Mesothelioma
epidemiology and
incidences
Although reported incidences have increased in the past
twenty years, mesothelioma is still a relatively rare cancer. About 2,000
people of mesothelioma are diagnosed in the United States each year. Mesothelioma occurs more often in men than in women and risk increases
as a person gets older, but mesothelioma can appear in either men or women at
young or old.
Commercial asbestos mining at Wittenoom, Western Australia, occurred between
nineteen forty five and nineteen sixty six. A cohort study of miners employed at the mine reported that while no
fatalities occurred within the first 10 years after crocidolite exposure, 85
attributable to MM had occurred by nineteen eighty
five. It is predicted that the number of cases within this study group will reach in excess of 700 by the year
twenty-twenty. By nineteen ninety four, 539 reported
fatalities due to MM had been reported in Western Australia.
Mesothelioma risk
factors
Working with asbestos is the major risk factor for mesothelioma.
A level of asbestos exposure exists in almost all cases. However, mesothelioma has been reported in some individuals without any known exposure to asbestos.
Asbestos is the name of a group of minerals that occur naturally as masses of strong, flexible fibers that can be separated into thin threads and woven. Asbestos has been widely used in many industrial products, including cement, brake linings, roof shingles, flooring products, textiles, and insulation. If tiny asbestos particles float in the air, especially during the manufacturing process, they may be inhaled or swallowed, and can cause serious health problems. In addition to mesothelioma, exposure to asbestos increases the risk of lung cancer, asbestosis (a non-cancerous, chronic lung ailment), and other cancers, such as those of the larynx and kidney.
The combination of smoking and asbestos exposure significantly increases a person's risk of developing cancer of the air passageways in the lung. The Kent brand of cigarettes used asbestos in its filters for the first few years of production in the
nineteen fifties and some cases of mesothelioma have resulted. Smoking current cigarettes does not appear to increase the risk of
mesothelioma.
Exposure
Asbestos has been mined and used since the late
eighteen hundreds. Since the early nineteen forties, millions of American workers have been exposed to asbestos dust. Initially, the risks associated with asbestos exposure were not known. However, an increased risk of developing mesothelioma was later found among
factory workers, construction personnel, and other tradespeople. Today, the U.S. Occupational Safety and Health Administration (OSHA) sets limits for acceptable levels of asbestos exposure in the workplace. By contrast, the British Government's Health and Safety executive (HSE) states formally that any threshold for mesothelioma must be at a very low level and it is widely agreed that if any such threshold does exists at all, then it cannot currently be quantified. For practical purposes, therefore, HSE does not assume that any such threshold exists. People who work with asbestos wear personal protective equipment to lower their risk of exposure.
Exposure to asbestos fibers has been recognized as an occupational health hazard since the turn of the century. Several epidemiological studies have associated exposure to asbestos with the development of lesions such as asbestos bodies in the sputum, pleural plaques and diffuse pleural fibrosis, asbestosis, carcinoma of the lung and larynx, gastrointestinal
tumors and diffuse mesothelioma of the pleura and peritoneum.
The documented presence of asbestos fibers 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
fibers. Although many authorities consider brief or transient exposure to asbestos
fibers as inconsequential and an unlikely risk factor, some epidemiologists claim that there is no risk threshold.
Family members and others living with asbestos workers 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 the chance of exposing family members to asbestos fibers, asbestos workers are usually required to shower and change their clothing before leaving
work.
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