about 58 tines less than the maxizun permissible ascunt. Mormal factors of @ilution by additional rainfall and/or by the influx ef lesser ecxtazinated be exPr ited tu ground water vouldreduce the level of activity. ~ dix Considerable effort has and is being mede to evaluate hazards fron airborne radioactive materials, including fission products, There are esr tainly many unansvered probless including the possible hasard from a single particle in the lungs. Despite the uncertainties and as yet incomplete enalysis of the inhaletion hasard, the preponderance of evidence today is — that the external gamma haserd fron fallout is the more liniting factor of the two®, (Eowever, see discussion on food contanination.) During Upshot-Knothols quite complete data were eollected of soncen- trations ef airborne activity on about 150 occasions in some 40 different localities within 200 niles of the Bevada Proving Grounds, These inaluded monitoring of all detonations, Histograms vere made of air concentrations versus tine after detonation for 30 occasions and estizates were meade of doses to the lungs, These data for the five comamities showing the highest air concentration are given in Table YI.b. The histogram for St. George (the high"2s hour average concentration of fallout ever measured {n a populated area) 4s reproduced in Appendix J. ®22 Hoc Committees Meeting, Washington, D.C. January 20, 1954. ay ms Ria J Noe