Chronic Inhalation Toxicity of a Kaolin-Based Refractory Ceramic Fiber in Syrian Golden Hamsters

AbstractKaolin-based refractory ceramic fiber (RCF) is a man-made vitreous fiber used primarily in industrial high-temperature applications, especially for insulation of furnaces and kilns. Because of its increasing use and potential for human exposure, a chronic toxicity/ carcinogenicity inhalation study was conducted in Syrian golden hamsters. Two groups of 140 weanling male hamsters were exposed via nose-only inhalation to either HEPA-filtered air (chamber controls) or 30 mg/m3 (-220 fibers/cm3) of “size-selected” RCF fibers (1 µm in diameter and -25 /jm in length) for 6 h/day, 5 dayslwk for 18 mo. They were then held unexposed until -20% survival (20 mo). A positive control group of 80 hamsters was exposed to 10 mg/m3 chrysotile asbestos (0.09 µm average diameter and 2.2 µm average length). Groups of 3 hamsters were sacrificed at 3, 6, 9, 12, 15, and 18 mo to follow the progression of lesions. Additional groups of 3 hamsters were removed from exposure at 3, 6, 9, and 12 mo and were held until 18 mo (r...