A glass of water might not require a prescription, but maybe it should.
Several studies have confirmed the presence of trace amounts of prescription drugs and other chemical contaminants in the nation's water supplies, and experts say there is no way to tell what the effects of chronic exposure to low levels of these chemicals in different combinations will be.
In response to an Associated Press report that pharmaceuticals were found in the drinking water of several major metropolitan areas, the city of Sandusky hosted a presentation from the U.S. Geological Survey about chemicals of emerging environmental concern in the water supply.
"Really, this was not a new discovery at all," said Donna Francy, hydrologist with the USGS. "What's really emerging is our concern about it."
Among the chemicals of emerging environmental concerns are human drugs, veterinary drugs, antibiotics, hormones, detergents, plastics, fragrances, steroids, insecticides and fumigants.
Caffeine is one of the most commonly found contaminants.
"It's just about everywhere," Francy said.
The presence of these chemicals in water sources can cause several problems.
In one study, researchers tested earthworms and found the worms had low levels of many chemicals in their bodies. This raised concerns the chemicals would then be transported up the food chain.
In a different study, researchers tested vegetables that had been fertilized with animal manure and found trace amounts of pharmaceuticals in the vegetables.
"It's the combined effects of many compounds at those low concentrations that we're not sure of," said Stephanie Janosy, biologist with the USGS. "At what point does this combined concentration become too much?"
When passed through the food chain, these chemicals can lead to the development of antibiotic-resistant pathogens.
If people or animals ingest too many hormones, it can lead to a disruption of the endocrine system, which can cause reproductive abnormalities such as reduced fertility, behavioral problems, impaired immune function and even cancer. Such results have been documented in laboratory animals, Janosy said.
Several studies have confirmed the presence of pharmaceuticals in low concentrations in water supplies throughout the country.
More than 60 percent of samples taken in a study of surface water supplies in North Carolina contained trace amounts of pharmaceuticals. Fifty percent of the samples contained pesticides.
"A lot of these same compounds show up in study after study," said Greg Koltun, surface water specialist with the USGS.
According to USGS experts, its not enough to just test the water. It's important to sample sediments for chemical contaminants as well.
Doug Keller, superintendent of city water services, said he will stay in touch with the USGS about a possible study of the water in the Great Lakes.