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Release: Immediate

Researchers report high outdoor radon concentrations in Iowa, Minnesota

IOWA CITY, Iowa -- Researchers at St. John's University in Collegeville, Minn. and the University of Iowa report that unusually high outdoor radon concentrations have been found in Iowa and Minnesota.

Their study indicates that in some areas of Iowa and Minnesota, the outdoor average radon concentration actually exceeds the national indoor average radon concentration of 1.4 picoCuries per liter (pCi/L) of air for single family homes. The study results are reported in the February issue of Environmental Health Perspectives, a publication of the National Institute of Environmental Health Sciences.

The researchers measured the annual average atmospheric radon concentration at 111 locations in Iowa and 64 locations in Minnesota. Environmental Protection Agency surveys have estimated the average outdoor radon concentration in the United States is approximately 0.4 pCi/L.

However, "the average radon concentrations found in the outdoor air in Iowa was twice the national average. In fact, some areas of western Iowa exceeded 1 pCi/L," said R. William Field, Ph.D., UI associate research scientist in preventive medicine and environmental health.

Daniel Steck, a physics professor at St. John's University and lead author on the paper, noted that, "even in Minnesota the average outdoor radon concentration was higher than expected." The average outdoor radon concentration in Minnesota was 0.6 pCi/L with some areas as high as 1.5 pCi/L.

The researchers, which also included Charles Lynch, M.D., Ph.D., UI professor of preventive medicine and environmental health, pointed out that the findings indicate that outdoor radon exposure should be accounted for in studies examining the relationship between radon exposure and lung cancer. Previous epidemiologic studies that examined the risk associated with radon exposure failed to consider the dose from outdoor radon concentrations.

The outdoor radon monitoring in Iowa was part of a National Institutes of Health-sponsored epidemiologic study in Iowa, which examined the health risks of radon exposure. The findings of that study will be out later this year.

Field said he was not totally surprised by the high outdoor radon concentrations in Iowa. "Previous studies have pointed out that Iowa has the highest mean indoor radon concentration in the United States. It follows that Iowa would likely have the highest outdoor mean radon concentrations in the nation," he said.

Field noted that the higher radon concentrations are due primarily to the glacial deposits that have occurred more than 10,000 years ago "The radium found in glacial tills is the primary source of both indoor and outdoor radon in the upper Midwest," he said.

The best way to reduce overall exposure to radon is to test your home and take action to reduce elevated indoor radon concentrations, Field added. The Environmental Protection Agency (EPA) suggests homeowners reduce the radon concentrations in their homes if the yearly average home radon concentration exceeds 4 pCi/L. More information on radon testing and mitigation is available toll-free from the EPA at (800) SOS-RADON.