Retrospective Estimation of Exposure to Short-lived 222Rn Progeny by Measurements of 210Pb in the Skull

The inhalation of 222Rn and its short-lived decay products results in the exposure of the respiratory tract followed by the skeletal deposition of 210Pb originating in the lung from 214Po. By measurement of the 210Pb activity in the skull it could be possible to estimate previous exposures for a known relationship between 210Pb content in the skeleton and exposure. The measurement technique consists of two arrays of low energy germanium detectors (LEGe) with a total active area of 8000 mm2 installed in a large shielded chamber. The interpretation of estimated 210Pb deposit in terms of exposure can be made by using 'conversion coefficients' KE(tm) for the relationship between the 210Pb activity A(tm) and cumulative exposure. The decision limit of 210Pb for the total skeleton in a counting time of 7200 s was estimated to be 17 Bq, or about 0.9 J.h.m-3 (250 WLM) of exposure. The results of the first measurements of a group of individuals living in high radon prone areas show a good qualitative correspondence with the expected 210Pb content of the skeleton.