Lifetime studies of 226Ra and 90Sr toxicity in beagles. A status report

Beagles at the University of California at Davis injected with 226Ra of fed 90Sr have been under lifetime study for over 18 years. This report summarizes the dose-response observations to June 30, 1978. Bone marrow dyscrasias were more numerous than bone cancers from 90Sr at dose rates to bone of about 2 to 20 rad/day, while bone cancers have been the dominating effect of 226Ra at dose rates of from 0.5 to about 20 rad/day. No radiogenic effects are yet apparent for skeletal doses below 0.5 rad/day. Results to date indicate that although bone cancer continues to be the important endpoint for 226Ra, other cancer types appear to be more important for 90Sr (such as soft-tissue cancers adjacent to bone), particularly at late times from lower skeletal dose rates