A comparison of the dose to cells on trabecular bone surfaces from plutonium-239 and radium-226 based on experimental alpha absorption measurements

The α dose to cell nuclei on human trabecular bone surfaces critical to osteosarcoma production has been computed. The dose calculations are performed for 226Ra and its daughters, and for 239Pu incorporated into bone. The dose rates are computed utilizing measured values of the α energy loss (stopping power) in polycarbonate which has an ionization potential similar to tissue. Recent data such as the ICRP Task Group radium retention (ICRP, 1973) for trabecular bone have been incorporated into the model. Trabecular bone cell dose rates are also calculated for the mouse and beagle dog and the results agree with observed individual toxicities and relative Pu/Ra toxicities. Results for human bone indicate that the accumulated dose to cells on trabecular bone surfaces is highly dependent upon the burial of plutonium due to bone growth. A sustained ICRP maximum permissible body burden of 0.1 μCi of 226Ra will give 8 rads to these cells in 10 yr whereas a maximum permissible body burden of 0.04 μCi of 239Pu yields 18 rads. The 30-yr values for these sustained skeletal burden are 25 and 30 rads respectively. (author)