Sunday, October 7, 2007

Epidemiology of Mesothelioma.

Mesothelioma Incidence Of Epidemiology

Although reported incidence rates have increased in the past 20 years, mesothelioma is still a relatively rare cancer. The incidence is approximately one per 1,000,000. For comparison, populations with high levels of smoking can have a lung cancer incidence of over 1,000 per 1,000,000. Incidence of malignant mesothelioma currently ranges from about 7 to 40 per 1,000,000 in industrialized Western nations, depending on the amount of asbestos exposure of the populations 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 continue to increas in other parts of the world. Mesothelioma occurs more often in men than in women and risk increases with age, but this disease 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 occupationally exposed to asbestos in the United States. Between 1973 and 1984, there has been a threefold increase in the diagnosis of pleural mesothelioma in Caucasian males. From 1980 to the late 1990s, the death rate from mesothelioma in the USA increased from 2,000 per year to 3,000, with men four times more likely to acquire it than women. These rates may not be accurate, since it is possible that many cases of mesothelioma are misdiagnosed as adenocarcinoma of the lung, which is difficult to differentiate from mesothelioma.

Risk Factors Of Epidemiology With Mesothelioma

Working with asbestos is the major risk factor for mesothelioma. A history of asbestos exposure exists in almost all cases. However, mesothelioma has also been known and reported in some individuals without any known exposure to asbestos. In some cases, mesothelioma has also been associated with irradiation, intrapleural thorium dioxide, and inhalation of other fibrous silicates, such as erionite.

The combination of smoking and asbestos exposure significantly increases a person's risk of developing cancer of the airways (lung cancer, bronchial carcinoma). Smoking modern cigarettes does not appear to be a factor in the risk of mesothelioma.

Some studies suggest that simian virus 40 may be acting as a cofactor in the development of mesothelioma.

Exposure To Epidemiology Of Mesothelioma

Asbestos has been mined and used commercially since the late 1800s. Its use greatly increased during World War II. Since the early 1940s, millions of American workers have been exposed to asbestos dust. At first, the risks associated with asbestos exposure were not publicly known. However, an increased risk of developing mesothelioma was later found among shipyard workers, people who work in asbestos mines and mills, producers of asbestos products, workers in the heating and construction industries, and other tradespeople. The U.S. Occupational Safety and Health Administration now sets limits for acceptable levels of asbestos exposure in the workplace, they have also created guidelines for engineering controls and respirators, protective clothing, exposure monitoring, hygiene facilities and practices, warning signs, labeling, recordkeeping, and medical exams. People who work with asbestos now wear personal protective equipment to lower their risk of exposure.

Exposure to asbestos fibres has been recognised as an occupational health hazard since the early 1900s. Several epidemiological studies have associated exposure to asbestos with the development of lesions such as asbestos bodies in the sputum, pleural plaques, diffuse pleural thickening, asbestosis, carcinoma of the lung and larynx, gastrointestinal tumours, and diffuse mesothelioma of the pleura and peritoneum.

The documented presence of asbestos fibres in water supplies and food products has fostered concerns about the possible impact of long-term and, as yet, unknown exposure of the general population to these fibres. Cases of mesothelioma have also been found in people whose only exposure was breathing the air through ventilation systems.

Family members and others living with asbestos workers unfortunetly have an increased risk of developing mesothelioma, and possibly other asbestos related diseases. This risk may be the result of exposure to asbestos dust brought home on the clothing and hair of asbestos workers. To reduce this external risk of asbestos workers carrying mesothelioma along to family members, new rules have been set in place which hold the workers accountable to shower before leaving the work place.


"Malignant mesothelioma and occupational exposure to asbestos: a clinicopathological correlation of 1445 cases" by V. L. Roggli, A. Sharma, K. J. Butnor, T. Sporn and R. T. Vollmer in Ultrastruct Pathol (2002) volume 26 pages 55-65 12036093.
"Advances in Malignant Mesothelioma" by Bruce W. S. Robinson and Richard A. Lake in The New England Journal of Medicine (2005) volume 353 pages 1591-1603 16221782.
"SV40 in human tumors: new documents shed light on the apparent controversy" by D. S. MacLachlan in Anticancer Res (2002) volume 22, pages 3495-3499 12552945.

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