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
women (Richmond et al., 1962; Van Dilla, 1965;
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
(Karcher, 1973; Cryer, 1972).
The only
Boni, 1969; Lloyd, 1966; Lloyd et al., 1970; ICRP,
significant difference in T!/? among adults is
indicates that the long-term T!/2 is about 22 d for
that between males and females wherethere is
a distinct difference in the average body weight
1979; NCRP, 1977).
Leggett (Leggett, 1987)
newborns, decreases to about 13 d by 1 y, and then
begins to increase again to about 30 d by 5 y.
In addition to the change in T!/? with age,
the fractional deposition of 137Cs in the short-
(Lloyd, 1973; NCRP, 1977; ICRP, 1979).
The
average biological half-life for 137Cs_ in
Japanese males, whose average body weight is
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
males, was determined to be about 85 d
compartment; this gradually changes to 0.10 and
commonto age, body weight, and sex.
compartment and 0.5 in the long-term
0.90 for the short- and long-term compartments,
respectively, for adults.
Table 6, abstracted
from Leggett (1987), shows the change with age
for the total body potassium, fractional
deposits, and T!/?.
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
Leggett (1986, 1987) has recently shown
that the strongest correlation for the biological
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 model of the form:
A(t)=a 0-693 t/T1 4 (1-gjo0-693 t/T2 ,
where
A(t)
= the !3’Cs activity in the body at
Lloyd (1973) has indicated that the correlation
time t after ingestion,
Table 6. Estimated compartmental fractions and half-times in the age-dependent retention function
for cesium.
Age
Total-body K
Short- plus
intermediateterm fraction
Short- plus
intermediateterm T!/2
(days)
Long-term
fraction
Long-term T!/?
(days)
Newborn
100 days
1 year
5 years
10 years
15 years
5.2
11.4
20.8
42.7
71.0
131.4
0.60
0.60
0.60
0.45
0.30
0.13
22
16
13
9.1
5.8
2.2
0.40
0.40
0.40
0.55
0.70
0.87
22
16
13
30
50
© 93
Adult
150
0.10
1.6
0.90
107
I000to).