Zinc may be creeping into the water supply, which could have an affect on brain function.
Zinc might be seeping into people's drinking water, getting into their brains, and causing problems with learning, memory, stress and more.
The danger, according to new research, is greatest for people who drink water from private wells that use galvanized pipes or tanks, especially in parts of the country where rocks or groundwater are naturally rich in zinc, such as the northern Rocky Mountains and central Florida, as well as in developing countries.
That's a rare set of conditions, and for the vast majority of Americans who drink from the tap, water is safe -- at least as far as zinc is concerned. The Environmental Protection Agency sets standards for levels of the mineral.
However, the new study, presented last week at a meeting Geophysical Society of America in Portland, Ore., suggests that people might want to be careful about how much zinc they're taking in through supplements, food and other sources, particularly this season when there's a tendency to down zinc-rich supplements, lozenges, nasal sprays, and pills in order to fight off both the regular flu and H1N1.
"If you're taking cold lozenges with zinc and you're taking a multivitamin with zinc and then you're drinking water that might even be well within the EPA standards, you could be consuming more zinc than you should be," said Kathryn Conko, a chemist at the United States Geological Survey in Reston, Va.
"All of these things can start to have an effect once you start layering them," she said.
Zinc is an essential nutrient that plays an important role in brain development, learning and memory, among many other basic processes in the body.
Getting enough of it allows more than 300 enzymes to do their work. Deficiencies have been linked to all sorts of problems, from diarrhea and death in children to immunity impairments and eye problems in adults.
"There's no tissue or organ or cell type that you can name that doesn't depend intimately on zinc," said behavioral neuroscientist Chris Frederickson, CEO of the zinc research company NeuroBioTex in Galvaston, Tex.
At the same time, getting too much zinc can be toxic, and there isn't a huge difference between recommended amounts and excessive amounts. The recommended daily intake is 8 milligrams per day for women and 11 milligrams for men.
Consuming just 50 to 100 milligrams per day can cause copper deficiency, which leads to anemia and other ills. Taking in more than 150 milligrams a day can lead to dizziness, lethargy and problems with muscle coordination.
There are more than 75 milligrams of zinc in a serving of 6 oysters, nearly 9 mg in a serving of beef shanks, 15 milligrams in a cup of some 100 percent fortified cereals and 15 milligrams in a common brand of men's multivitamins.
In experiments, Conko's colleagues saw mice become overly anxious while trying to complete stressful tasks after drinking water with lots of zinc in it. The animals also had trouble remembering spatial challenges. A closer look showed zinc build-up in their brains.
To see where in the U.S. the mineral might be causing problems, Conko looked to a national database of water quality in samples of well water. She found high levels of zinc in rocks and groundwater in a variety of regions, including southeast Idaho, southeast Arizona, south-central Texas and the tri-state area of southern Missouri.
Zinc can come from natural sources, and acidic water tends to leach it out of rocks. Zinc also gets into the environment from worn down tires on roads, mining and industrial processes.
Conko is hoping that word-of-mouth about her research will help her locate people at risk.
"I'm hoping someone will say, 'I know so-and-so and his Uncle Joe has one of those," Conko said. "As far as I know, that's the only way of finding these."