70 WORLDWIDE EFFECTS OF ATOMIC WEAPONS cent of the strontium in the root volume of soil and, on the average, 10 per cent of the plant is consumed. 3. A mayrepresent a local or worldwide area, depending on the assumption of extent of uniform spread of debris. 4. F was assumed to be 200 people supported per square mile of arable land. Other biological factors are ¢ and d; 4 was assumed to range from 0.05 for individuals having low-calcium metabolism to 0.60 for those having high-calcium metabolism, and d was assumed to be 0.70. GABRIEL: November 8, 1951, and December 3, 1951 The later GABRIEL calculations omitted considerations of oral absorption and bone deposition by calculating on the basis of n=? For standard MPC (1 wc), the values given in Table 5 are to be reduced by a factor of Yon0, which gives a range of 20 MT to 9 X 104 MT for a worldwide MPC on GABRIFL assumptions andresults in an effective spread factor of 4 & 103, REMARKS ON CALCULATION OF WORLDWIDE CONTAMINATION” “1. Important progress the calculations. This new sidering the ratio of Sr®° to This type of consideration has been made by the RAND GABRIEL on the basis of basis was reported by Dr. Mitchell. It consists in contotal Sr or total Ca in human boneandin the biosphere. is likely to give much more reliable and much more prectse values for the tolerance contamination than the previous basis in which it was assumed thata certain arbitrarily chosen fraction of the Sr°° would find its way “2. The calculation which I presented on the last day of the conference was Note also the absence of the “2( or -+-)8" uncertainty factor. The error assump- tion here was that the estimation “may be 100 too low—or approximately LO times too high.” ‘The assumed values of the parameters were the same as those in the earlier GABRIEL study. Using GABRIE!. assumptions (but not values), it may be interesting to derive the megaton limits (using the proper conversion factor from nominal bombs) for a worldwide uniform distribution, unrealistic a figure as it may be. These are given in Table 5. We have corrected $/A = 0.1 pg/mi?/nominal bomb. Table 5 predicated on a number of assumptions, four of which are definitely pessimistic. These are “(a) All the Srwhich is produced will fall out before appreciable radioactive decay. “(6) All the Sr°° will be in an exchangeable form and will remain exchange- able in the soil for all its radioactive lifetime. “(¢) The ratio of Sr to Ca in the human boneis the sameas in the soil from which the food is derived. “(d) The tolerance dose for Sr°* is one microcurie distributed uniformly through the bone. “In addition to these, two assumptions were made of which I do not know GABRIEL THRESHOLD LETHALITY (In terms of megaton yields) whether they are optimistic or pessimistic, namely, “(e) by weight. Range: 4 X 104 MT to 1.8 X 108 MT Megaton Limits for GABRIEL Threshold Lethality (10 pg) Larger than Less than 2.9 * 10% 1.8 tof metabolism 2.4 *105 1.5 * 107 GABRIEL, 1951 4X 10# 4™ 107 bhi te metabolism 71 into human bodies. The exact assumptions about the ratio of Sr” to the inert substances matter less than the adoption of the general principle of Dr. Mitchell. _D S/AX H/F G' Ca tdi) APPENDIX I GABRIEL, 1949, high-calcium The amount of exchangeable calcium in soil is one part per thousand “(f) The amount of Sr°° taken up is related to the amount of calcium taken up independently of the ratio of inert Sr to Ca. "In addition, an assumption is made whichis probably optimistic, namely, “(g) The redistribution of Sr°° by fertilizer, etc., does not change the ratio of Sr°° to Ca in the soil from which human food is derived. a. With the assumptions made under 2, the tolerance dose is reached with a total fission yield of about 1000 megatons. “4. Assumption (4) under paragraph 2 is clearly pessimistic. It would seem *The following remarks are the substance of a memorandum from Hans A. Bethe, Cornell University, dated June 24, 1953.