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.