31
tea, it became even more difficult to extrapolate
to body burden from food.
The excretion rate of Sr®° may be expressed as
the sum of two exponential functions for thefirst
the transport of low levels of Sr°° and other products through the ecological cycle in this and other
Sr® is excreted early, with a biological half-life of
40 days. The smaller fraction is excreted witha
It is obvious that further data are required on
communities to make possible assessment from
environmentaldata alone of the internal radia-
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
contaminatedarea.
Morereliable estimates of the Marshallese body
burdens can be obtained by whole-body gamma
spectrometry and by radiochemical urinalysis.
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
Radiochemical Analysis of Urine
value, estimated by Woodward*from urinary ex-
Strontivm-90. The urinary excretion levels of
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
higher by a factor of 20in March 1958 than in
March 1957.
TTT
10
ws ¢
3
"
J
1
4
a,
1
>
= 1.0
G08
o |
HB O.25
GO
ty~ 500 Days
\“ty~40 pays
,
ly
300
x
2YR ayn RETURNTORONGELAP
+
rif 4
i
600
900
12001500
figures for percent of equilibrium and equilibrium
cretion data. These values are subject to some un-
certainties, since they are based on a number of
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
at this time indicated a level of about 3.7 upC/g
Ca, which gives, upon application of the normall-
zation factor of 2 from vertebra to average skele-
ton,*’ an average skeletal value of 2 yuC/g. Thus
7]
1
|
the mean body burdenof Sr®* for exposed Rongelap people in 1958 was estimated to be 2 mpC,
or about 9% of the estimated equilibrium value of
4
23 mypC.°"
The estimated Sr*® body burden increased from
1800
2 mupC in 1958 to 6.0 myC in 1959, or 26% ofthe
TIME IN DAYS ~ AFTER MARCH |, 1954
estimated equilibrium value. The 1959 Sr®° mean
Figure 55. Urinary excretion of Sr
in exposed Marshallese.
urinary value in the exposed Rongelap inhabitants was 6.3 uuC/t or 10.5 wuC/24-hr urine, based
Table 32
Estimation®’ of Body Burden, in mpC, of Rongelap Population From Urinary Excretion Levels, 1958
Cs'¥7
Body burden
Equilibrated body burden
Percent of equilibrium
Daily intake
Zn*
Sr*°, Exposed
Exposed
Control
Exposed.
Control
2*
23
9
0.015**
900
1300
69
1206
1600
75
280
330
85
540
650
83
*3.7 Strontium units (SU) determined by bonebiopsy.
**15 SU assumingdaily calcium intake = 1 g.
2(?)
2.1-4.1
ro
aby asartrnhaael
tion hazard to human beingsliving in a fallout-
3 years following exposure. The majorfraction of