(WVLT) Pharmaceutical drugs have been found in the water systems of twenty-four major U.S. Cities, the closest Louisville, Kentucky.

So are we at risk here in East Tennessee and how does it get into the water?

Volunteer TV's Stephen McLamb has more.

When you takes a prescription drug it passes through the body, makes it's way to the wastewater treatment plant, then into the river before being picked up by a water treatment plant.

The dosage you get is extraordinarily small.

But a Maryville College professor's researcher says it's there and is having an effect on fish.

"A lot of pharmaceuticals end up in rivers and streams."

Maryville College biology professor Dr. Drew Crain has been doing research on pharmaceuticals in waterways and their affect on fish, in particular birth control medications.

He finds wastewater plants dumping into rivers is causing the feminization of male fish making them sterile.

It doesn't kill the fish.

Crain says, "but the population is being hurt. If a fish doesn't reproduce then the population is eventually going to crash."

River water eventually ends up in water treatment plants and then into your home.

Several U.S. cities have found pharmaceuticals in their drinking water.

So how about Knoxville?

Ted Tyree, KUB treatment plants manager says, "all the testing that we've done thus far shows that it's always been below detectable levels."

The city of Maryville recently scored a hundred on it's sanitary system check by the state.

Maryville, like other water systems, checks for many contaminants in parts per million but the pharmaceuticals found are in much smaller quantities.

Jeff Rose, Maryville Water Quality Control Director says,"they can detect those things down to parts per billion, parts per trillion, probably parts per quadrillion."

So are they a danger to you and your family?

Rose says, "nobody has ever said it's a real danger to people yet but it's definitely on the radar."

Tyree says, "so far the limited studies that have been done show that they don't necessarily have an affect at that low level but we need more research."

Tyree says people should never throw prescription medications into the toilet.

But Maryville may be in the clear on this issue.

Their water source is little river when comes from the mountains and there is no wastewater treatment plant on that river.