5
INTERNAL IRRADIATION
Radiochemical analyies of numerous urine sam-
ples of the exposed-population showedinternal
absorption
radioactive materials, probably
brought abo@
a¢hrough eating and drinking contaminated
‘and water and toa lesser
extent through inhalation. During the first few
days whenthe bodylevels were at their highest,
the maximum permissible concentrations were approachedorslightly exceeded only in the case of
strontium-89 and theisotopes of iodine. The concentrations were believed to be too low to result in
anyseriouseffects. Body levels fell rapidly, so that
by 2 and 3 years post exposure, they were far below the accepted maximum permissiblelevel; by 6
months activity in the urine was barely detectable.
den for 1959 was 0.57 uC. The mean body burden
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 appearto have
reached a maximum and actually to have dropped
in 1959, the Zn* ledels have shown a continued
increase which is probably related to the long bio-
logical half-life of the latter. The Sr®° level in.1958
estimated from,gxcretion data was2 mC, about
20 times as high.
957 before the return to
Rongelap. The
body burden in 1959 increased to 6.0 mC,about 20% of the estimated
- ultimate equilibriumvalue. Little of the body burden ofthe exposed group is apparently due to their
initial exposure, since at presentthereislittle difference between the levels of-the exposed and un-
In 1957 analyses of bone samples on one C225.populationstiving>i-Rongelap Island.
the men whodied showed 3.7 strontium-90 units/
calcium. Beginning in 1957, gamma spectroscopy :
by use of a low-levelcounting chamber was added
When ptese three isotopes have reached the?estimated equilibrium values, the body burdens will
Eo significance in terms of radiation
to the techniques of radiochemical anabysis. The
return of the Rongelapése to their homé‘island
(which after careful survey was consideredsafe for
OTHER STUDIES
active contamination) wasreflected in a rise in
their bodv burdens and increased urinaryexcretion of certain radionuclides. During the years
grouping studies in the Marshallese showed a rela-
since the original contaminating event, additional
quency, an extremely high R' gene frequency, and
habitation, despite a persisting lowlevel of radio-
weaponstests held in the area have contributed
to the fission products in the environment. Since
the diet includes a variety of imported foods, the
people are notliving in a “closed” environment,
and therefore may not be rapidly approaching
equilibrium with the environmentalfission products, as might be expected under other circumstances.
Body burdens of gamma-emittingfission prod-
ucts (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 radiochemicalanalyses. Both the
external dose measurements on Rongelap Island
andthe levels ofradioactive isotopes in the food
on the island indicated that someincrease in Cs'*",
Zn°*, and Sr®° body burdens wasto be expected
whenthe 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 bur-
Studtes of genetically inherited characteristics. Blood
tively high B genefrequency, a high N gene tre-
total absence of Kell and Diego factors. These
characteristics differ from those of Polynesians and
suggest relationship with Southeast Asians and
Indonesians. Haptoglobin studies showed thefrequency of the Hp' gene to be higher than in
European populations thus far tested and consistent with populationsliving near the equator.
Thedistribution of haptoglobin types showedthe
populationto be relatively homogeneous. Transfermns in all sera were type CC, the common European type. B-Amino-iso-butyric acid urinary levels
showed the Marshallese to be the highest excretors of this acid of any population thusfar reported. Levels in the exposed group were about
the sameas in the unexposed group, and nocorrelation was found with body burden level of
radionuclides; this indicates that there is probably
no correlation with radiation exposure. Hemoglobin
types were considered normal. Sickling tests showed
no sickling tendency in any ofthe people. Giucose-6phosphate dehydrogenase of the red cells appeared to
be deficient in the Marshallese. Considerable cau-