US EPA

On August 25, 2011, the draft Toxicological Review of Libby Amphibole Asbestos and the charge to external peer reviewers were released for external peer review and public comment. The Toxicological Review and charge were reviewed internally by EPA and by other federal agencies and White House Offices before public release. In the new IRIS process (May 2009), introduced by the EPA Administrator, all written comments on IRIS assessments submitted by other federal agencies and White House Offices will be made publicly available. Accordingly, interagency comments and the interagency science consultation draft of the IRIS Toxicological Review of Libby Amphibole Asbestos and the charge to external peer reviewers are posted on this site.

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).

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.

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).

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