f is the fraction of plutonium transferred from one location to another within the body where the subscripts refer to the compart- ments and the pathways listed in Figure 3 and Table 2 except BBN is the fraction from blood to bone, TBF & is the residence time of material following pathways f and g in the tracheobronchial region (days). Values of most of the parameters in the above equations are given in Table 2 (U.S. Nuclear Regulatory Commission, 1976). Trpegts assumed to be one hour of 1/24-day (Snyder, 1967; Kotrappa, 1968; 1969) while f is usually 0.003 percent (ICRP 2,,1959; ICRP 19, 1972). The parameter values for bone are £ BRN = 0.45 and TR = 100 years (ICRP 19, 1972). The radiological decay rate for 239Pu is 7.786 x 1078 (days)7}. The radiation dose rate to any of the compartments shown in Figure 3 or any other organ of the body is given by dD/dt = E y/m (19) where D is the dose to the compartment (rems), E = 51.2159 ce, is a dose rate factor (g rem)/yCi day)), ¢ is the effective energy absorbed in the compartment per disintegration of radionuclide (MeV/dis), y is the plutonium burden in the compartment (uCi), m is the mass of the compartment (g). Only the dose rate to lungs (pulmonary region) The usual values of the parameters in Equation partments are e€, = 53, e€, = 270, and = 7000 (ICRP 2, 1959) and mM = 00 as given by Snyder (1968; 1969). and bone is of interest. (19) for these two comas given by the ICRP (1967) and Kotrappa The biological half-time values (T?) in Table 2 range from less than one day to 1,000 days which corresponds to a minimum 4 value of about 6.9 x 10-" (days)~!. These X values are much larger than the radiological decay rate for *39Pu (A, = 7.786 x 1078 days7!) which can be neglected by comparison in Equations (1) through (17). The A, value for bone is small enough that Ay will have a very slight effect on Equation (18). Another consequence of the half-time values listed in Table 2 is the time it takes the compartments to reach the equilibrium burden of 239Pu resulting from a constant inhalation or ingestion rate. The time to reach about 99 percent of the equilibrium burden is about seven times the biological half-time. For the compartments of the lung model, the maximum half-time is 1,000 days (LMi) and the equilibrium time is no longer than about 7,000 days (about 19 years). Figure 4 shows the 233py organ burdens predicted previously (Martin and Bloom, 1976; 1977) and it can be seen that the pulmonary region (lung in Figure 4) and compartment 522