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Assessing human health risk from exposure to Libby amphibole asbestos

Partner: Montana Department of Environmental Quality (DEQ)

Challenge: Asbestos exposure following forest fires

Resource: Computer modeling in collaboration with the U.S. Forest Service

Project Period: 2012-2016

“The modeling results were used to scope and plan for the potential socio-political and management challenges resulting from a wildfire occurring in or threatening a portion of the Libby Asbestos Superfund Site. These results will also be used to assist the Montana DEQ in evaluating proposed remedies, and [they] are important in informing local and Montana Department of Natural Resources and Conservation firefighters in developing response actions to protect firefighters and the citizens of Libby and the surrounding area.” – Montana DEQ, Remediation Division Lisa Dewitt

As noted above, Libby amphibole asbestos (LAA) has been found to co-occur with the vermiculite ore that was mined in Libby, Montana starting in the 1920s. Due to the presence of asbestos, additional concerns have been raised about the potential for forest fires near the Libby Asbestos site to spread asbestos fibers, exposing firefighters and those living adjacent to the Libby site.

To address this potential health hazard, EPA ORD, in collaboration with Region 8 (Mountains and Plains), provided technical support to Montana DEQ in assessing the health risks associated with potential forest fires near the Libby Asbestos site in Montana. Specifically, ORD conducted experiments to understand the potential asbestos emissions, and Region 8 used these data in a model to assess whether these emissions would result in potential exposures. To obtain emissions data, ORD first burned forest floor material from a portion of the Libby Asbestos site, simulating a forest fire. During these simulated burns, particulate matter and gaseous emissions were measured and samples of the ash were analyzed to determine whether these samples contained asbestos. These data suggested that only a small fraction of the asbestos in the forest floor material was released into the gas phase.

EPA Region 8 then used these data, along with direct measurements of asbestos in the forest floor at the Libby site, and estimated combustion and meteorological conditions in a model to estimate potential asbestos exposures under various scenarios. Because of these modeling efforts, EPA was then able to provide Montana DEQ with the range of potential exposures for these scenarios. In addition, EPA is now able to model forest fires when they do occur to more accurately estimate exposures and health risks to firefighters and to the surrounding communities.

Read the synthesis report (link will open in a new tab or window) titled Emissions of Amphibole Asbestos from the Simulated Open Burning of Duff from Libby, Montana.