Table 10--ALLOWABLE MEGATONSOF FISSION ENERGY RELEASE AS A FUNCTION OF VARIOUS GENERAL POPULATION MPL’s Ay, max. bone level (no more Source of equilibrium bone level estimate and region United States Libby (13)-Ecological data Allowable MT of Fission yield testing) puc/g of Ca 10 puc/g of Ca 50 pyc/g of Ca 100 puc/g of Ca 1000 puc/g of Ca 3.9-—1.7 130 —-30C 650--1500 1300-3000 13,060—30,000 Kulp (6)-Ecological data 2 250 1250 2500 25,000 Eisenbud (76)-Milk data 4 120 600 1200 12,000 This paper-Bone data 1.9 250 1250 2560 25,000 Kulp (28)-Bone data This paper-Ecological data North Temperate Latitudes This report-Ecological data This report-Bone data World Average Kulp (6)-Ecological data This report-Ecological data This report-Bone data 1.5 300 3.5 140 1500 700 3000 1400 30,000 14,000 3.6 140 T00 1400 14,000 1.9 250 1250 2500 29,000 1.3 3.1 380 160 1900 800 3800 1600 38,000 16,000 1.7 150 1500 3000 30,000 2 250 1250 2500 25,000 World Average (no factor for distribution) Average x 1/5 (for nonuniformity) Average x 1/10 (for nonuniformity) 50 25 250 125 500 250 5,000 2,500 TET EG The most important question regarding the potential hazard of long-range Sr*® fallout is in relation to future weaponstesting. If there is an upper limit to the amount of Sr® in the bones of the population that can be safely tolerated, then the megaton equivalents of fission products that can be contributed per year to the biosphereby all nations is limited. If Sr® contamination from weapons testing by all nations continues at the same rate as has occurred during the past 5 years, equilibrium will be reached in about 100 years. At equi- librium the amount of Sr®® which will disappear each year from the environment, due to radioactive decay, will equal the amount that is being produced, and continuing weaponstests will not result in any further increase in the population bone levels. Libby'*1" and others!® have predicted that soil and bone levels at equilibrium with the present test rate will be 8 to 13 times the present values. On the basis of present average maximum equilibrium Sr®° bone levels postulated from the considerations set forth in this paper, the bones of the United States population will reach a steady state with the present testing rate at a value of 17 to 31 pyc per gram of Ca. The equilibrium value for the weighted average world population will be 15 to 28 pyc per gram of Ca. Libby’* has stated that something between 5 and 20 pyc per gram of Ca would be the aver- age maximum Srconcentration in the bones of the United States population if testing continued indefinitely at the average rate of the past 5 years. Kulp?® predicted an equilibrium level will be approached in the North American population of about 8 uc per gram of Ca in about 50 years, and Neuman’? in testimony before the Congressional Subcommittee suggested equi- librium bone levels of about 90 puc per gram of Ca may be reached in the northern United States. The values given above show disagreement by a factor of about 10. If, however, we accept as a reasonable average the values developed in this paper, the average Sr*° radiation dose to the bones of the population of the northern United States, at equilibrium with continued testing at the past rate, may be about 20 to 30 per cent of the average radiation dose from natural background, or about 20 to 30 per cent of the maximum permissible level adopted by the National and International Commissions. Since individual variations may result in a small number of people accumulating Sr*® burdens that are 5 times the average, the radiation dose to these few individuals may approach as an upper limit 100 to 150 per cent of the recom- 305