Formation of hydroxyl radicals and toxicity of tungsten oxide fibres

Occupational exposure to hard metal dust may cause interstitial pulmonary fibrosis and asthma. The cause of asthma is well established, whereas the cause of lung fibrosis is still under debate. Recently, slightly reduced airborne tunsten oxide fibres, the role of which in hard metal pneumoconiosis has never been accounted for, were detected in an air sample from a hard metal production plant. In this study, the capacity to generate hydroxyl radicals, toxicity to cultured human lung cells and haemolytic activity of tungsten oxide fibres were compared with crocidolite asbestos fibres. The results show (a) that tungsten oxide fibres can generate hydroxyl radicals, and (b) that tunsten oxide fibres were more cytotoxic to human lung cells than was crocidolite, but (c) that the haemolytic activity of tungsten oxide fibres was lower than for crocidolite.