Among the substances: caffeine, contraceptives, painkillers, insect repellent, perfumes and nicotine.
Scientists say that the problem is that these substances largely escape regulation and defy municipal wastewater treatment. And the long-term effects of exposure are unclear, they say.
The compounds are sold on supermarket shelves and found in virtually every medicine cabinet and broom closet, as well as farms and factories. And they are flushed or rinsed down the drain every day. But they do not disappear, researchers warn.
Hydrologists with the U.S. Geological Survey tested water samples in 30 states for 95 common compounds, an emerging class of contaminants known as pharmaceutical and personal care pollutants, or PPCPS. The results of the three-year analysis appear in the March 15 issue of journal Environmental Science and Technology.
The scientists found that the chemicals persist in the environment in concentrations as low as one part per billion or less. The results mirror similar studies of PPCPs in Europe and Canada.
Yet little is known about PPCPs' potential health and environmental effects. The use and disposal of 81 of the 95 compounds in the study are entirely unregulated, officials said.
"Compounds that we use in households or even consume can persist though wastewater treatment and affect resources on a pretty broad scale," said Herb Buxton, USGS coordinator of the USGS toxic substances hydrology program.
For example, many scientists suspect the widespread use of anti-bacterial agents in human medicines, household cleaners and veterinary medicines has encouraged the development of germs that are resistant to antibiotics.
The USGS study found at least 31 antibiotics and anti-bacterial compounds in water samples. The study also tallied traces of at least 11 compounds linked to birth control and hormone supplements.
Some studies have linked environmental exposure to hormones to deformed sex organs in wildlife, sex reversal in some fish and declining fertility in humans, as well as cancers and other diseases.
Scientists who did not participate in the USGS survey said PPCPs represent the "next big unknown" in environmental contamination.
Exposure to even tiny amounts may result in cumulative risks, they said, especially when the compounds combine in unanticipated ways.
"You don't need therapeutic doses of a drug to have an effect," said Christian Daughton of the Environmental Protection Agency's exposure research laboratory in Las Vegas. "Some organisms have potential to suffer multigenerational exposures. Parts per billion could have profound effects."
Industry and water utility officials said they expect the EPA to decide in the next few years how to regulate PPCPs.
They said promising new wastewater treatment technologies can break down many of the chemicals using biological methods, or even exposure to ultraviolet light.
"We're not ignoring it," said Alan Roberson, regulatory affairs director for the American Water Works Association in Washington. "One question is what do you do with the concentrated form of these chemical compounds if you take them out of the water."
In 1999-2000, USGS scientists collected samples downstream from cities, farms and factories. Many of the waterways contribute to municipal water supplies.
They included the Sacramento River at Freeport, Calif.; the South Platte River in Denver; the Mississippi River above Minneapolis/St. Paul; and the Charles River in Boston. Seven or more chemicals were found in half of the streams sampled.
In addition to caffeine, the USGS reported the most frequently detected compounds were coprostanol and cholesterol, which are byproducts of digestion. Also found frequently was DEET, a common insect repellent. Among the medications found were the blood thinner warfarin, antidepressants and blood-pressure medicine.
By Joseph B. Verrengia