Libby, Montana Workers Studied for Lung Cancer Risks

Previous studies of Libby workers documented increased risk of lung cancer and nonmalignant respiratory disease among highly exposed workers with at least 1 year tenure.

Reports of respiratory disease mortality among community residents and household contacts of Libby vermiculite workers suggested increased risk from transient exposure or ambient community exposure.

Cross-sectional radiographic screening conducted in Libby for the ATSDR revealed that 6.7% of community residents with no occupational or familial exposure have radiographic evidence of asbestos-related disease. These findings suggest that risk from asbestos-contaminated vermiculite may not be limited to those with high-intensity occupational exposure.

This report expands the previously studied occupational cohort to include all white men hired at Libby from September 1935 through December 1981. The intent here is to describe the mortality experience of workers exposed to Libby amphibole fibers (tremolite asbestos, winchite, richterite) over the full range of exposure and employment duration.

Occupational respiratory disease mortality among Libby workers is compared to that expected based on the mortality experience of the U.S. population, and standardized mortality ratios (SMRs) and standardized rate ratios (SRRs) for asbestosis, lung cancer, and all nonmalignant respiratory diseases are presented.