Study #1

Specificity of asbestos-induced chromosomal aberrations in short-term cultured human mesothelial cells

Cancer Genetics and Cytogenetics
Volume 41, Issue 1, August 1989, Pages 33-39
by Kenth Olofssona and Joachim Mark
Department of Pathology and Cytogenetics, Central Hospital, Skvde, Sweden

Abstract – Short-term cultured normal human mesothelial cells were exposed for 48 hours to three different asbestos compounds, crocidiolite, chrysotile, and amosite. In the concentration used (0.01 mg/ml) all three asbestiform minerals caused, within a few days, a significant increase of cells showing numerical and/or structural abnormalities. The abnormalities were analyzed in detail using banding techniques. The results were compared with the cytogenetic observations in 52 published cases of mesotheliomas. This comparison revealed only a few similarities as regards numerical deviations. The structural rearrangements in asbestos-exposed cultures, however, in many instances involved chromosome types and chromosome regions preferentially affected in mesotheliomas.

Study #2

Recovery of ingested asbestos fibers from the gastrointestinal lymph in rats

Environmental Research Volume 22, Issue 1, June 1980, Pages 201-216
by P. Sebastien, c, R. Masse, d and J. Bignon.

Abstract – Using the transmission electron microscope, asbestos fibers have been assessed in lymph fluid collected from the thoracic lymph duct in five groups of rats previously exposed to asbestos fibers (by ingestion). Ten rats were gavaged a single dose weighing approximately 20 mg. Five were given pure UICC chrysotile A while another group of five had pure UICC crocidolite. All the rats of the chrysotile group were positive animals with recovery rate values ranging from 6.9 107 to 3 105 (90% of the fibers being recovered during the first 16 hr following the gavage). The crocidolite group had only three positive animals and lower recovery rate values of 5.7 108 to 5.6 107. A third group was fed a synthetic diet containing 1%, by weight, chrysotile with a majority of short fibers (90% below 4 m). Of the 15 rats comprising this group, 13 were positive with maximum daily recovery rates ranging from 2.1 107 to 2.1 106. A group of eight rats fed the same kind of diet but containing a higher proportion of long fibers, showed only four positive animals, however, they had higher daily recovery rates ranging from 1.9 105 to 2.1 104. No fibers were encountered in the samples of the two control rats. This study demonstrates the passage of chrysotile and crocidolite fibers across the gastrointestinal wall, with the passage rate being higher for long fibers than short ones.

Study #3

Penetration of cells by asbestos fibers

Environ Health Perspect. 1974 December; 9: 255260
by J. M. G. Davis, R. E. Bolton, and J. Garrett

Abstract – Studies on the behavior of asbestos fibers within tissues have shown that the only cells that regularly contain asbestos are macrophages and their derivatives. However, these cells actively incorporate the asbestos fibers by the process of phagocytosis, and there is little evidence of direct penetration. Examination of the gut lining after prolonged asbestos ingestion has shown no evidence of dust penetration either through or between the epithelial cells. The structure and arrangement of these cells is discussed, and it is suggested that they are exceptionally well adapted to prevent penetration by any solid material.

Study #4

Static electrification of airborne asbestos: A study of its causes, assessment and effects on deposition in the lungs of rats

American Industrial Hygiene Association Journal, Volume 42, Issue 10 October 1981, pages 711 – 721
by J. H. Vincent; W. B. Johnston; A. D. Jones; A. M. Johnston

Abstract – The paper describes a series of experiments carried out in the laboratory to investigate how asbestos fibers might become electrostatically charged during the process of being made airborne, the magnitude and polarity of the charge per fiber, and the effect on lung deposition in rats. Measurements of the penetration of fibers through an electrostatic elutriator enabled the magnitude and distribution of charge in a cloud of fibers to be quantitatively assessed. Thus it was found that a typical fiber of UICC amosite, as dispersed in a typical animal exposure chamber, carried a net charge of magnitude equivalent to about 60 electrons. The distribution of charge was bimodal, suggesting that two charging mechanisms were taking place, the main one producing net negative charge and the lesser one producing net positive charge. These were attributed to materials in the dust dispenser used and with which the fibers came into contact during dispersal. It was found that the magnitude of charge on a typical fiber could be significantly reduced by the introduction of equal numbers of positive and negative gaseous ions from an a.c. corona discharge ionizer. Finally it was found that enhancement by up to 40% of the dust deposited into the slowest clearing part of the respiratory tract of experimental rats was brought about by the electrostatic charge on the airborne fibers. The implications of this finding in the field of occupational hygiene are briefly discussed.