Select Mortality and Cancer Incidence Among Residents in Various U.S. Communities that Received Asbestos-Contaminated Vermiculite Ore from Libby, Montana

Abstract

In response to the significantly elevated asbestosis mortality rates found in Libby, Montana, in 2000, this analysis evaluated whether other communities throughout the United States that received asbestos-contaminated vermiculite ore from Libby experienced similar excess rates of asbestos-related diseases. Standardized mortality ratios were calculated using state death certificates, and standardized incidence ratios were calculated using cancer registry records for populations living near facilities that processed or received Libby vermiculite. This analysis focused primarily on diseases that are directly associated with asbestos exposure (e.g., asbestosis; cancer of the peritoneum, retroperitoneum, and pleura, including mesothelioma; and mesothelioma). Lung cancer and cancers of the digestive system, also associated with asbestos exposure, were not included in the analysis because they have additional risk factors for which exposure information was not available. Data from 70 unique sites in 23 states were evaluated. No statistically significant excesses of asbestosis mortality similar to those in Libby were noted; however, 11 sites (plus a state with 6 pooled sites that were counted as 1 site) had excess rates of mesothelioma and cancer of the peritoneum, retroperitoneum, and pleura. Further investigation should be conducted at these sites with excess rates of mesothelioma and cancer of the peritoneum, retroperitoneum, and pleura by participating state health departments to determine whether exposure to Libby vermiculite might have been a contributing factor.