Thorium Concentration in Human Tissues from Two U.S. Populations

Abstract

The concentrations of natural alpha-emitting isotopes of thorium (228Th, 230Th and 232Th) have been determined in 22 sets of human tissue samples obtained at autopsy from Grand Junction, CO and in 10 sets from Washington, DC. Tissues included lung, pulmonary lymph nodes, liver, kidney, bone, a few gonads, spleen and thyroid. Personal data on each individual's age, sex, smoking history and occupation were obtained whenever possible. The concentrations of 228Th, 230Th and 232Th were highest in lymph nodes for both populations with 2.6 and 5.1 pCi/kg of 228Th, 4.60 and 11.10 pCi/kg of 230Th, and 2.8 and 7.8 pCi/kg of 232Th in Washington, DC and Grand Junction, CO, respectively. The order of concentrations of all three isotopes in ali other organs for both populations was as follows: Isotope Location Order of decreasing concentration 228Th Grand Junction Lymph nodes > bone > lung > kidney > liver Washington, DC Lymph nodes > bone > lung > kidney > liver 230Th Grand Junction Lymph nodes > bone > lung > kidney > liver Washington, DC Lymph nodes > lung > bone > liver > kidney 232Th Grand Junction Lymph nodes > lung > bone > kidney > liver Washington, DC Lymph nodes > lung > bone > liver > kidney The data suggest that the non-mining residents who lived in the vicinity of uranium mine tailings do not have elevated 230Th concentrations in their lungs, when compared to the residents of Washington, DC who are not exposed to such tailings. However, 230Th concentration in bone of Grand Junction subjects was just significantly higher (at p < 0.1) than that for Washington, DC subjects after suitable age adjustments. The data also suggest that 230Th is more available for accumulation in skeleton than would be supposed from its relative geochemical abundance.