Mesothelioma Causes - Working with asbestos tend the major risk factor for mesothelioma symptom. Did you know that in the
United States (USA), asbestos is the major cause of malignant mesothelioma and
has been considered "indisputably" associated with the development of
mesothelioma. Indeed, the relationship between asbestos and mesothelioma
is so strong that many consider mesothelioma a “signal” or “sentinel”
tumor. A history of asbestos exposure exists in most 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 , and
inhalation of other fibrous silicates, such as erionite. Some studies
suggest that simian virus 40 may act as a cofactor in the development
of mesothelioma. This has been confirmed in animal studies, but studies
in humans are inconclusive.
Asbestos was known in antiquity, but it was not mined and widely used
commercially until the late 19th century. Its use greatly increased
during World War II. Since the early 1940s, millions of American workers
have been exposed to asbestos dust. Initially, 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. Today, the official position of the U.S. Occupational
Safety and Health Administration (OSHA) and the U.S. EPA is that
protections and "permissible exposure limits" required by U.S.
regulations, while adequate to prevent most asbestos-related
non-malignant disease, they are not adequate to prevent or protect
against asbestos-related cancers such as mesothelioma. Likewise, 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 exist at all, then it
cannot currently be quantified. For practical purposes, therefore, HSE
assumes that no such "safe" threshold exists. Others have noted as well
that there is no evidence of a threshold level below which there is no
risk of mesothelioma. There appears to be a linear, dose-response
relationship, with increasing dose producing increasing disease.
Nevertheless, mesothelioma may be related to brief, low level or
indirect exposures to asbestos. The dose necessary for effect appears to
be lower for asbestos-induced mesothelioma than for pulmonary
asbestosis or lung cancer. Again, there is no known safe level of
exposure to asbestos as it relates to increased risk of mesothelioma.
How long does Mesothelioma duration?
The duration of exposure to asbestos causing mesothelioma can be short.
For example, cases of mesothelioma have been documented with only 1–3
months of exposure. People who work with asbestos wear personal
protective equipment to lower their risk of exposure.
Latency, the time from first exposure to manifestation of disease, is
prolonged in the case of mesothelioma. It is virtually never less than
fifteen years and peaks at 30–40 years. In a review of occupationally
related mesothelioma cases, the median latency was 32 years.Based upon
the data from Peto et al., the risk of mesothelioma appears to increase
to the third or fourth power from first exposure.