The alpha-emitting isotopes of uranium and thorium were determined in the lungs of 14 former uranium miners and in soft tissues and bones of three miners and two millers. These radionuclides were also determined in soft tissues and bones of seven normal controls. The average concentrations in pCi/kg wet weight in 17 former miners' lungs are as follows: U-238, 75; U-234, 80; Th-230, 79. Concentrations of each nuclide ranged from 2 to 325 pCi/kg. The average ratio of U-238/U-234 ws 0.92, ranging from 0.64 to 1.06. The mean ratio of Th-230/U-234 was 1.04, ranging from 0.33 to 3.54. The near equilibrium between Th-230 and U-238,234 indicates that the rate of elimination of uranium and thorium from lungs is the same in former uranium miners. The concentrations of U-234 and U-238 were highest in lung; however, the concentration of Th-230 in bones was either higher than or comparable to its concentration in lung.
The concentration ratios of Th-230/U-234 in bone of uranium miners and millers measured in our laboratory have been compared with results predicted by ICRP-30 metabolic models. These results indicate that the ICRP metabolic models for thorium and uranium were only marginally successful in predicting the ratio of Th-230/U-234 in bones, and that effective release rate of uranium from skeleton may be more rapid than predicted by the ICRP model.
United States Nuclear Regulatory Commission, "Concentrations of Uranium Isotopes in Uranium Millers' and Miners' Tissues" (1985). Health. Paper 2.