[Pulmonary fibrosis after inhalation of amorphous silicic acid]

Light- and scanning electron microscopical studies with energy dispersive x-ray microanalysis were performed on biopsy material obtained from two patients with longstanding occupational exposure to amorphous silica, in whom radiologically interstitial pulmonary fibrosis in vicinity of dust deposits, which could be identified as amorphous and rarely as crystalline silica, was found. The direct topographical relationship between the dust deposits and the tissue reaction indicate that the amorphous silica incorporated in the fibrotic foci is responsible for the development of the fibrosis.