Plutonium Concentration in Human Tissues

Abstract

The concentration of 238Pu, and 239,240Pu, and of 228Th, 230Th, and 232Th were measured in 10 sets of human tissues from Washington, DC, and 12 sets from Grand Junction, CO. The tissues were collected at autopsy by qualified pathologists from normal healthy persons most of whom died suddenly. The subjects had acquired plutonium from fallout of global nuclear testing and burnup of a space nuclear generator utilizing 238Pu. The median concentration of 239,240Pu was 0.08 pCi/kg in lung, 0.46 pCi/kg in tracheobronchial lymph nodes, 0.60 pCi/kg in liver, 0.02 pCi/kg in kidney and 0.17 pCi/kg in bone in Washington, DC subjects. Similarly, the concentration of 239,240Pu in Grand Junction subjects was found to be 0.17 pCi/kg in lung, 0.68 pCi/kg in lymph nodes, 0.55 pCi/kg in liver, 0.03 pCi/kg in kidney, 0.22 pCi/kg in bone and 0.08 pCi/kg in spleen. The median concentration in four gonads was 0.02 pCi/kg; the concentration in one thyroid was 0.01 pCi/kg. 238Pu was below the limit of detection in most organs except the liver where it ranged from 0.02 to 0.17 pCi/kg with a median concentration of 0.06 pCi/kg. The organ distribution pattern shows that most of the plutonium was accumulated in bone and liver with 54–60% in bone and 34–43% in liver. Only 3–6% was found in lung including lymph nodes; kidney, spleen, thyroid and gonads together contained around 1%. The analytical results show three major differences between plutonium and thorium concentrations and organ distributions: (1) for plutonium the liver is a major locus for storage (∼40% of that found in the total body), whereas little thorium is accumulated in the liver (around 4%); (2) the relative amounts of 230Th and 232Th are much higher in lung and lymph nodes (10–28%) than currently for plutonium (3–6%); (3) the ratio of thorium concentrations in lymph nodes to lung is significantly higher than the ratio of plutonium concentration in lymph nodes to lung showing thereby that fallout plutonium is more soluble than natural thorium.