2. Actions taken to reduce exposures should be those which show promise of significant exposure reduction when weighed against total expected exposures and the "costs" of the actions. ''Costs,'' in this context, are measured primarily in terms of costs to the Enewetak people as constraints on their activities or as dollar costs for cleanup or remedial action. In these evaluations, it should be emphasized that dosages through various pathways are estimated on the basis of environmental data and considerations of expected living patterns and dietary habits. While ''radiation standards" do not exist for environmental contamination levels in substances such as soil and foodstuffs, there is general agree- ment in terms of conservative models of these pathways and the relationships between a certain level in the environment and the likely dose to result from the pathway exposure. The area of plutonium in soils, however, is one for which there is no general agreement as to the quantitative relationship between levels in soils and dosages to be expected through the inhalation pathway, the primary one through which man can receive a significant dose from plutonium. The ICRP recommends a maximum permissible average concentration (MPC) of 1 picocurie per cubic meter (eCi/m3 ) of air for "insoluble" plutonium and 0. 06 pCi/m?3 for "soluble" plutonium for unrestricted areas. While the plutonium in the soil at Enewetak is thought to be typical of world-wide fallout, and therefore insoluble, 0.06 pCi/m3 will be used for the sake of conservatism. Appendix A of Enewetak Radiological Survey, NVO-140, presents two possible methods for deriving the exposures that may occur through the inhalation pathway for plutonium in soil. (This is the pathway of interest for the present although it is recognized that for the very distant future, ingestion may become more important by comparison. Table 250 of Anpendix IL shows that exposure to bone, liver, and lung from 239 py is expected to be a few hundredths of a rem in 30 years for pathways other than inhalation.) This material is produced as Attachment I of this section. The two methods presented are the ''resuspension-factor tt appreach and the mass-loading"' approach, Soil concentrations of *39Pu that woule be associated with the standard for *39Pu in air (0.06 pCi/m3 ) by the two methods are: IN}—-7