Asbestos Fibers and the Mesothelium Lining Get the Facts

The mesothelium is the lining that covers most of our internal organs. Mesothleioma is cancer of that lining, and it can take several different forms. One form is known as pleural cancer (cancer of the lungs). It can also take the form of peritoneal cancer (lining of the abdomen), pericardial cancer (cancer of the heart). If you have been diagnosed with mesothelioma, it is more likely than not that you have been exposed to asbestos at some point in your life.

There have been many experimental studies done to try and better understand this fatal disease. One study is called, "Asbestos exposure indices." By Lippmann M. - Institute of Environmental Medicine, New York University Medical Center, Tuxedo 10987. Environ Res. 1988 Jun;46(1):86-106. Here is an excerpt: "The ability of inhaled asbestos to produce asbestosis, lung cancer, and mesothelioma in both humans and animals is well established, and asbestos exposures in the occupational and general community environment are recognized as significant hazards. However, it has not been possible to establish realistic and credible dose-response relationships, primarily because of our inability to define which constituents of the aerosols produce or initiate the pathological responses. It is generally acknowledged that the responses are associated with the fibers rather than the nonfibrous silicate mineral of the same chemical composition.

Available data from experimental studies in animals exposed by injection and inhalation to fibers of defined size distributions are reviewed, alone with data from studies of fiber distributions in lungs of exposed humans in relation to the effects associated with the retained fibers. It is concluded that asbestosis is most closely related to the surface area of retained fibers, that mesothelioma is most closely associated with numbers of fibers longer than approximately 5 microns and thinner than approximately 0.1 micron, and that lung cancer is most closely associated with fibers longer than approximately 10 microns and thicker than approximately 0.15 micron. The implications of these conclusions on methods for fiber sampling and analyses are discussed."

Another important study worth taking a look at is called, "Asbestos fibers and interferon-gamma up-regulate nitric oxide production in rat alveolar macrophages." By Thomas G, Ando T, Verma K, Kagan E. - Department of Pathology, Georgetown University School of Medicine, Washington, DC. - Am J Respir Cell Mol Biol. 1994 Dec;11(6):707-15. Here is an excerpt: "The present study was undertaken to determine whether asbestos exposure induces the formation of nitric oxide (NO.) radical by rat alveolar macrophages (AM). For this purpose, AM from Sprague-Dawley rats were cultured for 48 h in the presence or absence of either chrysotile (serpentine) or crocidolite (amphibole) asbestos fibers.

The effects of asbestos fibers were compared with those of nonfibrogenic carbonyl iron particles. Nitrite (NO2-), the stable oxidation product of NO. in macrophage conditioned medium, was assayed by the Griess reaction. Production of NO2- by AM was significantly increased by both chrysotile (P

The purpose of this article is to raise awareness. We all owe these researchers a debt of gratitude. If you found either excerpt helpful, please read the studies in their entirety.