What Causes Mesothelioma?
Mesothelioma is a cancer
that occurs in the mesothelium, a thin membrane encompassing the body’s
internal organs and cavities. Mesothelioma is caused by asbestos
exposure. Asbestos fibers that are inhaled through the mouth and
nose may eventually become embedded in the lining of the lungs, causing harmful
inflammation of the pleura and resulting in mesothelioma
or asbestosis (scar tissue formation in the lungs). It has also been found that
swallowing asbestos fibers could contribute to a form of the
malignancy originating in the abdomen known as peritoneal mesothelioma.
Mesothelioma generally results from
occupational asbestos exposure, but there are instances of environmental
exposure that can also cause the disease. Oftentimes a family member can be
affected indirectly by second hand exposure from an asbestos worker’s soiled
work clothes.
Asbestos was an effective insulation
material. It was used liberally in commercial and industrial products in the United
States until being regulated in a joint effort between the Consumer Product
Safety Commission and the Environmental Protection Agency in 1989. Occupational
exposure was common among workers who encountered these products in many
industries including shipbuilding, power plants, and other industrial settings.
Asbestos insulation workers appear
to have the highest rate of asbestos related disease. One study reports that
almost six percent of asbestos workers fall victim to mesothelioma or
experience respiratory symptoms. Asbestos insulation workers
are over 300 times more likely to be diagnosed with mesothelioma than those
with no exposure history.
How
does exposure to asbestos cause mesothelioma?
Asbestos fibers are microscopic,
though they are also quite durable. For this reason, asbestos was used in a
number of different industrial compounds to enhance strength and resistance to
temperature extremes- two properties at which the mineral is highly adept.
Asbestos exposure most often occurred among individuals who worked extensively with asbestos
or asbestos-containing materials. Friable asbestos (meaning loose or airborne
fibers) is easily inhaled- often without the exposed person realizing.
When inhaled, asbestos lodges easily
in the outer lung tissue and within the mesothelium. The mesothelium is a thin membrane of cells which
produces a lubricating fluid on the surface of the organs. This lubricant allows
the lung and other internal structures to expand, contract, and move freely
without friction in the body cavity. There is a great deal of latency associated with mesothelioma between
exposure to asbestos and the onset of symptoms.
Pleural mesothelioma is the most
common variety of the disease and forms on the pleural membrane, which
surrounds the lung and chest cavity. Peritoneal mesothelioma is less common and
forms on the surface of the peritoneum, a thin membrane surrounding the
abdominal cavity. Pericardial mesothelioma is the least common variety of the
disease and forms in the cardiac cavity that envelops the heart, a mesothelial
membrane known as the pericardium.
Inhaled asbestos fibers are known to
be the cause of pleural mesothelioma, whereas ingested
asbestos fibers are the cause of peritoneal mesothelioma. While the exact
causal nature between asbestos and pericardial mesothelioma is not known,
physicians and cancer researchers surmise asbestos fibers in the
blood stream lodge in the outer layers of the heart’s ventricles and lodge in
the pericardium. Once asbestos fibers reach the surface of the peritoneum or
pericardium, the inflammation process is essentially the same as it is on the
surface of the pleura.
Primary workplace exposure to the
mineral was common in naval shipyards, power plants, railroad infrastructure,
and other industrial jobsites. However, asbestos-related mesotheliomas have
also been diagnosed in spouses or children of those exposed to asbestos.
Workers often brought home dangerous asbestos fibers on their clothing, hair,
or person. Those who came into contact with these fibers on the person or their
clothing have developed mesothelioma as a result.
Other
Contributing Factors
Mesothelioma is also causally
associated with a few other factors, but many of these are attributed to the
development of mesothelioma in conjunction with exposure to asbestos.
Smoking
Those who smoke are at a higher risk
of mesothelioma, though smoking is more commonly associated with traditional
lung carcinomas. Smoking tends to enhance risk even further in those who were
also exposed to asbestos.
Radiation
Exposure
While extremely rare, some
mesothelioma patients attribute their diagnosis to exposure to radiation rather
than exposure to asbestos. Radiation tends to transform and mutate cell growth
patterns and is more commonly associated with brain and blood cancers.
Carbon
Nanotubes
Research is extremely preliminary in
this study, but some laboratory studies indicate a molecular similarity between
asbestos mineral fibers and carbon nanotubes. Tests indicate a pronounced risk
of mesothelioma in some laboratory animals implanted with carbon nanotubes.
Source http://www.mesothelioma.com/mesothelioma/causes/
Source http://www.mesothelioma.com/mesothelioma/causes/
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