US EPA

EPA has finalized the, Toxicological Review of Libby Amphibole Asbestos: in support of the Integrated Risk Information System (IRIS). Now final, this assessment may be used by EPA’s program and regional offices to inform decisions to protect human health.

Libby Amphibole asbestos is a complex mixture of amphibole fibers, both mineralogically and morphologically. The mixture primarily includes tremolite, winchite, and richterite fibers with trace amounts of magnesioriebeckite, edenite, and magnesio-arfvedsonite. These fibers exhibit a range of morphologies (e.g. prismatic, ascicular, asbestiform)(Meeker et al., 2003). Exposure to Libby Amphibole asbestos results in the same types of adverse health effects as are seen with exposure to other amphibole mineral fibers. Epidemiologic studies of workers exposed to Libby Amphibole asbestos fibers indicate increased mortality from lung cancer, mesothelioma, asbestosis, and other nonmalignant respiratory diseases (McDonald et al., 1986a, 2004; Amandus and Wheeler, 1987; Amandus et al., 1987a; Sullivan, 2007; Larson et al., 2010a, Moolgavkar et al., 2010). Morbidity studies report increased asbestosis, pleural thickening and decreased lung function in exposed individuals (Weill et al., 2010; Larson et al., 1020b; Rohs et al., 2008, Peipens et al., 2003, ATSDR, 2001; Amandus et al., 1987b and McDonald et al., 1986 b.)

The final health assessment of the toxicity of Libby amphibole asbestos was prepared by staff in both EPA’s Region 8 Office and Office of Research and Development's National Center for Environmental Assessments (NCEA). The assessment is focused on a specific type of asbestos found as a consequence of the mining and processing of vermiculite in Libby, Montana. The assessment is also included on EPA's IRIS data base.

The project supports OSWER and Region 8 site clean-up and related risk management initiatives at the Libby Superfund site. As with all IRIS assessments, the development of the external peer review draft document required internal EPA review and OMB/interagency review. After an independent external peer review, the draft final document underwent a second round of EPA and OMB/interagency review before being finalized and included in the IRIS data base.

The project supports OSWER and Region 8 site clean-up and related risk management initiatives at this Superfund site. As with all IRIS assessments, the draft document will undergo agency review, OMB/interagency review and independent external peer review before being included on the IRIS data base.

This report is finalized. However, this assessment does not replace the existing IRIS listing for asbestos (EPA, 1988).

U.S. EPA. IRIS Toxicological Review of Libby Amphibole Asbestos (Final Report). U.S. Environmental Protection Agency, Washington, DC, EPA/635/R-11/002F, 2014.