Occupational exposure to crystalline silica and autoimmune disease.

Abstract

Occupational exposure to silica dust has been examined as a possible risk factor with respect to several systemic autoimmune diseases, including scleroderma, rheumatoid arthritis, systemic lupus erythematosus, and some of the small vessel vasculitidies with renal involvement (e.g., Wegener granulomatosis). Crystalline silica, or quartz, is an abundant mineral found in sand, rock, and soil. High-level exposure to respirable silica dust can cause chronic inflammation and fibrosis in the lung and other organs. Studies of specific 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 risk of autoimmune diseases. This lack of effect may be due to the limited statistical power of these studies to examine this association or because the lower- or moderate-level exposures that may be more common in the general population were not considered. Experimental studies demonstrate that silica can act as an adjuvant to nonspecifically enhance the immune response. This is one mechanism by which silica might be involved in the development of 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 immune tolerance or initiate autoimmunity. The specific manifestation of this effect may depend on underlying differences in genetic susceptibility or other environmental exposures.

Occupations and exposures in the work environment as determinants for rheumatoid arthritis

“…A similar mode of action has been suggested for silica. 21 In a previous publication, we presented results from a casereferent study of occupational determinants which both corroborated previous reports and indicated new relationships. 14 In order to further explore the impact of occupational exposures, a second case-referent study with prospective inclusion of cases has now been performed.…”

Occupational silica exposure and risk of various diseases: an analysis using death certificates from 27 states of the United States

“…60 In our analysis, although only two silicotics had systemic sclerosis, the MOR of 2.0 (95% CI 0.4 to 10.3) is suggestive of an association. However, the evidence for an association between this disease and crystalline silica exposure is equivocal.…”

“…59 Some of these mechanisms have been postulated to explain the role of crystalline silica exposure in autoimmune disease. 60 …”

Silica exposure is associated with increased risk of developing rheumatoid arthritis: results from the Swedish EIRA study

“…It has previously been proposed that increased release of inflammatory mediators from alveolar macrophages phagocytosing inhaled silica particles may activate macrophages/monocytes and lymphocytes systemically as well as in the rheumatoid synovium. [19][20][21][22][23][24][25] These cell types also have the potential to increase the production of matrix metalloproteinases (MMP)-enzymes involved in the degradation and remodelling of extracellular matrix, which have been shown to be associated with rheumatoid arthritis as well as with silicosis. [26][27][28][29] The production of MMP, as well as of inflammatory mediators such as tumour necrosis factor a and interleukin 1b, is regulated by the transcription factor nuclear factor kB, the activity of which appears to be influenced by silica exposure.…”