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Mesothelioma Risk Factors - Asbestos Exposure - Mesothelioma is a rare form of cancer in which malignant (cancerous) cells are found in the mesothelium, a protective sac that covers most of the body's internal organs.
The main risk factor for mesothelioma is asbestos exposure. Most people worked at varios jobs such as such as miners, ship builders, factory and railroad workers, mechanics and construction workers where they were exposed to asbestos. Asbestos fibers have also been known to be picked up through clothing or other articles. In fact, asbestos may still be found in 10-15% of schools throughout America. Exposure for as few as one or two months can lead to mesothelioma 10 to 50 years later. The long latency period means that people exposed to asbestos in the 1950's through the 1980's may now be seeing symptoms and are now being diagnosed with mesothelioma. About 8 million Americans may already have been potentially exposed by asbestos, which use of this material has been banned in the United States since approximately 1975.
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Since the late 1800's asbestos has been mined and used commercially in the United States. Initially the risks associated with asbestos was unknown. An increased risk of disease from asbestos was later revealed. It's important to realize that any exposure to asbestos increases your chance of developing mesothelioma. After exposure to the airborne fibers, the risk of lung cancer is 7 times greater than that of the general population and smokers who are exposed to asbestos have a risk 50-90 times greater yet. It should also be noted that not all workers exposed to asbestos will develop diseases related to their asbestos exposure. In fact, many people will experience no ill effects.
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Many men who served in the Navy were exposed to significant amounts of asbestos on their ships. The military stopped using asbestos in the mid-1970s, when it was becoming apparent that asbestos was dangerous and deadly. By then it was too late for the many thousands of veterans, merchant mariners and shipyard workers who had already been exposed. It was also too late for the family members of these victims who had come in contact with the deadly substance.
People should know that asbestos that is bonded into finished products such as walls, tiles, and pipes poses no risk to health as long as it is not damaged or disturbed. When asbestos fibers are disturbed and released into the air and inhaled, the asbestos fibers work their way into body tissues where they may stay indefinitely. If this happens, this places the exposed individuals
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at risk of developing an asbestos-related disease.
There are two main forms of asbestos -- serpentine and amphiboles. Serpentine fibers are curly and pliable. Chrysotile is the only type of serpentine fiber and it is the most widely used form of asbestos. Amphiboles are thin, rod-like fibers of which there are 5 main types-crocidolite, amosite, anthrophylite, tremolite, and actinolyte. Amphiboles (particularly crocidolite) are considered to be the most carcinogenic (cancer-causing). However, even the more commonly used chrysotile fibers have been associated with malignant (cancerous) mesotheliomas and should be considered dangerous as well.
It may be that asbestos causes cancer by physically irritating cells rather than by a chemical effect. When fibers are inhaled, most are cleared in the nose, throat, trachea (windpipe), or bronchi (large breathing tubes of the lungs). Fibers are cleared by sticking to mucus inside the air passages and being coughed up or swallowed. The long, thin, 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 directly 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. The risk of lung cancer among people exposed to asbestos is increased by 7 times, compared with the general population. Indeed, asbestosis, mesothelioma, and lung cancer are the three most frequent causes of death and disease among people with heavy asbestos exposure. Peritoneal mesothelioma, which forms in the abdomen, may result from coughing up and swallowing inhaled asbestos fibers. Cancers of the larynx, pancreas, esophagus, colon, and kidney have also been linked to asbestos exposure, but the increased risk is not as great as with lung cancer.
Although the risk of developing mesothelioma rises with the amount of asbestos exposure, it is clear that genetic factors also play a role in determining who develops the disease. This explains why not all persons exposed to high levels of asbestos dust develop mesothelioma.
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