EDCs also enter the Potomac watershed from antibiotics and synthetic hormones given to cattle and poultry to prevent disease and stimulate growth. Once excreted by the animals, the chemicals find their way to the river, usually via rain runoff. In Shenandoah and Potomac tributaries upriver, cattle are allowed to walk into the water, a form of "direct deposit," Blazer says.
"We don't have smoking guns that tell us what specific chemicals may be causing problems in the river," says Potomac Riverkeeper's Ed Merrifield, "and it could take years to find out what chemical or chemicals cause intersex fish."
Even if we could identify potentially dangerous EDCs, current municipal water-filtration methods in our area cannot remove them, nor does the EPA require them to. A recent USGS study of several rivers nationwide, including the Potomac, reported the same concentrations of some compounds in the river water before and after it went through the filtration process.
Many of the EDCs that flow into the Potomac River and other bodies of water are thought to be estrogenic, meaning they mimic estrogen hormones in the body.
"Estrogenic compounds are important, but they are just part of the picture," says the USGS's Luke Iwanowicz. "We have also found androgenic compounds in the river that we suspect come from livestock feeding, and we'd like to find out what else is in the river. A lot of people throw away anti-inflammatory medications, and I also want to see if there are thyroid hormones in the river. I'd be shocked if there weren't."
"The exposure to EDCs that we get just from drinking water is probably a very low level," Blazer says, "but we know EDCs get past the placental barrier and enter the embryo, when the organism is most sensitive, and this is when we really need to worry because very low levels at those times will have a harmful impact. The changes initiated by EDCs may not show up until the person goes through sexual maturity or later. There are all sorts of things we don't understand right now."
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Many products contain EDCs that can remain in the water coming out of your tap even after it's been treated. Read more.
In time, the impact of EDCs on humans will be better understood. The technology for measuring human exposure to synthetic chemicals has advanced in recent years. Centers for Disease Control and Prevention (CDC) labs now can monitor human blood and urine for more than 200 so-called halogenated and non-halogenated chemicals and their metabolites. These include pesticides and chemicals used in cosmetics, perfumes, detergents, toys, plastics, and fire retardants. But the ways in which different EDCs might combine in the human body will likely remain uncertain for some time.
The Washington Aqueduct, headquartered on MacArthur Boulevard in Northwest DC, is the major supplier of drinking water for the District and parts of Northern Virginia, including Arlington and Falls Church. The aqueduct distributes some 160 million gallons of drinking water a day, and on hot days up to 180 million gallons.
The Washington Suburban Sanitary Commission, in Maryland, distributes water from the Potomac to homes and businesses in Montgomery and Prince George's counties and has two reservoirs on the Patuxent River that distribute water to parts of Prince George's.
Fairfax Water serves Fairfax County and Alexandria; 55 percent of its water is drawn from the Potomac and the remaining 45 percent from the Occoquan Reservoir. These are the area's three major suppliers of tap water.
Tom Jacobus, general manager of the Washington Aqueduct, says current water-filtering technology doesn't neutralize EDCs that enter the system from the river's intake pipes, but he notes that those levels are very low.
"The problem right now is we don't know the effect of very low levels of EDCs on human health," Jacobus says. "So we are trying to decide what kinds of water treatments we may need to go after some of these endocrine-disrupting compounds. Right now I can say without qualification that our drinking water meets all federal standards and therefore is safe to drink. But that is not a good enough answer, because safe enough for whom? So we are looking into the possibility of installing ozone UV [a technology that has the capacity to remove many EDCs from water] to further ensure that we can neutralize the anthropomorphic activity of EDCs in the water, but there are significant costs to this and other new technologies as well."
The Blue Plains Advanced Wastewater Treatment Plant, in Southwest DC, the world's largest such plant, treats and discharges 370 million gallons of Washington-area wastewater a day—up to a billion gallons during rainstorms. Untreated water is piped in from the District, suburban Maryland, and Fairfax and Loudoun counties and is pumped back into the Potomac River after it undergoes tertiary treatment. Says George Hawkins, general manager of the District of Columbia Water and Sewer Authority: "We put back water into the Potomac that is often cleaner than the water in the Potomac. It is a remarkable technical achievement."
But just as the Washington Aqueduct doesn't filter out EDCs, neither does Blue Plains or upriver wastewater-treatment plants in Rockville and Poolsville, whose treated wastewater goes into the Potomac and finds its way to the Washington area's water-intake pipes, to be recirculated through our freshwater supply.
Hawkins, former director of DC's Department of the Environment, says the water industry is paying a lot of attention to EDCs. A local group formed to investigate the issue decided that not enough science is currently available about EDCs to justify the expense of trying to remove them.
"We need to know which of these new contaminants may pose the greatest health dangers so we can develop a plan," Hawkins says, "because right now our ability to detect these chemicals as low as one part per trillion has outstripped our ability to know what their consequences may be. But does this issue of endocrine disrupters keep us awake at night? You're doggone right it does."
In the best of all worlds, the Clean Water Act of 1972 might have eliminated the EDC problem in the water supply before it began, or at least reduced it, because a goal of the act was to prevent all manmade pollution from entering our waterways. While that law has led to improvements in the quality of many of our nation's waterways, it is also routinely ignored. According to EPA data reported in the New York Times in September 2009, between 2004 and 2009 there were 506,000 violations of the Clean Water Act nationwide.