38
B,, showed genegally high levels: the explanation
was not apparent,
Radionuclide body burden evaluation in the Marshal-
lese people has been complicated by several things.
The people were evacuated from their island soon
aftes che accident and did not return until 3 years
later. During the 5 years since the original con-
This study of the internal contamination ofthe
Marshallese has provided information (1) on the
movement of Cs'?*, Zn?*>, and Sr*" from the en-
vironment to man; (2) on the rate of equilibration
of these isotopes with the environment; and (3) on
the discrimination factors between food and man.
taminating event, additional weapons tests held
IMPORTANCE OF MEDICAL SURVEYS
in the environment. Finally, since the diet includes
The Japanese populations of Hiroshima and
Nagasaki being studied by the Atomic Bomb
Casualty Commission and the Marshallese population of Rongelap comprise the onlylarge groups
in the area have contributedto thefission products
a variety of imported foods, the people are not
living in a ‘“‘closed” environment, and therefore
may not be rapidly approaching equilibrium with
the environmental fission products, as might be
expected underother circumstances.
Body burdens of gamma-emitting fission prod-
ucts (such as Cs'3’ and Zn**) were measured ina
whole-body counter and checked by radiochem-
ical analysis of urine specimens. Body burdensof
Sr°° were estimated from urinary excretion as
determined by radiochemical analyses. Both the
external dose measurements on Rongelap Island
and the levels of radioactive isotopes in the food
on the island indicated that some increase in
Cs'37, Zn*°, and Sr*® body burdens wasto be expected when the people returned there in 1957.
The Cs'*" body burden in 1958 was about 0.68 uC,
about 60 times as great as in 1957, and the urinary
Cs'*? level rose by a factor of 140; the mean body
burden for 1959 was 0.57 uC. The mean bodybur-
den of Zn** estimated from whole-body counting
data was, in 1958, after the return to Rongelap,
0.36 uC, 8 times as high as in 1957, and 0.44 uC
in 1959. Thus, whereas the Cs’** levels appear to
have reached a maximum and actually to have
dropped in 1959, the Zn*levels have showna
continued increase which is probably related to
the long biological half-life of the latter. The Sr?°
level in 1958 estimated from excretion data was
2 mpC, about 20 times as high as in 1957 before
the return to Rongelap. The estimated body bur-
den in 1959 increased to 6.0 muC, about 20% of
the estimated ultimate equilibrium value. Little
of the body burden of the exposed group ts apparently due to their initial exposure, since &t
present there ts little difference betweenthe levels
of the exposed and unexposed populationsliving
on Rongelap Island. When these three isotopes
have reached their estimated equilibrium values,
the body burdenswill still be of small significance
in terms of radiation hazard.
1185608
of people exposed to acute doses of ionizing radia-
tion. The two studies parailel each other but differ
in certain important respects. The smaller number
of people in the Marshallese population andthe
paucity of vital statistics makestatistical analysis
of data on this group much moredifficult. However, the Marshallese studies have the advantages
that the dose of radiation received by the people
is better known; that the findings during the early,
acute period after exposure are well documented;
and that the people did not suffer from trauma,
thermal burns, or marked psychic disturbance, although they did have the complications of beta
burns and internal absorption of radionuclides.
Study of both groups has yielded valuable information on the acute effects in human beings of
radiations from atomic bomb detonations. Exam-
inations for the more subtle late effects of radiawon exposure are now receiving considerable emphasis. In the case of the Japanese, increased inctdence of leukemia and possibly other malignancies
as well as cataracts already has been reported. In
view of this finding, the next 5 years will be the
critical period for the developmentof leukemia in
the Marshallese. Animal experimentation has
indicated the possibility that still other late effects
may occur in the humanbeing such as premature
aging, shortening of life span, increase in degenerative diseases, genetic changes, etc. Therefore, con-
tinued careful examination of these populationsis
extremely important in order that such effects
may be documented, and therapeutic procedures
instituted wherever possible, should such effects
develop. In addition, in the case of the Marshallese, continued evaluation is indicated of the in-
fluence of persisting low levels of radioactive materials on Rongelap Atoll on the body burdensof
radionuclides of the people living there.
~
high incidenceof diabetes. Serum assav for vitamin