Table 3. Equilibrium Lung Burden of 239py Due to Chronic Particl ize Inhalation of 1 pCi/day AMAD ta) Micrometers 0.05 0.10 0.30 0.50 1.00 2.00 5.00 D Translocation Class W 4.26E-1 © 2.59E1 3.61E-1 2.60E-1 2.24F-1 1.66E-1 1.23E-1 7.93E-2 2.19E1 1.58E1 1.36E1 1.01E1 7.4650 4.82E0 (b) Y 2.56E2 2.17E2 1.56E2 1.34F2 9.97F1 7.37E1 4.77EL (a) AMAD is activity mean aerodynamic diameter. (b) D.W.Y. = Days, Weeks, Years. (c) Values are 739Py burdens in the pulmonary region of the lung. Numbers following E are exponents of 10. Parameter variations in the lung model are even more difficult to visual~ ize when their effect is on the rate of *3?Pu transport to blood (from where it goes to bone). Table 4 shows the effects of particle size, translocation class, fraction of 239pu in the gastrointestinal tract (GIT) which reaches blood, and ingestion to inhalation ratio (Hm/Am). Some of these data are plotted in Figures 6, 7, and 8. In these figures, the fraction from GIT to blood is assumed to be 0.901 for Class D, 3.0E-5 for Class W, and 1.0E-6 for Class Y. As with the lung burden, the variation from one translocation class to another is greater than the variation with particle size. The variations with particle size show a minimum value between 0.5 and 1.0 micrometers for day and week classes while the year class values decrease with increasing particle size. The maximum variation with particle size is less than a factor of 2 for day and week classes, but it is as much as a factor of 3 to 4 for the year class. The variation with translocation class for a given particle size is about a factor of 6 for the smaller particles at the lower Hm/Am values and all values of the fraction from GIT to blood (f.). For larger particles, the variation with translocation class can be’ greater than a factor of 50. It should be noted that an f, of 3.0E-5 is recommended by ICRP (ICRP 19, 1972), but they report experimental values ranging from 1.0E-6 to 0.001. The effects of variations in the biological half-time (tT?) for bone and the fraction from blood to bone (f )} are shown in Table 5 and Figure 9. The 239Pu is directly proportional BN £ (Equation (22)). The recommended value is 0.45 (ICRP 19, 1972) but values as high as 0.8 had been 528