Macro-distribution of naturally occurring alpha-emitting isotopes of U in the human skeleton

Argonne National Laboratory (ANL) exhumed the remains of two individuals who had received Pu by intravenous injection, performed Pu analysis on these remains, and then sent portions of individual bones to our laboratory. We analyzed these bone samples to determine the macro-distribution of naturally occurring alpha-emitting isotopes of U (234U and 238U). We found that the sacrum contained the highest concentrations of 234U and 238U (4.9 +/- 0.3 mBq g-1 of bone ash). Different ribs contained varying concentrations of 234U and 238U ranging from 0.26 +/- 0.2 to 1.6 +/- 0.4 mBq g-1 of bone ash for 234U, and from 0.16 +/- 0.1 to 1.5 +/- 0.4 mBq g-1 ash for 238U. The upper and lower values differ significantly at p = 0.001. Concentrations of 234U and 238U in vertebral bodies were lower than in left ribs numbers 1 and 2, but were similar to the concentrations in the other left ribs. The concentration of 235U was below the detection limit in each bone (lower limit of detection (LLD) = 4 X 10(-4) Bq per sample). The results indicate that the distribution of U isotopes is not uniform throughout the skeleton. Thus, the skeletal burden of U estimated from determinations in an individual bone sample may be quite erroneous until the fraction of total skeletal U contained in each bone is known.