SR-90 INDUCED BONE-TUMORS IN BEAGLE DOGS - EFFECTS OF ROUTE OF EXPOSURE AND DOSE-RATE

Bone tumours from beagles exposed by inhalation to (SrCl2)-Sr-90 at the Inhalation Toxicology Research Institute (ITRI), by chronic ingestion of Sr-90 at the Laboratory of Energy-Related Health Research (LEHR), and by injection of Sr-90 citrate at the University of Utah were analysed to determine if the bone tumour characteristics differed among the three studies. The range of average skeletal doses at which the bone tumours occurred was similar in all three studies, but differences in the skeletal distribution, histological phenotype, and time to death were observed. The differences observed were attributed to the difference in dose-rate pattern obtained in the chronic ingestion study, in contrast to the inhalation and injection studies. In general, however, the differences noted in bone tumour characteristics were subtle, and would be unlikely to make an impact on models developed to assess the risk of human exposure to Sr-90.