Investigation of the thorium content in human tissues

The content of natural alpha-emitting isotopes of thorium (Th-238, 230, and 232) have been determined in 22 sets of human tissue samples obtained at autopsy from Grand Junction, Colorado and 10 sets from Washington, DC. Lung, pulmonary lymph nodes, liver, kidney and bone were obtained for each case. Personal data for each individual's age, sex, smoking history, and occupation were obtained whenever possible. Radiochemical analysis was performed after tissue digestion, by solvent extraction, and electrodeposition, followed by solid state alpha spectrometric measurements using Si(Li) surface barrier detectors. Thorium-230 and 232 are distributed similarly in the body with the major fraction of the body burden present in bone (70%) followed by lung (20%) and lymph nodes (7%). Thorium-228 is found primarily in the skeleton (95%). For all isotopes, no significant difference was found between the concentration in tissue of smokers and non-smokers. The ratio of Th-230/232 in Colorado tissues was comparable to that of controls (Washington, DC) and probably reflects the relative geochemical abundance of the isotopes in local soils