Comments
"Occupational inorganic and coal dust exposures can be broadly categorized as strongly fibrogenic dusts (silica, asbestos, and coal) and other inorganic dusts and metal fumes that may also be associated with adverse respiratory effects (e.g., iron, emery, graphite, gypsum, marble, mica, perlite, plaster of Paris, Portland cement, silicon, silicon carbide, soapstone, talc, and welding fume particles)." [Asthma in the Workplace, p. 378] "The authors of a 1990 review concluded that (1) there is little evidence that occupational exposure to pure kaolin, talc, mica, or vermiculite carries any important risk for health; (2) long and heavy exposure to kaolin and mica may result in low-grade radiographic changes, but clinically important pneumoconioses in work forces exposed to these phyllosilicates are likely to be the result of contamination by silica or asbestos fiber;" [Murray, p. 1773-1774] "It is suspected that this lung airway defense system can be overcome by several different mechanisms: by the physical characteristics of the particle that prevent phagocytosis or cell movement, as seen in asbestosis; by direct cytotoxicity, as in the case of silica dust or cytoxic metals and compounds; or by simply overloading the clearance capacity of the system, which is most likely the mechanism of injury from normally non-fibrogenic 'nuisance' dusts." [Hendrick, p. 167]