only after hundreds of rep were accumulated and tumors only after 1500 or more," The permissible level referred to is that recom mended by the NCRP for industrial workers, The Committee noted that although "some children have accumilated a measurable amount of radicastive strontium in their bodies, the amount is 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 contaminatison in the atmosphere, it sould become one," Committee on Meteorologizel Aspects of Atomis Radiation Chairman - Harry Wexler ~ U, 5S. Weather Bureau In this part of the report there is the fullest discus— sicn of fallcut from nuzlear weapons, They distinguish between kilcton bursts when the cloud does not penetrate to the strato- sphere ard megaton bursts where the cloud does, They estimate that with surface bursts, i,e,, where the fireball touches the ground 70-80% of the residual radisacstivity falls out nearby, i.e.,- with small weapons a few miles, with larger cnes up to 300 miles or more, They emphasize the ease of predicting this "nearby" fall- out pattern after the fazt and the problem of predicting its pre cise pattern pricr to detsnation., They speak of intermediate fallout, i.e., material of small particle size released below the stratosphere and some 80% of which falls cut within three weeks in the same hemisphere in which it originated and tending to uneven distribution associated with rainfall and wind patterns alcng a broad band in the same general latitude as that of its origin, Finally, they refer to delayed fallout of material which has gained entry into the strato-— sphere, Jt is slow with an average storage time in the stratosphere of 10 years, plus or minus five years, AEC believes the latter figure ~ five years - is the more likely, This delayed fallout tends to distribute itself more ocr less uniformly over the surface of the earth over the years. \ NAS They state that "at present, the amcunt cf Sr 90 in the stratosphere from nuclear weapons tests is far tco small to approach maximum permissible concentration even if it were all deposited now," They urged a continuing pregram to check on the amount of radioactivity in the stratosphere as necessary so that if there were to be a greatly increased rate of thermonuclear weapons testing activi- ties we would know at the earliest moment whan it was time to slow down in terms of potential hazard from Sr 90 to man, There is also a discussion of the radioactivity from fallout cf the intermediate and delayed varisty, They point out that it