The iowa radon lung cancer study: contemporary and historical airborne radon (222rn) and radon progeny concentration

The use of contemporary radon (222Rn) gas concentrations to estimate retrospective radon-relateddoses can introduce substantial uncertainties in epidemiological analyses. These uncertainties tend tobias the results of radon-lung cancer epidemiologic studies towards the null. Temporal variability ofradon progeny over past decades and the variability in the dose effectiveness of airborne radonprogeny caused by indoor atmospheric differences are among the main sources of uncertainties in ourregion. Studies of glass exposed in radon chambers and in homes show that radon progeny depositedon, and implanted in, glass hold promise for reconstructing past radon and radon progenyconcentrations 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 210Po 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 210Po 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 (r2~0.5) between the total radon exposure estimated from contemporary annual-average radon gas measurements and the reconstructed historical average radon concentrations determined retrospectively from implanted 210Po activity; and that the use of the contemporary implanted activity improves the correlation between theretrospectively reconstructed and contemporary radon concentration by about 50% . Work isunderway to test the reconstruction in homes with measured radon histories and to compare ourmethodology with other groups.