Agent Name

Asbestos

CAS Number

1332-21-4; 12001-28-4; 12172-73-5; 77536-66-4; 77536-67-5; 77536-68-6; 132207-32-0

Formula

varies

Major Category

Mineral Dusts

Synonyms

Chrysotile; Amosite; Crocidolite; Anthophylite; Tremolite; Actinolite;

Category

Fibrogenic Dusts

Description

White or greenish (chrysotile), blue (crocidolite), or gray-green (amosite) fibrous, odorless solids; [NIOSH] Chrysotile is a curly fiber in intertwined bundles; Amphiboles are straight and needle-like in shape; [Sullivan, p. 1215]

Sources/Uses

Used to make cement pipe, vinyl floor tile, flooring felt, shingles, roofing felt, sealants and plasters, acoustic tile, paper products for insulation and filtering, brake linings and clutch facings, curtains, and spray-on products for fireproofing and insulation; [ATSDR Case Studies, Asbestos Toxicity] Serpentine group: chrysotile (95% of world's production); Amphibole group: amosite, crocidolite, actinolite, anthophylite, and tremolite. Tremolite and actinolite were not used commercially, but may contaminate ores of talc, vermiculite, and chrysotile. Anthophylite was mined only in Finland and not after 1970. [Rom, p. 298; Harber, p. 296; Rosenstock, p. 413-5]

Comments

In the past, the highest exposures occurred in insulators, shipyard workers, and other workers manufacturing asbestos products. Today, construction workers are the most heavily exposed from maintenance, renovation, and demolition of buildings insulated with asbestos years ago. [ATSDR Case Studies, Asbestos Toxicity] As a general rule, exposure to asbestos for less than 6 months is unlikely to cause interstitial fibrosis or pleural thickening. Among workers heavily exposed to asbestos with interstitial fibrosis, about 1/2 also have pleural thickening. Among those with pleural thickening, less than 30% have interstitial fibrosis. [Rosenstock, p. 367-9] Although the epidemiological evidence shows that asbestos exposure is associated mainly with restrictive lung function impairment, obstructive changes are also seen. [Asthma in the Workplace, p. 380] An obstructive pattern (reduced FEV1/FVC) is not likely to be seen in nonsmoking workers with asbestosis, and there is no evidence that asbestos causes emphysema. [Hendrick, p. 148] "The PCM [phase contrast optical microscopy] is considered a better predictor of disease risks compared to concentrations of all airborne particles by the impinger method . . ." Mean PCM fiber concentrations (fibers > 5 um/cc) for machine operators in an asbestos textile plant ranged from 78 (1930-1944) to 24 (1945-1964) to 17 (1965-1975). [PMID 17984198] In the analysis of two case control studies of lung cancer in Quebec from 1979-1986 and 1996-2001, the odds ratio for smoking was 9.03, for asbestos exposure 1.93, and for both 10.80. [PMID 19001953] Chrysotile fibers are much more easily cleared from the lungs by macrophages than amphibole fibers. The amphibole fibers (crocodolite and amosite) are more potent causes of lung cancer and mesothelioma. Chrysotile is associated with mesothelioma when "highly contaminated with amphiboles." [Sullivan, p. 1219-22]

Restricted

Asbestos in insulation materials banned in the US in 1975; [ATSDR Case Studies] Dutch laws prohibited the use of crocidolite in 1978 and all asbestos in 1993. EU laws prohibit manufacturing, use, import, or export since 2005; [www.ohici.nl]

Reference Link

OSHA Technical Links: Asbestos

Exposure Assessment
Skin Designation (ACGIH)

No

Bioaccumulates

Yes

TLV (ACGIH)

0.1 respirable fiber/cc

PEL (OSHA)

0.1 fiber/cc, STEL(OSHA) = 1 fiber/cc(30 min)

Half Life

very long;

Reference Link

ATSDR - ToxFAQs - Asbestos

Adverse Effects
Chronic Bronchitis

Yes

Fibrogenic

Yes

IARC Carcinogen

Known Carcinogen

NTP Carcinogen

Human Carcinogen

ACGIH Carcinogen

Confirmed Human

Links to Other NLM Databases
Health Studies

Human Health Effects from Hazardous Substances Data Bank:

Toxicity Information

Chemical Information

Search ChemIDplus

Biomedical References

Search PubMed

Related Information in HazMap
Diseases

Occupational diseases associated with exposure to this agent:

Processes

Industrial Processes with risk of exposure:

Activities

Activities with risk of exposure: