None of the variations examined are surprising except, perhaps, for the large range that occurs due to variations in the parameters of the lung model. However, the biggest variations are due to translocation class, and it is generally acknowledged the plutonium-bearing particles at NTS fall into the year translocation class. INTRODUCTION In previous publications (Martin and Bloom, 1976; 1977), we presencred models that attempt to characterize the general behavior of plutonium in a typical ecosystem at the NTS. The purpose of these models was to estimate the transport and accumulation of plutonium in the ecosystem and to provide a basis for estimating the radiation dose from 233pu that might be received by a hypothetical man who resides in and obtains most of his food from this ecosystem. The major transport pathways considered in these models are shown in Figure 1. The large square represents an arbitrary boundary of a contaminated area. Boxes represent the principal ecosystem components of interest and arrows represent net transport via the pathways indicated. Arrows which cross the arbitrary boundary represent net transport out of the system. The plutonium concentration in the soil is the principal factor forcing the transport system in Figure 1. The soil contamination resulted from nuclear safety tests carried out from 1954 through 1963. Other inputs to the system (e.g., fallout) are insignificant compared with existing levels. Air is contaminated by resuspension of plutonium-bearing soil particles. Vegetation is contaminated internally by root uptake from soil and externally by deposition of resuspended particles. Plutonium input to herbivores is due to ingestion of soil and vegetation and to inhalation. Plutonium could reach man by inhalation of contaminated air, by accidental ingestion of contaminated soil, and by ingestion of milk or meat (skeletal muscle or internal organs) from animals raised in the contaminated area. Drinking water for herbivores and man is assumed to come from deep wells or from sources outside the contaminated area and to contribute nothing to plutonium intakes by herbivores or by man. One of the major applications of the models developed on the bases of Figure 1 is to estimate whether and to what extent environmental decontamination might be required to limit or reduce potential health hazards to man from the plutonium at NTS. In previous publications (Martin and Bloom, 1976; 1977), we concluded that the principal exposure pathway for 233pu to man is via inhalation and the critical organs in terms of radiation dose are lungs and bone. It was estimated that inhalation accounts ror 100 percent of the plutonium that reaches the lungs and 95 percent of the plutonium that reaches bone, liver, and kidney. Table 1 (Martin and Bloom, 1977) indicates that ingestion could be significant at ratios of ingestion to inhalation in excess of 400. However, the 514