Study of long-term radon progeny in humans for retrospective evaluation of radon exposure

An individual in vivo monitor using seven Germanium detectors with a total area of 24,000 mm(2) was prepared for Pb-210 skull measurements. System calibration with anthropomorphic head phantoms and a straightforward efficiency estimation yielded a minimum detectable activity (MDA) of 6.7 Bq and a lower limit of detection (LLD) of 14 Bq (CL: 95%). Two selected persons were measured for 1 h each to reconstruct their cumulative radon exposure. From the added pulse height spectrum a Pb-210 activity in the skull of 3.1+/-7.2 Bq (result with 95%-CL) was estimated, but clear conclusions on their radon exposure using a new metabolism model of lead in man could not be drawn. Further improvements in the selection of highly exposed persons as well as head calibration and Lackground reduction are necessary using this attempt for retrospective exposure reconstruction.