Chrysotile inhalation

Using radioactive labeled UICC samples, the deposition and distribution of asbestiform fibers in the pulmonary cavity have been studied. For example, after thirty minutes of inhalation, the deposition of fibers in the respiratory track was shown to be proportional to the median aerodynamic particle diameter for the two UICC chrysotiles, amosite, anthophyllite, and crocidolite. The percentage of total deposited fiber in the lower respiratory tract varied inversely as the square root of the particle diameter (Morgan et al., 1975). 

Studies in animals have reported increased incidence of lung cancer following chronic inhalation exposure to chrysotile (Davis and Jones 1988 Gross et al. 1967 Reeves et al. 1974 Wagner et al. 1974, 1980a),... 

Animal studies also indicate that inhalation exposure to asbestos produces mesotheliomas. Mesotheliomas have been observed in rats exposed to chrysotile, amosite, anthophyllite, crocidolite, or tremolite at concentrations ranging from 350 to 1,600 f/mL for 1-2 years (Davis and Jones 1988 Davis et al. 1985 Wagner et al. 1974, 1980a) and in baboons exposed to either 1,110-1,220 f/mL for 4 years (Goldstein and Coetzee 1990) or 1,100-1,200 17mL for up to 898 days (Webster et al. 1993). Incidences of mesothelioma ranged from 0.7 % to 42% in these studies. 

As discussed in Section 3.4.4 inhaled asbestos fibers that are deposited in the lung are principally removed by mucociliary transport into the alimentary canal and eventually are excreted in the feces. Chrysotile fibers appear to be cleared more readily than amphibole fibers, and long fibers are cleared more slowly than short fibers (Coin et al. 1992 Morgan 1991). 

Bembe KA, Quinlan TR, Moulton G, et al. 1996. Comparative proliferative and histopathologic changes in rat lungs after inhalation of chrysotile or crocidolite asbestos. Toxicol Appl Pharmacol 137 67-74. 

Brody AR, Hill LH. 1982. Interstitial accumulation of inhaled chrysotile asbestos fibers and consequent formation of microcalcifications. Am J Pathol 109 107-114. 

Brody AR, Hill LH, Adkins B, et al. 1981. Chrysotile asbestos inhalation in rats Deposition pattern and reaction of alveolar epithelium and pulmonary macrophages. Am Rev Respir Dis 123 670-679. 

Case BW, Dufresne A, McDonald AD, et al. 2000. Asbestos fiber type and length in lungs of chrysotile textile and production workers Fibers longerthan 18 m. Inhal Toxicol 12 411-418. 

Coin PG, Osomio-Vargas AR, Roggli VL, et al. 1996. Pulmonary librogenesis after three consecutive inhalation exposures to chrysotile asbestos. Am J Resp Crit Care Med 154 1511-1519. 

Hesterberg TW, Hart GA, Chevalier J, et al. 1998b. The importance of fiber biopersistence and lung dose in determining the chronic inhalation effects of X607, RCFl, and chrysotile asbestos in rats. Toxicol Appl Pharmacol 153 68-82. 

Jones AD, Vincent JH, Addison J, et al. 1994. The fate and effect of inhaled chrysotile asbestos fibres. Ann Occup Hyg 38 619-629. 

McConnell EE, Chevalier HJ, Hesterberg TW, et al. 1994. Comparison of the effects of chrysotile and crocidolite asbestos in rats after inhalation for 24 months. In Mohr U, Dungworth DL, Mauderly JL, et al., ed. Toxic and carcinogenic effects of solid particles in the respiratory tract. Washington, DC ILSI Press, 461-467. 

McGavran PD, Butterick CJ, Brody AR. 1989. Tritiated thymidine incorporation and the development of an interstitial lesion in the bronchiolar-alveolar regions of the lungs of normal and complement deficient mice after inhalation of chrysotile asbestos. JEPTO 9 377-391. 

Monchaux G, Chameaud J, Morlier JP, et al. 1989. Translocation of subcutaneously injected chrysotile fibres potential cocarcinogenic effect on lung cancer induced in rats by inhalation of radon and its daughters. lARC Sci Pub 90 161-166. 

Pinkerton KE, Pratt PC, Brody AR, et al. 1984. Fiber localization and its relationship to lung reaction in rats after chronic inhalation of chrysotile asbestos. Am J Pathol 117 484-498. 

Quinlan TR, Berube KA, Marsh JP, et al. 1995. Patterns of inflammation, cell proliferation, and related gene expression in lung after inhalation of chrysotile asbestos. Am J Pathol 147 728-739. 

Robledo RF, Buder-Hoffinann SA, Cummins AB, et al. 2000. Increased phosphorylated extracellular signal-regulated kinase immunoreactivity associated with proliferative and morphologic lung alterations after chrysotile asbestos inhalation in mice. Am J Pathol 156(4) 1307-1316. 

Wagner JC, Berry G, Skidmore JW, et al. 1980a. The comparative effects of three chrysotiles by injection and inhalation in rats. lARC Sci Publ 30 363-372. 

Warheit DB, Harsky MA, Frame SR. 1996. Pulmonary effects in rats inhaling size-separated chrysotile asbestos fibers or />-aramid fibrils differences in cellular proliferative responses. Toxicol Lett 88 287-292. 

Warheit DB, Snajdr SI, Hartsky MA, et al. 1997. Lung proliferative and clearance responses to inhaled para-aramid REP in exposed hamsters and rats Comparisons with chrysotile asbestos fibers. Environ Health Perspect Suppl 105 1219-1222. 

Occurrence in Chiysotile Amphibole asbestos, identified as tremolite asbestos or actinolite asbestos, has been reported to be a minor contaminant in some deposits of chrysotile in Quebec. Part of the evidence that tremolite asbestos exists in certain chrysotile deposits mined in Quebec comes from observations of higher concentrations of tremolite asbestos fibers than chrysotile fibers in autopsied lung tissues of certain miners and millers who were chronically exposed to chrysotile ores (see Case 1994 for review). Inhaled tremolite asbestos fibers are more persistent in lungs than inhaled chrysotile fibers. 

Talc has been used in the manufacture of crayons for many years. Recently, it was reported in the U.S. press that tremolite asbestos, anthophyllite asbestos, and chrysotile were detected in some crayons at concentrations ranging from 0.03% to 2.86% (CPSC 2000). In response, the Consumer Product Safety Commission (CPSC 2000) examined crayons from several U.S. manufacturers to determine whether asbestos was present. Trace amounts of anthophyllite asbestos were found in some of the crayons. The CPSC (2000) concluded that the risk that children would be exposed to fibers through inhalation or ingestion of talc-containing crayons is extremely low, but recommended that, as a precaution, crayons should not contain these fibers. The manufacturers have agreed to reformulate their crayons using substitute materials (CPSC 2000). 

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