Document3 by NurulGayatri


									                 What Are The Four Main Risk Factors For Mesothelioma?

A risk factor is anything that affects your chance of getting a disease such as cancer. Different
cancers have different risk factors. For example, exposing skin to strong sunlight is a risk factor
for skin cancer. Smoking is a risk factor for cancers of the lung, mouth, larynx (voice box),
bladder, kidney, and several other organs. Having a known risk factor, or even several risk
factors, does not mean that you will get the disease. And some people who get the disease may
not have had any known risk factors.
These are the well known risk factors for the development of mesothelioma cancer:
1-Asbestos :
The main risk factor for developing mesothelioma is exposure to asbestos. In fact, most cases of
mesothelioma have been linked to asbestos exposure in the workplace.
Asbestos refers to a family of fibrous minerals made of silicate. It is a naturally occurring
mineral that can be found in dust and rocks in certain parts of the United States and other parts of
the world. There are 2 main forms of asbestos:
1-Serpentine (curly) fibers include chrysotile, the most widely used form of asbestos. 2-
Amphiboles are thin, rod-like fibers. There are 5 main types -- crocidolite, amosite,
anthrophylite, tremolite, and actinolyte.
Amphiboles (particularly crocidolite) are considered to be more likely to cause cancer. However,
the more commonly used chrysotile fibers are also linked with mesothelioma.
When chrysotile fibers in the air are inhaled, they tend to stick to mucus in the throat, trachea
(windpipe), or bronchi (large breathing tubes of the lungs) and are then cleared by being coughed
up or swallowed. But the long, thin amphibole fibers are less readily cleared, and they may reach
the ends of the small airways and penetrate into the pleural lining of the lung and chest wall.
These fibers may then injure mesothelial cells of the pleura, and eventually cause mesothelioma.
Asbestos fibers can also damage cells of the lung and result in asbestosis (formation of scar
tissue in the lung) and/or lung cancer. Peritoneal mesothelioma, which forms in the abdomen,
may result from coughing up and swallowing inhaled asbestos fibers. Because of its heat and fire
resistant properties, asbestos was once used in many products such as insulation, floor tiles, door
gaskets, soundproofing, roofing, patching compounds, fireproof gloves, ironing board covers,
and brake pads. The link between asbestos and mesothelioma has become well known, so its use
in the United States has decreased dramatically. Most use stopped after 1989, but it is still used
in some products.
People at risk for workplace asbestos exposure include some miners, factory workers, insulation
manufacturers and installers, railroad and automotive workers, ship builders, gas mask
manufacturers, and construction workers. Family members of people exposed to asbestos at work
also have an increased risk of developing mesothelioma because asbestos fibers can be carried
home on the clothes of the workers. The incidence rate for mesothelioma in men appears to be
dropping, probably because there is now much less direct exposure to asbestos in industrial
Asbestos was also used in the insulation of many older homes, as well as commercial and public
buildings around the country, including some schools.
The risk of developing mesothelioma is related to how much asbestos a person was exposed to
and how long this exposure lasted. People exposed at an early age, for a long period of time, and
at higher levels are more likely to develop this cancer.
Mesothelioma take a long time to develop. The time between first exposure to asbestos and
diagnosis of mesothelioma is usually between 20 and 50 years. Unfortunately, the risk of
mesothelioma does not drop with time after exposure to asbestos. The risk appears to be lifelong
and undiminished.
Zeolites are silicate minerals that are chemically related to asbestos. An example is erionite,
which is common in the soil in parts of Turkey. High mesothelioma rates in these areas are
believed to be due to exposure to this mineral.
There have been a few published reports of mesotheliomas that developed following exposure to
high doses of radiation to the chest or abdomen or after injections of thorium dioxide
(Thorotrast). This material was used by doctors for certain x-ray tests until the 1950s. Thorotrast
was found to cause cancers, so it has not been used for many years.
4-SV40 virus Some studies have raised the possibility that infection with simian virus 40 (SV40)
might increase the risk of developing mesothelioma. Some injectable polio vaccines given
between 1955 and 1963 were contaminated with SV40. As many as 30 million people in the
United States may have been exposed to the virus. But up till now there is no conclusive
evidence of increased cases of mesothelioma amongst people that have received this
contaminated vaccine.

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