b2Z of Table 26 shows that the body burdensof '*’Cs and °°Coare notsignificantly different among the various subdivisions by age and sex of the Rongelap resident population. The values given for the children may be overestimates, because the calibrations were in termsof an adult-size phantom only and the countifig geometry is such that a higher efficiency obtains for the children, espe- cially the smaller ones. Prior to 1962, the concentration of °°Sr in the urine was used asa basis for estimating *°Sr body burdens. Subsequently, the ratio of *°Sr to Ca in the urine has been used. Onthis basis the 1965 mean concentrations of 10.1 pCi °"Sr/liter and 0.093 g Ca/liter correspond to a body burden of 11.4 nCi. Data were not obtained on children in 1965. In previous years the urinary °°Sr to Ca ratios in children have been about twice that for adults. Urines for °°Sr analysis were not collected in 1966. Comparison of the 1965 survey data with the results from previous surveys (Figure 70) shows that the mean levels of '*’Cs and °°Sr have remained nearly constant since 1961, and that '*’Cs is at about the 1958 level. Further comparison with the 1954 and 1957 results indicates that the activities now being seen are almost entirely due to intake subsequentto the return of the Rongelap population to their homeatoll in 1958. If the ecological cycle were in equilibrium, it would be expected that, by virtue of physical de- cay, the specific activities of '°*Cs and °°Sr in the food and the corresponding body burdens of these radionuclides would have decreased about 9% during the interim 1961 to 1965. Actually there may have been a small decrease that is masked by the unknownoverestimationerror in the children. Even with a correction for this, the sustained levels suggest that increasing amountsofthe originally contaminated materials are getting into the food chain and thus maintaining the specific activity at the previous levels. This hypothesis is supported by data obtained from E. Held, University of Washington,* to the effect that soil and plant surveysindicate that the '*’Cslevels in plants haveremained about the same since 1961. There is no ready explanation of the mechanism for this. These findings are to be contrasted with those cited be- low for an Eskimo population. Table 28 showsthe relationship between ‘*'Cs body burden andits excretion rate for those resi- Table 28 Comparison of Body Burdens and Excretion Rates "Cs body burden, nCi ''Cs, nCi/ liter 8 508.9 15 51 33 38 405.6 484.8 971.2 575.0 773.9 Subject No. 39 11 20 27 40 +1 30 7 835 843 928 932 942 822 833 840 833 855 732.7 325.5 1326.0 1047.0 1209.0 728.9 1861.0 644.8 419.8 491.4 549.6 1058.0 694.6 636.9 1453.0 814.9 606.2 Urine volume,| Cs, nCi/ day Fraction; day 5.0 0.730 3.65 0.007 17 6.2 23.0 4.4 3.4 0.730 0.289 0.630 0.710 4.526 6.647 2.86 2.414 O.OLLI5 0.01343 0.00294 0.00419 6.0 0.500 3.600 1.2 2.1 3.1 4.7 2.2 0.6 19.0 3.2 L.3 6.5 97 18.0 4.5 3.4 6.0 2.0 3.6 0.645 0.940 1.320 0.560 0.890 1.800 0.630 0.350 1.340 1.040 0.350 0 40 0.035 1.000 0.800 1.750 0.500 0.774 1.974 6.732 2.63 1.958 1.08 12.35 2.86 2.01 6.76 3.395 972 3.758 5,10 4.80 3.50 1.80 Mean 0.00105 0.00373 0.00387 0.00507 0.00251 OQ.00161 0.00148 0.00663 0.00443 0.00478 0.01375 0.00617 0.00918 0.00549 0.00800 0.00329 0.00429 0.00296 9.004533 dents of Rongelap for whom individual urine specimens were analyzed. An average of 0.553%of the body burdenis excreted per day, the range being 0.105% to 1.375%. These values correspond to turnoverhalf-times of 120 days, 660 days, and 50 days, respectively. Except for some of the very slow turnover rates, these values fall within the ranges cited or reported for other populations. in which the means were 75, 74, 87, 115, and 135 days.*? Someof the lowest turnover rates in the Rongelap population may be ascribed to uncer- tainties in the completeness of the urine collections. Thusit is to be expected that the '*’Cs value would fall to near-zero levels in a yearofliving in a noncontaminated environment. That this fall does occur is shown bythe results with the Ebeve population, who have been absent from Rongelap for various times from | to 18 months. Becauseit is not a gamma-ray emitter, “"Sr is not detected by the whole-body counting method. (Theoretically it might be possible to estimate “Sr