infants through about 3 monthsis either breast milk or formula. Formulas are imported and diluted coconut milk to supplement or replace the milk from breast- or bottle-feeding. For a contain very low concentrations of 90S; daily total intake of 1.3 L/d, we assumethat, on _ representative of worldwide background concentrations. The concentration of 2Sr in breast milk ma milk and 5% is a mixture of equal parts coconut the average, 95% of the daily intake is breast milk and water. Consequently, the daily intake of %Sr from 4 to 8 months would be be determined from the OR. The OR@23252* has been reported to be 0.10 (Loughetal., 1960; Comar, 1967), indicating a discrimination across 0.043 pCi/L (0.95) 1.3 L/d the mammary barrier similar to that across the + 0.016 pCi/mL 1300 mL/d placental barrier. The OR is based upon the 90Sr = 0.053 pCi/d + 0.52 pCi/d = 0.57 pCi/d, per g of calcium and consequentlyis not directly of use in dose calculations. Thetotal g of calcium in the reference and target must be known so that the total amount of 79Sr transferred from a specific source to a specific target can be determined. A more convenient form for the data for dose calculations to infants using current models is the where the concentration of Sr in coconut milk at RongelapIsland is 0.016 pCi/mL and in breast milk is 0.043 pCi/L. Infant/Child (9 months to 1.4 y). At about age 9 months to 1.5 y, small quantities of local foods are given to the infants to supplement 90S; concentration per kg of mothers’ milk based on the mothers’ dietary intake. The average percentage of 90Sr ingested that is secreted per kg of milk was determined to be 0.31% for breast-feeding. The estimated 9Sr intake from consumption oflocal foods is assumed to be 20% of the adult intake and is 2.8 pCi/d. Thus, the daily intake of 90Sr is assumed to go from the 4- 4 women (Lough et al., 1960). Using this average value for the percentage of 99Sr to 8-month-old value of 0.57 pCi/d to about 3.4 pCi/d. Child (1.5 y to 3 y). The average daily ingested that is secreted in milk and the average 99Sr daily intake of 14 pCi/d at Rongelap Atoll for women, the concentration of 906r per kg (~1 L) of milk would be 0.043 pCi/kg. intake of 99Sr for the 1-y to 3-y age group from our diet model is 9.2 pCi/d (Appendix A, Table A-2). Child (4 y to 11 y). The average daily Thus, assuming that an infant's diet is about 1.3 L/d of milk, the daily intake of 9°Sr from birth through 3 months would be 0.056 pCi/d. The OR2in the first few months after intake of 9Sr for children 4-y to 11-y old from our diet model when imported foods are available is 8.2 pCi/d (Appendix A, Table A-3). birth is about 0.9 (Comaret al., 1965; Bryant and Loutit, 1964; Lough et al., 1963; Comar, 1967); that is, the infant nearly equilibrates with his diet. The or*scy changes to about 0.5 by ly (Bryant and Loutit, 1964; Comar, 1967; Kawamuraet al., 1986) and levels out at-about the adult value of 0.25 by age 3 to 5 y (Lough Teenage (12 y to 17 y). The average daily intake of %Sr for teenagers from our diet model when imported foods are available is 11 pCi/d " (Appendix A, Table A-4). Adult (2 18 y). The average daily intake of et al., 1960, 1963; Comar et al., 1965; Comar, 90Sr for adults from our diet model when 1967; Burton and Mercer, 1962). This type of imported foods are available is 14 pCi/d (Appendix A, Table A-1). The daily intakes of 99Sr for the various information has been incorporated in the ctr vwuu sh Ins retention model discussed later in the paper. Infant (4 to 8 months). We assumethat infants from 4 to 8 months occasionally receive fom “ & age groups, based on the data and assumptions described above, are summarized in Table 4. 10