Relation of trabecular bone morphology to plutonium and radium toxicity

Induction of bone tumors by 239Pu is probably related to irradiation of endosteal osteogenic cells of trabecular bone. Since 239Pu is initially deposited at endosteal surfaces, the longer it stays there without being covered with bone or resorbed, the greater the accumulated dose. The trabecular surface which is remodeled last receives the largest irradiation dose to its progenitor cells and presents the greatest probability of its endosteal cells undergoing neoplastic transformation. It is suggested that the slowest turning over trabeculae should be identified as those trabeculae which retain the initial 239Pu deposition at their surfaces, and no diffuse deposit interiorly at progressively greater times after injection. The important radiation dosage in 239Pu toxicity may be that around slowly turning over trabeculae which form the tail of the curve of frequency distribution of various turnover rates rather than the average radiation dose to surface cells. Although 226Ra uptake is selectively reduced initially in slower turning over trabeculae, that which is deposited persists longer such that the accumulated dose to osteogenic cells is probably greatest at increasing time intervals