58
high incidenceof diabetes. Serum assay for vitamin
B,, showed generally high levels; the explanation
was nol apparent.
Radionuclide body burden evaluation in the Marshallese people has been complicated by several things.
The people were evacuated from their island soon
after the accident and did not return until 3 years
later. During the 5 years since the original contaminating event, additional weaponstests held
in the area have contributed to the fission products
in the environment. Finally, since the diet inctudes
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 under other circumstances.
Body burdens of gamma-emitting fission products (such as Cs‘ and Zn**) were measured ina
whole-body counter and checked by radiochemical analysis of urine specimens. Body burdens of
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'"", Zn"*, and Sr”’ body burdens was to be ex-
pected when the people returned there in 1957.
The Cs''’ body burden in 1958 was about 0.68 uC,
about 60 umes 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 wC. The mean body burden of Zn** estimated from whole-body counting
data was, in 1958, alter the return to Rongelap,
0.36 wC, 8 times as high as in 1957, and 0.44 wC
in 1959. Thus, whereas the Cs'”’ levels appear to
have reached a maximum and actually to have
dropped in 1959, the Zn* levels have shown a
continued increase which is probably related to
the long biological half-lite of thelatuer. The Sr°”
level in 1958 estimated from excretion data was
2 mpC, about 20 times as high asin 1957 before
the return to Rongelap. The estimated body burden in 1959 increased to 6.0 mpC, about 20% of
the estimated ultimate equilibrium value. Little
of the body burden of the exposed group is apparently due to their iniual exposure, since at
present there ts litde difference between the levels
of the exposed and unexposed populations living
on Rongelap Island. When these three isotopes
have reached their estimated equilibrium values,
the body burdens will sull be of small significance
in terms of radiation hazard.
This study of the internal contamination of the
Marshallese has provided information (1) on the
movement of Cs'!", Zn”, and Sr*’ from the environment to man, (2) on the rate of equilibration
of these isotopes with the environment; and (3) on
the discrimination factors between food and man.
IMPORTANCE OF MEDICAL SURVEYS
The Japanese populations of Hiroshima and
Nagasaki being studied by the Atomic Bomb
Casualty Commission and the Marshallese popufauon of Rongelap comprise the only large groups
of people exposed to acute doses ofionizing radiation. The two studies parallel each other but differ
in certain important respects. The smaller number
of people in the Marshallese population and the
paucity of vital statistics make statistical analysis
of data on this group much more difficult. However, the Marshuilese 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 complicationsof 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. Examinations for the more subtle late effects of radiation exposure are now receiving considerable emphasis. In the case of the Japanese, increased incidence 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 development of leukemia in
the Marshallese. Animal experimentation has
indicated the possibility that still other late effects
may occur in the humanbeing such as premature
aging, shorteningoflife span, increase in degeneralive diseases, genetic changes, etc. Therefore, continued careful examinationof these populations is
extremely important in order that such effects
may be documented, and therapeutic procedures
instituted wherever possible, should such eHects
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 jiving there.