DEPOSITION AND CLEARANCE MODELING OF INHALED KAOLIN REFRACTORY CERAMIC FIBERS (RCF) IN HAMSTERS - COMPARISON BETWEEN SPECIES

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 dif ferences from those of an earlier study in rats regarding deposition a nd clearance of these fibers in the lung. Despite smaller airway size of hamsters, alveolar deposition per breathing cycle in the hamster wa s found to be higher than that in the rat due to the higher upper airw ay deposition in rats. The calculated mean deposited fiber size was fo und to be larger in the hamster, and there were more thin and long fib ers deposited in the hamster lung. It was also found that alveolar cle arance of refractory ceramic fibers was faster in the hamster. The cle arance rate in the hamster did not appear to be fiber size dependent b ut it varied with lung burden. The higher clearance tale in the hamste r resulted in a lower fiber accumulation per unit weight of lung after a long period of exposure. The results of the dosimetry model present ed here may contribute to an explanation of different tumorigenic resp onses observed in the hamster and rat.