PHILADELPHIA - Just a century ago, this historic city notched by the Delaware and Schuylkill treated these rivers as public sewers, but few cared until the waters ran black with stinking filth that spread cholera and typhoid. Today, municipal drinking water is cleansed of germs - but not drugs. | Bottled water not any better when it comes to drugs

Traces of 56 human and veterinary pharmaceuticals or their byproducts - like the active ingredients in medicines for pain, infection, high cholesterol, asthma, epilepsy, mental illness and heart problems - have been detected in Philadelphia's drinking water. Starting their winding journey in medicine cabinets and feed bins, they are what's left of drugs excreted or discarded from homes and washed from farms upriver.

Is Philadelphia worried? Not so far. Tens of millions of Americans here and elsewhere drink water that has tested positive for minute concentrations of pharmaceuticals, and they don't even realize it, The Associated Press learned during a five-month investigation.

Though U.S. waterways coast to coast are contaminated with residues of prescription and over-the-counter drugs, there's no national strategy to deal with them - no effective mandates to test, treat, limit or even advise the public.

Benjamin H. Grumbles, the U.S. Environmental Protection Agency's assistant administrator for water, told the AP the agency recognizes that this contamination in water supplies is a growing concern and that government has some catching up to do: "Our position is there needs to be more searching, more analysis."

He said the EPA has launched a four-pronged approach: to identify the extent of the problem, to "identify what we don't know and close the gap," to take steps using existing science and regulatory tools, and finally, to increase dialogue and awareness with water providers and state and local agencies.

Yet water regulators are barely budging:

• The government has set no national standards for how much of any pharmaceutical is too much in waterways or taps. Drugs in the environment are "not currently a priority" of the National Center for Environmental Health, says spokesman Charles L. Green, at its parent U.S. Centers for Disease Control and Prevention.

• Though the Food and Drug Administration can review the environmental impact of new drugs, it has never rejected one on this basis, according to Raanan Bloom, an FDA environmental officer. Most pharmaceuticals are excluded from environmental review on the basis of their presumed low concentrations in water.

• Even though residues of many types of prescription and over-the-counter drugs have been discovered in scores of watersheds and drinking water systems nationwide, the EPA says it awaits more survey data before considering action. The agency has little information "that goes into whether these substances are occurring in the environment … and at what level," says Suzanne Rudzinski, a manager at EPA's Office of Water.

• Though pharmaceutical sales are rising, plants that cleanse sewage or drinking water are not required to remove drugs. They aren't even required to monitor for them.

When contacted directly by the AP, many water utilities confirmed whether they had tested for the presence of pharmaceuticals in their water. But federal agencies and industry groups declined to identify the cities and treatment plants where traces of pharmaceuticals had been found during independent studies, citing confidentiality concerns.

Philadelphia has found more pharmaceuticals in its source and drinking waters than any of the other 61 big water providers surveyed by the AP. It tested for more drugs and byproducts than other utilities - a total of 72 - and it found 56, or three-quarters of those checked, in its drinking water. It found 63 - almost 90 percent of those checked - in its source waters. More study is planned.

However, water managers detected scant concentrations similar to other places, suggesting they found so much largely because they tested for a larger list of pharmaceuticals - not necessarily because their watersheds are more contaminated. David A. Katz, a deputy water commissioner for the city, said the water was tested so heavily out of vigilance: "We choose to know; we choose to look."

John Muldowney, who oversees the city's three drinking water treatment plants, said no immediate upgrades are planned to filter out pharmaceuticals. "Based just on the data that's available now … we would be risking spending a lot of money, a lot of public funds, for very little health benefit," he explained.

Government leaders seem largely to share that attitude. "We're not really doing anything on this right now," says a spokesman for U.S. Sen. Harry Reid, D-Nev., though he has earmarked funds in the past to study environmental drugs in his state.

Grumbles, the EPA's top water pollution official, said the agency has embarked on four studies specific to the presence of pharmaceuticals and personal care products in wastewater and fish tissue. One "national study," expected to be completed next year, will look at the inflow and outflow at nine sewage plants; another will study sludge from 74 randomly selected sewage treatment plants.

Just two months ago the agency developed three new methods to detect and quantify about 160 different pharmaceuticals and personal care products, including steroids and hormones, in wastewater and sewage sludge, Grumbles said.

A year ago, the federal government put out its first consumer guidelines for discarding leftover or expired medicines. The goal was to slow the flow of drugs flushed down the toilet. Though Grumbles acknowledged that human excretions are the major factor in spreading pharmaceuticals through the waste stream, he said it is important for all Americans to realize "the toilet is not a trash can."

But the guidelines immediately drew criticism from some environmentalists, water treatment experts and pharmaceutical researchers who say they are contradictory, confusing, and don't solve the problem.

The guidelines say that about a dozen specific drugs should still be flushed down the toilet to keep others from finding and abusing them. The rest should be mixed with something unsavory like coffee grounds and tossed into the trash. That just moves the problem, though: The drugs end up at landfills, where they can slowly seep into the groundwater.

The EPA is also engaged in a national study to examine how long-term health care facilities and nursing homes dispose of pharmaceuticals.

And what of the drug waste generated by millions of U.S. households? The EPA says it would be impractical to impose regulations on them, beyond the voluntary guidelines.

In coming years, public pressure is likely to grow, as more pharmaceuticals find their way into less water. At the same time, today's chemical tests that reveal pollutants in parts per trillion will no doubt be able to detect even finer levels in the future. The added knowledge may not equal bliss, though.

"There isn't such a thing as 100 percent pure water," said EPA scientist Christian Daughton, one of the first to sound warnings over pharmaceutical pollution. "Yet people have a tough time with the idea that water contains all kinds of chemicals."