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U.S. Geological Survey scientists and partners have created an onsite, time-saving technique for building inspectors to ascertain whether vermiculite insulation contains amphibole asbestos. The findings are featured in the April 2 edition of American Mineralogist.

Approximately one million homes in the United States contain vermiculite attic insulation. One of the major past sources of this vermiculite was commercially produced vermiculite insulation from Libby, Montana, containing trace levels of asbestiform amphibole, which is known to cause asbestos-related diseases. Although the Libby mine is closed and part of a Superfund site, the existing insulation in many older houses and buildings still needs to be tested for asbestos. When vermiculite insulation is found in an attic, evaluating it for asbestos has traditionally involved collecting a sample and submitting it for potentially time-consuming analyses at an off-site laboratory.


“The goal of this USGS study was to find an onsite way to test for asbestos by determining if near-infrared reflectance measurements, using portable spectrometers, could be used to reliably identify the source of vermiculite ore and therefore its potential to contain asbestos,” said Denver-based USGS scientist and first author Gregg Swayze. “We achieved this goal.”


Swayze and the team studied 52 expanded vermiculite samples from around the world, including attic insulation, commercial packing materials and horticultural products from Libby, Montana; Louisa, Virginia; Enoree, South Carolina; Palabora, South Africa; and Jiangsu, China. All of the nearly two dozen Libby vermiculite insulation samples examined with scanning electron microscopy in this study contained asbestiform amphiboles compared to relatively little asbestos to none in samples from the other locations. Spectroscopy accurately determined the origin of the vermiculite insulation samples. 


“Based on medical studies, there is general agreement that all Libby vermiculite insulation is potentially hazardous,” said Swayze. “This study demonstrates that spectrally determining the source of attic vermiculite as Libby, provides enough information to make a remediation decision.”


Vermiculite insulation can be analyzed while it is still in an attic using a portable spectrometer. Samples for potentially time-consuming off-site laboratory analyses do not need to be collected from an attic if the insulation is spectrally confirmed as vermiculite from Libby. Instead, a report can be generated and given to the owner while on site, along with information on remediation scenarios.


Photo of Vermiculite Attic Insulation from Libby, Montana
Photo of Vermiculite Attic Insulation from Libby, Montana(Credit: Gregg Swayze, USGS. Public domain.)
Scanning Electron Image of Vermiculite Asbestos
Scanning electron microscope image of elongate amphiboles, some of which are asbestiform, collected from attic insulation from Libby, Montana.(Public domain.)

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