Asbestos
The main risk factor for developing mesothelioma is exposure to asbestos. Asbestos refers to a family of fibrous silicate minerals. Asbestos re-used in many products, such as insulation, floor tiles, door gaskets, sound insulation, roofing, corrections compounds, fireproof gloves and ironing board covers, and even brake pads. As the link between asbestos and mesothelioma became known, the use of this material virtually ceased. Most ceased to use since 1989, but it is still used in some products. Experts attributed this drop in the use of asbestos in the fact that the pace of development of mesothelioma is no longer rising.
Nevertheless, up to 8 million Americans may already have been exposed to asbestos. Exposure to asbestos particles suspended in the air and building materials, much less dangerous, except when they are removed.
Because asbestos is a natural mineral, it can also be found in dust and rocks in some parts of the United States and the world.
U.S. Environmental Protection Agency, at least 733,000 schools and public buildings in the country today contain asbestos insulation. As many as 10% to 15% of schools in the United States may contain asbestos insulation. People who may be at risk of occupational exposure to asbestos, including some of the miners, factory workers, insulation manufacturers, railroad workers, ship builders, gas mask manufacturers and construction workers, particularly those related to the installation of insulation. Several studies have shown that family members of people exposed to asbestos at work have an increased risk of developing mesothelioma because of asbestos fibers carried home garment workers.
The incidence of mesothelioma in men is decreasing, probably because they are not directly exposed to asbestos in their work. But the incidence of mesothelioma for women is a constant, suggesting that they are exposed in such a way that is not directly related to the work, but in their environment at home or work. One example would be asbestos in the buildings where they work or live. A study in California as links to mesothelioma natural asbestos deposits in the mountains.
Another important point about the asbestos and mesothelioma is that the risk of mesothelioma do not fall with time after exposure to asbestos. The risk seems to be living and unchanged.
There are 2 main forms of asbestos - serpentine and amphibole.
Serpentine fibers curly and pliable. Chrysotile is the only type of serpentine fiber and it is the most widely used form of asbestos.
Amphiboles thin rod-type fiber. There are 5 main types - crocidolite, amosite, anthrophylite, tremolite, and actinolyte. Amphiboles (especially crocidolite) are considered the most carcinogenic (causing cancer).
Nevertheless, even the more common chrysotile fibers associated with malignant (cancerous) mesotheliomas and should be treated as hazardous good.
When asbestos fibers are inhaled, most of them have been cleared in the nose, throat, trachea (windpipe) and bronchi (large breathing tubes in the lungs). Fibers are cleared by sticking to the inside of the respiratory tract and mucous being coughed or swallowed. Long, thin fibers less easy to clean, and they can reach the ends of the small airways and penetrate into the pleural lining of the lungs and chest wall. Those fibers can directly injure mesothelial cells of pleura, and eventually cause mesothelioma.
Asbestos fibers can also damage the cells of the lung, and as a result of asbestosis (formation of scar tissue in the lungs), and / or lung cancer. The risk of lung cancer among people exposed to asbestos is increased 7 times compared with the general population. Indeed, asbestosis, mesothelioma and lung cancer 3 are the most frequent cause of death and illness among people with heavy exposure to asbestos. Peritoneal mesothelioma, which forms in the abdominal cavity may occur as a result of coughing and swallowing inhaling asbestos fibers. Cancer of the larynx, pancreas, esophagus, colon, kidney, and may also come from exposure to asbestos, but the increased risk is small.
The risk of developing mesothelioma is related to how many people exposed to asbestos, and how long this effect lasted. People are at an early age, over a long period of time, and at higher levels are likely to develop this cancer. Mesotheliomas take a long time. The time between the first exposure to asbestos and diagnosis of mesothelioma is usually between 20 and 50 years.
Radiation
It was published several reports on the pleural and peritoneal mesotheliomas, which developed after exposure to thorium dioxide (Thorotrast). This material was used in the past, some doctors X-ray tests. It was found Thorotrast cause cancer, it has not been used for many years.
Zeolite
This is a silicate mineral, chemically related to asbestos, common in soil Anatoli region of Turkey. In many cases of mesothelioma have been described in this region and may have been caused by this mineral.
Tobacco
While smoking is not associated with the development of mesothelioma, the combination of smoking and asbestos exposure significantly increases the risk of lung cancer. Asbestos workers who smoke also have a risk of lung cancer from 50 to 90 times higher than among the general population. More asbestos workers were dying of lung cancer than mesothelioma.
SV40 virus
Some recent studies have raised the possibility that infection with the simian virus 40 (SV40), may increase the risk of mesothelioma. Some injectable polio vaccines prepared between 1955 and 1963 were infected with SV40. About 10 to 30 million people are likely to have been exposed to the virus.
Intentional contamination of SV40 some laboratory animals, such as hamsters, causes mesotheliomas to develop. Researchers also found that could lead to SV40 mouse cells grown in dishes to become a cancer, and that asbestos increases the uterus, causing effect of SV40 in these cells. Other researchers examined samples of biopsies of human mesotheliomas and found SV40 DNA. Nevertheless, these fragments of SV40 DNA can also be found in noncancerous human tissues, and some researchers believe that SV40 is a virus found pollutants.
Other studies have found SV40 virus in the tissues of patients with mesothelioma, which did not seem to be pollutants. The study, which also looked at tissue from healthy people, SV40 virus has been linked to mesothelioma, if a person was exposed to asbestos. Researchers in the study thought SV40 infection was not caused by immunization against polio, but, of course, happened, as in other viral infections.
So far, the largest study on the matter in people, not found any increased risk for mesothelioma and other cancers in people who received contaminated vaccine as children. But the peak age range for the diagnosis of mesothelioma 50 to 70 years. Some researchers note that this problem may remain unresolved until a few people accidentally exposed to SV40 between 1955 and 1963 to reach this age range. Research in this important topic is still under way.
A recent study by the Institute of Medicine concluded that we do not yet know whether SV40 is responsible for some of mesotheliomas, and more research needs to be done.