Comparative toxicity of strontium-90 and radium-226 in beagle dogs

We are completing a 30-year study of the biological effects of 90Sr and 226Ra in the beagle in order to predict the possible long-term hazards to people from chronic exposure to low levels of irradiation. Animals received either radionuclide by several means of administration: (a) continual ingestion of 90Sr, (b) a single intravenous injection of 90Sr, or (c) a series of eight intravenous injections of 226Ra. Although administration of 90Sr and 226Ra ended at 540 days of age, the animals continued to receive chronic, low-level radiation doses from these bone-seeking radionuclides throughout life. This project is the largest single cohort study in beagles of internally deposited radionuclides. It is unique in use of the ingestion route for 90Sr and in exposure that began before birth and continued throughout development to adulthood with uniform labeling of the skeletons with 90Sr. The last of the dogs died in 1986 at age 18.5 years, but we are continuing to investigate the significance of these long-term exposures given at low dose rates with regard to cancer production, physiologic well-being, and shortening of life through the detailed records that were kept and by study of preserved materials. All the data have been successfully accumulated and entered into a main-frame computer data base management system. Current work is exclusively directed at preparing research papers summarizing the results and the associated biostatistical and survival analyses. 15 refs., 1 fig., 4 tabs