Iowa Residential Radon Lung Cancer Study
American Journal of Epidemiology, 151(11): 1091-1102, (2000)
“UI Study Finds Residential Radon Exposure Poses a Significant Lung Cancer Risk”

This is a five-year study for which data collection began in 1993. Over 1000 Iowa women took part in the study. Four hundred and thirteen of the participants were women who had developed lung cancer; the remaining 614 participants were controls who did not have lung cancer. The study was limited to women, because they historically tend to spend more time at home and they have less occupational exposure to other lung carcinogens.

Researchers found excess risks to be 50% higher for exposures that are roughly equivalent to 15-years spent at an average radon exposure of 4 pCi/L. The results suggest that residential radon exposure is a significant risk factor for lung cancer.

The Iowa Radon Lung Cancer Study has several strengths. First, independent pathologic review was performed for 96 percent of the cases. Second, the study was carried out in Iowa, which has the highest mean radon concentrations in the United States. Third, the high radon concentrations in conjunction with a strict quality assurance protocol contributed to accurate and precise radon measurements. Fourth, the IRLCS criteria requiring occupancy in the current home for at least the last 20 years eliminated the need to impute radon measurements from missing homes. Fifth, the linkage between radon measurements and retrospective participant mobility allowed for a refined exposure estimate. The IRLCS risk estimates are in general agreement with the National Research Council's predicted cancer risk associated with indoor radon exposure. Overall, the risk estimates obtained in this study suggest that cumulative radon exposure in the residential environment is significantly associated with lung cancer risk.

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