A COMPARISON OF SR90 COMPONENT OF HUMAN AND COWS' MILK

Abstract

INFORMATION on the concentrations of specific radionuclides in human milk as well as in cows' milk is needed to understand potential exposure to radiation of infants consuming these milks. Considerable data are available on radionuclide concentrations in cows' milk, but similar data for human milk are meager. To obtain data on radionuclide concentrations in human milk, samples of human milk were obtained from Denver, Colorado (July 9, 1959, through February, 1961), and Chicago, Illinois (December 21, 1959, through August, 1961). The Denver samples represented pooled human milk collected postpartum, while those from Chicago represented human milk from individual donors contributing to a milk bank. For comparison, samples of cows' milk corresponding to that consumed by the donors participating in the Chicago program were collected (November, 1960, through August, 1961). In turn, these samples were compared with samples collected monthly from the rawmilk network serving a portion of the Chicago milkshed. Samples were analyzed for calcium, potassium, strontium-90, and cesium-137, and the results are summarized in Tables I and II. As shown in Table I, the concentrations of strontium-90 and calcium in human milk samples from Denver and Chicago are similar, the mean geometric values being 0.62 and 0.56 picocurie of strontium-90 per liter (pc/1), and 0.24 and 0.25 gm of calcium per liter (gm/1), respectively. A comparison of the strontium-90 and the calcium concentrations of cows' milk with those of human milk from Chicago indicates that the concentration of strontium-90 in human milk is smaller by an order of magnitude, and that of calcium by a factor of approximately 5.