analysis of the human urine and of the tissues and urine of animals from Rongelap. The mean body burdens of che radionuclides in the Ailinginae group were approxinuttely one-half tho-e of Rongelap, and the mean body burdens of the Americans about one-fourth of the Ronugelap gronp. While the activity excreted per unit volume of urine was the same for adults and children from Rougelap, the total activity excreted in the urine in 24 hours by children under 15 years of age was significantly lower than that excreted by the adults. The total anrount of radioactive material in the G. TL. tract at one diy post detonation was estiniated to be Some in people fram Ronvelap. This activity was contributed chiefly by isotopes af short radiological and biolowical half-life and Tnutted solubilicy, and thus the levels of activity in the t ssues of the badly were relatively low. The concentration of radioisotopes at months post detonation was barely detectable ta the urine of most of the exposed individuals. The estimated dose to the thyraid from P* and other short-lived iodine isotopes was TU ” 9002181 creased the rate of excretion of activity 2.5 times. However, the decrease of the body burden was slisht, as the excretion rate was very Jowat this time, Analysis of the internal contamination indicates that the dose (o the tissue of the body was near, but, with exception of the dose to the thyroid, dict not exceed the miatxiniim permissible doze levels. The activity fixed in the body decreased rapidly as a functionof time. The contribution of the eects af internal contami. nation to the total radiation respouse observed appears Ca be small on the basis of the-estimated body burden of che radioelements. In view of the short half-life of the niost abundant fission products in the situation, the possibilicy that chronic irradiacion effects will oceur is small. 5.4 Internal Contamination of Animals Tyo: Istrreenan Cons tasixation of a nvunher of _ animals collected on Rongehip was studied. The ACtIVEEY in their urine was studied, and radiochemical analyses were made of various tissues. Phese data provided the basis for estimating the body burden of the radioisotopes in human bemgs, In addition, henutolowieal and pathoJomiead studies were nde, and attoradiographs of selected Cssues were prepared. AC tuber Of Che auntials are also beine studied for the ahd elie Me LS oI take At one day post detonation, the concentra- tion of Srwas calculated to be near the maximui permissible level for this nuclide. At later times following exposure, this longer-lived fission product presents the greatest potential Internal hazard. Ora] administration of calcium EDTA beginning 7 weeks post detonation to a representative group of individuals from Rongelap in- tn to 140 rep for Rongelap. lJodine is probably the most hazardous internal radioemitter at early times after exposure. The dose to the thyroid, althoneh greater than tolerance, was low compared to the partially or totally ablating doses of I used in the treatment of hyperthyroidism or carcinoma. pI ll il monucleir explosion, This internal contamination resulted from both inhalation and ingestion of fallout material. Hich levels of activity were found in water and on the external surfaces of plants. The contaniination of the internal portions of fruits and vegetables was small. Of the individual radionuclides, Sr, because of its high solubility and relatively Jong radioactive half-life was probably the isotope of greatest potential hazard in the environment. Few of the fission products present in the environment were readily absorbed from the lungs and the G. I. tract. Radiochemical analysis of the urine samples from the Rongelap people indicates that Sr, Ba andthe rare earth group together constituted 75 percent of the total beta activity of the urine at 45 days post detonation. Sr was the predominant radionuchde at this tine, contributing 42 percent of the total beta activity. Assays for fissile material in the pooled urine sainples were negative. The human body burden of individual radionuclides was estimated from? radiochemical RADIATION taal EFFECTS OF JONIZING tall 76