-3Engineering actions are those upon which the U.S. parties to cleanup and rehabilitation should place the greatest reliancefor assuring continuing "as low as practicable exposures." If the U.S. leaves the atoll in nominally safe condition, it can put the control in the hands of the people with a high degree of confidence fhat predicted exposures will not be exceeded to any significant degree. Advisory actions should be considered as a bonus in the exposure re- duction planning. If total exposures from all pathways exceed the recommended guides, remedial actions to reduce and control such exposures are judged to be needed. The guides are chosen recognizing that exposures of Eniwetok residents will be protracted in duration and that the health consequences of long-term low-level exposures are not now fully known and may never be known. Considering the exposure reduction achieved by engineering actions, it must be possible to maintain exposures of people below recommended levels; otherwise the U.S. parties must deliberate whether cleanup and rehabilitation of the atoll should be initiated now or at some later time. The area of plutonium in soils 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 (MCP) of 1 picocurie per cubic meter (pCi/m?>) of air for ‘insoluble'' plutonium and 0.06 pCi/m? for "soluble" plutonium for unrestricted areas. While the plutonium in the soil at Eniwetok is thought to be typical of world-wide fallout, and therefore insoluble, we will use the 0.06 pCi/m? value for the sake of conservatism. A guide for assessing the importance of a certain soillevel of Pu on Eniwetok can be arrived at by a set of conservative assumptions regarding the resuspension pathway. This is the "'critical'' mthway since