Assuzrtiona The following assumptions are ssde in estinating radiation doses to the lungs, &. Twenty per cent of the inhaled activity is deposited. B. There vill be no elimination of particles during their radlo~- active lifetines. There is uncertainty as to the biological half-life of particles in the lungs. In those communities showing the highest concentrations of fallout, the peak of airborne material (which accounted for the greatest percentage of total fallout) occurred only a few hours after detonation. If one assumes a radiological decay according to t7)+2 and a biological half-life of say 30 days, tho omission of biological half-life would not affect seriously the computed total dose. C. All of the activity is essociated vith particles in the respirable range of sizes. Fast data from cascade impactors indicate that about 90% of the activity is asscel ated with particles 5 alcrons or less in the commnities DB. The lungs are mifornly irradiated. B. The veight of the lungs is 900 grans. Y. ba individua) inhales 20 cubic meters per 24 hours. CEMALN 5 77