By contributor
updated 3/25/2010 8:24:55 AM ET 2010-03-25T12:24:55

Just by showering or bathing, you may be adding to the growing concentrations of medicines, hormones, and other health care products polluting the nation’s water supply, a new study shows.

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Experts have suspected that our drinking water supply was being contaminated by what we flush down the toilet, Dr. Ilene Ruhoy, an assistant professor at Touro University School of Medicine Nevada, Henderson, and co-author of the new study said Wednesday at the annual meeting of the American Chemical Society. A variety of prescription drugs can pass through our bodies and then be excreted either in urine or fecal matter.

Now researchers have found that medicines and other chemicals may also be flowing into the water while we're bathing and showering — and they might even be slipping through the laundry. Prescription drugs and other health care productsthat are applied to the skin can just wash off or rub off on clothes, while oral medications, such as steroids and antibiotics, can seep through the skin in our sweat, mix with the bathwater and then spiral down the drain, Ruhoy said.

Eventually the chemicals may end up in people’s bodies when contaminated drinking water is consumed.

“People like to think that when something goes down the drain it’s gone for good,” says Thomas Burke, a professor and associate dean at the Johns Hopkins School of Public Health. “It isn’t. It just goes into the water supply of the next town over.”

Scientists only recently learned that many American water supplies were contaminated with pharmaceuticals, says Herb Buxton, who manages the Toxic Substances Hydrology Program at the United States Geological Survey.

In 2002, Buxton and his colleagues first discovered that American streams, lakes and reservoirs containted measurable levels of pharmaceuticals. Over the years, they’ve compiled a long list of subtances, including steroids, antibiotics, the epilepsy drug carbamazepine and hormones such as estrogen that have been found in water supplies. In a 2010 study, published in Environmental Science & Technology, other government researchers found antidepressants in streams and the brains of the fish that swam in them.

“The amounts are usually low — several parts per trillion, when it comes to pharmaceuticals,” Buxton said. “But hormones, for example, can be active in our bodies at very low levels.”

Chemicals slip through treatment
While drinking water treatments and waste water processing clean up some contaminants, certain chemicals slip through the process, Buxton said.

Video: Protect yourself from dirty showerheads Health experts are mixed in their level of alarm over small amounts of medical contaminants in the drinking supply.

“I’m not worried,” said Joseph Graziano, dean of research and a professor pharmacology and of environmental sciences at the Mailman School of Public Health at Columbia University in New York. The amounts measured in the water are very small, he explained. “In the absence of a meaningful dose, I don’t think this should be a cause for alarm — vigilance yes, alarm no,” he said.

Burke, for his part, doesn’t go along with the assumption that a low dose means no effect. No one knows how prolonged exposure to low levels of hormones and medicines might impact the human body, Burke said. “But that’s only because we haven’t looked at this yet,” he added. This should be a wake-up call.”

Burke drew an analogy with water pollutants like trichloroethylene (TCE) and benzene that were ignored until the 1970s. These chemicals are now regulated under the Safe Drinking Water Act, he said.  

“Unfortunately, when there’s no information on health effects, we assume there aren’t any,” Burke said. “Absence of evidence doesn’t mean absence of effects.”

Ultimately, there isn’t much consumers can do except use moderation when applying medications and ointments, Ruhoy said.

So, next time you’re tempted to slather on the sunscreen or the steroid suffused anti-itch cream, remember that by using less you might be protecting the water you drink.

Linda Carroll is a health and science writer living in New Jersey. Her work has appeared in The New York Times, Newsday, Health magazine and SmartMoney.

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