1
a
tea, it became even more difficult to extrapolate
to body burden from food.
It is obvious that further data are required on
the transport of low levels of Sr°° and other products through the ecological cycle in this and other
communities to make possible assessment from
environmental data alone ofthe internal radiation hazard to human beingsliving in a falloutcontaminatedarea.
Morereliable estimates of the Marshallese body
burdens can be obtained by whole-body gamma
spectrometry and by radiochemicalurinalysis.
Radiochemical Analysis of Urine
Strontium-90, The urinary excretion levels of
Sr°° for the 5 years following exposureto fallout
are shown in Figure 55. The 4- and 5-yearlevels
were muchhigher,after the return of the Marshallese to Rongelapin July 1957, the mean being
higher by a factor of 20 in March 1958 than in
March 1957.
p
T
+
7
T
TT
U
t
14
1
519° EXCRETION ( 4uC/LITER)
10
<
°
|
1
1.0
7
0.6
4
1} ~40 DAYS
O.25
0
5]
e
iYR
300
a
2YR 3yp
we
600
.
RETIRN TORONGELAP
4yYR
5¥R
=1200
TIME IN DAYS — AFTER
500
assumptions; however, they can be checked by use
of other methods. For example, the estimated
body burdenof Sr®° in March 1958 was 2 ppC/g
Ca, based on the 24-hr Sr® output in urine (1 liter
per 24 hr), and this appeared to be of the right
order of magnitude compared with data from
boneanalysis. Two bone samples of vertebra and
ileum from a deceased 35-year-old Rongelap male
at this time indicated a level of about 3.7 puC/g
Ca, which gives, upon application of the normahization factor of 2 from vertebra to average skeleton,*”? an average skeletal value of 2 ppC/g. Thus
the mean bodyburden of Sr®° for exposed Rongelap people in 1958 was estimated to be 2 muC,
or about 9% of the estimated equilibrium value of
23 mpC.°°
7
The estimated Sr®° body burden increased from
oe bg
900)
The excretidn rate of Sr*® may be expressed as
the sun of two exponential functions for the first
3 years following exposure. The major fraction of
Sr” is excreted early, with a biological half-life of
40 days. The smaller fraction is excreted witha
half-life of 500 days. These excretion rates correspond to those reported by Cowan*! in a case of
accidental inhalation of Sr®*°, and were used in
extrapolating back to the one-day Sr*® body burden of the Marshallese.**.
The 1958 Rongelap body burdens of Sr®, Cs'*’,
and Zn* are presented in Table 32, and also
figures for percent of equilibrium and equilibrium
value, estimated by Woodward”from urinary excretion data. These values are subject to some uncertainties, since they are based on a numberof
1800
2 mpC in 1958 to 6.0 muCin 1959, or 26% of the
esumated equilibrium value. The 1959 Sr*° mean
urinary value in the exposed Rongelapinhabitants was 6.3 puC/} or 10.5 puC/24-hr urine, based
MARCH I, 1954
Figure 55. Urinan excretion of Sr*?
in exposed Marshallese.
DOE ARCHIVES
Table 32
Estimation” of Body Burden, in muC, of Rongelap Population From Urinary Excretion Levels, 1958
Csgi¥?
Sr°°, Exposed
Body burden
Equilibrated body burden
2
23
Percent of equilibrium
Daily intake
9
0.015**
7n*
Exposed
Control
Exposed
Control
900
1300
1200
1600
280
330
340
650
69
2(?)
75
85
2.14.1
'
83
*3.7 Strontium units (SU) determined bybone biopsy.
**15 SU assuming daily calcium intake = 1 g.
57
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