asbestos

asbestos, mineral

asbestos, common name for any of a variety of silicate minerals within the amphibole and serpentine groups that are fibrous in structure and more or less resistant to acid and fire. Chrysotile asbestos, a form of serpentine, is the chief commercial asbestos. Varieties of amphibole asbestos are amosite, used in insulating materials; crocidolite, or blue asbestos, used for making asbestos-cement products; and tremolite, used in laboratories for filtering chemicals. Asbestos is usually found comprising veins in other rock; in most cases it appears to be the product of metamorphism. Canada is the chief asbestos producing country; other producers are Russia, Zimbabwe, the Republic of South Africa, Cyprus, and the United States. Asbestos is mined both in open quarries and underground.

Since the 1960s, asbestos has been recognized as a potent carcinogen and serious health hazard. Inhalation of airborne asbestos fibers has been established as the cause of asbestosis (thickening and scarring of lung tissue) and as a cause of mesothelioma (a highly lethal tumor of the pleura) as well as of cancers of the lung, intestines, and liver. In 1972, the Occupational Safety and Health Administration began regulating asbestos and strengthening work safety standards. Large class action lawsuits were filed and won against asbestos companies, which had probable prior knowledge of the dangers involved. In 1989, the Environmental Protection Agency imposed a ban on 94% of U.S. asbestos production and imports, to be phased in over a seven year period. Most current asbestos exposure comes from asbestos in older buildings and products such as automobile brakes.

Bibliography

See P. H. Riordon and V. F. Hollister, Geology of Asbestos Deposits (1981); S. S. Chissick and R. Derricott, Asbestos: Properties, Applications and Hazards (1983).

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Asbestos, town, Canada

Asbestos (ăsbĕs`təs, äz'bĕstōs`), town (1991 pop. 6,487), SE Que., Canada. Asbestos is mined in the area and asbestos products are made in the town. Other manufactures include wood products and electrical equipment.

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asbestos

Any of several minerals that separate readily into long, flexible fibres. Chrysotile accounts for about 95% of all asbestos still in commercial use. The other types all belong to the amphibole group and include the highly fibrous forms of anthophyllite, amosite, crocidolite, tremolite, and actinolite. Asbestos fibre was used in brake linings, insulation, roofing shingles, floor and ceiling tiles, cement pipes, and other building materials. Asbestos fabrics were used for safety apparel and theatre curtains. In the 1970s it was found that prolonged inhalation of the tiny asbestos fibres can cause asbestosis, lung cancer, and/or mesothelioma, all serious lung diseases. The incidence of mesothelioma is most commonly associated with extensive inhalation of amphibole asbestos. In 1989 the U.S. government instituted a gradual ban on the manufacture, use, and export of most products made with asbestos.

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asbestos

a. any of the fibrous amphibole and serpentine minerals, esp chrysotile and tremolite, that are incombustible and resistant to chemicals. It was formerly widely used in the form of fabric or board as a heat-resistant structural material

b. (as modifier): asbestos matting

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asbestos [as′bes·təs]

(mineralogy)

A general name for the useful, fibrous varieties of a number of rock-forming silicate minerals that are heat-resistant and chemically inert; two varieties exist: amphibole asbestos, the best grade of which approaches the composition Ca₂Mg₅(OH)₂Si₈O₂₂(tremolite), and serpentine asbestos, usually chrysotile, Mg₃Si₂(OH)₄O₅.

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(jargon)

asbestos - Used as a modifier to anything intended to protect one from flames; also in other highly flame-suggestive usages. E.g., asbestos longjohns, asbestos cork award.