Occupational exposure to crystalline silica and autoimmune disease

Occupational exposure to silica dust has been examined as a possible risk f actor with respect to several systemic autoimmune diseases, including scler oderma. rheumatoid arthritis, systemic lupus erythematosus, and some of the small vessel vasculitidies with renal involvement (e.g., Wegener granuloma tosis). Crystalline silica, or quartz, is an abundant mineral found in sand , rock, and soil. High-level exposure to respirable silica dust can cause c hronic inflammation and fibrosis in the lung and other organs. Studies of s pecific occupational groups with high-level silica exposure (e.g., miners) have shown increased rates of autoimmune diseases compared to the expected rates in the general population. However, some clinic- and population-based studies have not demonstrated an association between silica exposure and r isk of autoimmune diseases. This lack of effect may be due to the limited s tatistical power of these studies to examine this association or because th e lower- or moderate-level exposures that may be more common in the general population were not considered. Experimental studies demonstrate that sili ca can act as an adjuvant to nonspecifically enhance the immune response. T his is one mechanism by which silica might be involved in the development o f autoimmune diseases. Given that several different autoimmune diseases may be associated with silica dust exposure, silica dust may act to promote or accelerate disease development, requiring some other factor to break immun e tolerance or initiate autoimmunity The specific manifestation of this eff ect may depend on underlying differences in genetic susceptibility or other environmental exposures.