Agent Name
CAS Number
1332-21-4; 12001-28-4; 12172-73-5; 77536-66-4; 77536-67-5; 77536-68-6; 132207-32-0
Major Category
Mineral Dusts
Chrysotile; Amosite; Crocidolite; Anthophylite; Tremolite; Actinolite;
Fibrogenic Dusts
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]
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]
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 (crocidolite 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] "While all forms of asbestos have been determined to cause mesothelioma, there is evidence that the quantitative risk of mesothelioma varies with asbestos fibre type, with higher unit risks usually observed for exposure to commercial amphibole asbestos minerals (mainly amosite and crocidolite) than for exposure to chrysotile asbestos." [PMID 31087402] Yields a similar estimate of cumulative lung cancer mortality: 0.1 fiber/mL when counting fibers greater than 5 um (electron microscopy); 0.1 fiber/mL when counting fibers (light microscopy); [PMID 29573442] "The update of the follow-up of this cohort confirmed an increased mortality from pleural cancer mortality in miners exposed to chrysotile and a lack of significant increase in lung cancer mortality." [PMID 28438787]
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; []
Reference Link #1
Biomedical References

Exposure Assessment

Skin Designation (ACGIH)
0.1 respirable fiber/cc
0.1 fiber/cc, STEL(OSHA) = 1 fiber/cc(30 min)
Half Life
very long;
Reference Link #2

Adverse Effects

Chronic Bronchitis
IARC Carcinogen
NTP Carcinogen
Human carcinogen
ACGIH Carcinogen
Confirmed Human

Diseases, Processes, and Activities Linked to This Agent


Activities with risk of exposure: