Dust from carbon fibre.

Carbon fibre, manufactured from a polyacrylonitrile fibre precursor, is used to reinforce plastic in the aircraft industry. When carbon fibre was fed into a hammer mill, only low concentrations of dust of respirable size could be produced and less than 1% of the respirable carbon particles were fibrous. The dust cloud contained a few transparent fibres, probably glass, of respirable size. When the dust was inhaled by guinea pigs nonfibrous particles were phagocytosed. The few carbon fibres found in the lung that were longer than 5 microns were still extracellular after 27 weeks and they were uncoated. No free transparent fibres were found in the lungs but fibre bodies with a ferruginous coating were probably derived from the transparent fibres. No pathological effects were observed.