Silica exposure

EH 74/2 Respirable crystalline silica exposure assessment document... 

Reliability of airflow measurements m assessing ventilation systems performance Cobalt - a review of properties, use and levels of exposure A review of respirable crystalline silica - Exposure and control... 

Recent (1990-2005) Epidemiologic Studies of Occupational Silica Exposure and Risk of Autoimmune Diseases... 

Issues regarding the influence of duration or intensity of exposure in relation to effect on autoimmune disease processes are questions that have not been established, with some inconsistencies seen in the epidemiologic studies (Table 25.2). Dose or intensity of silica exposure affects the clearance from the lung and silica-containing macrophages can be translocated to pulmonary lymph nodes. Increased production of immunoglobulins and of lymphocyte-derived interferon-gamma is seen at these sites.49... 

Englert H. et al., Male systemic sclerosis and occupational silica exposure-a population-based study, Aust. N. Z. J. Med., 30, 215, 2000. 

Stolt, R et al., Silica exposure is associated with increased risk of developing rheumatoid arthritis results from the Swedish EIRA study, Ann. Rheum. Dis., 64, 582, 2005. 

Gregorini, G. et al., Association between silica exposure and necrotizing crescentic glomerulonephritis with p-ANCA and anti-MPO antibodies A hospital-based case-control study, Adv. Exp. Med. Biol. 336, 435, 1993. 

Hogan, S. L. et al., Silica exposure in anti-neutrophil cytoplasmic autoantibody-associated glomerulonephritis and lupus nephritis, J. Am. Soc. Nephrol., 12, 134, 2001. 

Brown, J.M., Pfau, J.C., and Holian, A., Immunoglobulin and lymphocyte responses following silica exposure in New Zealand mixed mice., Inhal. Toxicol., 16, 133, 2004. 

In animal studies, significant increases in adenocarcinomas and squamous cell carcinomas of the lung have occurred in rats after inhalation or intratracheal instillation in rats, but not in hamsters. Increasing in vitro and in vivo evidence suggests that the rat lung tumor response to crystalline silica exposure is a result of marked and persistent inflammation and epithelial proliferation. However, other pathways such as a role for crystalline silica surfacegenerated oxidants or a direct genotoxic effect cannot be ruled out. 

Neukirch F, CooremanJ, KorobaeffM, et al Silica exposure and chronic airflow limitation in pottery workers. Arch Environ Health 49 459M64, 1994... 

Tsuda T, et al. A case-control study of the relationships among silica exposure, gastric cancer, and esophageal cancer. AmJInd Med 2001 39(l) 52-57. 

Silica exposure has been associated with increased incidences of scleroderma, a condition manifested by hardened, rigid connective tissue. In this respect, it is believed that silica acts by an adjuvant mechanism in which it enhances the autoimmune response caused by other agents, such as silicones or paraffin.8... 

Husgafvel-Pursiainen K, Kannio A, Oksa P, et al. 1997. Mutations, tissue accumulations, and serum levels of p53 in patients with occupational cancers from asbestos and silica exposure. Environ Mol Mutagen 30 224-230. 

Knowledge regarding renal injury and the development of anti-neutrophil cytoplasmic antibody (ANCA) positivity associated with silica exposure is rudimentary being hmited to epidemiological observations. Moreover, information about the health significance of the occupational exposure to other silicon containing compounds apart from silica and crystalline sihcates is lacking. 

Renal lesions observed after silica exposure have been associated with ANCA positivity suggesting a pathogenetic role of ANCA [64-67]. Other autoimmune manifestations have been reported in a cohort of 50 workers after occupational exposure to a scouring powder mainly containing silica [68]. Systemic symptoms were present in 32 of these subjects including Sjogren s syndrome (n=6), systemic lupus erythematosus (n=3), "overlap" syndrome (n=5) and with undifferentiated... 

Gregorini G, Tira P, Lancini L, Bozzola G, Maiorca R. Silica exposure as a risk factor in the development of necrotising and crescentic glomerulonephritis with anti-mieloperoxidase antibodies. Nephrol Dial Transplant 1991 6 773 (abstract). 

Goldsmith JR, Goldsmith DF. Fiberglass or silica exposure and increased nephritis or end-stage renal disease. Am J Ind Med 1993 23 873-881. 

Hogan SL, Cooper GS, Savitz DA, Nylander-French LA, Parks CG, Chin H, Jennette CE, Lionakin S, Jennette JC, Falk RJ. Association of silica exposure with anti-neutrophil cytoplasmic autoantibody small-vessel vasculitis a population-based, case-control study. Clin J Am Soc Nephrol 2007 2(2) 290-299. 

Kallenberg CGM. Renal disease-another effect of silica exposure. Nephrol Dial Transplant 1995 10 1117-1119 (Editorial Comment). 

Acute high-level silica exposures may be associated with natural and other disasters, such as earthquakes, volcanic eruptions, and building collapse. High-level exposure to respirable silica dust (particles <5 pm) can cause chronic inflammation and fibrosis in the lungs and other organs. Silica exposure in humans has also been associated with increased production of autoantibodies, serum immunoglobulins, and immune complexes. 

Occupational silica exposure and systemic autoimmune diseases... 

There have also been several cohort and case-control studies of silica exposure and scleroderma (Table 10) and six case-control studies of silica exposure and various forms of systemic small-vessel or ANCA-associated vasculitis. As with rheumatoid arthritis, almost all of these studies have reported a 2- to 3-fold increased risk of these diseases with silica exposure. 

Until recently, the evidence relating silica exposure to lupus was limited to case-reports, mostly of male lupus patients with silicosis and a history of exposure to very high levels of silica. Since 1995, three epidemiological studies in different populations (uranium miners in Germany, silicosis patients in Sweden, and a population-... 

Table 10. Recent (1985-2005) epidemiological studies of occupational silica exposure and risk of autoimmune diseases...

Increased cytokine production may also play a role in silica-induced autoimmune vascular disease. Adhesion molecule expression is elevated on vascular endothelial cells in response to TNF-a and IL-1. Adhesion molecules such as endothelial leukocyte adhesion molecule-1 (ELAM-1) and intercellular adhesion molecule-1 (ICAM-1) recruit inflammatory cells to specific sites on the vascular endothelium, and it has been hypothesized that vascular pathology following silica exposure may be the result of this interaction (Nowack et al., 1998). IFN-y is expressed at elevated levels by lymphocytes in silicotic thoracic lymph nodes and may be responsible for the long-lasting inducible nitric oxide synthase (iNOS) expression in these tissues (Friedetzky et al., 2002). The increase in IFN-y may also cause a shift towards a dominant Thl response, contributing to the maintenance of a chronic inflammatory state in silica-containing lymph nodes (Gam et al., 2000). 

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