Deposition and Clearance Modeling of Inhaled Kaolin Refractory Ceramic Fibers (RCF) in Hamsters—Comparison Between Species

Abstract

A dosimetry model of refractory ceramic fibers in the hamster lung has been developed based upon the data from recent exposure and recovery experiments conducted by the Research and Consulting Company in Geneva, Switzerland. The modeling results of hamsters showed significant differences from those of an earlier study in rats regarding deposition and clearance of these fibers in the lung. Despite smaller airway size of hamsters, alveolar deposition per breathing cycle in the hamster was found to be higher than that in the rat due to the higher upper airway deposition in rats. The calculated mean deposited fiber size was found to be larger in the hamster, and there were more thin and long fibers deposited in the hamster lung. It was also found that alveolar clearance of refractory ceramic fibers was faster in the hamster. The clearance rate in the hamster did not appear to be fiber size dependent but it varied with lung burden. The higher clearance rate in the hamster resulted in a lower fiber accumulation per unit weight of lung after a long period of exposure. The results of the dosimetry model presented here may contribute to an explanation of different tumorigenic responses observed in the hamster and rat.