Mississippi River Water Warning

There are newly discovered contaminants in the Mississippi River in Minnesota and it's having a measurable impact on fish.

You can't tell just by looking at them, but scientists have found male fish with "female characteristics."

In some extreme cases, scientists have found male fish carrying eggs inside their testes.

That's obviously not supposed to happen. But it is. And it's raising a lot of questions. The Twin Cities gets most of its drinking water from the same water these fish are swimming in.

Scientists from St. Cloud State University were on the river, fishing, all summer. But it's not fishing quite the way you or I might do it.

They use electro-shocking boats to stun the fish, often causing them to either swim to the surface, or in some cases, jump right into the boat. They've collected some 600 fish this way in an effort to better-understand the impact of an emerging kind of pollution known as endocrine disrupters.

Endocrine disruptors are specific chemicals - natural compounds - which make their way through our wastewater treatment plants. They also run off farm fields and through storm sewers, ultimately messing with the hormones of the fish.

Among the most common endocrine disrupters are estrogens. Women taking birth control pills - a form of human estrogen - ultimately end up flushing estrogen down the toilet and into the river.

It turns out even male fish carry genes that respond to the estrogens they absorb from the water. Normally those genes just lie there kind-of dormant because the male fish isn't usually exposed to so much estrogen. But now, he's literally swimming in it.

This is a microscopic image of the testes of a Mississippi River walleye. The green areas are the eggs he is carrying.   Source: U.S. GeologicalSurvey

Scientists have found male fish in our river producing 'proteins' needed for egg production. That's something male fish aren't even supposed to be doing. In some cases, they've actually found male fish producing eggs.

Heiko Schoenfuss, the lead researcher at St. Cloud State University, says there is already evidence that these compounds are impacting fish.

"My previous studies have found behavioral changes," he said. "Lower levels of survival in young fish exposed to these chemicals and adult fish - exposed as young fish - not being able to reproduce at the levels we'd expect."

Schoenfuss says manmade chemicals are involved here too. Chemicals found in hand soaps, herbicides and pesticides, even de-icing agents all make their way into the river and into the body of the fish. To further complicate matters for the fish, Schoenfuss says, when these chemicals enter the body of the fish they mimic estrogen.

Schoenfuss says it's completely unintentional, but very real.

"We're trying to understand what happens if these animals are exposed year after year, generation after generation to these drugs, to these personal care products," Schoenfuss said.

"What happens five, ten, 15 generations down the road," he asks.

This summer's survey was the largest, most comprehensive assessment of endocrine disruptors in the Mississippi River to date. In addition to the researchers from St. Cloud, the study involves the Minnesota Pollution Control Agency and the US Geological Survey. Together, they sampled 43 locations from near the headwaters all the way to the Iowa border.

Analysis included the 600 fish along with water and sediment samples at each location.

Kathy Lee, with the U.S. Geological Survey says scientists know very little at this point, in what will surely be an enormous field of study in the future. She says they're just beginning to understand the science.

While these compounds are not as long-lasting as some pollutants, Lee says, they bring their own set of challenges.

"It's more of a continuous source, and some of these compounds probably aren't as persistent as PCB's, but the fact is they're ever present," she said.

The manmade chemicals at issue here are largely unregulated in Minnesota or anywhere else in this nation.

Some researchers are beginning to focus on the threat this may pose to humans. One hundred percent of the drinking water in Minneapolis comes from the Mississippi River. It supplies much of the rest of the metro as well.

State Representative Jean Wagenius says Minnesota's response has been slow and inadequate.

"The people of Minnesota just assume that we're taking care of the water quality in this state. They assume we're doing our job," Wagenius said.

When asked if this is a safe assumption today, she replied, "Not anymore."

Perhaps our greatest help may come from the nation's capitol. Congress held hearings on the issue a few weeks back. Lawmakers hammered the Environmental Protection Agency for being slow to react.

Congressman are concerned, not just because of what's been found here in the Mississippi River, but because they've found the same thing in the Potomac River as well.

Schoenfuss says more work must be done.

"We are getting closer to understanding the impacts on an individual fish," he said. "But knowing what happens to an individual fish doesn't necessarily mean that you understand what happens to the entire fish population. We have half the answer."

Early results of his ongoing study have turned up no new cases of inter-sexed fish. But they have several cases of male fish producing the egg protein.

Schoenfuss said there's a lot more they've found in the river, including Prozac, Wellbutrin, Acetaminophen, Ibuprofen, and plenty of caffeine.

And they're just beginning to study the impact these drugs are having on fish.