Metabolism and Toxcity of Inhaled 144 Ce in Rats

Abstract

To aid in assessing the hazard associated with airborne radio-cerium, two groups of rats were exposed by inhalation to heat-treated ${}^{144}{\rm Ce}$ hydroxide aerosols resulting in body burdens of ∼3.0 (0.85-6.6) or ∼170 (79-300) μCi ${}^{144}{\rm Ce}/{\rm kg}$ body weight. Following initial rapid clearance, the ${}^{144}{\rm Ce}$ had an effective half-time of 130 days in lung. Based on average kinetics of whole-body and lung retention, estimated cumulative β-radiation doses to lungs of the high-level rats were 620 rads at 100 days, 1000 rads at 300 days and 1150 rads at 600 days postinhalation exposure, per μCi initial lung burden. Estimated cumulative doses to lungs to time of death averaged 5100 rads and ranged from 2400 to 8800 rads. Other organs of interest, for which β-radiation doses were calculated, are skeleton, liver and tracheobronchial lymph nodes. ${}^{144}{\rm Ce}$ also concentrated significantly in kidneys. Median survival times were 135 and 393 days postexposure for the high-level and lo...