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Thursday, May 10, 2007

What Causes mesothelioma

The exact method by which asbestos causes mesothelioma isn’t known with certainty. Animal models have provided some understanding of the type of damage that asbestos fibers can do, but the exact mechanism hasn’t been found yet. After asbestos became a commercially successful product, it was soon apparent that asbestos workers were an at-risk population.

Starting at the turn of the century, British investigators discovered a relationship between exposure to high levels of asbestos and respiratory disease. These early studies were often suppressed by government at the request of the asbestos industry. (k) By the mid 50’s American medical researchers had joined the chorus of concerned professionals identifying asbestos as hazardous. Much of their work was never published or was suppressed and/or disputed by scientists in the pay of the asbestos lobby.

Figure G: Amphiboles Protruding, Brook T. Mossman, UVM College of Medicine.

Asbestos fibers have been detected in many resected surgical specimens from mesothelioma patients. In pleural mesothelioma, asbestos fibers are found trapped in the tissues from the lower parts of the lung and they are sometimes concentrated into nodules or spots on the parietal pleura, the primary location for mesothelioma in the thoracic cavity. Although smoking while exposed to asbestos is known to significantly increase lung cancer risks, smoking does not appear to be implicated in the formation of mesothelioma.

Genetic susceptibility may also contribute to the cause of malignant mesothelioma. Two population of two small villages located in Turkey has been environmentally exposed to a rare asbestos-like fiber called erionite for generations. (Please see erionite on the Understanding Asbestos page for more information.)

In an initial study, 50% of the men in one village contracted malignant mesothelioma while the other village had only one case. This was a woman who was originally from the first village. Further research into the residents of these two communities has confirmed an inheritable genetic predisposition to malignant mesothelioma in the presence of asbestos-like fibers.

Current research has repeatedly found abnormalities in mesothelioma cases where deletions of chromosome regions 1p, 3p, 9p, and 6p, and the loss of chromosome 22 have been observed. It is believed that these deletions affect tumor suppressor genes, allowing for the development of mesothelioma. The mechanism for genetic suppression of tumor development is discussed below.

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