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THE IOWA RADON LUNG CANCER STUDY: CONTEMPORARY AND HISTORICAL AIRBORNE RADON ( 222 Rn) AND RADON PROGENY CONCENTRATIONS

Daniel J. Steck 1 and R. William Field 2
1 Physics Department,
St. John’s University, Collegeville, MN 56321 USA 2 College of Medicine, Department of Preventive Medicine and Environmental Health,
University of Iowa, Iowa City, IA 52242 USA

The use of contemporary radon ( 222 Rn) gas concentrations to estimate retrospective radon-related
doses can introduce substantial uncertainties in epidemiological analyses. These uncertainties tend to
bias the results of radon-lung cancer epidemiologic studies towards the null. Temporal variability of
radon progeny over past decades and the variability in the dose effectiveness of airborne radon
progeny caused by indoor atmospheric differences are among the main sources of uncertainties in our
region. Studies of glass exposed in radon chambers and in homes show that radon progeny deposited
on, and implanted in, glass hold promise for reconstructing past radon and radon progeny
concentrations in a variety of atmospheres.
We developed an inexpensive track registration detector for the Iowa Radon Lung Cancer Study that
simultaneously measures contemporary airborne radon concentrations, surface deposited alpha
activity density, and implanted 210 Po activity density. The contemporary surface deposited activities
are used to estimate the contemporary airborne radon progeny concentrations. They are also used to
interpret the implanted activity 210 Po as a retrospective measure of the cumulative radon and radon
progeny exposure.
Over two thousand retrospective reconstruction detectors were placed in more than 1000 homes for a
one-year exposure period. A preliminary analysis of approximately 1500 of these detectors showed
that: the detectors performed well in the field with >95% retrieval after 1 year; the detectors met
accuracy and precision goals (10%); that there is good correlation (r 2 ~0.5) between the total radon
exposure estimated from contemporary annual-average radon gas measurements and the reconstructed
historical average radon concentrations determined retrospectively from implanted 210 Po activity; and
that the use of the contemporary implanted activity improves the correlation between the
retrospectively reconstructed and contemporary radon concentration by about 50% . Work is
underway to test the reconstruction in homes with measured radon histories and to compare our
methodology with other groups.
Key words: radon, radon progeny, retrospective, dose, glass, surface activity, implanted activity, lung
cancer, epidemiology.