Imprecision in estimates of dose from ingested 137Cs due to variability in human biological characteristics

An attempt has been made to quantify the variability in human biological parameters determining dose to man from ingestion of a unit activity of soluble 137Cs and the resulting imprecision in the predicted total-body dose commitment. The analysis is based on an extensive review of the literature along with the application of statistical methods to determine parameter variability, correlations between parameters, and predictive imprecision. The variability in the principal biological parameters (biological half-time and total-body mass) involved can be described by a geometric standard deviation of 1.2-1.5 for adults and 1.6-1.9 for children/adolescents of age 0.1-18 yr. The estimated predictive imprecision (using a Monte Carlo technique) in the total-body dose commitment from ingested 137Cs can be described by a geometric standard deviation on the order of 1.3-1.4, meaning that the 99th percentile of the predicted distribution of dose is within approximately 2.1 times the mean value. The mean dose estimate is 0.009 Sv/MBq (34 mrem/mu Ci) for children/adolescents and 0.01 Sv/MBq (38 mrem/muCi) for adults. Little evidence of age dependence in the total-body dose from ingested 137Cs is observed.