1376, (4.5 em) in the residential areas has little effect since that action influences only the external gamma dose. Removal of successive 15 cm layers of soil in the subsistence agricultural areas, however, may reduce the bone dose by significant amounts. Removal of the top 15 cm layer, for example, may reduce the 30 year bone dose from 57 Rem to 19 Rem, while removal of an additional 15 cm may bring the dose down to 10.7 Ren. Since soil removal-vs-bone dose reduction would possibly be most effective for pandanus and breadfruit, a variation on the estimates of Table 9 may be obtained by preferentially stripping soil in areas where these trees are to be grown. For case D-1, for example, if pandanus and breadfruit are grown in the subsistence agricultural areas only in sections from which 15 cm 2. 7 ne ah; fs Vae ns of soil have been removed, the resulting bene dose may drop from 57 Rem to ty GC? St 9 Fos Pe ee FU 17 ON he . Tr re nen wand . additiconsl as om 1 the dese may drop to 23.7 Ren. The maximum dose reduction that can be achieved is through importation of clean soil from the southern isiands or from outside the atoll. 90... concentrations in the average profile(Table 6) do not get as low as those on the southern islands even at a depth of 180 cm. To achieve this meximum effect, however, sufficient clean soil has to be imported to encompass the entire root system of the mature trees and the water supply for these crops must not have 906, levels higher than those found in the southern islands. granular. Any replacement soil should be coarse and Such soil is less likely to blow away or wash away. Given these conditions, the 57 Rem bone dose of case D1 may be reduced to 18.9 Rem (57-39.1 + 2.1 (0.45) (the 2.1 Rem from Table 241 and 0.45 from Table 243 of NVO-140). SL at at Cat F make at,