o~—am se: = - - ~ INTERNAL DFPOSITION OF RADIONUCLIDES 5.3 ee a Internal Contamination in . a e Human Beings Tne Interna. 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 oceurs during the first few davs 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. Thius, the study made is essentially that of an equi- librium condition. The urine samples were sent to laboratories m the United States for analysis, since the high background encountered in the field masked the relatively low leveis of activity in the aliquot samples used. A field laboratory is most desirable fora raypid survey, and was shown to 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 (LAST). Similar samples colJected 44 divs post detonation were also sent there. On the 23rd, 24th and 47th days post detonation, 24-hour urine collections from each wdividual from Rongelap and Ailinginae were sent tothe New York Operations Office, Atomic Energy Commission (NYOO-AEC) for analysis. In addition, samples from representative individuals in these groups were collected 214, 3 and 6 months post detonation and sent to NYOO-AEC. * The USNRDI, collected samples from each ember of the exposed aronps at 43 and 46 days post. detonation, Samples fron representa: tives of these vroups were also collected at 294. 3 and G6 months by the USNRDL. In addition, samples from a representative group ofti Amen- cans and 20 Marshallese were collected for G consecutive days heuvinning 383) days post detonation. 9002114 5.31 69 Mechods As a complete radiochemical analysis of all the urine samples was not feasible, samples were analyzed for only Sr, Batt". the rare earth, group and fissile 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 the field, a seanming method for beta measurement consisting of a basic oxalate precipitation with a Janthanum 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 Ix" background, A carbonate precipitation of the entire 24-hour sample increased 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 UO, standard, and an, appropriate correction for self-absorption was nade using a Srstandard. 5.32 Findings and Interpretations 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 activily decreased rapidly asa function of time, as it was derivedchiefly 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 pust detonation, and at G month’, the activity inthe urine was barely detectable in most of the midividuals. Comparison of the means of the urine sam- ples for the adults from Rongelap and Allinginae and from Aanericans from Rongerik indicated that at 43 days post detonation the