Canadians' tap water may contain tiny traces of prescription drugs, a new federal study has found.

A study of water samples taken from locations near 20 drinking water treatment plants in southern Ontario found evidence of nine different drugs. They ranged from the painkiller ibuprofen, cholesterol-lowering drugs and antidepressants, such as Prozac.

The drugs are making it into the water supply because the human body doesn't always absorb all the medication it ingests. Some is excreted as solid waste, and the particles aren't removed in the treatment process.

"It's an element of modern life that tends to unnerve us," said Duncan Ellison of the Canadian Water and Wastewater Association.

The study, conducted by researchers from the National Water Research Institute for the federal government, has yet to be formally published. But it has been submitted to a British journal entitled Water Research and should be published in the new year.

The quantities of drugs involved would be equivalent to a single drop of water in an entire swimming pool.

Those overseeing water quality say tap water is still safe.

Environmentalists counter by saying any quantity of prescription drugs in water is unacceptable, even if the drugs themselves have already been tested for safety.

"They certainly aren't tested in combination," said Angela Rickman of the Sierra Club. "So we're being exposed at any given time to three or four or five or any number of pharmaceuticals and no one knows the effect of that exposure."

There are also questions of the impact on aquatic life, on fetuses and on those who are ill or infirm.

As an example of what can happen, male smallmouth bass in a nicotine-polluted section of the U.S.'s Potomac River have started producing eggs.

Municipal governments, who bear operational responsibility for treating drinking water, say they are working on what is a complicated problem.

"There are research activities going on now to determine what we can do about it," Ellison said.

Experts say another way to solve this problem is to design better drugs that are fully metabolized by the body.

However, CTV's Paula Newton said designing such drugs is likely years away, as are any studies to determine whether prescription drug traces in treated drinking water are a health hazard.

With a report from CTV's Paula Newton