826. Asbestos

Nomenclature

Amianthus.

Description and references

A family of naturally occurring, flexible, fibrous mineral silicates. Divided into two groups: serpentine and amphibole. Most common form is chrysotile [Mg6(Si4O10)(OH)8], the fibrous form of serpentine (see also magnesium silicates). Subdivisions of amphibole are anthophyllite [(Mg,Fe)7(Si8O22)(OH)2] (low iron content); amosite [Fe5Mg2(Si8O22)(OH)2]; actinolite [Ca2(Mg,Fe)5(Si8O22 )(OH)2]; tremolite [Ca2Mg5(Si8O22)(OH)2]; crocidolite or blue asbestos [Na2Fe32+Fe23+(Si8O22)(OH)2]. Commercially important forms: chrysotile, anthophyllite, amosite, crocidolite. Review of occupational use and carcinogenic risk: IARC Monographs 14, 1-106 (1977); of toxicology and human exposure: Toxicological Profile for Asbestos (PB2001-109101, 2001) 441 pp. Review of properties and industrial applications: C. R. Jolicoeur et al. in Kirk-Othmer Encyclopedia of Chemical Technology vol. 3 (John Wiley & Sons, New York, 4th ed., 1992) pp 659-688; of electron microscopic analysis of airborne fibers: P. N. Breysse, Crit. Rev. Anal. Chem. 22, 201-277 (1991). Symposium on asbestos-related disease: P. J. Landrigan, H. Kazemi, Eds., Ann. N.Y. Acad. Sci. 643, 1-628 (1991).

Properties

Fire resistant fibers. Chrysotile attacked by acid; amphiboles, acid resistant.

Caution

The effects of respiratory exposure to asbestos are subacute or chronic and exhibit a latent period. Nonmalignant respiratory diseases attributable to asbestos exposure include chronic pulmonary fibrosis (asbestosis), fibrotic pleural plaques, pleuritis, and diffuse pleural thickening. Neoplastic diseases associated with occupational exposure to airborne asbestos include lung cancer and mesothelioma. See Patty's Industrial Hygiene and Toxicology vol. 2A, G. D. Clayton, F. E. Clayton, Eds. (Wiley-Interscience, New York, 4th ed., 1993) pp 849-864. Potential symptoms of overexposure are dyspnea, interstitial fibrosis, restricted pulmonary function and finger clubbing; eye irritation. See NIOSH Pocket Guide to Chemical Hazards (DHHS/NIOSH 97-140, 1997) p 22. Asbestos and all commercial forms of asbestos are listed as known human carcinogens: Report on Carcinogens, Eleventh Edition (PB2005-104914, 2004) p III-21.

Use

Heat-resistant insulators, cements, furnace and hot pipe coverings, inert filler medium (laboratory & commercial), fireproof gloves, clothing, brake linings. NaOH treated asbestos, Ascarite, has been used to absorb CO2 in combustion analysis.