62 of Table 26 showsthat the body burdens of **"Cs and *°Coare notsignificantly different amongthe various subdivisions by age and sex of the Rongelap resident population. The values given for the children may be overestimates, because thecali- brations were in terms of an adult-size phantom only and the counting geometry is such that a higher efficiency obtains for the children, especially the smaller ones. Prior to 1962, the concentration of °°Sr in the urine was used as a basisfor estimating °°Sr body burdens. Subsequently, the ratio of °°Sr to Ca in the urine has been used. On this basis the 1965 mean concentrations of 10.1 pCi **Sr/liter and 0.093 g Ca/liter correspond to a body burdenof 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 thatfor adults. Urines for °°Sr analysis were not collected in 1966. rie Comparison of the 1965 survey data with the results from previous surveys (Figure 70) shows that the mean levels of '*"Cs and *°Sr have re- mained 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 *°Srin the food and the corresponding body burdensofthese 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 unknownoverestimation errorin the children. Even with a correction for this, the sustained levels suggest that increasing amounts of the originally contaminated materials are getting into the food chain and thus maintainingthe 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 plantsurveys indicate that the ‘*’Cslevels in plants haveremained about the samesince 1961. There is no ready explanation ofthe mechanism forthis. These findings are to be contrasted with those cited be- low for an Eskimo population. Table 28 shows the relationship between *?’Cs body burden andits excretion rate for those resi- Table 28 Comparison of Body Burdens and Excretion Rates L37 Cs body ICs Subject burden, nCi/ Urine No. ni liter volume, | day day 508.9 405.6 484.8 971.2 575.0 732.7 525.5 773.3 1326.0 1047.0 1209.0 5.0 6.2 23.0 4.4 3.4 1.2 2.1 6.0 5.1 4.7 2.2 0.730 0.730 0.289 0.650 0.710 0.645 0.940 0.500 1.320 0.560 0.890 3.65 4.526 6.647 2.86 2.414 0.774 1.974 3.600 6.732 2.63 1.958 0.00717 O.O1LI5 0.01343 0.00294 0.00419 0.00105 0.00375 0.00387 0.00507 0.00251 0.00161 8 15 51 53 58 59 1! 20 27 40 41 50 73 835 843 928 932 94? 822 833 840 853 855 7289 1861.0 6448 419.8 491.4 5496 1058.0 69446 636.9 1455.0 8149 606.2 06 19.0 52 1.5 6.5 9.7 18.0 45 5.1 6.0 2.0 3.6 37g 1.800 0650 0.550 1.340 1.040 0.350 0.540 0.835 1.000 0.800 1.750 0.500 nCi/ 1.08 12.35 2.86 2.01 6.76 3.395 9.72 3.758 5.10 4.80 3.50 1.80 Mean Fraction/ 0.00148 0.00663 0.00443 0.00478 0.01375 0.00617 0.00918 0.00540 0.00800 0.00329 0.00429 0.00296 0.00553 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 turnoverrates, 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 uncertainties in the completeness of the urine collections. Thusit is to be expected that the '*’7Cs value would fall to near-zero levels in a year ofliving in a noncontaminated environment. Thatthis fall does occuris shown bythe results with the Ebeye population, who have been absent from Rongelap for various times from 1 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