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

To study the biological effects of repeated inhalation exposures to a beta emitter compared to those seen after a single inhalation exposure, Beagle dogs were exposed in different regimens to a relatively insoluble form of 144Ce, in a fused aluminosilicate matrix. Four groups of 9 dogs each were exposed once every 8 wk for 2 yr (13 exposures). The exposures were conducted (1) to increase the lung burden by 2.5 (93 kBq) 144Ce/kg body weight with each exposure, (2) to re-establish lung burdens of 9.0 or 4.5 μCi (330 or 170 kBq) 144Ce/kg body weight, and (3) to expose controls to fused aluminosilicate particles containing nonradioactive Ce. The most prevalent findings have been pulmonary carcinomas (10 dogs) and hemangiosarcomas in the tracheobronchial lymph nodes (5 dogs). All 144Ce-exposed dogs are now dead; observations are continuing on the 4 remaining control dogs at 11.8 yr after the first exposure. 2 tables