Natural Thorium in Human Bone

Abstract

The 232Th concentration in rib bone from 38 humans ranged from <0.1 to 72 ng/g ash. Values increased with age and were fitted by the expression: Y = (0.16 ± 0.02)T, where Y is the 232Th concentration in ng/g bone ash and T is the age in years. Evaluation of the retention of the 228Ra produced by the decay of 232Th is not possible for human exposure to environmental sources since direct intake of naturally occurring 228Ra is too large.