Toxicity of 91Y inhaled in a relatively insoluble form by beagle dogs. VIII

Studies of the radiation hazards due to inhalation of 91Y in fused aluminosilicate particles have been undertaken 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 longevity 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, 52 dogs have died in the longevity study between 113 and 2514 days after exposure. Forty of these dogs, with cumulative radiation doses to lung between 8,300 and 60,000 rads, died with clinicopathologic findings of radiation pneumonitis and/or pulmonary fibrosis at 113 to 1011 days after exposure. Eleven dogs that died between 1115 and 2376 days after exposure with cumulative doses to lung ranging from 16,000 to 25,000 rads had pulmonary carcinomas. One of these dogs also had a mediastinal hemangiosarcoma. One dog that died at 1847 days after exposure with a cumulative dose to lung of 9,700 rads, had a hemangiosarcoma of the spleen. Four exposed dogs, alive from 2206 and 2669 days after exposure with doses to lung of 15,000 to 17,000 rads, have radiographic lesions suggestive of lung tumors. Forty-four exposed dogs with doses to lung of 2,400 to 18,000 rads and 12 control dogs remain alive from 2198 to 2751 days after inhalation exposure and will continue to be studied throughout the remainder of their life span with attention directed toward determining the relationship between radiation dose, dose rate and biologic effects