Published By: Agency for Toxic Substances and Disease Registry
Contributors:
Summary
Libby is the county seat of Lincoln County, in northwest Montana. Vermiculite was mined from
“Zonolite Mountain” near Libby from the early 1920s until 1990 and was processed for export in
and around the town of Libby. The vermiculite mined in Libby is contaminated with amphibole
asbestos fibers (Libby Asbestos, or LA). Mining and processing operations, as well as home use
of Libby vermiculite products, resulted in the spreading of LA throughout the town. Unusually
high numbers of people in Libby have been diagnosed with asbestos-related respiratory disease;
deaths from asbestos-related respiratory diseases are also elevated. Since 1999, the
Environmental Protection Agency’s (EPA’s) Emergency Response Branch has been conducting
sampling and removals to address the most highly contaminated areas in the Libby valley. Since
the proposal of the Libby Asbestos site to the National Priorities List (NPL), these activities have
been transitioning over to the Superfund Branch for long-term cleanup.
People were exposed to LA by many different exposure pathways in the past, and as long as
source materials are present, the possibility for further exposure remains. Source materials are
defined as any material (including waste rock, soil, building materials, or insulation) containing
LA which, when disturbed, could produce elevated levels of LA fibers in air. The size of source
areas can range from the residential scale to the industrial scale. However, many of the largest
and most highly contaminated areas have been or are being cleaned up. As of late fall 2002,
characterization of contamination in Libby homes and businesses to prioritize cleanups through
the EPA Superfund program is almost complete.