Association between cumulative fiber exposure and respiratory outcomes among Libby vermiculite workers

J Occup Environ Med. 2012 Jan;54(1):56-63. doi: 10.1097/JOM.0b013e31823c141c.


Objective: To examine the association between cumulative fiber exposure and health outcomes in workers (n = 336) with Libby amphibole exposure.

Methods: Exposure-response relationships were explored by the use of logistic regression, with cumulative fiber exposure modeled in categories and as a continuous variable.

Results: The use of spline functions with lifetime cumulative fiber exposure as a continuous variable showed that the odds of localized pleural thickening were significantly elevated at less than 1 f/cc-y. Odds of parenchymal abnormalities, restrictive spirometry, and chronic bronchitis were also significantly elevated at 108, 166, and 24 f/cc-y, respectively.

Conclusions: The odds of several pulmonary health outcomes are correlated with cumulative exposure to Libby amphibole. That relatively low-lifetime cumulative exposures are associated with localized pleural thickening has implications for the non-cancer-risk assessment for Libby amphibole.

MeSH terms

  • Aged
  • Aluminum Silicates / toxicity*
  • Asbestos, Amphibole / toxicity*
  • Bronchitis / chemically induced*
  • Bronchitis / epidemiology
  • Cohort Studies
  • Female
  • Humans
  • Lung / drug effects*
  • Lung / physiopathology
  • Male
  • Middle Aged
  • Occupational Diseases / chemically induced*
  • Occupational Diseases / epidemiology
  • Occupational Exposure*
  • Pleural Diseases / chemically induced*
  • Respiratory Function Tests
  • Risk Assessment
  • Spirometry


  • Aluminum Silicates
  • Asbestos, Amphibole
  • vermiculite