The use of track registration detectors to reconstruct contemporary and historical airborne radon (Rn-222) and radon progeny concentrations for a radon-lung cancer epidemiologic study

Epidemiologic studies that investigate the relationship between radon and l ung cancer require accurate estimates for the long-term average concentrati ons of radon progeny in dwellings. Year-to-year and home-to-home variations of radon in domestic environments pose serious difficulties for reconstruc ting an individual's long-term radon-related exposure. The use of contempor ary radon gas concentration's as a surrogate for radon-related dose introdu ces additional uncertainty in dose assessment. Studies of glass exposed in radon chambers and in a home show that radon progeny deposited on, and impl anted in, glass hold promise for reconstructing past radon concentrations i n a variety of atmospheres. We developed an inexpensive track registration detector for the Iowa Radon Lung Cancer Study (IRLCS) that simultaneously m easures contemporary airborne radon concentrations, surface deposited alpha activity density, and implanted Po-21() activity density. The implanted ac tivity is used to reconstruct the cumulative radon and radon progeny exposu re from the age of the glass and the ratios of the contemporary deposited a ctivities to airborne radon gas activity. We placed over 2500 of these dete ctors in more than 1000 homes and retrieved 97% of them after a one-year ex posure period. A preliminary analysis of the 1280 detectors that have under gone quality assurance review shows that the modules are meeting their accu racy and precision goals (10%). There is good correlation (r(2)similar to 0 .5) between the total radon exposure estimated from contemporary radon gas measurements and historical average reconstructed from the implanted Po-210 surface activity. The linear regression slope of the airborne radon exposu re to implanted activity is the same as the room model slope based on typic al room parameters. This correlation improves (r(2)similar to 0.7) when the deposited surface activity measurements are added to the linear regression . Thus, track-registration detectors can contribute to accurate radon-relat ed dose assessment in epidemiologic studies. Additional work is planned to incorporate the deposited activities in a more sophisticated reconstruction model.