a1
tea, it became even moredifficult 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 assessmentfrom
environmental data alone of the internal radiation hazard to human beingsliving in a falloutcontaminated area.
More reliable estimates of the Marshallese body
burdens can be obtained by whole-body gamma
spectrometry and by radiochemical urinalysis.
The excretion rate of Sr°° may be expressed as
the sum of two exponential functionsfor the first
3 years following exposure. The majorfraction 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'*",
The urinary excretion levels of
and Zn® are presented in Table 32, and also
figures for percent of equilibnum and equilibrium
value, estimated by Woodward*from urinary excretion data. These values are subject to some un-
higher by a factor of 20 in March 1958 than in
of other methods. For example, the estimated
body burden of Sr*° in March 1958 was 2 puC/g
Ca, based on the 24-hr Sr®° outputin urine(1 liter
Radiochemica! Analysis of Urine
Strontium-90.
Sr®° for the 5 years following exposure to fallout
are shown in Figure 55. The 4- and 5-yearlevels
were muchhigher,after the return of the Marshallese to Rongelap in July 1957, the mean being
March 1957.
certainties, since they are based on a numberof
assumptions; however, they can be checked by use
per 24 hr), and this appeared to be ofthe right
order of magnitude compared with data from
bone analysis. Two bone samples of vertebra and
it
Lt
ileum from a deceased 35-year-old Rongelap male
at this time indicated a level of about 3.7 uuC/g
zation factor of 2 from vertebra to average skele-
Ca, which gives, upon application of the normali-
ton,’ an average skeletal value of 2 puC/g. Thus
the mean body burden of Sr*° for exposed Rongelap people in 1958 was estimated to be =2 muC,
or about 9% of the estimated equilibrium value of
23 muC.*°
The estimated Sr*" body burdenincreased from
2 mpC in 1958 to 6.0 muC in 1959, or 26% ofthe
estimated equilibrium value. The 1959 Sr® mean
urinary value in the exposed Rongelap inhabit-
4
a_i
$190 EXCRETION ( pC/LITE R)
o
th~40 Days
iY
R
5
‘
Oo
300
YR
‘
600
RETURN TO RONGELAP
SYR,
900
4
1200
ayYR
5 YR
a
4
‘
i500
1800
TIME IN DAYS — AFTER MARCH |, 1954
Figure 55. Urinary excretion of Sr*°
ants was 6.3 wuC/I or 10.5 weC/24-hr urine, based
in exposed Marshallese.
Table 32
Estimation*®’ of Body Burden,in muC, of Rongelap Population From Urinary Excretion Levels, 1958
Cs137
Sr®°, Exposed
Body burden
Equilibrated body burden
Percent of equilibrium
Daily intake
2*
23
9
0.015**
*3.7 Strontium units (SU) determined by bonebiopsy.
**15 SU assuming daily calcium intake = 1 g.
Zn®™
Exposed
Control
Exposed
Control
900
1300
1200
1600
280
330
540
650
69
2(?)
75
85
2.1-4.1
83