performed previously on Enjebi Island and background studies similar to that of 1 were performed later on Eneu Island. The “normal” or “background” mass loading (the mass of solid material per unit volume of air) measured by. gravimetric methods for both atolls is approximately 551g m-3. The Bikini experiments at Bikini Atoll show that about 34 ug m3 ofthis total is due to sea salt, which is present across the entire island as a result of ocean, reef, and wind actions. The mass loading due to terrestrial origins is, therefore, about 21 pg m-3. The highest terrestrial mass loading observed was 136 ug m-3 immediately after bulldozing. Concentrations of 239+240Py in collected aerosols were determined in areas (1) with normal ground cover and conditions in coconut groves, (2) with high-activity conditions, i.e., areas being cleared by bulldozers and being tilled, and (3) with stabilized bare soil, i.e., cleared areas after a few days of weathering. The plutonium concentration in the collected aerosols is different from the piutonium concentration in surface soil for each of these situations. We have defined an enhancement factor (EF) as the 239+240Pu concentration in the collected soil aerosol mass (corrected to sea-salt mass) divided by the 239+240Pu concentration in surface-soil (0- to S-cm). The EF obtained for normal conditions (using standard, high-volumeair samplers) is less than 1; the EF for the worst-case, high resuspension conditions is 3. The observed EF's at Bikini and Enewetak Atolls are summarized in Table 3. The EFof less than 1 (EF < 1) for the normal, open-air conditions is apparently the result of selective particle resuspension in which the resuspended particles have a different plutonium concentration than is observed in the total 0- to 5-cm soil sample. In other words, the particle size and density, and the corresponding radionuclide concentration of normally resuspended material, is different from that of a representative 0- to 5-cm soil sample. In addition, approximately 10% of the mass_ observed on the filter is organic matter, which has a muchlower Pu concentration than the soil. Similarly, the enhancement factor of 3 for highresuspension conditions results from the increased resuspension of particle sizes with a higher plutonium concentration than that o the total 0- to 5-cm soil sample. the high-volume air sampler data for a particular condition and repr enhancement that occurs around indi to their daily activities. These da summarized in Table 3. The total e factor used to estimate the amountof plutonium is the EF multiplied b Consequently, the total enhance (TEF) used for normal resuspension ¢ 1.5 (0.82 x 1.9) and for high re conditions, 2.9 (3.1 x 0.92). To calculate inhalation exposure, that a person spends 1 h d-! in high conditions (mass loading = 136 pg m under normal resuspension condit loading = 21 pg m-3) and has a brea 23 m? per day (1.2 m3 under high r conditions and 21.6 m3 under normal r conditions). The radionuclide concentratio in surface soil (0- to 5- cm) for Rongelap Islanfi complete the information necessary for calguiation of plutonium and americium intake through inhalation. The median 239+240Pu and 241Am qbncentration in surface soil in the island interiorfregion is a factor of 6 higher than the 239+240Py and 241Am concentration in surface soil in the Willage and housing area (Table 4). We assume for the 1 h d=! in high resuspension conditiong that the resuspended soil aerosol is based o@ the island interior value for Pu and Am concpntration in surface soil and that a person breaths 1.2 m of air during that 1 h period. The 29h spent in normal resuspension conditions is b down as follows: e 7hd-! in non-occupatiogal activity conditions in the island interior (isfand interior median Pu and Am concentrationg in soil) in which 8.4 m3 ofair is breathed. e 7hd-! in non-occupational activity in the village area (village median and Am concentration in soil) in which 8.4[m3ofair is breathed. * 9hd-! in resting conditions area (village median Pu and Am c in soil) in which 4.8 mé ofair is br the village