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Vermiculite Mining in Libby, Montana

In June 2009, federal environmental officials declared a public health emergency under the Superfund law in Libby, Montana. Between the early 1920s and 1990, the town of Libby, Montana was the site of the largest vermiculite mine in the United States. According to the United States Environmental Protection Agency (EPA), it is estimated that the Libby mine produced over 70 percent of all vermiculite sold in the U.S. until 1990, when the mine closed.

The vermiculite from Libby, sold under the commercial name Zonolite (after the nearby Zonolite Mountains), was used in the majority of vermiculite insulation made and used in the U.S. The EPA further estimates that vermiculite insulation was used in more than 35 million homes.

Vermiculite is a natural mineral formed by hydration of certain basaltic minerals that expands with the application of heat. The Vermiculite Association states that “vermiculite has been demonstrated as being safe to use, and no serious health risks have been found resulting from exposure to vermiculite.”

However, Vermiculite can contain a variety of associated minerals such as mica, feldspar, and other minerals that are found in the soil in and around the mining area. The minerals found in vermiculite are unique to a particular deposit and may include naturally occurring minerals which could pose a health risk if present in significant quantities.

The vermiculate mine in Libby was found to be heavily contaminated with asbestos. When asbestos fibers are disturbed and become airborne they can be inhaled into the lungs, where they can cause significant health problems. Diseases that are known to be caused by exposure to asbestos include asbestosis, mesothelioma and lung cancer.

Consequently, many of the former miners, their families, and residents of Libby were affected by the asbestos and continue to suffer health problems. Over 200 people in the town have died from asbestos-related diseases. The health emergency declaration requires the federal government to provide screenings and health care for Libby residents with asbestos-related disease.

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