Toxicity of 144Ce inhaled in a relatively insoluble form by immature Beagle dogs. VII

Immature Beagle dogs (approx. = 3 months of age at exposure) have been exposed by inhalation to a relatively insoluble form of 144Ce (in fused aluminosilicate particles) to compare the resulting patterns of metabolism, dosimetry and biological effects with those seen in dogs exposed at 12 and 14 months of age and at 8 to 10.5 years of age. Five blocks of longevity animals, each consisting of 10 exposed dogs and one control, are currently being studied. The initial lung burdens of the 144Ce-exposed dogs range from 0.004 to 140 μCi 144Ce/kg body weight. Three dogs with initial lung burdens of 73 to 120 μCi 144Ce/kg body weight died at 66 to 121 days after exposure with pulmonary injury and congestive heart failure. One dog with an initial lung burden of 140 μCi 144Ce/kg body weight died at 91 days after exposure with severe radiation pneumonitis and minimal pulmonary fibrosis and another dog whose initial lung burden was 70 μCi 144Ce/kg body weight died at 511 days after exposure with pulmonary injury that was mainly fibrotic in nature. Four dogs with initial lung burdens of 52 to 79 μCi/kg body weight had primary pulmonary hemangiosarcomas and died between 618 and 738 days, with cumulative average absorbed beta doses to lung of 23,000 to 31,000 rads. Two of these dogs, 1027S and 1024D, died within the past year. One dog with an initial lung burden of 28 μCi/kg body weight was euthanized at 1227 days after exposure with an hemangiosarcoma of the mediastinum. Within the past year, Dog 627S, with an initial lung burden of 48 μCi/kg body weight, died 1732 days after exposure with hemangiosarcoma primary in the liver or spleen. A dog with an initial lung burden of 12 μCi/kg body weight died from epilepsy at 1520 days after exposure. Serial observations are continuing on the surviving 37 exposed and five control dogs