Variations in the Carcinogenicity of Tremolite Dust Samples of Differing Morphology

Abstract

Six samples of tremolite of different morphological type were prepared as dusts of respirable size and used in intraperitoneal injection studies in rats. Three "asbestiform" tremolites produced mesotheliomas in almost all animals, although with significantly different tumor-induction periods. A brittle type of fibrous tremolite which, when manipulated to prepare "respirable dust," produced a sample with relatively few asbestiform fibers remaining nonetheless produced tumors in 70% of rats. Two samples of nonfibrous tremolite produced respirable dust samples containing numerous elongated fragments with aspect ratios greater than 3:1, which therefore fitted the definition of respirable fibers. Both these samples produced relatively few tumors, although one had more long "fibers" than did the brittle tremolite that produced 70% of tumors. This study has therefore demonstrated that different morphologic forms of tremolite produce dusts with very different carcinogenic potential. Carcinogenicity does not depend simply on the number of elongated particles injected, and we need to develop methods of distinguishing carcinogenic tremolite fibers from relatively innocuous tremolite dusts, with similar numbers of elongated particles of similar aspect ratios.

Asbestos fiber length as related to potential pathogenicity: A critical review

“…Additional studies by the group found that relatively thick basalt as well as ceramic fibers also induced tumors [Pott et al, 1988]. Davis et al [1991] studied the effects of intraperitoneal injection of rats with tremolite from various sources. While tremolite is considered a non-commercial amphibole, it is of importance when discussing human asbestos exposure since tremolite has been reported by some, but not all, investigators to be a component of chrysotile asbestos and other commercially exploited minerals [Hammar and Dodson, 1994;Srebro and Roggli, 1994;Wright et al, 2002].…”

Revision of French Occupational Exposure Limits of Asbestos and Recommendation of Measurement Method: Can the Dimensional Characteristics of the Asbestos Fibers (Long, Thin, Short) Be Taken Into Account?

“…Thus, it appears difficult to peremptory interpret the data but it is true that some results agree in showing that TAFs are toxic in animals. Thus, comparative studies among samples containing a greater or lesser extent of TAFs show that the samples containing a higher percentage of this class were the most active (Adamson et al, 1993;Adamson and Bowden, 1987;Berman et al, 1995;Bertrand and Pézerat, 1980;Davis et al, 1991a;Davis et al, 1991b;Donaldson et al, 1989;Donaldson et al, 1989;Goodglick and Kane, 1990;Lemaire et al, 1985;Oehlert, 1991;Wagner, 1990aWagner, , 1990b. Statistical analyses have linked the highest probability of tumors to the classes representative of TAFs.…”

Risk assessment due to environmental exposures to fibrous particulates associated with taconite ore

“…Associated with this is the determination that such cleavage fragments are less potent in producing human cancer as well as cancer in experimental animals (Davis et al, 1991;Nolan et al, 1991;Federal Register, 1992;Ilgren, 2004;Gamble and Gibbs, 2008).…”