NEW HAVEN ---- Medications leaking into groundwater are producing strange effects on the frogs of Connecticut, effects that could be a harbinger of safety concerns for humans, too, researchers say.

A team led by David Skelly, professor of ecology and associate dean for research at the School of Forestry and Environmental Studies at Yale University, has found that male frogs are developing eggs in their reproductive tracts.

The reason for this, he said, is the presence of estrogen, the female hormone, and related compounds that are infiltrating the groundwater supply.

"I think people should stay tuned." Skelly said. "Not just to the frog research, but to a whole range of research going on right now that is changing how we measure and understand water quality."

As Skelly said, "The production of eggs in male frogs is, as far as we can tell, not normal."

Skelly's team found that deformities were concentrated in suburban and urban areas, which was something of a surprise for the scientists because it was previously thought that chemicals used on the farm were mostly to blame, particularly the widely used cornfield herbicide atrazine.

"But in agricultural areas, only 7 percent of the frogs show these deformities," he said. "In urban and suburban areas, it's about 20 percent."

Skelly's group studied frogs in about 15 towns and cities around Connecticut, and they found that, just about everywhere they looked, males were found with eggs forming in their testes.

"We decided to focus on Avon, because they have outstanding records on who has a septic tank and who's connected to the sewers," Skelly said. "You'd think that every town would have these records, but they don't. Avon is also a typical suburban town."

He added that although his work focused on Connecticut, it is likely that similar findings exist in suburbs throughout the nation.

The team set out to determine how water in the waste stream might be entering the ponds and bogs where frogs congregate. To do this, they used caffeine as a "marker." The caffeine was from the coffee, tea and chocolate that humans consume; it passes through the body more or less unchanged, and then gets flushed down the toilet.

Skelly notes that not all of the wastewater from homes makes it to sewage-treatment plants.

"It fact, the sanitary-sewage systems are designed to leak," he said. "We found caffeine in about half of the ponds. The assumption that many people have is that every little bit of nasty stuff that enters the sanitary-sewer system winds up in the waste-treatment plant. It doesn't."

Most of the estrogen compounds that find their way into the waste stream, and later into the landscape, are probably eliminated from people who consume the drugs, he said, rather than discarded in the trash.

"When these medicines leave your body, chemically, they're intact," he said.

Medications that contain estrogen include birth-control pills, some skin creams, prostate cancer medications and dozens of others. There are about 90 prescription pills, creams and injections that contain estrogen and its sister compounds according to the University of Maryland School of Medicine.

John Herlihy, director of water quality and environmental management for the Aquarion Water Co., said the problem of drugs filtering into the drinking water isn't nearly as acute in Connecticut as it is in other states. Connecticut is one of the only two states in the nation ---- Rhode Island is the other ---- is which all municipal water comes from protected reservoirs or groundwater aquifers, he said.

"When it occurs in the human supply, it's because those water bodies are receiving wastewater discharge," he said. "A lot of the cities use river water, and those rivers are also used to discharge waste ---- the Mississippi River, for example. But Connecticut has a completely different situation. Here, we have laws and regulations that prohibit the use of river water that has wastewater discharge."

Most states depend, some more than others, on river water, which can have effluent from waste-treatment plants upstream. In the case of communities that draw water from the lower Mississippi River, some of their drinking water has passed through several people, and a few animals, too, on its way from watershed to faucet.

That, in and of itself, should be no cause for concern, experts say, as waste-treatment and water-treatment plants keep contaminants well within safe levels.

Pharmaceuticals, however, add an unknown factor to the mix.

"That's why I live in Minnesota," said Paige J. Novak, associate professor of civil engineering at the University of Minnesota, half jokingly. Novak is one of a number of scientists around the nation on the cutting edge of developing ways to remove drugs from the wastewater stream and, in particular, estrogen compounds.

She said that bacteria already present in wastewater treatment plants "do a pretty good job" of breaking down estrogenic compounds. But she added that this is the next frontier of wastewater treatment, and that it's expected that the EPA will tighten the regulations in this regard for wastewater plants.

Meanwhile, Enesta Jones, an EPA spokeswoman, said that, in tests, the treatment of drinking water with either chlorine or powdered activated carbon can remove most of the estrogen and its related compounds.

Still, most experts say that there still isn't a single, best procedure that has been arrived at to solve the problem, in either the water treatment or waste treatment end.

"It is my understanding the estrogen can be removed in the waste treatment process, but that the best treatment plant design for doing this has not been established," said Susanna Eden, professor of applied research at the Water Resources Research Center of the University of Arizona.

And an in-depth investigative report published by The Associated Press last year found traces of pharmaceuticals in the drinking water supplies across vast stretches of the United States, although Connecticut wasn't part of the story. But in every water supply checked, drugs were found in miniscule amounts.

Still, Skelly notes that as things stand now, the water-treatment and waste-treatment plants were not designed to handle this problem.

"We could end up medicating the natural world, and even re-medicating ourselves," he said, noting that the federal Environmental Protection Agency, which regulates pollutants in the environment, and the Federal Drug Administration, which regulates drugs, are not on the same page.

"It was decided early on that the battery of chemicals that the EPA was going to regulate were not going to include medicines. I can't get a good answer for why this was the case," he said.

There's hope on the horizon, though. "Finally in 2010, the EPA has placed a whole bunch of pharmaceuticals on their list," he said.

"If pharmaceuticals are found in a pond, it's because it's from wastewater, said Aquarion's Herlihy. "That, by law, should not be there. So the focus here needs to be on managing waste."

As for Skelly's frogs, he notes that they're not too far apart from humans, at least genetically. "There are potential implications for human health ---- maybe not so much in Connecticut, but certainly around the U.S. and the world, because as time goes on, wastewater will increasingly be used for drinking water."