Minnesotans are pretty confident about their water. After all, we have the source of the Mighty Mississippi and more than 14,000 lakes. Why should we worry about water?
But some Minnesotans are worried, and for good reason. Scientists are increasingly aware of pollutants that were unknown or immeasurable just a few years ago. One documented effect has been the "feminization" of fish in the Mississippi River because of estrogen-like chemicals in the water.
Just how worried should we be? The presence of these contaminants in Minnesota's rivers and lakes is a source of "concern, not alarm," says Heiko Schoenfuss, one of the leading researchers in the field.
These "contaminants of emerging concern," or CECs, are getting the attention of scientists and environmentalists because of what we do know, but also because of what we don't know.
These contaminants are widespread in our rivers and lakes at relatively low concentrations, says Mark Ferrey, an environmental scientist at the Minnesota Pollution Control Agency (PCA). They can cause observable changes in the reproductive organs of some fish.
Schoenfuss, director of the Aquatic Toxicology Laboratory at St. Cloud State University, says we don't yet know what long-term effects they could have on populations of fish, other organisms, ecosystems and even humans.
Of greatest concern to researchers is a group of contaminants known as "endocrine disruptors," notably the female hormone estrogen and a variety of man-made chemicals that mimic it.
Naturally occurring estrogen, produced mainly by the ovaries, is the primary influence on the female reproductive system's development, maturation and function. It is excreted in the urine of humans, all mammals, and many other species. However, it is the widespread use of synthetic, or man-made, estrogen and other estrogen-like chemicals that is triggering scientific concern.
Estrogenic substances can be found in things we use every day, such as detergents, prescription drugs, fragrances, birth control pills and patches, and personal care products such as body wash and shampoo. Hormones are also used in animal food.
These chemicals can get into surface water -- rivers, streams and even relatively remote lakes -- through the effluent from sewage treatment plants, agricultural runoff, leaching from landfills, and drainage from rural septic systems.
Once in the water, estrogen-like chemicals enter the bloodstreams of aquatic animals, including fish. They "deceive" the estrogen receptors in the fish because their molecular structure is so similar that receptors can't tell the difference.
The result is a disruption of the fish's reproductive system, ranging from diminished size and strength to the production of eggs and ovarian tissue in the male fish's testicles.
Feminization was first noted in the mid-1990s, when intersex fish were found in waters around Great Britain. These were dismissed early on as anomalies.
During the past decade, however, such fish were found in the United States, even in states like Minnesota with relatively low population-to-water ratio. In 2002, the U.S. Geological Survey discovered high concentrations of estrogenic compounds across the country.
Even as scientists work to learn more about the prevalence and long-term impact of the contaminants, Ferrey says an agency like the PCA can't regulate such chemicals unless the Minnesota Legislature authorizes it to do so -- and that requires more information than is now available.
Schoenfuss says people who are aware of the problem rarely oppose action, partially because it would save money in the long run, and also because "people [in Minnesota] get very concerned when the safety of their water, whether it's the water they swim in or the water that comes out of their tap, is threatened."
But the lack of opposition may also be due in part to the fact that not enough is known yet to make CECs a debatable issue.
Schoenfuss says there's no need to wait for regulation. Citizens, he says, can reduce CECs going into the environment by not using more laundry detergent, body wash or other household products than needed.
He also recommends disposing of unused medications and other drugs responsibly. Some areas have instituted anonymous drug take-back programs to reduce the quantity of drugs that are flushed down the toilet or dumped into landfills.