PHOENIX -- A vast array of pharmaceuticals -- including antibiotics, anti-convulsants, mood stabilizers and sex hormones -- have been found in the drinking water supplies of at least 41 million Americans, an Associated Press investigation shows.

READ: 3/10/08 - Tap Water Holds Traces Of Drugs

In the course of a five-month inquiry, the AP said it discovered that drugs have been detected in the drinking water supplies of 24 major metropolitan areas, including Tucson.

A 5 Investigates report on March 1, 2006, first warned Valley residents of the findings of pharmaceuticals in the watershed.

Here is a transcription of the report by Morgan Loew as it aired on CBS 5 News:

The Northwest Water Reclamation Plant in Mesa is considered a state-of-the-art sewage treatment facility.

By the time the wastewater runs its course through the pipes, chambers and filters, it's ready to be recharged into the water table, known as the "aquifer."

"It is disinfected and filtered just like drinking water is but it's not quite drinking water yet," said Richard Bradford of the city of Mesa.

The soil beneath these ponds finishes the job and the water is considered drinkable by the time it reaches the aquifer.

But new technology is finding the most advanced wastewater facilities are not capable of removing some of the most common chemicals flushed and poured down millions of drains every day.

Prescription drugs, antibiotics, birth control and non-prescription drugs are the dozens of compounds that simply "cling" to the water, everything from Tylenol to tumor-reducers.

"Anything you use in your home we find in the wastewater," said Gail Cordy, a retired hydrologist with the U.S. Geological Survey.

She said the big questions remain unanswered.

"Should we be concerned? We really don't know at this point," she said.

The Santa Cruz River in Southern Arizona is like a living science experiment.

Its waters are 100 percent effluent, treated waste-water, and scientists are only beginning to learn what the chemicals in the water are doing to the wildlife.

David Walker has spent the last year and a half exposing these fish to varying levels of treated effluent meant to mimic the conditions in the Santa Cruz.

He said what he has found is just plain weird.

"The female fish are becoming more masculine and the male fish are becoming more feminine over time," he said. "It is a possibility that some of the effects we see in these fish can also occur in humans."

To determine whether this is a widespread problem, the U.S. Geological Survey conducted a landmark study of 139 rivers and streams across the country.

It found 80 percent of them contained one or more pharmaceuticals.

"You know, everywhere in the U.S., they discharge effluent into their streams and waterways," said Cordy.

Researchers said they know some of the chemicals are reaching the groundwater through rivers and recharge projects.

The chemicals are also getting to the Valley through our main water source.

Every toilet that flushes in the City of Las Vegas leads to Lake Mead, which drains into the Colorado River. From there, it follows the CAP Canal, which ends up in your home.

"These chemicals are present in very low concentrations in the Colorado River," said Paul Westerhoff, ASU associate professor.

Westerhoff said he thinks cancer-fighting medicines may pose the largest problem.

"These therapeutic drugs are designed to kill human cells and I think there's a greater concern of what's the risk of those classes of chemicals," Westerhoff said.

For now, the treatment method used at the Mesa facility is considered among the most effective.

But even here, some pharmaceuticals, including anti-epileptic medications, are ending up in the aquifer, leading to the unanswered question: Are we polluting the aquifer instead of saving it?

It's important to point out that researchers are finding very small traces of these chemicals. so drinking a glass of water would have no effect on anybody.

What they're concentrating on is the "long-term" exposure to people.