IOWA CITY, Iowa -- Long-term exposure to radon in the home is associated with lung cancer risk and presents a significant environmental health hazard, according to a study led by researchers at the University of Iowa College of Public Health.
The Iowa Radon Lung Cancer Study, funded by the National Institute of Environmental Health Sciences, included investigators from the UI, St. John's University in Collegeville, Minn. and the University of Kansas. The results are published in the June 1 issue of the American Journal of Epidemiology.
From 1993 to 1997, the researchers studied 1,027 Iowa women -- 413 who were newly diagnosed with lung cancer and 614 "controls" -- ages 40 to 84 who had lived in their homes for the past 20 years or more. The women studied in both groups included smokers as well as nonsmokers. Women were studied because they typically have less occupational exposures to substances that may cause lung cancer, and historically have spent more time in the home.
The researchers found that close to 60 percent of the basement radon concentrations for both the lung cancer cases (study participants with lung cancer) and the control group (participants without lung cancer) exceeded the U.S. Environmental Protection Agency action level for radon of 4 picoCuries per liter (pCi/L). The researchers found that 33 percent of living areas for the lung cancer cases, and 28 percent of the living areas for the control group, exceeded the EPA's action level of 4 pCi/L.
Even at the EPA action level of 4 pCi/L, an approximate 50 percent excess lung cancer risk was found among the women in the study after correcting for the impact of smoking, according to Charles Lynch, UI professor of epidemiology and the study's principal investigator.
"What this indicates is that residential radon exposure is a significant cause of lung cancer," Lynch said.
At least four radon detection devices were placed in different areas in each of the study subjects' homes for one year. The researchers linked these multiple home radon measurements, as well as estimates on radon exposure outside the subjects' homes, with the subjects' past mobility history -- where and how much time they had spent outside or inside their homes or in the workplace, for example. With this information, the researchers were able to determine actual detailed exposure estimates for each study participant.
"This study incorporated the most sophisticated radon exposures analysis ever performed in a residential epidemiologic study," said R. William Field, Ph.D., UI research scientist in epidemiology and lead author of the journal article. "Most previous studies have focused on only one or two radon measurements in a home to determine a person's radon exposure. We linked where the study participants spent their time over the past 20 years with the radon concentrations gathered from inside and outside the home and came up with a more accurate measurement of exposure."
Previous studies have shown that Iowa has the highest average radon concentrations in the United States. Radon -- a naturally occurring odorless, tasteless and colorless radioactive gas -- is produced by the breakdown of radium in soil, rock and water. The high concentrations in Iowa and the upper Midwest are due primarily to glacial deposits that occurred more than 10,000 years ago, Field noted.
"Many homes and other buildings, such as schools and offices, have high radon concentrations," Field said. "Our research provides direct evidence that residential radon exposure is tied to an increased risk for lung cancer."
The best way to reduce overall exposure to radon is to test homes and take steps to reduce elevated indoor radon concentrations. Information on radon testing and mitigation is available toll-free from the EPA by calling (800) SOS-RADON or by visiting the EPA Web site at http://www.epa.gov/iaq/radon/. Additional information about the study is available at the following Web site: http://www.cheec.uiowa.edu/misc/radon.html.
The American Journal of Epidemiology is the premier scientific journal devoted to the publication of empirical research findings and methodologic developments in the field of epidemiologic research.
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