Malignant Mesothelioma Controversy Depends on Type of Asbestos Fiber

Few credible researchers deny the association between asbestos exposure and mesothelioma.  However, some hold to a theory that suggests the type of asbestos fiber can make a difference on disease development.  One interesting study is called, "Asbestos fiber type in malignant Mesothelioma: An analytical scanning electron microscopic study of 94 cases" by Victor L. Roggli, MD, Philip C. Pratt, MD, Arnold R. Brody, PhD - American Journal of Industrial Medicine Volume 23 Issue 4, Pages 605 – 614.  Here is an excerpt: "Abstract - Although the association between asbestos exposure and malignant mesothelioma is indisputable, controversy continues regarding the relative contribution of the various types of asbestos fibers to the development of mesothelioma. We examined the types of asbestos fibers recovered from lung parenchyma in more than 90 cases of malignant mesothelioma from the United States, using an analytical scanning electron microscope. Almost half of the patients were former asbestos insulators or shipyard workers. The fibers were recovered from lung tissues obtained at autopsy or surgical resection by means of a sodium hypochlorite digestion procedure. Amosite absestos was identified in 81% of the cases and accounted for 58% of all fibers 5 m or greater in length.

Tremolite/actinolite/anthophyllite were identified in 55% of the cases and accounted for 10% of all fiber types. Chrysotile was identified in 21% of the cases and accounted for 3% of fibers exceeding 5 m in length. Crocidolite was found in 16% of the cases and accounted for 3% of fibers exceeding 5 m in length. Nonasbestos mineral fibers (commonly found in the lungs of the general population) were observed in 71% of the cases and accounted for 25% of all fibers 5 m or greater in length. The findings in this study are at odds with the assertion that crocidolite asbestos is responsible for most mesotheliomas in the United States."

Another interesting study is called, "Asbestos-related malignant mesothelioma: growth, cytology, tumorigenicity and consistent chromosome findings in cell lines from five patients" by K. Pelin-Enlund, K. Husgafvel-Pursiainen, L. Tammilehto, M. Klockars, K. Jantunen, B.I. Gerwin, C.C. Harris, T. Tuomi, E. Vanhala, K. M Attson and K. Linnainmaa - Carcinogenesis Volume 11, Number 4 Pp. 673-681.  Here is an excerpt: "Seven mesothelioma cell lines were established from clinical specimens from five patients with asbestmrelated malignant pleural mesothelioma. The cells in culture show either epithelial or mixed epithelial/fibrosarcomatous growth with an average doubling time of 30 h. Giant multinucleated cells are common in all the cell Lines, as well as long thin microvllli on the cell surfaces. All cell lines were cytokerath pitive and they stained negatively for monocyte—macrophage markers. AU seven cell lines and one long-term tissue culture from a sixth mesothelioma patient were characterized cytogenetically. hyotype analyses revealed complex structural and numerical abnormalities, primarily involving chromosome 1, 4, 5, 6, 7, 8, 9, 11, 12, 13 and 22. An excess of chromosome material of the short arm of chromosome 5 was seen consistently in six cell lines and in the long-term culture. In cell lines from four patients, changes in chromosome 13, mainly monasomy 13, were observed. The marker chromosomes observed in the e d y passages were conserved and few additional changes appeared in later passages. Six of the cell lines tested for tumorigenicity in athymic nude mice were weakly positive."

Another study is called, "Inflammation generating potential of long and short fibre amosite asbestos samples." By K Donaldson, G M Brown, D M Brown, R E Bolton, J M Davis - Br J Ind Med 1989;46:271-276.  Here is an excerpt: "Abstract - Previous studies have shown that long thin asbestos fibres are more pathogenic in in vivo and more active in in vitro assays than short fibre samples. In the present study a long fibre amosite asbestos sample and a short fibre sample prepared from it were tested for ability to cause inflammation in the peritoneal cavity of the mouse; a UICC sample intermediate in fibre size and an inert compact dust, TiO2, were also tested. The ability of the dust samples to cause inflammation, as judged by macrophage and neutrophil recruitment, was ranked in the order long fibre greater than UICC greater than short fibre greater than TiO2. Ability of amosite samples to cause inflammation was therefore related to the proportion of long fibres. The enhanced ability of long fibres to cause inflammation and cause macrophage activation is probably a key factor in the ability of long fibres to cause pulmonary fibrosis and may also be important in fibre carcinogenesis."

If you found any of these excerpts, please read them in their entirety.  We all owe a debt of gratitude to these researchers.