Risk of silicosis in a Colorado mining community

Am J Ind Med. 1996 Nov;30(5):529-39. doi: 10.1002/(SICI)1097-0274(199611)30:5<529::AID-AJIM2>3.0.CO;2-O.


We investigated exposure-response relations for silicosis among 134 men over age 40 who had been identified in a previous community-based random sample study in a mining town. Thirty-two percent of the 100 dust-exposed subjects had radiologic profusions of small opacities of I/O or greater at a mean time since first silica exposure of 36.1 years. Of miners with cumulative silica exposures of 2 mg/m3-years or less, 20% had silicosis; of miners accumulating > 2 mg/m3 years, 63% had silicosis. Average silica exposure was also strongly associated with silicosis prevalence rates, with 13% silicotics among those with average exposure of 0.025-0.05 mg/m3, 34% among those with exposures of > 0.05-0.1 mg/m3, and 75% among those with average exposures > 0.1 mg/m3. Logistic regression models demonstrated that time since last silica exposure and either cumulative silica exposure or a combination of average silica exposure and duration of exposure predicted silicosis risk. Exposure-response relations were substantially higher using measured silica exposures than using estimated silica exposures based on measured dust exposures assuming a constant silica proportion of dust, consistent with less exposure misclassification. The risk of silicosis found in this study is higher than has been found in workforce studies having no follow-up of those leaving the mining industry and in studies without job title-specific silica measurements, but comparable to several recent studies of dust exposure-response relationships which suggest that a permissible exposure limit of 0.1 mg/m3 for silica does not protect against radiologic silicosis.

Publication types

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

MeSH terms

  • Adult
  • Case-Control Studies
  • Colorado / epidemiology
  • Dust / adverse effects*
  • Humans
  • Likelihood Functions
  • Logistic Models
  • Male
  • Maximum Allowable Concentration
  • Middle Aged
  • Mining*
  • Occupational Exposure / analysis
  • Odds Ratio
  • Prevalence
  • Radiography
  • Silicon Dioxide / adverse effects*
  • Silicosis / diagnostic imaging
  • Silicosis / epidemiology*
  • Silicosis / prevention & control
  • Time Factors


  • Dust
  • Silicon Dioxide