INTERNAL DEPOSITION OF RADIONUCLIDES 5.3. Internal Contamination in Human Beings Energy Commission (NYOO-AEC) for an- alysis. In addition, samples from representative individuals in these groups were collected 2%, 3 and 6 months post detonation and sent to NYOO-AEC. The USNRDLcollected samples from each memberof the exposed groups at 43 and 46 days post detonation. Samples from representatives of these zroups were also collected at 214, In addition, samples froma representative group of 6 Americans and 20 Marshallese were collected for 6 consecutive days heginning 33 days post detonation. Methods As a complete radiochemical analysis of all Tue INTERNAL CONTAMINATION Study was begun 15 days post-detonation with the collection of pooled 24 hour urine samples from the Marshallese and American groups. Maximum activity in the urine occurs during the first few days after internal contamination. By 1 week an approximate equilibrium state is reached in which the contaminants remaining in the body are firmly fixed, chiefly in the skeletal tissues. The activity in the urine then derives from radioelements which have been replaced in the natural process of biological turnover, Thus, the study made is essentially that of an equilibrium condition. The urine samples were sent to laboratories in the United States for analysis,since the igh background encountered in the field masked the relatively law levels of activity in the aliquot samples used. .\ field laboratory is most desirable for a rapid survey, and was shownto be feasible, if adequate facilities are provided for the counting of the samples. The first urine: samples, mentioned above, were collected for the Tos Alamos Scientific Laboratory (ASI). Similar samples collected 44 duys post detonation were also sent there. On the 23rd, 24th and 47th days post detonation, 24-hour urine collections from each individual from Rongelap and Ailinginae were sent to the New York Operations Office, Atomic 3and 6 months by the USNRDIL. 5.31 69 the urine samples wasnot feasible, samples were analyzed for only Sr®®, Ba'**. the rare earth group andfissile material. These analyses are the most useful for evaluating the concentration and identity of all the potentially hazardous internally deposited radioactive isotopes. Measurement was also made of the gross beta activity of all the samples. To facilitate the processing of the large number of urine samples sent from thefield, a scanning method for beta measurement consisting of u basic oxalate precipitation with a lanthanum carrier was employed on an aliquot of the 24-hour urine samples. This method rapidly concentrates the radioactive elements into a small volume and eliminates the normal K® background. A carbonate precipitation of the entire 24-hcur sample incrensed the sensitivity of measurement sufficiently for analysis of samples collected later than 214 months post detonation. The beta activity was counted with a thin end window Geiger-Muller counter. The counter was calibrated with a U.O,; standard, and an appropriate correction for self-absorption was made using a Sr® standard. 5.32 Findings and Incerpretations 1. Beta Activity of the Urine. Internal deposition of radioactive elements was evidenced by the presence of significant amounts of beta activity in the urine, This activity decreased ” rapidly as a function of time, as it was derived chiefly from short-lived radioisotopes. For example, at 3 months post detonation, the mean activity of the urine of adults from Rongelap was 28 percent of the value measured 45 days post detonation, and at 6 months, the activity in the urine wasbarely detectable in most of the individuals. Comparison of the means of the urine samples for the adults from Rengelap and Ailinginae and from Americans from Rongerik indicated that at 45 days post detonation the