Long-term retention of 210Pb in man: a unique case of internal contamination.

Knowledge of the long-term effective half-life of 210Pb in man is essential for estimating the cumulative exposure to inhaled short-lived radon daughters from measured values of the 210Pb skeletal burden. For this purpose, the effective half-life has been obtained from sequential measurements of 210Pb made in vivo during a 10-y period and by bioassay of 210Pb excreted in the urine of an individual with a 43-y-old body burden. The long-term effective half-lives obtained by these two methods were 18.1 +/- 4.8 y and 15.8 +/- 0.8 y, respectively. These values are not very different from the estimate of 12.3 y previously adopted by the ICRP.