Mixed dust fibrosis

Silicon toxicity is virtually limited to occupational exposure to silicon compounds e.g. miners, sandblasters, bricklayers, pottery workers in which inhalation of the compounds has been associated with the diseases of the lung. The later being evidenced by nodule formation and acute silicosis, mixed dust fibrosis and diatomite pneumoconiosis. 

Classic (Nodular) Silicosis 178 Mixed Dust Fibrosis 178 Silicoproteinosis 178 Clinical Features 179 Radiological Evaluation 180 Chest Radiograph 180 Computed Tomography/... 

Fig.5.2a,b. A 72-year-old retired tunnel worker with silicotic nodules and mixed dust fibrosis, a Posterior-anterior chest radiograph shows ill-defined multiple small nodules and reticular opacities in both upper lobes, b Photomicrograph obtained at autopsy performed 2 years after chest radiograph shows two pneumoconiotic nodules with stellate appearance. The left nodule shows irregular shape without whorled appearance (arrows) typical of silicotic nodule. The right nodule also shows irregular shape but has a central whorled appearance of silicotic nodule. Emphysema is identified around the nodules... 

The various talcs can result in several distinctive radiographic appearances. The nodular pattern consists either of opacities some 3-5 mm in diameter, identical to those of silicosis, or of appearances similar to mixed dust fibrosis . These changes sometimes favor the middle lung fields but may be distributed throughout all zones (Fig. 12.8a). There are large opacities similar to those of silicotic conglomerations or coal progressive massive fibrosis, which may show evidence of cavity formation (Jones et al. 1994) (Fig. 12.9a). 

Silicosis occurs in industries in which the air is polluted by silica dust, e g., pottery, metal grinding, sandblasting and mining in rock. The inhaled silica gives rise to the production of diffuse fibrosis in the lungs moreover it facilitates the growth of the tubercle bacillus so that tuberculosis is a possible complication. A special form of silicosis, called anthracosis (black lung), occurs in coal miners who are exposed to a mixed dust, mainly of coal, with a small proportion of silica. 

Aluminum metal (CAS 7429-90-5) Dusts can cause mild eye and respiratory tract irritation, Long-term inhalation of large amounts of fine aluminum powders or fumes from aluminum ore (bauxite) has been associated with reports of pulmonary fibrosis (Shaver s disease). Acute exposures in aluminum refining ("pot room") has been associated with asthma-like responses, Industrial processes used to produce aluminum have been associated with an Increased incidence of cancer in workers, 10 mg/m (metal and oxide) 5 mg/m (pyrophoric powders, welding fumes) 2 mg/m (soluble salts, alkyls NOC) 0 3 1 (powder) Oxidizes readily. Fine powders and flakes are flammable and explosive when mixed with air. Reacts with acids and caustic solutions to produce flammable hydrogen gas. 

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