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UI study looks at radon concentrations from private wells in Iowa

IOWA CITY, Iowa -- Researchers at the University of Iowa College of Medicine report that more than half of the private wells in Iowa they sampled for radon concentrations exceed the Environmental Protection Agency (EPA) proposed standard for public drinking water supplies.

Drs. William Field and Burton Kross, researchers in the UI department of preventive medicine and environmental health, measured the radon concentrations in a random sample of 352 private Iowa wells. They found that 183 (52 percent) of the wells had radon levels higher than the EPA's proposed standard of 300 pCi/L (picoCuries per liter) for public drinking water. Their findings are reported in the February issue of the journal Health Physics.

"As many as 745,000 rural residents in Iowa use groundwater from private sources as their primary water supply, so the potential for high radon concentrations in private well water is a concern," Field says. "This is especially significant when you consider that, as a state, Iowa has the highest airborne radon concentrations in the United States."

Radon gas in the home is a serious health hazard. Excessive radon exposure can lead to lung cancer and other health problems.

In the study, the radon concentrations from the private well sites ranged from minimal concentrations to 2,342 pCi/L, with an average of 429 pCi/L. The researchers found that both well depth and indoor air radon screening levels correlated with waterborne radon concentrations. However, Field notes, these correlations have little predictive value.

"We found that glacial drift aquifers tended to have the highest radon concentrations, although radon concentrations varied among all the aquifer classifications," he says. "Surface water supplies, such as rivers, have very little or no radon."

Radon can become airborne from water, entering the home from showers, humidifiers, clothes washers, dishwashers and boiled water from cooking. Exposure to waterborne radon may occur by both drinking water containing radon and breathing radon gas that has been released by household water.

The researchers note that the report should be kept in perspective, since it takes 10,000 pCi/L of radon in water to produce 1 pCi/L of radon in the indoor air of the home. "Radon from water sources in the home is only a small component of the radon gas that comes into a home. Most airborne radon gas in Iowa homes comes in through cracks in the foundation of a home," he says.

Field suggests testing your home for airborne radon before performing any test for waterborne radon. If your home's airborne radon concentrations are low, there is no need to test for waterborne radon.

Currently there are no national radon standards for either private or public water supplies. The EPA has directed the National Academy of Sciences to evaluate the appropriateness of the proposed standard of 300 pCi/L in public water supplies. A final national radon standard for public water supplies, however, most likely will not be set until the year 2000.

In the meantime, Field suggests that homeowners test their homes for airborne radon and follow EPA recommendations for both testing and lowering radon concentrations. Additional information about radon testing is available toll-free by calling 1-800-383-5992.