Objectives: To describe asbestos-related mortality among manufacturing workers who expanded and processed Libby vermiculite that contained amphibole fiber.
Methods: Standardized mortality ratio was calculated for 465 white male workers 31 years after last Libby vermiculite exposure.
Results: Two workers died from mesothelioma, resulting in a significantly increased standardized mortality ratio of 10.5 (95% confidence interval, 1.3 to 38.0). These workers were in the upper 10th percentile of cumulative fiber exposure, that is, 43.80 and 47.23 fiber-years/cm3, respectively. One additional worker with cumulative fiber exposure of 5.73 fiber-years/cm3 developed mesothelioma but is not deceased. There were no other significantly increased standardized mortality ratios.
Conclusions: Workers expanding and processing Libby vermiculite in a manufacturing setting demonstrated an increased risk for the development of mesothelioma following exposure to the amphibole fiber contained within this vermiculite ore source.
From the Department of Environmental Health (Drs Dunning, Levin, Rice, LeMasters, Adjei, Rohs, and Lockey, Mr Borton and Mr Hilbert), University of Cincinnati College of Medicine, Cincinnati, Ohio; the Department of Rehabilitation Sciences (Dr Dunning), University of Cincinnati College of Allied Health Sciences, Cincinnati, Ohio; the Department of Internal Medicine, Pulmonary Division (Drs Adjei, Rohs, and Lockey), University of Cincinnati College of Medicine, Cincinnati, Ohio; and National Center for Environmental Health and Agency for Toxic Substances and Disease Registry (Dr Kapil), Centers for Disease Control and Prevention, Atlanta, Ga.
Address correspondence to: James E. Lockey, MD, MS, Departments of Environmental Health, University of Cincinnati College of Medicine, 3223 Eden Ave, ML 0056, Cincinnati, OH 45267 (firstname.lastname@example.org).
This study was supported by funds from the Comprehensive Environmental Response Compensation and Liability Act trust fund through a cooperative agreement with the Agency for Toxic Substances and Disease Registry (ATSDR), US Department of Health and Human Services, Centers for Disease Control and Prevention ATSDR grants U50/ATU573006s and 1R01TS000098-1. In addition, this study was partially supported by the National Institute of Environmental Health Sciences grant ES10957 and by the US Environmental Protection Agency Region 8, as part of the management of the Libby Asbestos Superfund Site.
Drs Lockey, Dunning, and Levin, Mr Hilbert, and Mr Borton received partial funding by a grant from ATSDR. Dr Lockey served as a fact and state-of-the-art witness for the US Department of Justice for the District of Montana, Missoula Division, in the case of United States of America v WR Grace et al.
The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the Agency for Toxic Substances and Disease Registry or the Centers for Disease Control and Prevention.