eon
T. M. BEASLEY, E. E. HELD and R. M. CONARD
sa frequency
3 of males and
, were included
of those indiernal radiation
blood samples
cit count rate
33% (20) conere weighed in
approximately 1/100th of the maximum
permissible body burden which has been established for non-occupationally exposed individuals considering the total body as thecritical
organ.93) Previous measurementsof 55Fe body
burdens during a period of increasing 55Fe
fallout generally showed that **Fe body burdens
of females were higher than those of males.(4-5)
food volumes.
Presumably this is due to higher turnover rates
of iron in females than in males, with the result
‘+t therefore the
their environment. As environmental levels of
55Fe decrease, females should, on the average,
reflect this change by exhibiting lower 55Fe
. previous years
: years applied
> weight generdividual esti-c likely to be
in the males
i body burdens
maximum ob-
was
1.0 #Ci,
of Rongelapese
55Fe
(uCi) *
0.43 + 0.17
0.40 + 0.27
247
from the northeast Pacific Ocean decreased
eightfold between 164-1667. Assuming that a
first order reaction governed the removal of
°*Fe from the mixed layer of the ocean (upper
100 m) he calculated the effective half-life for
55Fe loss as 11 months. Measurementsin cattle
and rain waters show decreases, but at lesser
rates."©) Tron-55 body burdens of adult males
in Richland, Washington, decreased approxi-
that females are more nearly at equilibrium with
mately 4 fold between 1667 and 1970,
corresponding to an effective 55Fe half-life of
LS yr. If the 55Fe turnover rates of Richland,
body burdens than those of males. Figure 1]
shows that more female body burdens tended
insular populations, we conclude that people
from maritime cultures would exhibit similar
and perhaps faster turnover rates of 55Fe
because of the short ‘“‘ecological half-life’@5) of
toward values <0.4 wCi, while male body
burdens were more normally distributed, about
a mean of 0.43 wCi. Regression analysis of age
on body burdens showed a significant correlation (P <0.001); older individuals had
higher 55Fe body burdens. Table 2 shows a
tabulation of the average 55Fe body of males
and females by age groups. The number of
samples per age group is admittedly small yet
the general increase of 55Fe body burden with
age appears qualitatively consistent with earlier
data obtained by analyzing blood from Seattle,
Washington, residents are similar to those of
this radionuclide in the marine environment.
The highest “Fe body burdens previously
measured were in female natives at Bethel,
Alaska, during 1966.) The average body
burden of 18 females was 1.1 wCi. During the
same year, the average *5Fe body burden of
females and males at Tokai-mura, Japan was
0.92 wCi and 0.63 wCi respectively.’
We
determined the ®*5Fe body burdens of 32 females and 37 males from Tokai-mura from
blood collected in October 1970;
the average
Washington males in 1966.
‘values were 0.12 and 0.17 respectively. Thus,
Comparison of the 55Fe body burdens of not only do the Rongelapese have significantly
peoples of different countries") requires knowl- higher *5Fe body burdens than those of the
edge of the turnoverrates of 55Fe in the environ- Tokai-mura residents, but the decrease in the
ment and in humans. Jenninos"4) has shown 55Fe body burdens of this latter group from
that the ®5Fe specific activities of salmon taken 1966 to 1970 appears comparable to that for
Table 2. Average body burden of Fe in Rongelapese
restdents of different ages
Age
Males
Females
16-20
21-31
32-42
4353
54-64
>64
16-20
21~31
32-42
43-53
54-64
>64
Number of
samples
Body burden
(uCi)
8
0.31
_4
5
2
6
3
6
12
5
7
2
2
0.33
0.52
0.58
0.53
0.48
0.23
0.34
0.33
0.66
0.57
0.66
Richland, Washington, males.
As previously stated, all of the donors of the
Rongelap study were subjected to external
radiation during the accidental contamination of
Rongelap Atoll in 1954. Because of the high
levels of radioactivity at the Atoll, the Rongelap
natives were moved to Majuro Atoll where they
resided for 3.5 yr. Following exposure in 1954,
whole body counting and urinalysis disclosed
measurable quantities of internally deposited
fallout radionuclides.
By 1957, however, the
only radionuclides present in the Rongelapese in
significantly measurable quantities were °5Zn,
WCs and *Sr.29 No 55Fe analyses were per-
formed at that time so body burdens of this
radionuclide are not known. However, based