Drugs detected in the drinking water of at least 41 million Americans include antibiotics, anti-anxiety medications, pain relievers and even sex hormones, according to an Associated Press report released this week. Among 62 major metropolitan areas, 24 had pharmaceutical-tainted water supplies. Drugs were also found in 28 of the cities' watersheds. That includes New York, so maybe it really is the water.

The source? It's the drugs we take and flush down the toilet, as well as waste from our overmedicated livestock and pets. Most drinking water isn't treated to remove pharmaceuticals. Nor does the federal government require testing of our water for drugs.

Water utilities countered that the drugs were present in only tiny trace amounts. And hey—to feel a trace less anxious, a tad sexier—things could be worse, right?

Not quite. The problem, scientists say, is that small concentrations of some medications can cause worrisome effects, such as proliferation of human breast cancer cells in lab tests. In wildlife, pharmaceuticals have been linked to development of egg yolks in male walleyes and male genitals in female fish. That'’s more than a tad too many hormones, we'd say. Not to mention bass that swim both ways, producing sperm and egg cells, and lower sperm counts in endangered razorback suckers—we kid you not. If drugs continue to collect in our water, things may get interesting, at the very least, for the rest of us.

How best to avoid these watery enhancements? Bottled water is not the answer, as it's less stringently regulated and tested than tap.

What to do:

Run your tap water through an activated carbon filter, such as those found in Brita and Pur carafe, faucet and under-the-sink filters. "They [activated carbon filters] do remove some, though not necessarily all drugs, because it depends upon the structure of the drug," says Dr. David Carpenter, director of the Institute for Health and the Environment at the State University of New York at Albany. "They're very good at removing pesticides," he adds. Carbon filters also absorb toxic heavy metals, such as lead,and get rid of chlorine, the presence of which can make the effects of pharmaceuticals more harmful.

Keep most old medications out of waterways by blacking out labels and securely wrapping and disposing of them in trash, out of children's reach. For a list of drugs that the government advises should be flushed, click here.

Ask your pharmacist if your state has a takeback program for old drugs.

This article originally appeared in Plenty in March 2008. The story was added to MNN.com.