Contamination from Local Fallout The ‘“‘Strontium-Calcium Observed Ratio” 1OR) of Comar et al (1956) was used to denote the preferential utilzation of calcium in the following manner. Sr. Ca of sample OR yampie-preeursor = eenepe Sr Ca of precursor The Sr®discrimmation ratio in the chain from soil (5s) to bone {bj via plants (p) can be expressed as follows: ORvonenoit = (OR) (OR) = (0.7) (0.25) = G18 Vhe value OR,,,, == 0.25 is an approximate valuc obtained expenmentally on rats fed a stock laboratory dict (Comar et al, 1956). This discnrmination factor of 4 tor calcium against strontium from dict to bone m man has becn reported by Schulert ct al (1959a) and Brvant ct al 6395S). A more appropnate value tor the rats in this situation might be the ORwuneaer = U-10 ubtamcd by a stud, of wild Kangaroo rats lining in the Nevada desert ‘Alexander et al. 19561. The bods burden iw the. , srt Cay, = Sr Cay OR, OR, |. | = (54% 108)(0.7) 10.16; = 974 pye Sr¥"/g Ca Thevaluc thus obtained 1 anproximatch twice the value of 47 to S43 auc srg of caloum obtamed by direct radiochemical analysis of the tissues of rats living on the iskind dumng the 2-+car penod following ds tonation, This difference in the indirect environmental estimate of the bods burden of ds:Ca as compared with the direct analysis may reficct either errors in the discrmination ratios or a lack of equilibrium between the Sr"/Ca in the animals with the soil at 2 vears. Since 13 rats of the same average age analyzed at 4 vcars had values close to those of rats collected at 2 vears, at 443 = 18] puc Srg of calcium (Held. 1955), it must be assumed that the discrimination ratios are not suffcientl, accurate for this estimahon. It 1s obvious that applving the samc technique of estimating the Sr” body burdens of the Marshallese people is also difhcult because of the uncertainty of their dict and the discontinuous nature of their habitation on Rongclap Island. Dunning (1957) has estimated the future Sr’ body burdens in the Marshallese from the Sr®/Ca in an “average” food supply which was about 360 ppc Sr"/g of calcium in 1956. This figure would be reduced to a daily intake of about 100 pyc Sr°?/g of calcium if consumption of land crabs which have a high Sr*° content were eliminated. These estimates of average dictary intake are very approximate since the dict is not well known. A more extensive study made in 1958 viclded Sr® ‘Calevels of 67.5 ype Sr°/g of calcium somewhat lower than those of Dunning’s in 1956 (table 6). This study was bascd on an analysis of the avcrage diets of 14 males on Rongelap (Held, 1958) and a radiochemical study carried out by Harley (1959). It was assumed that half of the daily calcium (0.8 g) was from 32]