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Mesothelioma Disease

Although pleural mesothelioma may have been initially described as early as the mid-18th century, for many years the form of cancer now known as malignant pleural mesothelioma was not recognized. The connection between pleural mesothelioma and asbestos exposure was pretty much accepted as fact by the mid-20th century, although doctors and medical researchers had had suspicions since the turn of the 20th century.

Despite the fact that virtually everyone has been exposed to asbestos fibers at some point and that pleural mesothelioma is one of the deadliest forms of cancer, it is still a fairly rare disease. Only 3,000 cases are diagnosed every year, out of approximately 1.5 million who contract some form of cancer annually. Approximately 80 percent of these are cases of pleural mesothelioma, while peritoneal and pericardial forms of mesothelioma disease make up virtually all the rest. A minuscule number of men contract testicular mesothelioma, but there have been only 100 confirmed cases of this form of the disease.

Asbestos and Pleural Mesothelioma

The primary cause of pleural mesothelioma is asbestos exposure. Both serpentine (chrysotile, “white” asbestos) and amphibole varieties of asbestos cause the disease. Chrysotile and three types of amphibole asbestos – crocidolite, amosite and tremolite – have commonly been present in buildings and machinery. It should be pointed out however that only the first two were used in commercial products; the third was never exclusively mined commercially, but was found as a contaminant in many products that included talc and modeling clay.

Serpentine fibers are somewhat curly and amphibole fibers resemble microscopic spears or needles. The exact mechanism of how these fibers cause cancer once they are embedded in the lung is not known precisely. What is known is that the fibers have the potential to puncture through the lining of the lung once they are inhaled. Current theory suggests that their presence causes a chronic inflammation; this auto-immune reaction in turn may cause some kind of cellular mutation at the DNA level that results in malignancy.

Other Known Causes

Although the majority of pleural mesothelioma disease cases are linked to asbestos, there are other types of exposure that appear to play a part. Minerals such as zeolite and taconite seem to be complicit in the disease. While these are not asbestiform minerals, it is worth noting that the crystalline structure of these particulates is similar to amphibole asbestos.

Thorium oxide, a radioactive substance once used to process X-rays may also be a culprit. Like zeolite, this substance has a hard-edged, crystalline structure at the molecular level.

Finally, there is SV40, a simian virus that contaminated a large batch of polio vaccines in the late 1950s and early 1960s. People who received this vaccine may be at higher risk for developing mesothelioma.

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