Research conducted by the Environmental Protection Agency in Libby , Montana on the source of asbestos exposure from contaminated vermiculite suggests that vermiculite-contaminated soil found outside of homes and businesses is the primary source of asbestos exposure for most residents. The research suggests that most asbestos exposure in Libby residents is coming from the soil outside of homes, with indoor exposure coming from dirt tracked in on shoes or carried in by domestic animals.
Researchers were careful to note that in homes where asbestos-containing construction materials have been disturbed, or not well-contained within the walls of the home, the vermiculite in the soil is probably not the principal exposure agent, but such homes are no more common in Libby than in any other town.
The research may result in changes to how the Environmental Protection Agency assesses remediation risks in Libby or elsewhere, and may change the agency’s official definition of a “clean site”. Paul Peronard, EPA’s on-site coordinator for Libby, said “ This is a powerful data set, [and] it will help us define the first part of endgame” – the agency’s term for the process of deciding that a site has been properly cleaned. Researchers examined several indoor and outdoor activities, ranging from mowing the lawn to relaxing in front of the TV, and played out “scenarios” where researchers would engage in the activity while wearing collectors that gathered samples from the air and soil researchers were breathing or walking on.
The researchers performed their test at a variety of sites, including both untreated and remediated properties. One encouraging result of the study: casual outdoor activity in Libby resulted in relatively low exposure to asbestos fibers. However, the study also indicates that it will be difficult to determine the success of any particular remediation effort, as the number of factors that assessment must consider has expanded considerably. The study did not attempt to determine whether contaminated vermiculite resulted from the mining activities at Libby or were part of the background asbestos level of the area prior to industrial activity. The US Geological Survey is expected to conduct a future study in the area to attempt to discover the extent of the natural vermiculite contamination.