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Journal of Occupational & Environmental Medicine:
doi: 10.1097/JOM.0b013e3181dc6d45
Original Articles

Vermiculite Worker Mortality: Estimated Effects of Occupational Exposure to Libby Amphibole.

Larson, Theodore C. MS; Antao, Vinicius C. MD, MSc, PhD; Bove, Frank J. ScD

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Objective: To examine the relationship between cumulative fiber exposure (CFE) and mortality in a retrospective cohort study of vermiculite workers exposed to Libby amphibole (n = 1862).

Methods: Extended Cox regression was used to estimate the hazards associated with CFE as a time-dependent covariate of multiple-cause mortality.

Results: The Cox models for mesothelioma, asbestosis, lung cancer, and non-malignant respiratory disease were significant with rate ratios that increased monotonically with CFE. The model for deaths due to cardiovascular disease was also significant (rate ratio for CFE ≥44.0 f/cc-y vs <1.4 f/cc-y was 1.5; 95% confidence interval = 1.1 to 2.0).

Conclusions: By using a within-cohort comparison, the results demonstrate a clear exposure-response relationship between CFE and mortality from asbestos-related causes. The finding of an association between CFE and cardiovascular mortality suggests persons exposed to Libby amphibole should be monitored for this outcome.

©2010The American College of Occupational and Environmental Medicine


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