about S58 timee less then the maximus parmissible amount. Mermal facters of dilution by additional rainfall and/or by whe influx of lesser contaminated ’ - ground water would reduce the level of activity Ait Considerabie effort has and is being made to evaluate hasards from eirborne radioactive asterials, including fission products. There are ser- tainly many unanswered probleas inoluding the possible basard from a aingle particle in the lungs Despite the uncertainties end as yet incomplete analysis of the inhalation hazard, the crejonderance of evidence today is that the external gamms hasarc fros fallout is the more limiting factor of the twot, (However, see discussion on fooc eontanination.) Daring Upshot-Knothole quite complete data were ecllected ef eoneentrations of airborne activity an about 14° >secasions in some 40 different localities within 2% miles of the Nevada ‘roving Grounds, monitoring of all detonations. These ineluded Histograms vere uace of air eoncentrati ns versus tine after detonation for 30 oecasians and estinates were made of doses to the lung:. These dats for the f.ve coammities shovingthe highest air concentration are giver in Table ¥. b The histograa for 36. George (the nighyed hour average concentration of fallout ever ceasured in a populated area) is reproduced tn append‘: J, #ic Hoc Committees “eeting. «ashingtor, vanuary 20, 1944. o?.ngeowetee EI at WhN