Incidence of Mesothelioma:

Although incidence rates of mesothelioma have increased in the past 20 years, mesothelioma is still a relatively rare cancer. The incidence rate is approximately one per 1,000,000. The highest incidence is found in Britain, Australia and Belgium: 30 per 1,000,000 per year. Incidence of malignant mesothelioma currently ranges from about 7 to 40 per 1,000,000 in industrialized nations.

Depending on exposure of asbestos during the past several decades, it has been estimated that incidence may have peaked at 15 per 1,000,000 in the United States in 2004. Incidence is expected to increase in other parts of the world. Mesothelioma occurs more often in men than in women and risk increases with age, but mesothelioma can appear in either men or women at any age. Approximately one fifth to one third of all mesotheliomas are peritoneal.

Between 1940 and 1979, approximately 27.5 million people were exposed to asbestos in US. Between 1973 and 1984, there has been a threefold increase in the diagnosis of pleural mesothelioma in males. From 1980 to the late 1990s, the death rate from mesothelioma in US increased from 2,000 per year to 3,000, with men four times more likely to get it than women. These rates may not be accurate, as it is possible that many cases of pleural mesothelioma are misdiagnosed as adenocarcinoma of the lung, which is very difficult to differentiate from mesothelioma.

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Risk factors

Anything that increases chance of contracting a disease is considered as a risk factor. Like strong exposure to sunlight is a risk factor for developing skin cancer or smoking is a risk factor in developing lung cancer.

In case of mesothelioma Exposure to asbestos is the major risk. Genetic factors are also play a important role, As mesothelioma is now known to occur in those who are genetically pre-disposed to it. A history of asbestos exposure exists in almost all cases of mesothelioma. However, mesothelioma has been reported in some of the individuals without any exposure to asbestos. In rare cases, mesothelioma has also been associated with irradiation, Thorotrast (intrapleural thorium dioxide), and inhalation of other fibrous silicates, such as erionite.

Asbestos is the name of a group of silicate fibers (minerals) that occur naturally in environment, flexible fibers that can be separated into thin threads and woven. Asbestos has been broadly used in many industrial products, including cement, roof shingles, brake linings, flooring products, textiles, and insulation. If tiny asbestos particles float in the air, especially during the manufacturing process, they may be inhaled or swallowed by employers, and can cause serious health problems in them. In addition to mesothelioma, exposure to asbestos increases the risk of lung cancer, asbestosis (a non-cancerous, chronic lung disease), and other cancers, of the larynx and kidney.

Smoking does not seem to increase the risk of mesothelioma. The Kent brand of cigarettes used asbestos in its filters for the first few years of its production initially in the 1950s and some cases of mesothelioma have resulted. But smoking modern cigarettes does not appear to increase the risk of mesothelioma. However the combination of smoking and exposure to asbestos significantly increases a person’s risk of developing cancer of the airways like lung cancer, bronchial carcinoma etc.

Some studies suggest that some virus such as simian virus 40(SV 40) may act as a cofactor in the development of mesothelioma. In early experiments with laboratory animals, researchers found that intentional infection with SV40 could cause mesothelioma to develop, and that asbestos increased the cancer-causing effect of SV40. Studies of both mesothelioma patients and healthy people, showed that SV40 virus was not linked to mesothelioma unless the person was also exposed to asbestos.

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