What is mesothelioma?

Risk factors for malignant mesothelioma

Risk factors are those activities that increase the chance of getting a particular condition or disease. Malignant mesothelioma is a very rare cancer, and the vast majority of cases are associated with exposure to asbestos (either its production or use in various industries). In fact, because asbestos is used so widely in the building and other industries, even in those cases where a history of asbestos exposure is not evident, it is likely that the victim was exposed without his/her knowledge. Other risk factors that are associated with malignant mesothelioma less often include:

• Radiation. Cases of malignant mesothelioma have been reported after exposure to radiation, but the association is not very strong. The use of Thorotrast (thorium dioxide), a radioactive substance used for 'contrast' x-ray studies in millions of people between 1930 and 1955, has also been associated with malignant mesothelioma (particularly peritoneal mesothelioma).
• Polio vaccine. Between 1955 and 1963, some batches of polio vaccine were contaminated with the Simian Virus 40, which has been detected in certain rare cancers, including malignant mesothelioma.
• Erionite. This is a type of zeolite silica stone containing fibrous/wool-like strands that is widely used for house construction in the Cappadocian region of Turkey, where ~1% of the population dies from malignant mesothelioma each year.
• Chronic pleural disease. In one study of 35 patients with malignant mesothelioma, 3 had evidence of long-term pleural tuberculosis, but not of asbestos exposure.

Note that smoking tobacco does not appear to increase the risk of developing malignant mesothelioma in those exposed to asbestos. However, smoking does greatly increase the risk of developing bronchogenic lung cancer (i.e. arising in the breathing tubes/airways).