63 from its bremsstrahlung spectrum, but in practice the complications caused by the presence of gamma-rayemitters and bythesize of the human body renderthis method infeasible.) Comparison of the excretion rates of *°Sr and '9™Cs with the body burdensof **"Cs measured by whole-body counting provides a clue to the *°Sr body burdenstatus. A quantitative value cannot be deduced, however, because the factors relating the behavior ofthe two nuclides are not sufficiently well established. The study by Hardy, Rivera, and Conard*™ summarized in Appendix 18 is pertinent to this problem. '*’Cs and *°Sr retentions were fol- lowed for 190 days after ingestion of representative Rongelapfood items by one ofthe investigators. The '*7Cs ingested was almost quantitatively ab- sorbed from the gastrointestinal tract, but 50% of the *°Sr was excreted via the feces in the first 10 days and maybe regarded as not having been absorbed. By the end of the study almostall of the. 87Cs and about 75% of the *°Sr had been excreted in the urine and feces. The exactfigure for retention is dependent on the correction used for activi- ties ingested in the normaldiet, and these were not measured. In this study the biological halftime for '*’Cs was estimated as 74 days. For both '87Cs and *°Sr the urinary excretion rates were markedly elevated during the ingestion period and for a few days afterward. This confirmsotherre- sults to the effect that the excretion rates found are strongly affected by the recent diet and, when there has been a recent intake of high activity food, the excretion rates do not provide accurate indices of the body burdens. Comparison of '?’Cs Levels in Marshallese and Alaskan Eskimos It is ofinterest to comp.re the '*’Cs body burden findings in the Rongelapese with those reported for certain Alaskan Eskimos. Thefindings in the Eskimo population in August 1965 are shownin Table 29.%° It may be noted that the results for adult Eskimos are equal, within statistical limits, to those for the adult male Rongelapese. For the Eskimo population the 1965 data run about 30% lower than the comparable 1964 data, and this trend parallels the findings in the local caribou, one of the principal componentsoftheir dict.** The Federal Radiation Council Radiation Protection Guides*® is cited asrecommending a limit of 3000 nCi '*’Cs in individual adults for this population, Table 29 Cesium-137 Body Burdens for Residents of Anaktuvuk Pass, Alaska** Body nCi per Age, yt No. persons burden, nCi kg body wt. >21 15-20 3-14 23 5 22 92958 490+ 42 170417 15.7+£1.0 9.5+1.0 6.20.3 16 900=-60 16.041.3 >21* *“Controls” —- members of a group who werefirst counved in 1963 and are re-examined periodically. and opinions are expressed to the effect that the current body burdens do not constitute a radiological health hazard.** These opinions are consistent with those that have governedthe policies applicable to the Rongelapese. Radiochemical Analysis of Coconut Crabs A food item that has been of special interest throughout the Rongelap medical surveysis the coconut crab (Birgus latro). Becauseofits high *°Sr content, it has been banned as a food. The following concentrations of °°Sr and ‘*’Cs were found in a crab taken from RongelapIsland in 1965 (radiochemical analysis by the Health and Safety Lab- oratory): **Sr, 66,600 pCi/kg original matter; 87s, 12,700 pCi/kg original matter; stable Ca, 92.) g/kg original matter. Previous analyses of crabs taken from Rongelap Island have been reported in the 7, 8, and 9-10 year reports.*-’° For *°Sr the results have run: at 7 years 1140 pCi *°Sr/g Ca; 8 years 1317, 1086, 1113, and 1378 pCi *Sr/g Ca; and 9-10 years 865, 628, and 780 pCi *Sr/g Ca, and 39,292, 45,318, and 66,234 pCi '*’Cs/kg. The 1965 results for *°Sr are slightly below the averagefor the previoussurvey and for '*’Cs are reduced to about % the previovs results. All these results are markedly lower th... those that have been obtained with crabs from the more heavily contaminated islets of Eniatok and Kabelle (Figure 71). The crab data may be compared with the data on Rongelap subject No. 73, who hadthe highest '87Cs body burden (25,400 pCi/kg) and was excret- ingactivity in concentrationsof 78,000 pCi '3’Cs/z Ca and 50 pCi *°Sr/g Ca. It seems clear from this that becauseofits relatively high °°Sr content the