Amphibole asbestos is the generic commercial designation for a group of naturally occurring mineral silicate fibres of the serpentine and amphibole series. These include the serpentine mineral chrysotile (also known as ‘white asbestos’), and the five amphibole minerals – actinolite, amosite (also known as ‘brown asbestos’), anthophyllite, crocidolite (also known as ‘blue asbestos’), and tremolite (IARC, 1973; USGS, 2001). The conclusions reached in this Monograph about asbestos and its carcinogenic risks apply to these six types of fibres wherever they are found, and that includes talc containing amphibole asbestiform fibres. Erionite (fibrous aluminosilicate) is evaluated in a separate Monograph in this volume.
The Differences between Chrysotile and Amphibole Asbestos
Many studies are conducted each year in pursuit of further knowledge of the specific biological effects of amphibole asbestos fibers in the human body. Since six unique fibers are identified as asbestos, a discrepancy has arisen regarding the effects of each individual fiber type. Chrysotile is a silicon-based fiber, identified as a serpentine mineral with a long and bendable character.amphibole asbestos
. The other five minerals, amosite, tremolite, crocidolite, anthophyllite, and actinolite, are identified as amphiboles, are iron-based, and have a more strong and durable character.amphibole asbestos
Their different chemistries result in very different effects within the human body and in the lungs specifically. Generally, chrysotile fibers are able to flush out of the lung cavities at a greater rate than amphibole fibers and are more soluble, meaning they are able to break apart more easily. Recent reviews of chrysotile and amphibole fibers determine a significant difference in their potency in causing mesothelioma and lung cancer.
Geographic Occurrence Of Amphibole Asbestos
Major asbestos deposits can be found in rock formations in the United States, Canada, South Africa, and the former Soviet Union. In the United States, asbestos occurs in 20 states and has been mined in 17 states (Asbestos Facts, U.S. Geological Survey). Serpentinite, the most common source for chrysotile, is present in the Appalachians, Cascades, Coast Ranges of California and Oregon, and in other mountainous areas.amphibole asbestos
Currently, chrysotile is the only type of asbestos mined on a large scale. Small amounts of tremolite amphibole asbestos are still mined in India. Commercial production of crocidolite and amosite has ended in South Africa.amphibole asbestos