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THE IOWA RADON LUNG CANCER STUDY
Phase I: RESIDENTIAL RADON GAS EXPOSURE AND LUNG CANCER

R. William Field 1 , Daniel J. Steck 2 , Brian J. Smith 1 , Christine P. Brus 1 , Eileen F. Fisher 1 , John S.
Neuberger 3 , and Charles F. Lynch 1
1 College of Medicine, Department of Preventive Medicine and Environmental Health,
University of Iowa, Iowa City, IA 52242 USA 2 Physics Department, St. John’s University, Collegeville, MN 56321 USA. 3 Department of Preventive Medicine,
University of Kansas School of Medicine, Kansas City, KS 66160 USA.

Exposure to high concentrations of radon (222Rn) progeny produces lung cancer in both underground
miners and experimentally exposed laboratory animals. The goal of the study was to determine
whether or not residential radon exposure exhibits a statistically significant association with lung
cancer in a state with high residential radon concentrations.
A population-based, case-control epidemiologic study was conducted examining the relationship
between residential radon gas exposure and lung cancer in Iowa females who occupied their current
home for at least 20 years. The study included 413 incident lung cancer cases and 614 age-frequency-matched
controls. Participant information was obtained by a mailed-out questionnaire with face-to-face
follow-up. Radon dosimetry assessment consisted of five components: 1) on-site residential
assessment survey, 2) on-site radon measurements, 3) regional outdoor radon measurements, 4)
assessment of subjects’ exposure when in another building, and 5) linkage of historic subject mobility
with residential, outdoor, and other building radon concentrations. Histologic review was performed
for 96% of the cases.
Approximately 60% of the basement radon concentrations and 30% of the first floor radon
concentrations of study participants’ homes exceeded the U.S. Environmental Protection Agency
action level of 150 Bq m-3 (4 pCi/L). Large areas of western Iowa had outdoor radon concentrations
comparable to the national average indoor value of 55 Bq m-3 (1.5 pCi/L).
Excess odds of 0.24 (95% CI = -0.05 – 0.92) and 0.49 (95% CI = 0.03 – 1.84) per 11 WLM5-19 were
calculated using the continuous radon exposure estimates for all cases and live cases, respectively.
Slightly higher excess odds of 0.50 (95% CI = 0.004 – 1.80) and 0.83 (CI = 0.11 – 3.34) per 11
WLM5-19 were noted for the categorical radon exposure estimates for all cases and the live cases.
A positive association between cumulative radon gas exposure and lung cancer was demonstrated
using both categorical and continuous analyses. The risk estimates obtained in this study indicate that
cumulative radon exposure presents an important environmental health hazard.
Keywords: case-control studies; dose-response relationship (radiation); epidemiologic methods;
epidemiologic studies; lung neoplasms; radon, smoking, women’s health