postabe ns 120 aD * at a tye yo key ets rete ea EDEN ate tae NEN eeES SERRE wetata + 7 RADIATION STANDARDS, INCLUDING FALLOUT strontium 90/Ca ratio than a diet in which milk is the only source of calcium. Indeed, estimates of the factor by which the strontium 90/Ca ratic of milk must be multiplied to give that in total diet range from 1.2 to 1.3.1. Results of calcium measurements in our pasteurized milk network indicate a value slightly greater than one for the calcium content. However, for purposes of calculating the ranges, this difference is ignored. Applying these factors, a range of estimates of annual average daily intake of strontium 90 may be obtained from the annual average strontium 90 concentrations in milk. table I. These are given in TaBLeE I.—-EHstimates of average daily intakes of strontium 90 for each year, 1957-61 Strontium Year Average milk concentration (upe/l) 16 18 111 8 8 Dally intake range (uuc) Conversion factor, 1,2 7 10 13 10 10 Conversion factor, 1.3 8 Ww 14 10 10 1 Raw milk network. It is worth noting that greater strontium 90 intakes which involve proportionately greater calcium intakes would not result in greater concentrations of strontium 90 in the bone (and subsequent radiation doses). This results from the fact that the concentration of strontium 90 in bene is related to the strontium/Ca ratio in the diet rather than the strontium 9%) content alone. TOTAL DIET SAMPLING Before comparing these estimates of intake with Federal Radiation Council guidance it is useful to consider a more direct estimate of average intakes for 1961 from the Public Health Service institutional food sampling network. During 1961, the Public Health Service has operated an institutional diet sampling program which studies the dietary intake of strontium 90 by young people between the ages of 5 and 18 This program, now consisting of 21 sampling points, collects a full 7-day-week diet of 21 meats plus soft drinks, candy bars, etc., on a monthly basis at boarding schools or institetions throughout the United States, The analytical programfor this study is designed around three procedures: (1} Strontium 80, (2) total radium, and (3) gamma scan for the estimate of other gamma-emitting radionuclides. This program was initiated in December 1960. The results of the calendar year 1961 representing the first full year of operation of the program are available for seven stations. These are shown in table VI. The annual average daily intake of strontium 90 for the stations varied between 5 and 10 pyc/day with an overall annual average intake for the population group under study of 7 wuc/day. It ean be seen, then, that the average daily intake of strontium 90 measured by this system is somewhat lower than that predicted from the values for strontium 0 in milk. Comparisons of these estimated average daily intakes with the guidance of the Federal Radiation Council shows that all of the intakes were in range fF. Intakes at the upper limit of range I continuedindefinitely would result in radiation doses to bone and marrowone-thirtieth of the RPG’s for normal peacetime operations. 1HASL 88, 1960. URGEARORAESaaSRORESEDRRHedate,