Dose-response associations of silica with nonmalignant respiratory disease and lung cancer mortality in the diatomaceous earth industry

Am J Epidemiol. 1997 Apr 15;145(8):680-8. doi: 10.1093/aje/145.8.680.


The potential carcinogenicity of crystalline silica to humans remains a controversial issue. The authors conducted an historical cohort mortality study of 2,342 male workers exposed to crystalline silica, predominantly cristobalite, in a diatomaceous earth mining and processing facility in California. During the years 1942-1994, mortality excesses were detected for nonmalignant respiratory diseases (NMRD) (standardized mortality ratio = 2.01, 95% confidence interval (CI) 1.56-2.55) and lung cancer (standardized mortality ratio = 1.29, 95% CI 1.01-1.61). NMRD mortality rose sharply with cumulative exposure to respirable crystalline silica; allowing for a 15-year latency, the rate ratio for the highest exposure stratum (> or = 5.0 mg/m3-years) was 5.35 (95% CI 2.23-12.8). The rate ratio for lung cancer reached 2.15 (95% CI 1.08-4.28) in the highest exposure category. These associations were unlikely to have been confounded by smoking or asbestos exposure. The findings indicate a strong dose-response relation for crystalline silica and NMRD mortality. The lung cancer results, although less convincing, add further support to an etiologic role for crystalline silica.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Asbestos / adverse effects
  • California / epidemiology
  • Dose-Response Relationship, Drug
  • Drug Synergism
  • Humans
  • Lung Neoplasms / chemically induced*
  • Lung Neoplasms / mortality*
  • Male
  • Middle Aged
  • Respiratory Tract Diseases / chemically induced*
  • Respiratory Tract Diseases / mortality*
  • Risk
  • Silicon Dioxide / adverse effects*


  • Asbestos
  • Silicon Dioxide