Abstract
Over a 70-year period, a mine near Libby, MT supplied nearly 80% of the world’s vermiculite. Raw vermiculite, which was contaminated with naturally occurring amphibole in veins throughout the deposit, was shipped to processing sites throughout the United States for exfoliation. In this pilot study, tree bark samples were collected near processing facilities in Spokane, WA, Santa Ana, CA, Newark, CA, and Phoenix, AZ in an effort to determine if areas surrounding these facilities are today contaminated with Libby amphibole asbestos (AA). From areas surrounding each of the four historical processing sites, Libby AA was detected in a subset of the bark samples. At the Santa Ana, Newark and Phoenix facilities, actinolite-tremolite and other high Fe Ca-bearing amphibole were also measured from the bark samples. In addition, chrysotile was frequently measured in samples collected from each of the sites. From the results of this pilot study, it is evident that tree bark can serve as reservoirs of asbestos, and indicators of past and current contamination. These data also suggest that areas outside of these historical processing facilities may today have some level of existing contamination resulting from the operation of these facilities.
Highlights
Prior to 1990, up to 80% of the world’s vermiculite was derived from a mine near Libby, Montana [1]
An Environmental Protection Agency (EPA) assessment published in 2009 showed that Libby amphibole was detected in the soil and indoor dust at the Newark, Santa Ana, and Phoenix historical Libby vermiculite processing facilities [44]
The results from tree bark analyses collected near these same areas indicate that trees in the residential/commercial areas surrounding these facilities can serve as reservoirs for asbestos fibers
Summary
Prior to 1990, up to 80% of the world’s vermiculite was derived from a mine near Libby, Montana [1]. The vermiculite ore mined from Zonolite Mountain seven miles northeast of Libby was contaminated with fibrous and asbestiform amphibole in veins throughout the deposit [2], containing a combination of winchite (84%), richterite (11%) and tremolite (6%) [3]. In October 2002, Libby was added to the Environmental Protection Agency’s (EPA) National Priorities List, and in June 2009 the town of Libby was designated a public health emergency. This is the only time EPA has made such a declaration.
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