ae
.
for three days increased the dver-all miean actiVity in thé 24 nbuef urines of the treated peaple
by a factor of 2.5 times compared with the pretreatment control excretion. Since the rate of
excretion of activity at this time was about 0.1 per cent, 24 hours, the observed increase in
excretion did not significantly alter the total body burden. This study and previous animal work
sugeest that EDTA, perhaps administered 1.V. and at early intervals, might have been of considerably greater value in increasing the excretion of some of the internally deposited fission
raat
products.
“2
5.9
DISCUSSION
-
The fallout material probably entered the exposed people through both the inhalatton and
ingestion routes. The relatively hirge particle size indicates that the probability of toliudliation
Of vairborne contamination was small. This is based on the observation that in general only
particdes 0.1 to 3 po in diameter reach the alveoH on inhahation and Chat larger particles are
filtered out by the nose and upper respiratory passage and awallowed.™ In addition, the lungs
and air sacs of chickens autopsied in the period 24 to 100 days post-detonation showed low
levels of contamination, while the gastrointestinal tract and its contents were relatively active.
The high levels of activity found in the liver are also compatible with this hypothesis indicating
ingestion as the route of entry. Autopsy findings on five pigs indicate substantially the same
results.
In peneral the mean gross beta activities in the urine of Rongelap and Ailinginae groups
were found to be roughly proportional to the calculated external dose and therefore to the concentrations of airborne fission products. However, a comparison of mean beta activities of the
Ailinginae and American groups show the latter to have a somewhat lower amount of internal
contamination than the former though the groups received approximately the same calculated
external duse. The difference may well lie in the fact that the Ailinginae people continued to
eat contaminated fuod and drink contaminated water up tc the time of evacuation. The American
personnel probably ingested less contaminated food. Their water was distilled and stored in
closed contuiners which precluded the possibility of radioactive contamination. It is also pos-—
sible that indoctrination of the American group as to the inhalation hazard and perhaps their
more adequate shelter was responsible for the lower am. unt of internal centamination received. Radiounalysis of urine simples of the Japanese fishermen, who were exposed to the
same fallout, indicated that they had received approximately the same amount of internal con- tamination as did the Rongelap adult group. The lower urine activities found in the Marshallese
individuals under 15 years miy indicate that with active bone growth occurring, the internally
deposited fission products were more firmly fixed and therefore less readily excreted. lt does
not seem likely that the children were subjected to any less internal radioactive contamination
than were the adults.
5.6 CONCLUSION
The degree of internal radiation hazard was too low to have contributed significantly to the
acute radiation syndrome observed. Efforts to correlate individual body burdens with their
clinical or hematological findings (platelet and white blood cell levels) were unsuccessful. Due
{o the ability of the skeletal system to concentrate fission products, any injury to the body from
these internal emitters would most likely be determined by the radiation effect on the bone.
The concentration and type of internal radioactive contaminants, however, minimize the proba-
bility of any significant long term effects from the internal radiation.
The possibility of synergistic effects from the combined exposure to external and near
tolerance doses of internal radiation is also very slight. The occurrence of such a synergism
has been demonstrated where animals were subjected to relatively high doses of internal emitters (2 j:c¢/gm) in addition to high external doses. The only suggestion of such a combined effeet in this situation was from the hematological response ot served in these exposed human
bemps, which did not foliow precisely the time course chara-teristically seen in lower mammais after short exposure to external radiation.
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