methods of estimating gamma doses anc since there are uncertainties in evsluating the hasards of such tranuitory air concentrations as from fallout, and experienced sinee the preponderance of evidence from past nuelear test series indicates that the external gamza hazard is wore limiting than the inhalation one, it vas recommended in the January 20, 1954 meeting to strike from the record the past recomendations for maxizun permissible air concentrations. It was recomeended that an air monitoring program be continued for documentary purposes and for whatever value the data might have in the future when new analyzes might be nade in the light of additional knowledge. 4 further discussion of the single particle problem may be nade. In arriving at the reeommendstion “... nor is it desirable that any indivi-e cual particle in this size range have activity greater than 10°* eicroeuries colculatad four hours after the biast" a computation was made that the average radiation dose from such a particle to e sphere one-half a alllineter in raciue woule be 3c5 reps.§ However, the conclusions may be misleading. in the case of a single particle, relatively large doer ‘ae delivered near the particle and szall doses at a greater distance. one jousible estimate of this phenomenon. many and difficult to evaluate. Appendix L suggests The parazeters involved here are For example, how long will a particle rezain in one place in the lung and what dose will be delivered during that tine? It has been suggested** that in the upper respiratory passage 20—mleron claneter particles are the upper limit of sise for deposition and that "Cilia *:inutes, Meeting of Comeittee to Consider the Feasibility and Conditions For a Freliminary Radiologie Safety shot for Jangie. L.4.5.L. May 21 and 22, 1951, EE ce3060, A status report. Sept. 15, 1954.(CONPIDENTIAi). BL