Vermiculite worker mortality: estimated effects of occupational exposure to Libby amphibole.
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 > or =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.
Larson
Theodore C
TC
Division of Health Studies, Agency for Toxic Substances and Disease Registry, Atlanta, GA 30341, USA. thl3@cdc.gov
Antao
Vinicius C
VC
Bove
Frank J
FJ
D000368:Aged; D000538:Aluminum Silicates; D017636:Asbestos, Amphibole / Q000009:adverse effects*; D015331:Cohort Studies; D004305:Dose-Response Relationship, Drug; D006801:Humans; D008875:Middle Aged; D009009:Montana / Q000453:epidemiology; D009026:Mortality / Q000639:trends*; D016273:Occupational Exposure / Q000009:adverse effects*; D016016:Proportional Hazards Models; D012189:Retrospective Studies
D000538:Aluminum Silicates; D017636:Asbestos, Amphibole; C003760:vermiculite