1967; Lloyd, 1966), to 20 to 50 d for children (Karcher et al., 1969; Boni, 1969; Naversten, 1964; Bengtsson et al., 1964; Lloyd et al., 1966, 1970), and to 110 d and 85 d for adult men and with body weight and age is only significant when infants, juveniles, and teenagers are included and that there is no correlation with either for adult males or adult females women (Richmond et a]., 1962; Van Dilla, 1965; Boni, 1969; Lloyd, 1966; Lloyd etal., 1970; ICRP, (Karcher, 1973; Cryer, 1972). The only newborns, decreases to about 13 d by 1 y, and then begins to increase again to about 30 d by 5 y. (Lloyd, 1973; NCRP, 1977; ICRP, 1979). The average biological half-life for 137Cs in significant difference in T'/? among adultsis 1979; NCRP, 1977). Leggett (Leggett, 1987) indicates that the long-term T'/?is about 22 d for that between males and females where there is a distinct difference in the average body weight In addition to the change in T'/? with age, Japanese males, whose average body weightis the fractional deposition of 197Cs_ in the short- significantly less than for U.S. and European and long-term compartments also changes (Leggett et al., 1984). The fractional deposition for newborns is 0.5 in the short-term compartment and 0.5 in the long-term males, was determined to be about 85 d respectively, for adults. that the strongest correlation for the biological compartment; this gradually changesto 0.10 and 0.90 for the short- and long-term compartments, Table 6, abstracted from Leggett (1987), shows the change with age for the total body potassium, fractional deposits, and T1/2. Models have been proposed indicating that the long-term T!/? for 137Cs is correlated with age (Boni, 1969; McCraw, 1965; Weng and Beckner, 1973; Fisher and Snyder, 1967), body weight (Eberhardt, 1967; Cryer, 1972), and sex (Clemente et al., 1971; Boni, 1969). However, (Uchiyama et al., 1969; Fujita, 1966). Lloyd indicates that it is more likely that the T'/? for 137Cs is correlated with some other factor commonto age, body weight, and sex. Leggett (1986, 1987) has recently shown half-life of 137Cs appears to be with the total - amountof potassium (K) in the body. The model proposed by Leggett is the standard twocompartment modelof the form: A(th=a e0.693 t/T14 (1-a)e0-693 t/T2 , where A(t) = the 137Cs activity in the body at Lloyd (1973) has indicated that the correlation time t after ingestion, PETAes er en ea te tS AL. bee 50 RE ERT Arm rn Table 6. Estimated compartmental fractions and half-times in the age-dependentretention function for cesium. Age Total-body K Short- plus Short- plus intermediate- term fraction (days) intermediate- term T1/2 Long-term fraction Long-term T?/? (days) Newborn 100 days 5.2 11.4 0.60 0.60 22 16 0.40 0.40 22 16 1 year 5 years 20.8 42.7 0.60 0.45 13 9.1 0.40 0.55 13 30 0.13 2.2 0.87 93 10 years 15 years Adult 71.0 1314 20GRZ5 150 0.30 °° 0.10 5.8 1.6 0.70 0.90 50 107