vt
teal it became even more difficult to extrapolate
to beady burden from food.
{tis obvious that further data are required on
the transport of lowlevels of Se” and other prod:
uets Ghrough the ecological cycle in this and other
communtties to make possible assessment from
environmental data alone of the internal radia-
tion hazard to human beings living in a fallout-
contaminated area.
More reliable estimates of the Marshallese bodv
burdens can be obtained hy whole-body gamma
spectrometry and byradiochemical urinalvsis.
Radiochemical Analysis of Urine
Strontium-90. The urinary excretion levels of
Sr’ for the 5 vears following exposure to lallout
are shown in Figure 55. The 4- and 5-vear levels
were much higher, after the return of the MarshalIese to Rongelap in fuly 1957, the mean being
higher bya factor of 20 in March 1958 than in
March 1957.
[
-t0
we
2
_
Oe
YR
O
0G
2¥R
800
SY,
900
tHhdays The smaller fraction is excreted witha
half-life of 300 days Uhese excretion rates correspondto those reported by Gowan’! in a case of
accidental inhalation of Sr'", and were used in
extrapolating back to the one-day Sr°" body burden of the Marshallese.”
Vhe 1958 Roneelap body burdens of Sr’, Cs'"'"
and Zn" are presented in Vable 32, and also
hgures for percent ofequilibrium and equilibrium
value, estimated by Woodward“ from urinary excretion data. These values are subject to some un-
certainties, since they are based on a number of
assumptons, however, they can be checked by use
of other methods. For example, the estimated
bedyv burden of Sr in March (958 was 2 pCge
Ca, based on the 24-hr Sr”? output in urine (1 liter
per 2! hr), and this appeared to be of the right
order of magnitude compared with data from
bone analysis. Two bone samples of vertebra and
eum from a deceased 35-year-old Rongelap male
at this time indicated a level of about 37 puC/e
Ca, which gives, upon application of the normali-
4
42
zk
= 19
“ez! 300 Days
© 06
\ a
o
By -0 Days
The excretion rate of Sr" may be expressed as
the sum of two exponential functions for the first
i vears followeng exposure “Uhe marpor fraction of
Sr excreted early, with a biological half-life of
zation factor of 2 from vertebra to average skele.
:
'
ton,’ an average skeletal value of 2 puC/2. Thus
the mean body burden of Sr" for exposed Rongelap people tn 1958 was estimated to be 2 muC.
or about 9% of the estimated equilibrium value of
.
RETURN TO RONGE LAP
4ay7R
3 YR
‘
12001500 1800
23 mpc."
_—
.
:
yaa
‘
Che estimated
Sr
body burden increased
from
2 meCin 1958 to 6.0 mueC in 1959, or 26% of the
TIME IN DAYS — AFTER MARCH |, 1954
Figere 55 Urinary excretion of Sr"
estimated equilibrium value. The 1959 Sr” mean
urinary value tn the exposed Ruongelap inhabit-
iexposed Marshallese.
ants was 6.3 ap€/tor 00.9 gay 24-hr urine, based
Table 32
Estimation’ of Body Burden, in muC, of Rongefap Population From Urinary Excretion Levels, 1998
Csi
Sr“. Exposed
Body burden
Equilibrated body burden
Percent of equilibrium
Hailv intake
QF
23
9
O.015**
"37 Strontuim units (SU) determined by bonc biopsy.
"15 SUassuming daily calcium intake = | g.
vn"
Exposed
Control
Ex posed
Controt
8.8)
1300
69
1200
1600
75
280
30)
i)
540}
650
K3
2(7)
21-41