WASHINGTON, D.C. The recent discovery of male bass with female reproductive organs in two West Virginia rivers west of Washington, D.C., has once again focused public attention on the negative effects of so-called endocrine disruptors on certain fish species.
Public health and environmental officials across the country have yet to agree on a viable approach to remove endocrine disruptors from waters that support black bass and other freshwater fish species.
The U.S. Environmental Protection Agency (EPA) defines an endocrine disruptor as "an external agent that interferes in some way with the role of natural hormones in the body." The endocrine system in humans and animals circulates hormones that are produced by the endocrine glands. These glands include the adrenal, pituitary and thyroid glands, the pancreas, the testes and the ovaries. Hormones produced by these glands regulate the function of major organs and other physiological systems.
The discovery of endocrine disruptors in West Virginia waters was an unexpected and unwelcome development for federal and state agencies that had recently studied Cacapon Creek and the South Branch of the Potomac River. In 2003, researchers were trying to determine the cause of high smallmouth bass mortality rates in the South Branch. They dissected over 100 bass and found that 42 percent of the male fish contained eggs. During a follow-up survey in spring 2004, fisheries biologists examined 66 male smallmouth bass from the South Branch, and almost 80 percent of the fish had either eggs or other female reproductive characteristics.
There was much initial speculation about the source of the reproductive anomalies found in the male bass. Chicken manure, human hormones and even caffeine were suggested as possible causes. Investigators refused to speculate and cautioned that more research was needed in order to identify the exact substances that had affected the male bass.
"Thousands of chemicals have been identified as endocrine disruptors," cautioned Bret Preston of the West Virginia Division of Natural Resources. West Virginia officials have no plans to issue a fish consumption advisory based solely upon the discovery of intersex condition in bass.
Male bass with female reproductive characteristics have led some researchers to investigate the female hormone estrogen as a possible cause of the anomalies.
While there are a variety of ways that bass might come into contact with estrogen, one of the most likely explanations is exposure to sewage plant effluent. Urine and feces from women on oral contraceptives or hormone replacement treatment typically contain abnormally high levels of estrogen. Modern sewage treatment plants do not remove or even test for estrogen, so the hormone is released into waterways along with sewage plant effluent.
England is the only country in the world that measures and limits estrogen levels in sewage plant effluent.
There's growing evidence to suggest that estrogen is linked to the "feminization" of male bass. A number of studies in this area have been conducted or are in progress. One recent study was conducted by the Canadian government agency, Environment Canada. This research showed that male fish living close to sewage plant effluent outfalls had a measurably higher incidence of "feminization" than fish living in other locations.
Perhaps the most comprehensive research on the relationship between estrogen and reproductive endocrine disruptors in fish was conducted by two British academics, Alan Pickering and John Sumpter. Pickering is a retired professor. Sumpter is the director of fish physiology studies at Brunel University near London. Their joint study, "Comprehending Endocrine Disruptors in Aquatic Environments," was published in the American Chemical Society journal, Environmental Science and Technology.
Pickering and Sumpter studied 24 wastewater effluent sites in eight European countries. At a number of the sites they detected high levels of estrogen. The researchers focused on ethinyl estradiol (EE2), a synthetic form of estrogen which is the active ingredient in most birth control pills. Pickering and Sumpter placed special emphasis on EE2 because it's potent even in low concentrations and does not readily biodegrade.
One of the study's most dramatic findings concerned the effect of EE2 on gender balance in some fish populations. Near wastewater effluent outfalls, some of the fish populations contained abnormally high percentages of females. Pickering and Sumpter hypothesized that estrogen from sewage effluent caused such acute reproductive endocrine disruptions in male fish that they were unable to reproduce and probably died sooner than the females.
As a result of their research, Pickering and Sumpter concluded that "deleterious impacts of estrogenic effluents on fish populations is one of the most important (questions) that still needs to be answered."
In a recent interview, Sumpter was more definitive about the relationship between estrogen and reproductive endocrine disruptors. "There are some locations in the UK," he said, "where effluent does appear to be causing significant (and probably adverse) effects on the reproductive systems of wild fish."
Because much of the research involved English freshwater fish ("coarse fish"), Sumpter was asked if his conclusions might also be applicable to black bass. He replied: "My guess is that if black bass lived in UK rivers, in some locations concentrations of estrogen would be high enough to cause (negative) effects."
Britain's Environment Agency, the rough equivalent of our EPA, is sufficiently concerned about estrogen in sewage effluent that it plans to request approximately $80 million to build two state-of-the-art demonstration sewage treatment plants designed to filter estrogen out of wastewater. The plants would employ activated charcoal filtration technology. In addition, the effluent from 17 existing sewage treatment plants would be monitored to determine how much estrogen is being released into waterways.
Britain's independent water industry authority must decide if it will include the two pilot plants in its 2005-2010 work plan. If the pilot plants are approved, the cost of construction and operation would be covered by higher water and sewer rates for consumers.
According to Dr. Sumpter, "the superclean effluent (from the pilot plants) will be monitored chemically and biologically" to determine its impact on controlled fish populations. However, Dr. Sumpter expressed concern about the use of activated charcoal to filter sewage effluent. "Treatment with charcoal will remove many chemicals on top of the estrogens," he said. "If the cleanup process proves advantageous to fish living downstream (from the pilot plants), how will one know if the reduced effects are a consequence of estrogen removal?"
Another unanswered question is the extent to which estrogen from sewage effluent might affect humans who ingest the endocrine disruptive hormone.
Dr Louis Guillette Jr., a zoology professor at the University of Florida, said that "eating contaminated fish could work through a (human) endocrine system" and possibly cause neurological and thyroid system problems. Dr. Sumpter said a recent study demonstrated that "rats fed fish contaminated with estrogen chemicals (exhibited) adverse reproductive effects."
Due to medical ethics concerns, the direct effects of endocrine disruptors on humans have not been studied. Until rigorous medical research shows a direct connection between elevated estrogen levels and negative health effects in humans, public health and environmental officials are unlikely to devote significant time and money to reducing estrogen levels in fish populations.