39 seems to indicate a reduction in relative immunological capacity or at least lowered antibodyreserves in the exposed people. The tendencyfor the depression of these moieties to be relatively greater in the older groups may imply a radiation-induced aging effect. Since such studies were not carried out earlier, it is not possible to say when these changes developed. However, at 3 years post exposure, when the people were challenged with tetanus toxoid, primary and secondary responses were found notto besignificantly different in the exposed and unexposed populations.° Also, in spite of slight depression of blood elements andreduced serum globulin levels, the exposed Marshallese people, on the basis of our observations over a 15-year period since the accident, have shown no recognizable impairmentof immunological capacity as evidenced by the incidence of, or suscepti- bility to, illness or diseases.5® If the serum protein changesare a recent development, then such im- pairment may vet become apparentif the people are faced with a virulent antigenic challenge in the future. Thelack of any differences between the exposed and unexposed people in transformation of lymphocytes in response to PHA stimulationis somewhat unexpected in view of the above findings. However, the lymphocyte levels in the exposed group have not been depressed as severely as some whole-body counter with an 11'4-in. NaI(TI) crvstal. Radioisotope levels in the exposed and unex- posed people were indistinguishable by this method, both groups showingelevated total body burdens of 10 to 20 nCi !37Cs and 1/1000 this amount of ®°Co. Also in 1965 radiochemical urine analyses were done on 24-hr samples from 23 people and on two pooled samples. The results showed no increase in internal body burdens since 1961; therefore, no whole-body counts were considered necessary during the next 3 years (1966- 1969). However, urine samples were collected for radiochemical analyses* as follows: 24 in 1967, 22 in 1968, and 23 in 1969. The urines were analvzed first for 137Cs by gammaspectroscopy by counting the wet ashed samples on top of an 8 X 4-in. NalI(T1) crystal. Then the residues were dissolved and analyzed radiochemically for !37Cs and 9°Sr. Calcium was determined by the oxalate-permanganate titration method. Because of their high 9°Sr and 137Cs content, coconut crabs on Rongelap Atoll have been banned for use as food. Several crabs were brought back for radiochemical analysis during the past 3 vears. Our group at BNL has been given the responsibility for monitoring the radioactive body burdens of the Bikini people when they return to live on their homeisland.°? They are now living on Nuli of the other blood elements, which indcates that Island, several hundred miles to the south. In order to obtain base-line data, 24-hr urine samples ESTIMATION OF INTERNAL BODY BURDENS OF RADIONUCLIDES IN MARSHALLESE Sr, and 137Cs for 1967, 1968, and 1969 are listed in there maybe nosignificant depression of lymphocytes capable of responding to PHAstimulation. Thelast evaluation of body burdens of gamma emitting isotopes in the Marshallese was done in 1965 on 179 Rongelap people!! in a shadow-shield were collected from 14 of the people at Kili in 1969 and brought back for radiochemical analvses. Individual results of radiochemical urine analvses on the Rongelap and Bikini people for calcium. *Radiochemical analyses were done at the Environment: Studies Division, Health and Safety Laboratory, AEC, New York, by Mr. Edward P. Hardy. Table 17 Summary of Marshall Island Radiochemical Urine Analvses, 1967-1969 1967 Rongelap exposed Rongelap unexposed Kili 1968 1969 90S; 137s, 9057 137s, 9Sr, 137Cs, pCi/liter nCi/liter pCi/liter nCi/liter pCi/liter nCi/liter 4.8 4.8 2.5 2.7 3.0 5.6 2.8 2.8 4.9 4.1 3.4 2.9 0.48 0.34