21
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 throughthe ecological cycle in this and other
communities to make possible assessment from
environmental data aloneof the internal radiation hazard to humanbeingslivingin 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
jot
RETURN TO RONGELAP
fee EER SR
C309
800
900
certainties, since they are based on a numberof:
assumptions; however, they can be checked by use
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
per 24 hr), and this appeared to beof the right
order of magnitude compared with data from
bone analysis. Two bone samples of vertebra and
ileum from a deceased 35-year-old Rongelap male
zation factor of 2 from vertebra to average skele-
or about 9% of the estimated equilibrium value of
23 mpC.°°
7
RS
1200
den of the Marshallese.**.
The 1958 Rongelap body burdensof 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 un-
ton,’ an average skeletal value of 2 upuC/g. Thus
the mean body burden of Sr*° for exposed Rongelap people in 1958 was estimated to be =2 myC,
a
a
accidental inhalation of Sr®®, and were used in
extrapolating back to the one-day Sr*? body bur-
Ga, which gives, upon application of the normali- —
11
a
a
er
i
oO
iy
—-
1,~40 DAYS
half-life of 500 days. These excretion rates cor-
respond to those reported by Cowan”! in a case of
at this time indicated a level of about 3.7 uuC/g
n
519° EXCRETION ( upC/LITER)
5
Sr°° for the 5 years following exposure to fallout
are shown in Figure 55. The 4- and 5-year levels
were muchhigher, after the return of the Marshallese to Rongelap in July 1957, the mean being
higher by a factor of 20 in March 1958 than in
March 1957.
The excretion rate of Sr®° may be expressed as
the sum of two exponential functions for 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 with a
The estimated Sr*° body burden increased from
18001800
2 muC in 1958 to 6.0 mpC in 1959, or 26% ofthe
TIME IN DAYS — AFTER MARCH|, 1954
estimated equilibrium value. The 1959 Sr®*° mean
in exposed Marshallese.
ants was 6.3 wyC/I or 10.5 pwC/24-hr urine, based
Figure 55. Urinary excretion of Sr
urinary value in the exposed Rongelap inhabit-
Table 32
Estimation®® of Body Burden, in mpC, of Rongelap Population From Urinary Excretion Levels, 1958
Cs!37
Sr*°’, Exposed
Body burden
Equilibrated body burden
Percent of equilibrium
Daily intake
.
2*
23
9
0.015**
*3.7 Strontium units (SU) determined by bone biopsy.
**15 SU assuming daily calcium intake = 1 g.
in®*
Exposed
Control
Exposed
Control
900
1200
280
540
69
75
85
1300
1600
2(?)
330
650
2.1-4.1
83