Libby Amphibole Asbestos

CASRN 1318-09-8

IRIS Toxicological Review of Libby Amphibole Asbestos (External Review Draft)

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EPA is conducting a peer review of the scientific basis supporting the human health hazard and dose-response assessment of Libby Amphibole Asbestos that will appear in the Integrated Risk Information System (IRIS) database.


U.S. EPA. IRIS Toxicological Review of Libby Amphibole Asbestos (External Review Draft). U.S. Environmental Protection Agency, Washington, DC, EPA/635/R-11/002A, 2011.

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This draft health assessment of the toxicity of Libby amphibole asbestos was prepared by staff in both EPA’s Region 8 Office and ORD/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 will be included on EPA's IRIS data base when finalized. 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 this external peer review draft document required internal EPA review and OMB/interagency review. After an independent external peer review, the draft final document will undergo a second round of EPA and OMB/interagency review before being finalized and then included on the IRIS data base.

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.)


Date Description
03-Aug 2007The Libby Amphibole Asbestos assessment was initiated in 2007. It was nominated for assessment by the IRIS Program because it supports OSWER and Region 8 site clean-up and related risk management initiatives at this Superfund site. An assessment for Libby Amphibole Asbestos is not currently on IRIS.
04-May 2011EPA hosted an interagency science consultation on the draft IRIS Toxicological Review of Libby Amphibole Asbestos.
05-Aug 2011EPA released the draft IRIS Toxicological Review of Libby Amphibole Asbestos for public review and comment, and announced the public listening session. [Federal Register Notice Aug 25, 2011]
06-Dec 2011EPA's Science Advisory Board (SAB) announced a public peer review meeting on the draft IRIS Toxicological Review of Libby Amphibole Asbestos that was held on Feb 6 -8, 2012 in Alexandria, VA. [Federal Register Notice Dec 23, 2011]
07-Jan 2013EPA's SAB released the final report from the "Review of EPA's Draft Assessment Entitled Toxicological Review of Libby Amphibole Asbestos (August 2011)"


Following external peer review, the assessment will be revised taking into consideration external peer review and public comments. It will then be revised as appropriate and will undergo a final EPA internal review and a science discussion with other federal agencies and White House offices, and will be posted to the IRIS database. This Assessment does not replace the existing IRIS listing for asbestos (EPA, 1988).

Additional Information

Comments on the assessment may be submitted and reviewed using the e-Government Web site. From the site, select “Environmental Protection Agency” and the keyword “EPA-HQ-ORD-2011-0425 (for the docket ID) to comment on this report.

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This download(s) is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not been formally disseminated by EPA. It does not represent and should not be construed to represent any Agency determination or policy.

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