NEW YORK - An array of pharmaceuticals - including antibiotics, anticonvulsants, mood stabilizers, and sex hormones - have been found in the drinking water supplies of at least 41 million Americans, an Associated Press investigation found.
The concentrations of these pharmaceuticals are tiny, measured in quantities of parts per billion or trillion, far below the levels of a medical dose. And utilities insist that their water is safe.
But the presence of so many prescription drugs - and over-the-counter medicines like acetaminophen and ibuprofen - in so much of our drinking water is heightening worries among scientists of long-term consequences to human health.
In the course of a five-month inquiry, the AP discovered that drugs have been detected in the drinking water supplies of 24 major metropolitan areas - from southern California to northern New Jersey, from Detroit to Louisville, Ky.
Water providers rarely disclose results of pharmaceutical screenings, unless pressed, the Associated Press found.
For example, the head of a group representing major California suppliers said the public "doesn't know how to interpret the information" and might be unduly alarmed.
When people take pills, their bodies absorb some of the medication, but the rest of it passes through and is flushed down the toilet. The wastewater is treated before it is discharged into reservoirs, rivers, or lakes.
Then, some of the water is cleansed again at drinking water treatment plants and piped to consumers. But most treatments do not remove all drug residue.
While researchers do not yet understand the exact risks from decades of persistent exposure to random combinations of low levels of pharmaceuticals, recent studies, which have gone virtually unnoticed by the public, have found alarming effects on human cells and wildlife.
"We recognize it is a growing concern, and we're taking it very seriously," said Benjamin H. Grumbles, assistant administrator for water at the US Environmental Protection Agency.
The Associated Press reviewed hundreds of scientific reports, analyzed federal drinking water databases, visited environmental study sites, and treatment plants and interviewed more than 230 officials, academics, and scientists.
They also surveyed the nation's 50 largest cities and a dozen other major water providers, as well as smaller community water providers in all 50 states.
Here are some of the key test results:
The federal government doesn't require any testing and hasn't set safety limits for drugs in water. Some providers screen only for one or two pharmaceuticals, leaving open the possibility that others are present.
Of the 62 major water providers contacted, the drinking water for 28 was tested. Boston is among the 34 that haven't been tested, along with Baltimore, Chicago, Houston, Miami, New York, and Phoenix.
The investigation also indicates that watersheds, the natural sources of most of the nation's water supply, also are contaminated. Tests were conducted in the watersheds of 35 of the 62 major providers surveyed by the Associated Press and pharmaceuticals were detected in 28.
Yet officials in six of those 28 metropolitan areas said they did not go on to test their drinking water: Fairfax, Va.; Montgomery County in Maryland; Omaha; Oklahoma City; Santa Clara, Calif.; and New York City.
Of the 28 major metropolitan areas where tests were performed on drinking water supplies, only Albuquerque; Austin, Texas; and Virginia Beach, Va., said tests were negative.