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

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.