Toxicity of 91Y inhaled in a relatively insoluble form by Beagle dogs. X

The radiation hazards from inhalation of 91Y in fused aluminosilicate particles are being studied in Beagle dogs to assess the biological consequences of inhaling a relatively insoluble, energetic beta emitter with an intermediate effective half-life in the lung. A radiation dose pattern study in which 30 dogs were serially sacrificed from 0 to 320 days after inhalation exposure to 91Y in fused aluminosilicate particles has been completed. A life span study is in progress in which 96 dogs were exposed to achieve initial lung burdens ranging from 11 to 300 μCi 91Y in fused aluminosilicate particles/kg body weight and 12 dogs were exposed to stable yttrium in fused aluminosilicate particles. To date, 60 dogs have died in the longevity study between 113 and 3390 days after exposure. Forty of these dogs, with cumulative radiation doses to lung between 8300 and 60 000 rads, died with clinicopathologic findings of radiation pneumonitis and/or pulmonary fibrosis at 113 to 1011 days after exposure. Fifteen dogs that died between 1115 and 2841 days after exposure with cumulative doses to lung ranging from 16 000 to 25 000 rads had pulmonary carcinomas. Two dogs have died with hemangiosarcomas with primary sites not in the lung. Deaths are beginning to occur that cannot be easily associated with the radiation exposure. Thirty-six exposed dogs with doses to lung of 2400 to 18 000 rads and 11 control dogs remain alive and will be studied throughout the remainder of their life span