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.

RACM
Regulated Asbestos-Containing Material is (a) friable asbestos material, (b) Category I non-friable ACM that has become friable, (c) Category I non-friable ACM that will be or has been subjected to sanding, grinding, cutting or abrading, or (d) Category II non-friable ACM that has a high probability of becoming or has become crumbled, pulverized, or reduced to powder by the forces expected to act on the material in the course of demolition or renovation operations.

Acute Exposure
Exposure to a chemical for a duration of 14 days or less, as specified in the Toxicological Profiles.

Serpentine
In the asbestos varieties, the brucite and silicate layers bend into tubers that produce the fibers. Chrysotile asbestos is a fibrous member of the serpentine group. "Serpentine" comes from mottled shades of green on massive varieties, suggestive of snake markings.

Pericardial mesothelioma
Pericardial mesothelioma is a highly lethal and fortunately rare cardiac neoplasm

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.

Risk Ratio
The ratio of the risk among persons with specific risk factors compared to the risk among persons without risk factors. A risk ratio greater than 1 indicates greater risk of disease in the exposed group compared to the unexposed.

Asbestosis
A chronic lung disease, resulting from the scarring of the lung tissues by asbestos fibers.

Actinolite
One of the six types of asbestos.

Class IV asbestos work
Means maintenance and custodial activities during which employees contact but do not disturb ACM or PACM and activities to clean up dust, waste and debris resulting from Class I, II, and III activities.