CRYSTALLINE SILICA: Crystalline silica is an abundant mineral found in multiple occupational exposures. It is a recognised occupational risk factor for some systemic auto-immune diseases such as progressive systemic scleroderma and Caplan-Colinet's syndrome, or just suspected in Goujerot-Sjögren's syndrome, periarteritis nodosa and systemic lupus erythematosus. WEGENER'S GRANULOMATOSIS: A rare disease of unknown of unknown aetiology, the disease is characterised by granulomatous vasculitis affecting the upper respiratory tracks, lungs and kidneys, associated with glomerulonephropathy. THE ROLE OF SILICA PARTICLES: Studies have shown that crystalline silica may be implied in Wegener's disease. Associated with other factors, notably with a genetic predisposal, silica particles might, through the release of reactive oxygen radicals and inflammatory cytokines, trigger-off immunopathological mechanisms. The latter would be manifested by exocytosis of the proteinase 3 and myeloperoxidase antigens on the surface of the polynuclear neutrophils.