Occupational exposure to crystalline silica and risk of systemic lupus erythematosus: A population‐based, case–control study in the Southeastern United States

Abstract

Objective. Crystalline silica may act as an immune adjuvant to increase inflammation and antibody production, and findings of occupational cohort studies suggest that silica exposure may be a risk factor for systemic lupus erythematosus (SLE). We undertook this population-based study to examine the association between occupational silica exposure and SLE in the southeastern US.Methods. SLE patients (n ‫؍‬ 265; diagnosed between January 1, 1995 and July 31, 1999) were recruited from 4 university rheumatology practices and 30 community-based rheumatologists in 60 contiguous counties. Controls (n ‫؍‬ 355), frequency-matched to patients by age, sex, and state of residence, were randomly selected from driver's license registries. The mean age of the patients at diagnosis was 39 years; 91% were women and 60% were African American. Detailed occupational and farming histories were collected by in-person interviews. Silica exposure was determined through blinded assessment of job histories by 3 industrial hygienists, and potential medium-or high-level exposures were confirmed through followup telephone interviews. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were estimated by logistic regression.Results. More patients (19%) than controls (8%) had a history of medium-or high-level silica exposure from farming or trades. We observed an association between silica and SLE (medium exposure OR 2.1 [95% CI 1.1-4.0], high exposure OR 4.6 [95% CI 1.4-15.4]) that was seen in separate analyses by sex, race, and at different levels of education.Conclusion. These results suggest that crystalline silica exposure may promote the development of SLE in some individuals. Additional research is recommended in other populations, using study designs that minimize potential selection bias and maximize the quality of exposure assessment.Crystalline silica dust has been associated with systemic autoimmune diseases in humans, most notably with scleroderma, rheumatoid arthritis, and the small vessel vasculitides, and is one of the few environmental agents identified as a possible risk factor for systemic lupus erythematosus (SLE) (1-3). Commonly known as quartz, crystalline silica is an abundant mineral in rock, sand, and soil. The highest exposures to silica are known to occur in the dusty trades industries, such as mining, sandblasting, and quarrying, and in foundries and metal works, as well as in other jobs that use quartz-containing

Prevalence of systemic lupus erythematosus and systemic sclerosis in the First Nations population of Alberta, Canada

“…This may reflect a true predominance of SLE and SSc among First Nations females, and is consistent with previous studies of SARD in First Nations populations, which also reported a genetic predisposition to autoimmune disorders and more severe disease phenotypes (7)(8)(9)(10)(11). It is interesting, however, to hypothesize that this increased prevalence is a result of environmental exposures in a population predisposed to SARD, since, for example, silica exposure has been suggested as an environmental trigger for SARD (30,31). Although a protective factor conferring improved survival could also increase prevalence estimates, this seems less likely given the more severe disease phenotypes and difficulties accessing health care reported in First Nations populations.…”

Silica exposure and systemic vasculitis.

“…The issue of latency was also addressed by Parks et al (2002), who evaluated occupational exposure to silica and the risk of systemic lupus erythematosus (SLE). In this population-based, case-control study, the authors observed an association between silica and SLE, with medium or high-level silica exposures found in individuals working in farming or trades.…”

Antigen-Presenting Cell Population Dynamics during Murine Silicosis

“…Intrapulmonary deposition of silica results in a granulomatous inflammatory response that progresses to interstitial fibrosis, as well as systemic immune deficits (1)(2)(3)(4). Although significant efforts have been made through industrial hygiene standards to control ambient exposures, silicosis remains a prevalent health problem, particularly in developing nations.…”