As a result, the Sr/Ca ratio in the fetus and newborn is approximately 1/8 to 1/10 that of the adult, and the resulting dose to the fetus is less than that to adults. The dose to a young infant teing breast fed wili of course also be less than thet calculeted fcr adults. wD 0.9;294 that is, th The OR body /diet Tor young infants is young infant nearly equilibrates with his diet. However, the mothers' milk, as discussed previously, has a Sr/Ca ratio ~ 90.1 that of the adult diet. The OR body /diet then decreases tc 0.5 for a l-year-old and by atrrroximately 2 or 4 years of ase has reached the adult value of 0.25. 2,4,6 Sirilsr data are available for Cs. Cesium-137 is metabolized an turned over rore rapidly in preenant women than in nonpresnant women. As a result, ° E Cs incorroration in the fetus and the resulting exposure are less than would be exrected from normal retenticn times coservea Tor adults. Exrerimental cata further indicate that. for the fetus and Tor breast-fed infants the concentraticn o exceeds that of the mother or of other adults. in reports by Rundo,” iinura et al., calculated for an adult for 137 Cs and Cook and Snyder. the dose is a conservative estimate for the fetus and the newborn. Cs — A considerabie body oF evidence is availabdie which indicates > Cs in the body is a function of age, with a more rapid turnover for younger ages. + R ' The biological half-time arrears to “ys ~ (ig