ey 164 THE SHORTER-TERM BIOLOGICAL HAZARDS OF A FALLOUT FIELD take up Ifrom fallout even in the order of magnitude directly measured which is 1/1000th of the level measured in bovine thyroids for the same period. However, statistical confidence is established at two defendable limits of possible 2uptake by human thyroid tissue. Thus: (a) The median value of range-fed cattle corrected 10 estimated day the cattle left the range is 0.6 millimicrocuries per gram thyroid. (6) The observed mean human thyroid T* content as of day of death is 0.0006 millimicrocuries per gram thyroid. (ce) Human Ilevels in thyroid could have been established at 0.0021 willimi- crocuries per gram thyroid with a certainty of P=0.01. (d) There is only 1 chance in 1,000 that human values could have exceeded 0.0026 millimicrocuries per gram thyroid during the observation period. Thus it is probable that human thyroid contains less than 0.43 percent or 1/230th of the LU burden in cattle thyroid following atomic detonation, Therefore, we can accept thatirradiation of thyroid from 1™ content in man in the high I fallout. period of June to October 1956 is less than 1.3 rep (median thyroid irradiation, range cattle June—Oct. 1956) 230 (confidence value for ratio of cattleto eO056irep uman) However, the probable value is estimated as 1,03 _ 13 rep X Tig)0.001 rep for accumulatedirradiation exposure of human thyroid tissue by contained I" fallout. ADDENDUM Data collected in 1957, whencontinental U. 8. tests were being conducted, shows that during the period from May 20 to July 31 statistically significant amounts of radioactivity were found in human thyroids. During this period the average value for 41 human thyroids obtained in the San Francisco area was 0.0014 milli- microcuries per gram of wet. tissue while that for 87 range cattle thyroids was 0.63 milli- microcuries per gram of wet tissue. Therefore the ratio of human thyroid radioactivity to cattle thyroid radioactivity was 1/460 as compared to a ratio of less than 1/1000 during the THE EXCRETION OF RADIOACTIVE FISSION FRAGMENTS BY MAN DURING CONTINENTAL AND OVERSEAS WEAPONS TESTS By Ane: G. Scurnopt, James B. Harrenrmne and Kent T. Woopwarp Bikini tests of 1956. This indicates different relative uptakes of I between humans and cattle in the two periods, The highest human value was 0.0056 millimicrocuries per gram while the highest cattle value was 4.0 milli- microcuries per gram, a value approximately twice the maximum observed in cattle during the period reported above. The present. con- centration of I" in human thyroids wouldstill besignificantly clevated at one-half the observed counting rate. REFERENCES 1, Lester Van Mropuesworta. (1954). Nueleonies, 12, 56 2. Lester Van Mippieswortn. (1956), Science, 128, 982 DISCUSSION Hardin B. Jones Dr. Linpaere (UCLA). Were those cattle from the bayarea also? Dr. Jones. These cattle were from northern California, Dr. Lrnpaerc. But from the west, Dr. Jonus. Yes. Dr. Linppura. Weare going to present some data this afternoon regarding the occurrence of iodine near the test site or more specifically, near the fallout pattern, which would suggest the values presented are very conservative in a shortperiod of time anyway. Walter Reed Army Institute of Research, Washington, D.C. The excretion of iodine-131 and strontium-90 has been measured, during Operation Teapot, in human urine specimens collected on a routine basis at selected stations throughout the United States and in foreign countries. A complete account of the work referred to herein is given in “Recovery of Radioactive Iodine and Strontium from Human Urine-—Operation Teapot”, Walter Reed Army Institute of Research Document 00-55 (AFSWP-893) by 3. B. Harigering, Ariel G. Schrodt e¢ al. The excretion of several of the principal fission products is being measured during Operation Redwing. Data will be available in a forthcoming report. Details of the chemical separation procedures and the low-level counting techniques used may be found in the AFSWP-893 Document. The program was set up to obtain 24-hour urine specimens from 10 individuals at each of a number of stations throughout the United States and overseas. The selected continental stations (Table I) are shown on the map (fig. 1). The data from the widely scattered overseas stations will not be presented here, but are available in AFSWP-893. In Figure 2, the average activity of iodine-131 per group of 24-hour urine specimens is plotted versus the collection time. Along the lower abscissa are indicated the dates which correspond with the collection week numbers of the upper graph. The x's scattered below the upper graph in Figure 2 indicate the passage of clouds at the altitude shown in relation to the shot times. No outstanding correlation is seen. Tasuk J.--CONTINENTAL COLLECTION STATIONS A. Letterman Army Hospital, San Francisco, Calif. B. Fitzsimmons Army Hospital, Denver, Colo. C. Brooke Army Hospital, San Antonio, Tex. D. Walter Reed Army Hospital, Washington, DB. ©. E. H. J. K. L. Fairchild Air Force Base, Spokane, Wash. March Air Force Base, Riverside, Calif. Nellis Air Force Base, Las Vegas, Nev. Luke Air Foree Base, Phoenix, Ariz, Lockbourne Air Force Base, Columbus, Ohio M. Tinker Air Force Base, Oklahoma City, Okla. NX. Hill Air Force Base, Ogden, Utah Q. Seott Air Force Base, Bellville, Ill. P. Selfridge Air Force Base, Mount Clemens, Mich. 8. Donaldson Air Force Base, Greenville, S.C. . T. MacDill Air Force Base, Tampa, Fla. W. Westover Air Force Rase, Chicopee Falls, Mass. X. Camp Mercury Air Force Base, Nev. The lower graph in Figure 2 shows the gummed paper data supplied by Hisenbud’s group. There is not the good correlation between the biological data and the physical determinations that we had hoped might obtain. Camp Mereury, Nevada (fig. 3) is of especial interest because of its proximity to the test site. Thefigure is self-explanatory. Figure 4presents the data from Oklahoma ity. Unfortunately our collection program ceased just at the time the iodine-131 excretion reached its highest point, so we were unable to record any subsequent data. 165