58
high incidence of diabetes. Serum assay for vitamin
B,, showed generally 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
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 thefission products
in the environment. Finally, since the diet includes
a variety of imported foods, the people are not
living in a ‘“‘closed” environment, and therefore
may not be rapidly approaching equilibrium with
the environmentalfission products, as might be
expected underother circumstances.
Body burdens of gamma-emitting fission products (such as Cs'3? 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
movement of Cs'*", Zn**, and Sr®° from the en-
vironment to man; (2) on therate 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 popu-
external dose measurements on Rongelap Island
and thelevels of radioactive isotopes in the food
on the island indicated that some increase in
lation of Rongelap comprise the only large groups
of people exposed to acute doses of ionizing radiation. The two studies parallel each other butdiffer
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 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,
Cs'*", Zn®, and Sr* body burdens wasto be ex-
thermal burns, or marked psychic disturbance, al-
determined by radiochemical analyses. Both the
ma
This study of the internal contamination of the
Marshallese has provided information (1) on the
pected when the people returned there in 1957.
The Cs'** body burden in 1958 was about 0.68 uC,
about 60 timesas great as in 1957, and the urinary
Cs'** level rose by a factor of 140; the mean body
burden for 1959 was 0.57 pC. The mean body burden of Zn** estimated from whole-body counting
data was, in 1958, after the return to Rongelap,
0.36 pC, 8 times as high as in 1957, and 0.44 pC
in 1959. Thus, whereas the Cs’*’ levels appearto
have reached a maximum andactually to have
dropped in 1959, the Zn® levels have shown a
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 mpzC, about 20 times as high as in 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 initial exposure, since at
presentthereis little 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 burdenswill still be of small significance
in termsof radiation hazard.
though 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 beingsof
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 inci-
dence of leukemia and possibly other malignancies
as well as cataracts already has been reported. In
view ofthis 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 degenerative diseases, genetic changes, etc. Therefore, continued careful examination of these populations ts
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 thein-
fluenceofpersisting low levels of radioactive materials on Rongelap Atoll on the body burdens of
radionuclides of the people living there.