Metabolic and dosimetric studies after inhalation of 227Th in rats with regard to the risk of lung and bone tumors.

227Th (alpha-emitter, half-life 18.7 days) was inhaled by rats from solution in nitrate form. Organ doses were calculated after whole body measurements and measuring of activity concentrations in the organs over a longer incorporation period. An initial deposition of 100 nCi 227Th in the lung resulted in mean total doses of 150 rad in lung and 36 rad in bone. The data for kidney and liver were 2 rad and 0.1 rad, respectively. For long-term experiments two dosages were applied to two groups of animals with mean values of 900 rad and 300 rad in the lung. The consequences for lung and bone tumor induction are discussed.