Occupational exposures and risk of systemic lupus erythematosus

Our plain-English summary of Occupational exposures and risk of systemic lupus erythematosus, by C.G. Parks, G.S. Cooper (Autoimmunity, 2005).

The study

• Authors: C.G. Parks, G.S. Cooper
• Journal: Autoimmunity
• Published: 2005;38(7):497-506
• Type of article: Review
• Cited by: 30 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

This review summarizes the growing body of epidemiologic and experimental research pertaining to the relationship between SLE and occupational exposures, such as crystalline silica, solvents, and pesticides. Epidemiologic studies, using different designs in different settings, have demonstrated moderate to strong associations between occupational silica exposure and SLE. Recent experimental studies of silica in lupus-prone mice provide support for the idea that, in addition to its known adjuvant effect, silica exposure increases the generation of apoptotic material, an important source of self-antigen. Despite compelling experimental studies of the organic solvent trichloroethylene (TCE) in lupus-prone mice, there is little evidence of an overall association of SLE and occupational exposure to a broad classification of solvents in humans. However, there is a lack of data on SLE in occupational cohorts with exposures to TCE or other specific solvents. One epidemiologic study reported an association of pesticide mixing and SLE, while a recent experimental study reported accelerated disease in pesticide-treated lupus-prone mice. Other occupational exposures worth investigating include asbestos, metals, and UV radiation. Attention should also be given to the role of gene-environment interactions, which may require large, multi-site studies that collect both genetic material and occupational exposure data. The quality of exposure assessment is an important consideration in designing and evaluating these studies. The use of pre-clinical endpoints (e.g. high-titer autoantibodies) in occupational cohorts with well-characterized exposure histories may reveal occupational risk factors for autoimmunity, and may also provide baseline data for studies of determinants of progression to SLE.

In plain English

This article was a review, not a new study. The authors summarized published human and animal research on systemic lupus erythematosus (SLE) and workplace exposures, mainly crystalline silica, solvents and pesticides. They also discussed asbestos, metals and ultraviolet light. They described the human silica studies as showing moderate to strong associations with SLE. In one Swedish registry study, silicosis patients had a risk ratio of 23.8 (95% confidence interval 10.3 to 47.0) for SLE-related hospitalization compared with all other hospitalized patients. The only study of workplace solvents and SLE found no association for solvents as a general category. Data on specific solvents were lacking. One case-control study linked mixing pesticides with SLE (odds ratio 7.4, 95% confidence interval 1.4 to 40), which the authors called strong but imprecise. Applying pesticides showed no association. On asbestos, the authors described a Libby, Montana study: 22% of residents, versus 6% of controls, had high-titer antinuclear antibodies. None of those subjects had a diagnosis of systemic autoimmune disease. The authors concluded that crystalline silica has the most human data supporting an association with SLE.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Review of published epidemiologic and experimental studies
• Who was studied: Published human studies (Table I lists epidemiologic studies published since 1990) and animal studies, mostly in lupus-prone mice, on occupational exposures and SLE
• Exposure: Occupational exposures, mainly crystalline silica, solvents (including trichloroethylene) and pesticides; asbestos, heavy metals (lead, cadmium, mercury) and ultraviolet radiation were discussed as exposures worth further study
• Main results:
  • Across the reviewed human studies of silica, which used different designs in different settings, the authors described moderate to strong associations between occupational silica exposure and SLE
  • In a Swedish registry study cited in the review, the risk ratio for SLE-related hospitalization among silicosis patients compared with all other hospitalized patients was 23.8
  • Table I gives this risk ratio with a 95% confidence interval of 10.3 to 47.0
  • In a southeastern United States case-control study cited in the review, the association between silica dust exposure and SLE showed a dose-response pattern
  • The only study of occupational solvent exposure and SLE, a case-control study, found no association with the general category of solvents
  • The authors noted a lack of data on SLE in occupational cohorts exposed to trichloroethylene or other specific solvents
  • In one case-control study, mixing pesticides was reported by 8% of SLE cases and 1% of controls, giving a strong but imprecise association
  • For pesticide mixing the odds ratio was 7.4 (95% CI 1.4 to 40); no association was seen with applying pesticides (reported by 11% of cases and 15% of controls)
  • In a cited study of the asbestos-exposed community of Libby, Montana, 22% of Libby residents compared with 6% of controls had high-titer antinuclear antibodies
  • None of the Libby subjects had a diagnosis of systemic autoimmune disease
• The authors' conclusion: The authors concluded that crystalline silica is the agent with the most human data supporting an association with SLE. They also concluded that understanding the causes of SLE will likely require large, multidisciplinary studies of interactions between environmental exposures and genetic factors.
• Limitations the authors state:
  • The authors noted that the autoantibody findings in the Libby, Montana asbestos study involved relatively small numbers of individuals
  • The authors noted that studies of gene-environment interactions in SLE are limited by the small sample size typical of case-control studies

Topics

Medical terms in this study, explained in our Lexicon: Occupational Exposure, Crystalline.

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