Tremolite
Tremolite may occur in fibrous form (an asbestos). It is not used commercially in the United States, but is a common impurity in chrysotile asbestos and vermiculite mined from deposits in Libby, Montana.

Permissible Exposure Limit (PEL)
An Occupational Safety and Health Administration (OSHA) allowable exposure level in workplace air averaged over an 8-hour shift of a 40 hour workweek.

Parenchymal fibrosis
It is easily conceivable that prolonged retention of some types of minerals in the lung would be a stimulating factor for inflammatory and neoplastic processes, leading in turn to parenchymal fibrosis and peripheral cancer.

Lethal Concentration(50) (LC50)
A calculated concentration of a chemical in air to which exposure for a specific length of time is expected to cause death in 50% of a defined experimental animal population.

Crocidolite asbestos
One of the six types of asbestos. Crocidolite or "blue asbestos," is found in specialized high temperature applications.

Friable asbestos
Any material containing more than one percent asbestos, and that can be crumbled or reduced to powder by hand pressure. (May include previously non-friable material which becomes broken or damaged by mechanical force.)

Asbestosis
A progressively restrictive fibrosis of the lung and is recognized as a disabling and fatal occupational disease.

Mesothelioma
A rare malignant tumor of the lung membrane which lines the chest and abdominal cavity. Malignant mesothelioma is a cancerous tumor of the pleura (lining of the lung and chest cavity) or peritoneum (lining of the abdomen) that is almost always caused by sustained exposure to asbestos.

Vermiculite
A chemically inert, lightweight, fire resistant, and odorless magnesium silicate material that is generally used for its thermal and sound insulation in construction and for its absorbent properties in horticultural applications. Vermiculite mined from Libby, Montana has been demonstrated to contain various amounts of asbestiform tremolite-like amphibole minerals.

Asbestos Containing Material (ACM).
Any material or product that contains more than one percent asbestos.