53
puuC/! indicates a body burden in the exposed
Rongelap group of 280 mpC (+49%) with an
equilibrated body burden of 330 mpC.°° The Zn**
level was therefore 85% of the estimated equilibrium level in 1958 (see Table 32).
Whole-Body Counting With
the Gamma Spectrometer
Cesium-137. The body burdens of Cs'*" of the
various groups studied during the 1959 survey are
presented in Table 34. The variations in levels
within each groupare quite large. If Cs'** body
2 eee
burdenis expressed in units per unit body weight,
no significant difference is found between persons
older and younger than 15 years. The mean Cs'*’
level tends to be slightly lower for females than for
males, but again the differenceis not significant.
It is to be noted that nosignificant difference was
found between the Rongelap exposed, the Rongelap unexposed, and the Ailingnae groups. How-
ever, the mean Cs'*’ body burden of the Utirik
group (4.3 muC/kg) is (as in the case of Sr°°)
Rongelap people after they returned to their original island in 1957: the body burdenin 1958 was
about 0.68 #C, about 60 timesas great as in 1957,
and the urinary level rose by a factor of 140, because of the ingestion of Cs'*’ in food on Rongelap
during the 9 monthssince their return. The average Cs'*’ content of 250 Americans studied in
1958 was 6.6 mpC or “oo of the mean Rongelap
body burden.*?
The average daily intake of Cs'*" for an inhabitant of Rongelap in 1958 (average of 13 daily
rations) was estimated to be 3.9 muC.** This is
about 1.3% of the nonindustrial maximum permissible daily intake, which is the product of the
maximum permissible concentration®’ and the
daily intake of water:
about one-third that of the Rongelap exposed’
(210°* pC /ml) x (1.5 x 10% mi /day)
Rongelap group in 1959 was 0.57 uC (12.0
Zinc-65. Zn*° wasfirst detected by Miller®** in
1957 in the seven Marshallese examined at
Argonne National Laboratory by whole-body
spectrometry, althoughit had been observed in
high concentrationsin fish as early as one year
following the 1954 detonation.** Body burdensof
group (12.0 mpC/kg).
The mean Cs'*? body burden of the exposed
myC/kg) compared to 0.68 uC in 1958. Thelevel
has fluctuated over the years since the original
contaminating event. (See Figure 57, which shows
values obtained by whole-body gammaspectrometry and by extrapolation from urinalysis data.)
Unlike Sr*°, which is firmly fixed in the skeletal
tissue, Cs'*’ has a relatively short biological halflife, and thus readily reflects the environmental
1000
—T
gsoof
cs!97 EXCRETION (uyC/ LITER)
level. The slight increase in environmentallevel
of Cs'*? during the 1956 and 1958 periods of
weapontesting was reflected in an increased body
burden in the Marshallese. As pointed out, a very
marked increase in Cs'*’ was also observed in the
T
T
T———T
+
:
4
600 +
4
4007
“4
ty
~ 70 DAYS
A,
200 F
4
100 F
4
ao
oO
L
30
TIME
l
60
4
90
i
"
120
i
150
ia
igo
IN DAYS - AFTER MARCH |, 1954
Figure 56. Urinary excretion of Cs'"
in exposed Marshallese.
= 300 muC/day .
Zn* in 1957, measured directly, averaged 44
myC in five Rongelap inhabitants (Figure 57) and
350 mpC in two Utirik inhabitants. Miller, in
1957, determinedaneffective half-life of 110 days
for the elimination of Zn*, which gives a biological half-life of 200 days. However, a value of 89
days was obtained for the biological half-life in
two patients over a 2-month period.**
The mean body burden of Zn** estimated from
whole-body counting data was 0.36 uC in 1958
after the return of the Rongelap people to their
island, or 8 times the 1957 value (Figure 57).
The estimated Zn®intake in food (2 to 4 mpC/
day) can be largely accounted for by the Zn®
levels reported for fish. In 1956, fish from Ronge-
lap Lagoon were found to contain 0.6 myC Zn*
per lb muscle, or 7.5 mpC per |b whole fish.*®
The 1959 body burdens of Zn® are presented in
Table 35. As with Cs’*’, the variation within any
group is large, and no significant difference is
found in Zn® per unit body weight correlated