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Release: May 16, 2002

UI study finds health risk from residential radon exposure higher than previously estimated

The health risk posed by residential radon exposure may have been substantially underestimated in previous studies, according to investigators in the University of Iowa College of Public Health. Long-term exposure to radon gas in the home is associated with increased lung cancer risk and presents a significant environmental health hazard.

"Our findings indicate that the exposure assessment models used in many previous studies may have underestimated the risk posed by residential radon exposure by 50 percent or more," said lead author R. William Field, Ph.D., a research scientist with the UI Department of Epidemiology. The results of the study appear in the May 2002 issue of the Journal of Exposure Analysis and Environmental Epidemiology.

The UI researchers examined several exposure assessment methods used by previous residential radon studies performed in North America, Europe and China. They compared these models to a more comprehensive exposure method that linked a person's movement to various radon measurements within a home. All of the models were assessed using the same study population. The exposure methods used by previous studies all produced lower risk estimates than the comprehensive method. The researchers noted that the higher risk estimates for the comprehensive exposure method was attributable to decreased radon exposure misclassification. The highest degree of error was noted for methods that based risk solely on basement radon measurements.

"While radon concentrations tend to be highest in basements, people typically spend limited time there," Field said. "A more accurate assessment of risk can be formulated by linking multiple radon measurements taken within a home to where and how much time an occupant spends in the home."

Lung cancer is the leading cause of cancer deaths in the United States. Although the majority of lung cancer deaths are attributable to the voluntary habit of smoking, researchers estimate that residential radon exposure accounts for approximately 19,000 of the 160,000 lung cancer deaths that occur each year in the United States.

"Because of the magnitude of lung cancer incidence and its poor survival rate, even secondary causes of lung cancer, such as prolonged residential radon exposure, are important," Field said.

Other UI College of Public Health researchers involved in the study include co-investigators Charles F. Lynch, M.D., Ph.D., UI professor of epidemiology and medical director of the Iowa Cancer Registry, and Brian J. Smith, Ph.D., assistant professor of biostatistics. Daniel J. Steck, Ph.D., professor of physics at St. John's University in Collegeville, Minn., is also a co-investigator in the study.

Radon is a naturally occurring, odorless, tasteless and colorless radioactive gas that is produced by the breakdown of radium in soil, rock and water. Previous studies have shown that Iowa has the highest average radon concentrations in the United States. The high concentrations in Iowa and the upper Midwest are due primarily to glacial deposits left more than 10,000 years ago. Additional information on radon health effects and testing is available by calling 1-800-SOS-RADON.

The Journal of Exposure Analysis and Environmental Epidemiology is the official publication of the International Society of Exposure Analysis.