The effects of variations in the average soil concentration (C_) are easily seen from the equations. Both A_ and H_ are directly proportional to C_ and, therefore, the 239py burdens” and the corresponding radiation doserates for lungs and bone are also directly proportional to C This relationship was recognized in previous studies (Martin and Hloom, 1976; 1977) and was used to normalize all calculations to 1 pCi/g soil and to determine an acceptable soil concentration at NTS. Since Cy can have values which range over several orders of magnitude, the estimated radiation dose rates to lungs and bone can also range over several orders of magnitude. The nominal value of the mass loading factor used previously (Martin and Bloom, 1976; 1977) is 100 ug/m3. Measured air concentrations of *39Pu at NTS are in good agreement with predictions based on this value (Anspaugh et al., 1975). However, this parameter can also range over several orders of magnitude and the inhalation rate (A_) is directly proportional to L_.. Variations in L_ can also affect but the effects may be smaller and less obvious. Also, since inhalation is far more significant than ingestion in transporting 2339pu to bone and is the exclusive mechanism for transport to lungs, the range of variation in dose rate to the lungs is directly proportional to the range in L values, and the rate to bone is also directly proportional for alt practical purposes. It is much more difficult to visualize from the equations the effects of variations in the fractions and half-times involved in the lung model as well as the ingestion to inhalation ratio. Table 3 shows the equilibrium lung burden of 239py due to a chronic inhalation of 1 pCi/day as a function of particle size and translocation class. The dose rate to lungs is directly proportional to the burden. These data are plotted in Figure 5. The data show that the burden decreases with increasing particle size, within the range of respirable particle sizes. For a given translocation class, the maximum variation is about a factor of five to six. There is a much larger variation from one translocation class to another with the year class (insoluble, immobile particles) being about 600 to 700 times greater than the corresponding particles in the day class (soluble, mobile particles). 526