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.

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

Abatement
Removal or controlling release of asbestos fibers. Includes operations and maintenance (O & M), encapsulation, enclosure, and removal.

Stage 1 Mesothelioma
Stage 1 mesothelioma affects one layer of the pleura only. It may have grown into the covering of the heart (pericardium) and the diaphragm

Suspect material
Building material suspected of containing asbestos, e.g., surfacing material, floor tile, ceiling tile, thermal system insulation, and miscellaneous other materials.

Chrysotile Asbestos
A fibrous member of the serpentine group of minerals. Chrysotile asbestos fibers are flexible and have a curved morphology. It is the most common form of asbestos used commercially, also referred to as white asbestos.

Immunologic Toxicity
The occurrence of adverse effects on the immune system that may result from exposure to environmental agents such as chemicals.

Actinolite
One of the six types of asbestos.

Minimal Risk Level (MRL)
An estimate of daily human exposure to a hazardous substance that is likely to be without an appreciable risk of adverse noncancer health effects over a specified route and duration of exposure.

Recommended Exposure Limit (REL)
A National Institute for Occupational Safety and Health (NIOSH) time-weighted average (TWA) concentrations for up to a 10-hour workday during a 40-hour workweek.