urine activity concentration to body burden.
Equation 3 was obtained by
integrating Eq. (2).
Equations (1) and (2) were used to determine the instantaneous fraction of
atoms removed or added to the atom uptake per unit time, Ky and then the initial daily activity ingestion rate required to produce the measured or derived
body burden.
Equation (3) was used to determine the number of disintegrations
that occurred in the body during the residence interval of an individual living
on Rongelap or Utirik Atoll.
If the mean residence time in the diet is much much longer than the resi-
dence interval, then constant continuous uptake is achieved.
Equations (1) and
(2) can be converted to the constant continuous equations by replacing Ky with
-.
Single uptake expressions are obtained by setting P® equal to zero.
In
some cases only radioactive decay may remove the nuclide from dietary items; for
these cases K, would equal zero.
In the case of the former Bikini residents,
the maturing of coconut trees during residence on Bikini Atoll caused a continuously increasing dietary uptake of
tive value.
value for
137
Cs.
Thus, K_
E
was found to have a negz
In the case of Rongelap and Utirik, Ky was found to have a positive
137,
S,
65
Zn,
60
Co, and
90
Sr.
This indicated that in addition to
radioactive decay, some other removal mechanism decreased the radioactivity in
dietary items during the residence interval.
For the nuclide 3 Fe, only one me:
surement was published by the BNL Medical Program (Be72); thus an estimate of K,
was not possible.
K, was determined by using Eq. (1) or (2) and the population subgroup mea
body burden or urine activity concentration.
Portions of these bioassay data
are illustrated for adult males and females in Figures 2 to 6.
Two consecutive
urine or body burden data points were used to eliminate the unknown ingestion