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.

Asbestos, 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.

or blue asbestos

Gray-blue to green, highly fibrous (asbestiform) form of the amphibole mineral riebeckite. It has higher tensile strength than chrysotile asbestos. The major commercial source is South Africa, where it occurs in Precambrian banded-iron formations; it is also found in Australia and Bolivia.

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Any of several minerals that separate readily into long, flexible fibres. Chrysotile accounts for about 95percnt 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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