Chronic Inhalation of Short Asbestos Fibers

Response to a letter to the Editor by Dr. David Egilman and Mr. John Schilling regarding the article by Donovan et al. (2011)

“…The results, therefore, support previous suggestions that long asbestos fibres are more dangerous than short" (p. 673). Later, Platek et al (1985) conducted a study in monkeys and rats to determine the biological effects after inhalation of chrysotile fibers less than 5 µm and reported that "no significant differences in histochemical data were seen between the exposed and control groups" (p. 327).…”

“…We recognize that smaller fibers can remain in the air longer and can travel further than larger fibers. We remind readers, however, that fibers shorter than 5 µm have not been shown to be biologically relevant, which was the reason our analysis focused on the longer fibers (Stanton, 1973;Stanton et al, 1977;Davis et al, 1978;ERG, 2003aERG, , 2003bPlatek et al, 1985;Berman, 2010). In response to their assertions that some of our assumptions were not valid or were at odds with published data, we reran our models to evaluate a wider range of fiber widths and settling velocities (including some of the values that Egilman and Schilling state we should have used).…”

“…The EPA guidance document cited by Egilman and Schilling used fiber lengths of 1, 2, and 5 µm and an aspect ratio of 5:1, whereas we present results for fiber lengths of 5 and 10 µm, with aspect ratios of 12.5 to 25 for 5 micron fiber lengths and 25 to 50 for 10 micron fiber lengths. Fiber lengths of 5 µm and greater are considered the fibers that are biologically significant rather than those in the 1-2 µm range (Stanton, 1973;Stanton et al, 1977;Davis et al, 1978;Platek et al, 1985;ERG, 2003aERG, , 2003bBerman, 2010).…”

Evaluation of Asbestos Exposure in Dumanli Village (Çanakkale-Turkey) From a Medical Geology Viewpoint: An Inter-Disciplinary Study

“…In chronic respiration experiments using short chrysotile fibers in rodents, no fibrotic lesions were observed (Platek, et al, 1985). The potential for cell proliferation, damage, injury and alveolar macrophages releasing oxidants is greater with exposure to long fibers (Adamson and Bowden, 1987;Donaldson, 1989;Mossman, et al, 1989).…”

Coalinga Fibre – A Short, Amphibole-Free Chrysotile

“…However, the inability of researchers to obtain sufficient quantities of 'pure' short fibre chrysotile, devoid of significant numbers of long fibres, confounded interpretation of the experiments. One of the first long-term inhalation studies to use a highly purified, short fibre chrysotile sample was conducted by Platek et al [12], who exposed rodents and primates to a preparation produced by intense milling. Although no tumours were obtained, other workers [6] felt that the study could have been confounded by a loss of crystallinity induced by the milling with a consequent loss of biological activity [13].…”