Asbestos fibres: amosite

Donaldson K, Brown GM, Brown DM, et al. 1989. Inflammation generating potential of long and short fibre amosite asbestos samples. Br J Ind Med 46 271-276. 

Dogra, S., and Donaldson, K. (1995). Effect of long and short fibre amosite asbestos on in vitro TNF production by rat alveolar macro[4iages The modifying effect of lipopolysaccharide. Ind Health 33, 131-141. 

Surface-complexed iron [Fe ] observed after intrapleural injection of 30 mg of either amosite, crocidolite, and chrysotile both genuine and saturated with Fe in Sprague-Dawley rats corresponded to oxidant generation, measured as barbituric acid reactive products of deoxyribose, and more covalently closed, circular DNA strand scission induced by these asbestos fibres (Ghio et al. 1994). 

Amphibole (crocidol-ite and amosite), serpentine (chrysotile), wollastonite, riebeglass beads Human and rabbit mesothelial cells in vitro Oligonucleosomal DNA fragmentation, loss of membrane phospholipid asymmetry, and nuclear condensation Asbestos fibres, not control particles, induced apoptosis in mesothelial cells by all assays. Induction of apoptosis was dose-dependent for all types of asbestos, with crocidolite (5 ng/cm ) inducing 15.0 1.1 % apoptosis versus control particles <4 %. Apoptosis induced by asbestos, but not by actinomycin D, was inhibited by extracellular catalase, superoxide dismutase in the presence of catalase, hypoxia (8 % oxygen), deferoxamine, 3-aminobenzamide [an inhibitor of poly(ADP-ribosyl) polymerase], and cytochalasin B. Only catalase and cytocha-lasin B decreased fibre uptake. Broaddus et al. (1996) Escape from asbestos-induced apoptosis could allow the abnormal survival of mesothelial cells with asbestos-induced mutations... 

There are three important types of asbestos, blue (crocidolite), brown (amosite) and white (chrysotile). Asbestosis is a reaction of the lung to the presence of asbestos fibres which, having reached the bronchioles and air sacs, cause a fibrous thickening in a network distribution, mainly in the lower parts of the lung . There follows a loss of elasticity in the lung tissue, making breathing difficult, and this is related to the concentration of fibres inhaled and the duration of exposure. 

Davis JM, Addison J, Bolton RE, et al. 1986a. The pathogenicity of long versus short fibre samples of amosite asbestos administered to rats by inhalation and intraperitoneal injection. Br J Exp Pathol 67 415-430. 

Lung, throat and stomach cancer. These can be caused by all types of asbestos, however Chrysotile is considered to be less dangerous than the fibres of the Amphibole mineral group such as Amosite and Crocidolite. 

Asbestos. Asbestos is a generic name for naturally occurring mineral silicate fibres of the Serpentine and Amphibole series. In the Serpentine series is Chrysotile, commonly kno m as white asbestos. In the amphibole series are Actinolite, Amosite or Mysorite (commonly known as brown asbestos), Anthophyllite, Crocidolite (commonly known as blue asbestos) and Tremolite. All types of asbestos can be hazardous to health, blue and brown asbestos being the more dangerous types. ICAO A2... 

The association between exposure to asbestos dust and the development of lung carcinoma and diffuse mesotheliomata of the pleura and peritoneum has been well documented (Selikoff and Lee 1978). Both crocidolite and amosite were capable of augmenting the oncogenic effect of benzo[a]-pyrene. This putative synergistic effect was evident when fibres and chemicals were added to cultures of murine fibroblast cultures as simple mixtures and when benzo[a]pyrene was adsorbed to the surface of the fibres (Brown et al. 1983). 

Nitric oxide may interact with the surface of mineral fibres. Cigarette smoke which increases the risk of asbestos-induced lung cancer contains up to 600 [ig NO per cigarette (lARC 1985) raised the fibre-bound NO from 34 to 85 pg NO/g fibre (Leanderson et al. 1997). NO was found in different amounts on chrysotile B, crocidolite, amosite and siUcon carbide whiskers. There was a strong correlation between the amount of NO and the specific surface area of these fibres (r = 0.98). NO could not be demonstrate on rockwool fibres, manmade vitreous fibres MMV21 and MMV22 or silicon nitride whiskers. 

Asbestos (anthophyllite, tremolite-actinolite, amosite, crocidolite, chrysotile), nonasbestos fibres Analytical electron microscopy of 50 lung tissue samples from Matsubase, where pleural plaques are endemic Number of asbestos bodies and fibres/ 5 g wet lung tissue frequency of pleural plaques size parameter of fibres Dy mineral type Anthophyllite (mean length 25.1 n, mean diameter 0.84 (un) might be responsible for the increased prevalence of pleural plaques in Matsubase. The aspect ratio of anthophyllite (mean = 38.7) was lower than that of amosite (mean = 81.8), which, as reported hy Murai and Kitagawa (1992), was found predominantly in cases of pleural mesothelioma. Murai et al. (1997) Differences in fibre size may be related to the strength of the carcinogenicity to the pleura. 

Unless the employer is licensed under the Asbestos (Licensing) Regulations or the extent of the exposure will not exceed the action level (that is, where the cumulative exposure in a 12 week period to crocidolite or amosite is 48 fibre-hours per millilitre of air, or for other types of asbestos 120 fibre-hours per millilitre of air) he shall not commence any work for the first time until 28 days after he has notified the enforcing authority in writing of his intention to carry out the work. However, the enforcing authority may agree to a shorter time. 

Donaldson K, Brown DM, Miller BG, et al. Bromo-deoxyuridine (BRDU) uptake in the lungs of rats inhaling amosite asbestos or vitreous fibres at equal airborne fibre concentrations. Exp Toxicol Pathol 1995 47(2-3) 207-211. 

Modern experience is that all forms of asbestos are equally hazardous, although for different reasons. Previously, attention was focused on blue asbestos (crocidolite), followed by amosite, or brown asbestos. The latter is often a component of tiles. Chrysotile, white asbestos, not only produces asbestosis following even quite modest exposures, but also cancer of the lung. Analysis determines the fibre type or types, which indicates the requirements for protection although this work will be restricted to HSE licence holders. 

Donaldson K, Golyasnya N, Davis JMG. Long and short amosite asbestos samples comparison of their chromosome-damaging effects to cells in culture with the results of other in vitro and in vivo assays of toxicity. In Davis JMG, Jaurand MC, eds. Cellular and Molecular Effects of Minerals and Synthetic Dusts and Fibres. Berlin, Springer-Verlag, 1994 221-226. 

Somers ANA, Mason EA, Gerwin BI, Harris CC, Lechner IF. Effects of amosite asbestos fibers on the filaments present in the cytoskeleton of primary human meso-thelial cells. In Brown RC, et al. eds. Mechanisms in Fibre Carcinogenisis. New York Plenum Press, 1991 481-489. 

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