less than 200 rads, are below the lowest dose: which caused adverse biological effects seen i experiments using beagles. For example, Bair colleagues at Battelle-Northwest have not obse lung effects below about 2000 rads in dogs 10 12 years following a single inhalation exposur ?39pu0,.79 However, these animal data must be interpreted with caution, as lung tumor incide is essentially 100 percent at the lowest plutc exposure levels. Recently beagles have been exposed to low initial alveolar depositions, but additional <4 Fig. 9. ? on the dose-response function will not be avai al for many years. The tn vivo counter with detectors in position for counting the chest. The estimated initial alveola deposited plutonium in beagles which developed tumors ranged from 0.2 to 3.3 uCi per total or or ahout 3 to 45 nCi per gram of bloodless dog counting time, the comparable value is about 3.5 n- Park and his associates !® estimate that this a ci. of plutonium is 100 to 1500 times the estimate Positive counts were obtained for 14 of 21 per- sons measured. These counts suggested chest burdens ranging from 3 to about 10 nCi. However, in no case maximum occupational lung burden in man (i.e., 0.016 uCi or about 0.03 nCi per gram of blood1l lung). As a conservative estimate based upon did the estimated chest burden exceed the MDA at the extrapolation of their data to the 15-year mea 95 percent confidence level. life span of beagle dogs, these authors feel t jects with positive chest Seven of the 14 sub- counts had estimated chest initial deposits of about 70 nCi in the lung ( burdens of 7 nCi or greater and may be considered i nCi per gram), which cause premature death i: (at the 68 percent level of confidence) to have beagles, are about 30 times the concentration statistically significant chest burdens of from 7 alent to the maximum permissible occupational to 1O-nCi. burden for man. For reference, 10 nCi is about 2/3 of the maximum permissible lung burden for occupational workers (16 nCi). If maintained indefinitely, this This conclusion, of course, based on the assumption that lung tumor develo is related to plutonium concentration and not burden will deliver about 15 rem per year to the the total amount of plutonium in the lung. lung, assuming uniform distribution of energy example, throughout the organ. the If one uses the 68 percent confidence level, i: Fo: if tumor induction is somehow related total number of cells at risk (therefore, t number and size of plutonium particles), then i certain qualitative statements can be made about relative sizes of human and dog lungs may be ur the chest measurements. important and the 70 nCi which causes premature For example, the estimates of lung burdens of subject Nos. 1 and 2, who most death from lung cancer in the dog may be about likely received exposure to plutonium oxide, were 5 times approximately 10 nCi. sidered to be the maximum occupational lung bur Subject Nos. 4 and 9, who worked in the Recovery Group, each had a chest burden ox about 8 nCi. These relatively small the total amount of plutonium (70/16) « for man. 28 The experimental data obtained from rodent values are not surprising, in view of the known are not as translocation of plutonium from the lung to other reports that the frequency of malignant neoplas tissues as a function of time following inhalation. of the lungs of rats exposed to plutonium by in The cumulative radiation doses to the lungs clear nor as encouraging. Moskalev™ halation is 2 or 3 times higher than in the con of some of our subjects have been estimated pre- group at doses ranging from 41 to 234 rads. viously by Langham? (Table V). alev states that, assuming the biological effec 16 The values, all Mo