Analysis of Asbestos Fibers in Lung Parenchyma, Pleural Plaques, and Mesothelioma Tissues of North American Insulation Workers^a

Abstract

Asbestos fibers and ferruginous bodies (FBs) in lung parenchyma, lung cancer tissues, pleural plaques, and pleural and peritoneal mesothelioma tissues from 13 North American insulation workers were analyzed and quantified using an analytical transmission electron microscope and a polarized microscope. Diseases from which these workers suffered included asbestosis, lung cancer, and mesothelioma. They had been occupationally exposed to materials containing chrysotile and amosite; their pathological diagnoses, occupational and cigarette smoking histories, and clinical summaries have been reported. Large numbers of FBs were found in the lungs and small numbers found in extrapulmonary sites. Most of the FBs had cores of amosite fibers. In all instances, lung parenchyma and lung cancer tissues showed chrysotile and amosite fibers in high concentrations (63.1 x 10(6) and 150.2 x 10(6) fibers/g dry tissue as mean values, respectively). Crocidolite fibers were seen in seven of the 13 cases, but in much smaller numbers. Other amphiboles were rarely found. In pleural plaques and in pleural and peritoneal mesothelioma tissues, amosite fibers were markedly fewer in number, whereas chrysotile fibers were seen in similar numbers as in the lungs. No significant differences in the size distribution of asbestos fibers were seen in the different sites. However, the mean widths of chrysotile fibers were thinner than those of amosite fibers. These results strongly suggest that translocation of inhaled asbestos fibers from the lung to other tissues, such as the pleura and the peritoneum, occurs frequently, and that chrysotile may be more actively translocated from the lung, compared to amosite or amphibole asbestos. The likelihood of translocation seems to be strongly related to the thinness of the fibers. Translocated chrysotile fibers may play an important role in the induction of either malignant mesothelioma and/or hyaline plaques, since the asbestos fibers detected in both these sites were mainly chrysotile.

Multi‐walled carbon nanotubes translocate into the pleural cavity and induce visceral mesothelial proliferation in rats

“…This translocation also probably occurs in humans since asbestos fibers have been detected in human pleural lesions. (36) However, the mechanism and route of translocation are unclear. It has been suggested that penetration through the visceral pleura, possibly driven by increased pulmonary interstitial pressure and assisted by enhanced permeability of the visceral pleura due to asbestosinduced inflammation might be a major route.…”

Peritoneal Mesothelioma and Asbestos: Clarifying the Relationship by Epidemiology

“…Heller [63] found asbestos fiber burdens ranging from 56,738 to 1,963,250 fibers per gram wet weight tissue in the tumor tissue among six of seven women with peritoneal mesothelioma. Kohyama et al [72] looked for asbestos fibers and ferruginous bodies (iron coated asbestos fibers) in lung parenchyma, lung cancer tissues, pleural plaques, and pleural and peritoneal mesothelioma tissues from thirteen North American insulation workers; fibers were found in extrapulmonary sites. Amosite fibers were fewer in number in both pleural plaques and pleural and peritoneal mesothelioma tissues than in lung tissue, whereas chrysotile fibers were seen in similar numbers as in the lungs.…”

Asbestos-Related Research: First Objectivity then Conclusions

“…Given the possibility of a post-depositional movement of chrysotile fibers from the lung to the pleura [43][44][45][46][47][48], such statements are an over simplification. The rate of asbestos retention cannot be characterized only on the basis of measurements of fiber contents in pulmonary tissues -The proportion of chrysotile fibers (as opposed to the amphiboles) was shown to be higher in parietal pleura than in lung tissue [43].…”

“…Moreover, the accelerated clearance of chrysotile from the lung can be partly caused by a disintegration of chrysotile (but not amphibole) fibers into thin fibrils, which are more difficult to identify. The total number of fibrils would increase due to fiber splitting [47,49,50], possibly together with the carcinogenic effect, as the split fibrils can move to the pleura [45,47,48]. Asbestos fibers have been identified in the pleura by autopsy, chrysotile being the predominant asbestos form found in pleural plaques [51] and pleural/mesothelial tissues in general [46,52].…”

“…In the author reply [71], the arguments from [67] have not been adequately responded, being dismissed by a declaration that the studies [68,69] "appear to support the concepts put forward by Bernstein et al" followed by self-references [71]. Other reports and reviews [43][44][45][46][47][48]51,56,58,63,[72][73][74][75], not supporting the authors' concept, are also not cited in the voluminous reviews [41,55]. Another example: Bernstein et al cite a rather nondescript phrase from the review "Mesothelioma from chrysotile asbestos" [55,76] that chrysotile is an "exclusive or overwhelming fiber exposure", disregarding the main conclusion: "Chrysotile asbestos, along with all other types of asbestos, has caused mesothelioma" [76].…”