se mation*of sr, 0018933 Measurements have been made to determine the existing levels at the earth's surface, the quantity stored in the stratosphere, and the deposition rate. Samples of fallout have been taken from the soil and vegetation, by gummed tape and pot-type collectors on the ground,and by air-filter samplers at the surface and in the troposphere and stratosphere (References 8, 23, 39, 40, 41, 42, 43, 44, 45), Based on this work, it was estimated in the fall of 1956 that the sr 7° levels were about 22 me /mi? in the midwestern section of the United States, 15-17 me /mi* for similar latitudes elsewhere and perhaps 3-4 mc/mi® for the rest of the world (References 38, 39 }» The total amount / in the stratospheric reservoir, if uniformly distributed over the area of the globe, would increase these figures by about 12 me/mi*, The deposi- tion rate of the stored material was considered to be around 10% per annum, It was further estimated that if these levels were maintained for fifteen years the concentration in the human skeleton would be about 1% of the maximum permissible (Reference 24), The quantity of radioactivity in the storage reservoir was estimated by summation of the contributions of all the bursts through Operation REDWING which have deposited debris in the stratosphere, The available fraction of the weapon was determined by subtracting the local and intermediate fallout from the total, The intermediate fallout is thought to SAN BRONO FRG 29