Abstract
Vermiculite is a mineral that expands when rapidly heated. Expanded vermiculite is used in construction and consumer materials (e.g., loose-fill insulation, acoustic finishes, spray-on insulation, and concrete mixes for swimming pools), agricultural and horticultural products (e.g., potting mixes and soil conditioners) and in industrial products (e.g., brake shoes and pads, drilling muds, furnaces, and insulation blocks). Expanded vermiculite granules are shaped like small accordions, and vary in color from silver/gold to gray/brown. Vermiculite has been an established commercial commodity for well over 50 years, and is currently used throughout the world. Vermiculite ore mined near Libby, Montana, which accounted for more than half the worldwide production of vermiculite from 1925 to 1990, was contaminated with asbestos and asbestos-like fibers. Workplace exposure to these fibers caused a serious health problem in local miners and millers, as well as some downstream workers. Mining stopped at the mine near Libby in 1990. However, concerns remain about health effects from environmental and other occupational exposures to asbestos-contaminated vermiculite, especially vermiculite that has been installed as loose-fill insulation in homes and other buildings. Much of the vermiculite from the mine near Libby was used in the manufacture of Zonolite Attic Insulation. However, not all Zonolite product was made with vermiculite from that same mine.