ESTIMATED STRONTIUM-90 CONTENT AT BIRTH

Abstract

Specific activities in the infant at birth were estimated as a function of the strontium-90/calcium ratio in the milk consumed by the mother by: See Equation in the PDF File. where b: 90Sr/Ca ratio in Cincinnati milk during ninth month of pregnancy [values for Figure27 (published every month in Radiological Health Data) from Vol. 1, no. 4 (July 1960) to Vol. 4. no. 12 (December 1964); monthly average values were obtained by the Public Health Service by analyzing raw milk during 1960 and pasteurized milk there-after]; c: 90Sr/Ca ratio in mixed diet (including milk) divided by 90Sr/Ca ratio in milk; c = 1.4, based on Table XIX, p. 54 in 1964 UNSCEAR Report;1 d: 90Sr/Ca ratio in newborn divided by 90Sr/Ca ratio in average adult diet; d=0.09, based on Table XXV, p. 332 in 1962 UNSCEAR Report.2 The strontium-90/calcium ratio in the bone of the newborn is 0.126 (strontium-90/calcium)milk during the preceding month, as shown in Figure 26. Estimated values for a specific month are within 40% of the measured values from Table XXIV. The strontium-90/calcium ratios at birth were converted to specific activities by dividing by 0.29 mg per gram, the average ratio of stable strontium to calcium at birth (Table XVIII). The ratio of the specific activity in bone to diet, based on the estimated specific activity at birth and the range of dietary values in Table XL, was between 3/20 and 7/3. The ratio was lowest in the earliest and latest infants, and was less than unity in all except Infant 22 and for a few periods in Infants 23 and 25.