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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 increasing
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 three-fold increase in the diagnosis of pleural
mesothelioma in caucasian males. From 1980 to the late 1990s, the rate of
deaths from mesothelioma increased from 2,000 to 3,000 a year. in the late
1990se in annual deaths from mesotheilioma., 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.
Working with asbestos is the major risk factor for mesothelioma. A
history of asbestos exposure exists in almost all cases. However,
mesothelioma has been reported in some individuals without any known
exposure to asbestos. In rare cases, mesothelioma has also been associated
with irradiation, intrapleural thorium dioxide (Thorotrast), and
inhalation of other fibrous silicates, such as erionite.
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 noncancerous, 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 airways (lung
cancer, bronchial carcinoma). The Kent brand of cigarettes used asbestos
in its filters for the first few years of production in the 1950s and some
cases of mesothelioma have resulted. Smoking current cigarettes does not
appear to increase the risk of mesothelioma.
Some studies suggest that simian virus 40 (SV40) may act as a cofacror
in the development of mesothelioma.
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