Pathology of silicon carbide pneumoconiosis

Silicon carbide is a widely used synthetic abrasive manufactured by heating silica and coke in electric furnaces at 2400 degrees C. Until recently it had been considered a relatively inert dust in humans and animals. However, several roentgenologic surveys had revealed lesions similar to low-grade silicosis. A recent epidemiological study has revealed a 35% incidence of pulmonary problems. Tissues from three such workers were available for light microscopy. A mixed pneumoconiosis was found, and lesions can be summarized as follows: (a) abundance of intraalveolar macrophages associated with a mixture of inhaled particles including carbon, silicon, pleomorphic crystals, silicon carbide, and ferruginous bodies showing a thin black central core; (b) nodular fibrosis, generally profuse, containing silica and ferruginous bodies and associated with large amount of carbon pigment; (c) interstitial fibrosis, less prominent than the nodular form; (d) carcinoma in two cases. We believe this pneumoconiosis is sufficiently characteristic to be recognized as a distinct entity. The Stanton hypothesis on fiber properties and carcinogenesis could be applied to silicon carbide dust. At present, it appears that the occupational hazard is limited to the manufacturing process and powdered product used in some industries.