Part One of Two
The Potomac River is under attack! What else would you call it when people use the Potomac, one of America’s great rivers, as a sewer to dump Chinese snakehead fish and Florida alligators? Although the recent discovery of these exotic castaways demonstrates the casual disregard that people have for the Potomac, there is a more sinister assault taking shape. Environmental contaminants from unknown sources are causing male bass to produce eggs--a condition known as intersex.
The discovery of intersex fish began with an investigation of a Potomac River fish kill in 2002. The dead fish had skin lesions and specimens were examined by different laboratories to determine the cause of the lesions as well as cause of death. In 2003, biologists at the U. S. Geological Survey’s Leetown Science Center in Jefferson County discovered the intersex anomaly. As to what causes intersexing has been a focus of their research since then.
Biologists suspect that endocrine-disrupting compounds (EDCs) are the culprit. That suspicion, however, does little to narrow the search for the actual compound or compounds that are responsible. For example, certain pesticides and herbicides are EDCs. And you cannot rule out pharmaceutical hormones. When excreted, the hormones in birth control pills find their way untouched through a wastewater treatment plant and end up in the river.
The same is true for other hormones; including those mixed in livestock feed. And it’s just not the man-made stuff that causes problems. Soy beans, red clover, and a whole host of other plants naturally produce phytoestrogens.
According to the West Virginia Department of Environmental Protection, several sampling points on the South Branch of the Potomac exhibit above-acceptable levels of antibiotics. And there’s Roxarsone, an organo-arsenic compound fed to poultry. The arsenic (according to my reading) does not contaminate the chicken but passes through in the manure. In time, the arsenic in the manure drops out and is detectable as arsenate in water samples, especially those samples taken during a runoff event.
Get the picture? The sources for EDC contamination are many-from poultry barns to suburban lawns to households. The local grocery, pharmacy, and hardware store provide us with chemicals that we use routinely and without second thought in our daily lives.
To better understand the complexity of intersex fish and what it means for humans, my one big question has been, "If wastewater treatment plants do not remove the suspect EDCs, then does the downstream water treatment plant remove them before they can enter a municipal drinking water system?" The answer should be obvious to the non-scientist.
With so many variables in play, and no simple, sure-fire way to remove EDCs from the river, perhaps we should consider an alternative method to clean up the Potomac.
The basic principle of water treatment has not changed much since the Chinese developed it some 5,000 years ago. The operative word in water treatment is "dilution." Whereas Chinese farmers used a series of settling ponds to dilute toxins, we supplant the ancient process with concrete settling basins, sand or activated carbon filters, and a shot of ozone or chlorine to kill bacteria. But the end goal is the same-reduce toxins from parts per million to parts per billion, and so forth.
Our mountains are tall enough to shortchange the Potomac watershed on rainfall, but they aren’t tall enough to provide a snow melt into the dry months of summer. If the Potomac had a stronger summertime flow, we wouldn’t be researching intersex fish or discussing the impact of EDCs.
I, for one, would hate to see the Potomac’s tributaries dammed at every pinch point just to dilute EDCs. But that may be the best solution available if intersex bass turn out to be the canaries in the coal mine. Regardless, the recipe for success calls for more water or less chemistry-dilution.
At present, we cannot draw definitive conclusions from the water and fish studies that have been done. Some bass exhibit intersex, others do not, and other fish species seem perfectly fine. We have no sure cause for the intersex phenomenon. And we do not have a chemical profile of the Potomac.
What we have at this point is a hunch. Playing a hunch often leads to conjecture. Conjecture invariably leads to hyperbole. And hyperbole occupies a special place in America-Washington, DC.
In Part Two, I will discuss the federal solution.
Dr. Robert E. Putz, Founder of the Freshwater Institute at Shepherdstown, WV contributed to this article.