Low leveis of pat49,,440 were also present on Rongelap as indicated by the low levels of this isotope in the spectra of some of the people measured on Rongelap. It should be noted that not all of the subjects showed a dis~ tinct peak at 1.6 mev. For example, the spectrum shown in Figure 5 has very little net activity above 1.2 mev. The presence of the large 1.6 mev peek in the background, however, makes it difficult accurately to evaluate the ad peak at 1.46 mev, which shows up clearly in the 1957 spectrum. The differences between the 1957 and 1958 body burdens of cs? and an°> reflect the different levels of these isotopes in their diet. It is not known whether they have reached equilibrium with the increased amounts of these isotopes in their present environment, Because of the relatively short biological half lives of cs3? and zn®?, Little of the present levels can be attributed to the original activity which was absorbed in 1954, Therefore most of the activity represents Cs 137 and ane ingested relatively recently. BE. Late effects The acute effects of exposure of this population to fallout radia» tion have subsided, That the dose of whole-body gamma radiation had been in the sublethal range was substantiated by the following findings: the early symptoms of nausea and vomiting were mild, transitory, and did not recur; the hematopoietic depression was insufficient to result in clinical evidence of increased susceptibility to infection or in gross bleeding; no obvious effects on fertility, or on children who were irradiated in-utero, or on the course of pregnancies were noted; and lastly, no deaths have occurred that appeared to resemble acute or late radiation deaths that have been described. At 4 years posteexposure, the only remaining evidences of the initial radiation exposure to be found are (1) the lag in complete recovery of certain peripheral blood elements to the levels of the comparison oL5e