Table I. Pulmonary deposition of plutonium ( 239+240 Pu) for worst- and best-case conditions on Bikini Atoll. Inhalation Condition Dust Soil Pu Personal Enhancement _ Pulmonary rate aerosol activity dosimeter Respirable | deposition (m?/h) (g/m?) (aCi/g) factor factor fraction (aCi/h) Bare field, during tilling 1.04 136 15.3 3.1 0.92 0.24 1476 1.04 21 15.3 0.83 2.64 0.19 139 0.83 21 15.3 0.83 1.86 0.19 78 0.83 21 8 0.41 1.1 0.19 12 0.023 28 4.1 2.5 i> 0.24 Stabilized field, heavy work In and around houses, light wosk light work seenta Se GaPh4 Coconut grove, At roadside, one vehicle/h® 1.58 + BGS a Exposure to one !0-s, median, vehicular dust pulse not including background (BG). b Assumed value. © Radionuclides inhaled via background mass loading. normal and high-activity conditions at Bikini Atoll indicate that the pulmonary deposition 239+240,, n 241, and would be less than 0.3 (Table |). The gut transfer factors used for are 10° 4 and 5 x 107 respectively, as recently suggested by the ICRP. 23 Both plutonium and americium are considered to be class-W particles. The dose contribution from the inhalation pathway is a major source of exposure to the transuranic radionuclides, but both the inhalation pathway and the transuranics will contribute a minor portion of the total doses predicted over the next several decades. The transuranic radionuclides that must be considered in evaluating the inhalation pathway are 23942405, 24 ay and 241 a as well as the 241 ay that in the future will result from the radiological decay of 24l Pu currently present. Because of the low-energy beta radiation (0.02! MeV maximum) and a much shorter half-life (14 y), the doses from atl ny are less than one tenth those from 23942405, The concentrations of 2*!am in the soil (pCi/g) at most of the atolls are approximately 70 to 75% of the 23942405, concentrations. However, more 24) am will result from the decay of 241 oy, The parent-daughter relationship for 241 py to 241 am is shown in Fig. 2. The maximum 24 am activity that will result from an initial 14 241 Pu