- 12 Page 8, lines 6-8 - "This gradual conversion of the soluble plutonium compounds to small colloidal size particles at focal points of activity may be the result of the self-chelating properties of tetravalent plutonium in solution." Comments: It is not clear what is either meant here or what assumptions have been made to reach this conclusion. Page 8, lines 9-11 and line 17 - "In recent studies of rat inhalation of 238P U9 , Sanders(!1) has demonstrated a substantially increased risk per rad for small lung burdens of aged, ‘crushed' 238Pu0, microspheres." ",.ethe greater mobility and wider redistribution of the 238Pu05 microspheres..." Comments: The material to which Sanders (11) exposed rats was not"'crushed' ?38pu0, microspheres." It was material derived from crushed 238pu0, microspheres, It had been stored in a saline solution for a long period of time and had been altered to a non-crystalline form of plutonium (i.e., it had no detectable x-ray diffraction pattern) thought to be solubilized in the saline and "monomeric" in form. In addition, it should be pointed out that the smallest initial deposition in this study was 5 nCi, or about 300 times the current maximum permissible occupational lung burden for humans of 0.016 nCi/gm (assuming a 1000 gm lung). The low rad dose, in contrast to this ~~ deposition, was due to the rapid alveolar clearance of the inhaled 23850, Page 9, lines 20-22 - "It is proposed that these two tumors may be attributed to secondary protons ejected by alpha interactions with hydrogen atoms, The expected yield is one proton per 10 alpha inter- actions," Comments: It is not clear exactly who is making the proposed mechanism of induction of the two tumors referred to, what the basis is for the proposed conclusion, or what evidence is available to support it.