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Mortality in Vermont granite workers and its association with silica exposure
  1. Pamela M Vacek1,
  2. Dave K Verma2,
  3. William G Graham3,
  4. Peter W Callas1,
  5. Graham W Gibbs4,5
  1. 1Department of Medical Biostatistics, University of Vermont, Burlington, Vermont, USA
  2. 2Program in Occupational Health and Environmental Medicine, McMaster University, Hamilton, Ontario, Canada
  3. 3Department of Medicine, University of Vermont, Burlington, Vermont, USA
  4. 4Safety Health Environmental International Consultants, Devon, Alberta, Canada
  5. 5Department of Medicine, University of Alberta, Edmonton, Alberta, Canada
  1. Correspondence to Pamela M Vacek, University of Vermont, Department of Medical Biostatistics, 105 Carrigan Drive, Burlington, VT 05405, USA; Pamela.Vacek{at}


Objectives To assess mortality in Vermont granite workers and examine relationships between silica exposure and mortality from lung cancer, kidney cancer, non-malignant kidney disease, silicosis and other non-malignant respiratory disease.

Methods Workers employed between 1947 and 1998 were identified. Exposures were estimated using a job–exposure matrix. Mortality was assessed through 2004 and standardised mortality ratios (SMRs) were computed. Associations between mortality and exposure to silica were assessed by nested case–control analyses using conditional logistic regression.

Results 7052 workers had sufficient data for statistical analysis. SMRs were significantly elevated for lung cancer (SMR 1.37, 95% CI 1.23 to 1.52), silicosis (SMR 59.13, 95% CI 44.55 to 76.97), tuberculosis (SMR 21.74, 95% CI 18.37 to 25.56) and other non-malignant respiratory disease (SMR 1.74, 95% CI 1.50 to 2.02) but not for kidney cancer or non-malignant kidney disease. In nested case–control analyses, significant associations with cumulative exposure to respirable free silica were observed for silicosis (OR 1.13, 95% CI 1.05 to 1.21 for each 1 mg/m3-year increase in cumulative exposure) and other non-malignant respiratory disease (OR 1.10, 95% CI 1.03 to 1.16) but not for lung cancer (OR 0.99, 95% CI 0.94 to 1.03), kidney cancer (OR 0.96, 95% CI 0.84 to 1.09) or non-malignant kidney disease (OR 0.95, 95% CI 0.84 to 1.08).

Conclusions Exposure to crystalline silica in Vermont granite workers was associated with increased mortality from silicosis and other non-malignant respiratory disease, but there was no evidence that increased lung cancer mortality in the cohort was due to exposure. Mortality from malignant and non-malignant kidney disease was not significantly increased or associated with exposure.

  • Epidemiology
  • cancer
  • silicosis
  • mortality studies

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  • Funding This study was supported by the Crystalline Silica Panel of the American Chemistry Council (ACC) through a contract with the University of Vermont (contract CS-2004-6.0-UV-Vacek). ACC had no role in data collection, statistics analysis or interpretation of results.

  • Competing interests None.

  • Ethics approval This study was conducted with the approval of the University of Vermont Research Protection Office, Committees on Human Research.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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