Carborundum is a synthetic abrasive manufactured through fusion of high grade
silica sand and finely ground
carbon in an electric furnace at 2,400 degrees C. It had been considered an inert dust until recently. Two recent epidemiologic studies in Quebec have documented an excess of
interstitial lung disease in plant workers and some 30 workers have received workman compensation. Histopathologic lesions have been described in four of the workers. To further investigate the
carborundum pneumoconiosis, nine groups of eight sheep were exposed once in the tracheal lobe to either 100 ml saline, 100 mg
latex beads in 100 ml saline, 100 mg
graphite in 100 ml saline, 100 mg
carborundum particles in 100 ml saline, 100 mg ashed
carborundum particles in 100 ml saline, 100 mg of
quartz (Minusil-5) in 100 ml saline, 100 mg
crocidolite fibers in 100 ml saline, 100 mg
carborundum fibers in 100 ml saline, and 100 mg ashed
carborundum fibers in 100 ml saline solutions. The animals had BAL at two-month intervals and autopsy at month 8. The BAL analyses of cellularity, cytotoxicity and fibrogenicity, in association to necropsy histopathology, documented that all particles except for
quartz were inert. The two-
carborundum fiber samples produced a similar sustained nodular
fibrosing alveolitis and
crocidolite asbestos fibers produced a peribronchiolar
fibrosing alveolitis of comparable severity. Thus, the major bioactive dusts in the
carborundum manufacturing process are
quartz particles and the
carborundum fibers generated in the process. The latter have fibrogenic activities comparable to
asbestos fibers of similar size and are likely to contribute to the pathogenesis of the
interstitial lung disease of
carborundum workers.