You may be taking drugs every day and not even realize it.
A five-month investigation by The Associated Press found low levels of pharmaceutical drugs -- including antibiotics, mood stabilizers and sex hormones -- in the drinking water of at least 41 million Americans.
The AP's investigative team found traces of drugs in 24 of the 62 major metropolitan water systems it checked.
Have a glass of water in Philadelphia, for example, and you're drinking tiny amounts of at least 56 pharmaceuticals or their byproducts.
Lake Meade, which is about 30 miles southeast of Las Vegas, supplies drinking water for Nevada, Arizona and California, and testing found trace levels of birth control, steroids, narcotics and other drugs in that water supply.
"It's a wake-up call for America," said Richard Pienciak, the AP's national investigative editor. "The unanswered question at this point is whether 50 years of exposure to small amounts of pharmaceuticals will have long-term adverse effects on the human body. "
How do all those drugs get in the water?
People's bodies don't absorb all the medication they take, so some of it is excreted and flushed into the sewers. Sewage treatment plants don't remove the drugs. The treated water then flows into lakes, rivers and reservoirs, and finally to drinking water plants, which typically don't screen for drugs.
Scientists are seeing effects on animals. Some male fish, for example, have developed female traits and have reproductive problems. Scientists believe the cause may be exposure to human birth control hormones.
"There is no way that having pharmaceutical drugs in the water supply is going to be of any benefit," said David Carpenter, of the Institute for Health and Environment at the State University of New York in Albany.
In addition, with so many drugs in the water supply, people are ingesting them in combinations never intended. Medical experts worry that overexposure to antibiotics can lead to antibiotic resistance and an inability to fight infection.
The pharmaceutical industry points out the levels of drugs detected are minuscule. It says the amount of medication in the water supply is the equivalent of a single small pill in an Olympic-size swimming pool.
"No studies have demonstrated any effects on human health," said Marjorie Powell, an attorney representing the pharmaceutical industry.
The U.S. Environmental Protection Agency said in a statement that it is concerned about "a growing number of pharmaceuticals in water." Still, the EPA says water in the United States is some of the safest in the world.
There is some new advice to avoid exacerbating the problem. Instead of flushing unneeded medications down the toilet, the new recommendation is to discard drugs by diluting them with water or coffee grounds, putting them in a tight container and throwing them in the garbage.
The best way to filter drugs out of tap water is called reverse osmosis, but it's considered too expensive for treatment plants to implement without proof that the pharmaceuticals in the water are a real health threat.
Reverse osmosis home kits are available from major plumbing supply outlets. Typical home water filters aren't designed to filter out drugs.