Concentrations of alpha-emitting isotopes of U and Th in uranium miners' and millers' tissues.

The concentrations of alpha-emitting isotopes of U (234U, 235U, and 238U) and Th (228Th, 230Th, and 232Th) were determined in soft tissues and bones of three deceased U miners and two deceased U millers. The soft tissues generally included lung, liver, kidney, spleen, gonad and heart. The concentrations of U isotopes in the miners' lungs varied up to a factor of 18, suggesting that the accumulations of U in lungs at the time of death varied drastically. The concentrations of 230Th in the miners' lungs were similar to the concentrations of 234U and 238U. The concentrations of U isotopes and 230Th in millers' lungs also differed by a factor of almost 10. The most noticeable difference between the concentrations of U isotopes (238U and 234U) and 230Th was in the skeleton of U miners and millers. The 230Th/234U concentration ratios were as high as 94 in bones of miners and as high as 23 in millers. These results suggest that the fraction of Th transferred from blood to bones is much higher than the fraction of U transferred, and that the residence time of Th in skeleton is much higher than the residence time of U as suggested in ICRP Publication 30.