of the contaminants may be much less visible than those being released from an industrial discharge pipe. They could be coming from the waste products of animals that we consume or from chemicals we apply to our croplands and to our lawns. These compounds may not remain in one form in the environment, but rather may morph into an array of different metabolites, each one with its own environmental potency.