“% 5.5 DISCUSSION . . The fallout material probably entered the exposed people through both the inhalation and ingestion roufes, The relatively large particle size indicates that the probabUlity of inhalation of airborne contamination was small, This is based on the observation that in general onty particles 0.1 to 3 yin diameter reach the alveoli on inhalation and that larger particles are filtered oul by the nose and upper respiratory passage and swallowed.” 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 general 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 amountof internal contamination than the former though the groups received approximately the same calculated external dose. The difference may well lie in the fact that the Ailinginae people continued to eat contaminated food and drink contaminated water up to the time of evacuation. The American personnel probably ingested less contaminated food. Their water was distilled and stored in closed containers which precluded the possibility of radioactive contamination. It is also possible that indoctrination of the American group as to the inhalation hazard and perhaps their more adequate shelter was responsible for the lower am. ant of internal centamination re- ceived, Radioanalysis of urine samples of the Japanese fishermen, who were exposed to the same fallout, indicated that they had received approximately the same amount of internal contamination as did the Rongelap adult group. The lower urine activities found in the Marshallese individuals under 15 years may indicate that with active bone growth occurring, the internally deposited fission products were more firmly fixed and therefore less readily excreted. It 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 to 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 (2c/gm) in addition to high external doses. The only suggestion of such a combined effect in this situation was from the hematological response ot served in these exposed human beings, which did not follow precisely the time course charavteristically seen in lower mammals after short exposure to external radiation. anoeee . aoa * > 96 er ry ee products. ra eeee a v for three days increased the 6ve¥-all niean activity in thé 24° ADut urines of the treated people 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 suggest 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