Nex at aR te ,: i “ SBPye! Sit ah ve FES 3h a aT : fission products in fallout, namely Strontium-90, they stated "there seems to be no reason to hesitate to allow a universal human strontium burden of 1/10 of the permissible yielding 20 rep in a lifetime,.... Visible changes in the skeleton have been reported only after hundreds of rep were accumulated and tumors only after 1500 or more," The permissible level referred to is that recommended by the NCRP for industrial workers, The Committee noted that although "some children have accumulated a measurable amount of radioactive strontium in their bodies, the amount 1s quite small~--a thousandth of what is considered a permissible dose, The Committee concluded, "then, that Strontium-90 is not a current threat, but if there were any substantial increase in the rate of contamination in the atmosphere, 16 could become one," Committee on Meteorological Aspects of Atomic Radiation Chairman - Harry Wexler - U, S, Weather Bureau In this part of the report there is the fullest discussion of fallout from nuclear weapons, They distinguish between kiloton bursts when the cloud does not penetrate to the strato- sphere and megaton bursts where the cloud does, that with surface bursts, They estimate 1.¢e,, where the fireball touches the ground 70-80% of the residual radioactivity falls out nearby, i,e., with small weapons a few miles, with larger ones up to . 300 miles or more, They emphasize the ease of predicting this "nearby" fallout pattern after the fact and the problem of predicting its precise pattern prior to detonation, They speak of intermediate fallout, 1,e., material of small particle size released below the stratosphere and some 80% of which falls out within three weeks in the same hemisphere in which it originated and tending to uneven distribution - 10 - Enclosure II.