Asbestos Fibers Disrupt Chromosome Behavior

Asbestos Fibers Disrupt Chromosome Behavior

The development of mesothelioma disease has been linked to asbestos exposure.  One interesting study examining this relationship is called, “The Hygiene Standard for Chrysotile Asbestos” – The Lancet, Volume 311, Issue 8062, Pages 484-489.  Here is an excerpt: “Abstract – Previous studies, including the analysis on which the current 2 fibres/cm3 hygiene standard is based, may have underestimated the risk of morbidity or mortality following exposure to low levels of asbestos dust. Accurate dose-response data at levels below 2 fibres/cm3 are unlikely to be available for the foreseeable future, and the biologically plausible assumption that excess cancer mortality is approximately proportional to dust level should be provisionally accepted. It may be reasonable, however, to postulate a safe threshold for mortality from asbestosis. If excess mortality from asbestos-related disease is proportional to dust level for each cause, approximately 10% of male asbestos workers might, under certain assumptions, eventually die of asbestos-induced disease after 50 years’ exposure at 2 fibres/cm3. Peritoneal mesothelioma is usually due to crocidolite (blue asbestos) or other amphiboles, but exposure to chrysotile (white asbestos) alone may lead to a substantial risk of pleural mesothelioma. These predictions are based on rather small numbers in a single factory, and further studies in other working environments are required. Fibre counts based on optical microscopy are likely to be less relevant than total counts by electron microscopy, and excess mortality is virtually confined to men first exposed more than 20 years ago, when little or no accurate data on dust levels were collected.”

Another interesting study is called, “Behavior of Crocidolite Asbestos during Mitosis in Living Vertebrate Lung Epithelial Cells” by Jeffrey G. Ault, Richard W. Cole, Cynthia G. Jensen, Lawrence C. W. Jensen, Lori A. Bachert, and Conly L. Rieder – Cancer Res February 15, 1995 55; 792.  Here is an excerpt: “Abstract – Asbestos has been described as a physical carcinogen in that long thin fibers are generally more carcinogenic than shorter thicker ones. It has been hypothesized that long thin fibers disrupt chromosome behavior during mitosis, causing chromosome abnormalities which lead to cell transformation and neoplastic progression. Using high-resolution time lapse video-enhanced light microscopy and the uniquely suited lung epithelial cells of the newt Taricha granulosa, we have characterized for the first time the behavior of crocidolite asbestos fibers, and their interactions with chromosomes, during mitosis in living cells. We found that the keratin cage surrounding the mitotic spindle inhibited fiber migration, resulting in spindles with few fibers. As in interphase, fibers displayed microtubule-mediated saltatory movements. Fiber position was only slightly affected by the ejection forces of the spindle asters. Physical interactions between crocidolite fibers and chromosomes occurred randomly within the spindle and along its edge. Crocidolite fibers showed no affinity toward chromatin and most encounters ended with the fiber passively yielding to the chromosome. In a few encounters along the spindle edge the chromosome yielded to the fiber, which remained stationary as if anchored to the keratin cage. We suggest that fibers thin enough to be caught in the keratin cage and long enough to protrude into the spindle are those fibers with the ability to snag or block moving chromosomes.”

A third study worth mentioning is called, “Asbestos content of the soil and endemic pleural asbestosis” by Todor Burilkov and Liliana Michailova – Research Institute of Labour Protection and Occupational Diseases, Sofia, Boul. Petko Napetov 34, Bulgaria – Environmental Research – Volume 3, Issues 5-6, December 1970, Pages 443-451.  Here is an excerpt: “Abstract – Soil samples from a tobacco-growing region with dispersed, asbestos outcroppings were analyzed. The content of fibrous minerals (anthophyllite, tremolite, sepiolite) of the soils in this region fields was considerable. Endemic pleural plaques occur in the human population. Soil samples from an area with no outcroppings of asbestos were also examined and were observed to be free of asbestos and other fibrous minerals. No pleural plaques are found in the farming population in this area. The results of this mineralogical study support our hypothesis that pleural plaques may be caused not only by occupational air pollution, but also by the inhalation of asbestiform particles derived from the soil in certain areas.

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