30 It is obvious that use of this techniquetoestimate the Sr®® body burdens of the Marshallese The value OR,., =0.25 is an approximate value obtained experimentally on rats fed a stock laboratory diet.*? The discrimination factor of 4 for calcium against strontium from diet to bonein man has been reported by Schulert** and Bryant.** A more appropriate valuefor the rats in this situa- peopleis also complicated by the uncertainty of their diet. The estimates of average dietary intake of the Marshallese since their return to Rongelap are approximate, because the diet has varied during the past several years. A study made in 1958 yielded daily Sr*°/Ca intake levels of 67.5 Sr units (uaC Sr*°/g Ca), provided that coconutcrabs (see Figure 4) were excluded from their diet.**-*® The tion might be the ORjone-aiet = 0.16 obtained by a study of wild kangaroorats living in the Nevada desert.** The Sr*° body burden is then Sr®°/Ca levels in the various foods are shownin (Sr°°/Ca), = (Sr°?/Ca),(OR,_,)(OR,_,) Table 31. This study was based on the analysis of various food samples in what may be considered an average diet. The data were obtained froma study of the diets of 14 males on Rongelap.*’ It was assumed that half the calcium in the diet was derived from food not native to RongelapIsland. =(8.4 x 10°)(0.7)(0.16)=924 wuC Sr°°/g Ca. The value obtained in this manneris approxi- mately twice the value 470 to 545 paC Sr°/g Ca obtained by direct radiochemical analysis of the tissues of rats living on the island during the2year period following detonation.*® This difference From the discrimination factor of 4 and the daily intake of 67.5 Sr units, the equilibrium Sr®° body burden for the Rongelap peopleis calculated as =17 muC. This is very close to the equilibrium between the indirect environmental estimate of the body burden of Sr°°/Ca and the results of direct analysis may reflect either errors in the dis- body burden (23 mpC) estimated by Woodward crimination ratios or perhaps lack of equilibrium between the Sr°°/Ca in the animals and in the soil at 2 years. The latter possibility exists, since, although the 13 adult rats analyzed by Held*’ at 4 years had values close to the 2-vear level, 443 181 pC Sr*°/g Ca, the life span of the rat is only 2 years. from the urinalysis data.*° ° Another effort was made tn the 1959 survey to gather samples of meals to be assaved for Sr°°/Ca content. However, since the Marshallese were foundto subsist to a large extent on foodsnotindigenous to the area, such as C rations, rice, and ~ Table 31 Estimate of Sr** in Diet of Rongelap Adults. 1958 A B Daily intake,* g (wet wt) Ca content, mg/g Meat from mature coconut Meatfrom drinking coconut Milk from green coconut 89 75 116 0.075 0.14 0.15 Arrowroot Breadfruit Fish 58 45 139 Pandanus,edible portion Clams Crabs, land Total 79 45 14 AxB Daily Ca intake,mg D E DE Fraction of total Caintake** sr’ content, puC/gCa Contribution to total daily Sr’ intake, upC/g Ca 6.7 10.5 17.4 0.008 0.013 0.022 1,200 210 1,000 9.6 2.7 22.0 2.10 0.60 0.13 121.8 27.0 18.1 0.152 0.034 0.023 19 260 280 2.9 8.8 6.4 4.00 180.0 0.225 449 0.56 0.15 4.00 660 11.9 56.0 0.015 0.070 The diet also included imported foods: rice, canned C rations, flour, tea, milk,salt, and sugar. *Based on average daily diet of 14 Rongelap maies.*’ **Based on total calcium intake of 0.8 g/day. 930 3 (4,000) 14.0 | (280.0) 67.5