Biological effects of repeated inhalation exposure of Beagle dogs to relatively insoluble aerosols of 144Ce. XII

Beagle dogs were exposed in different inhalation exposure regimens to a relatively insoluble form of 144Ce to study the biological effects of repeated inhalation exposures as compared with those from a single inhalation exposure. Four groups of 9 dogs each were exposed once every 8 wk for 2 yr (13 exposures). The exposures were conducted to (1) increase the lung burden by 2.5 μCi (93 kBq) 144Ce/kg body weight with each exposure, (2) re-establish lung burdens of 9.0 or 4.5 μCi (330 or 170 kBq) 144Ce/kg body weight, and (3) expose controls to the insoluble matrix containing nonradioactive Ce. Pulmonary carcinomas (10 dogs) and hemangiosarcomas in the tracheobrochial lymph nodes (5 dogs) were the most prevalent findings in the 144Ce-exposed dogs. All 144Ce-exposed dogs are now dead. Two control dogs died during the past year and observations are continuing on the two controls remaining alive at 12.8 yr after the first exposure. 2 tables