Mesothelioma is a terrible diagnosis to get. It is an aggressive cancer that attacks the tissue that lines internal organs, most often the pleura lining the lungs. Most patients get a life expectancy along with their diagnosis and treating this cancer is challenging. Mesothelioma is rare, and although one major risk factor is well known, the actual causes of this kind of cancer remain mostly a mystery.
Unlike other forms of cancer, mesothelioma is known to have a definite and overwhelming risk factor: exposure to asbestos. People who spend their careers working in an environment with this mineral are at the greatest risk for developing mesothelioma, and yet not all who are exposed to asbestos will get the diagnosis. There are also some cases of people having this cancer who were never exposed to asbestos, so there must be other causes as well.
Asbestos is the Most Common Cause of Mesothelioma
In recent decades, the association between long-term exposure to asbestos and the development of malignant mesothelioma cancer has become well-established. Although the latency period (or the time from initial asbestos exposure to the first display of symptoms of mesothelioma cancer) for mesothelioma is quite long, the majority of mesothelioma patients are people whose vocations involved repeated exposure to asbestos-containing materials over a lengthy time period.
Most people with mesothelioma worked in construction, shipyards, HVAC, or in vinyl manufacturing—all occupations which frequently involve working with materials that contain asbestos. Thus, most cases of malignant mesothelioma can establish a clear line between asbestos exposure and development of the cancer.
What Is Asbestos?
Asbestos is a naturally occurring mineral that has insulating and fire-retardant qualities, which is why is it is often used in industrial products and factories. Asbestos fibers exist in to primary forms, including serpentines and amphibole. In either case, this dangerous substance always consists of tiny fibers that are invisible to the naked eye. In fact, they are over a thousand times thinner than the average human hair. Though they are microscopic fibers, asbestos is strong and durable.
How Asbestos May Cause Mesothelioma
When asbestos fibers are swallowed or inhaled through the mouth or nose – often without a person realizing – the fibers become embedded in the mesothelium, a thin membrane lining that covers several of the body’s organs. Mesothelium cells are responsible for producing a kind of natural lubrication that coast the surface of vital organs. This lubricating fluid permits the body’s organs to expand and contract as they perform their various functions. The embedded asbestos fiber can then cause harmful internal inflammation and lead to cancerous tumors.
Pleural mesothelioma (in which the cancer forms on the membrane surrounding the lung and chest cavity) is caused by inhaling asbestos fibers, while Peritoneal mesothelioma (in which the membrane surrounding the abdominal cavity is affected) results from ingesting asbestos fibers. It may also be that inhaled fibers are able to move to other areas of the body, which would explain pericardial mesothelioma, the cancer of the lining of the heart, and testicular mesothelioma.
Primary Asbestos Exposure
There are a variety of different ways that a person can be exposed to asbestos fibers. The first and most common mode of exposure is occupational exposure, which can take place at a variety of different workplaces.
Because asbestos is frequently used in industrial production, occupational exposure is most common among people who work in or around shipyards, military bases, automotive factories, mills, and mines. Products that may contain asbestos include insulation, roofing, flooring materials, pipes, pipe fittings, electrical wiring, and paint.
Given that occupational exposure to asbestos is responsible for the majority of mesothelioma cases, employees working in high risk industries should be particularly attentive to any symptoms or warning signs that arise.
Secondhand Asbestos Exposure
The second most common means of asbestos exposure is secondhand exposure, or frequent contact with someone that works in a high risk industry such as those previously mentioned. It is quite common that family members and spouses can affected indirectly from exposure to a loved one’s work clothes, or gear. Second-hand asbestos exposure can also result from living in an area where asbestos pollution is released into the air. These polluted areas are typically in close proximity to asbestos factories, industrial shipyards, mines, mills, and construction demolitions.
Natural Asbestos Exposure
The third, and least common, mode of exposure results from people coming into asbestos that naturally occurs in nature. This can happen when individuals come into contact with asbestos fibers that are found in underground rock that has become exposed. These fibers can be released when the rock is mined and used for commercial building materials.
Recent Research shows Asbestos is not the Only Cause
Although asbestos exposure is the most common cause of this rare cancer, recent research has come to light that indicates that asbestos is not the only factor which can influence mesothelioma development. There are now cases of mesothelioma patients who have never been exposed to asbestos in their lives, which has brought up the question, “where did the mesothelioma come from, if not from asbestos?” Researchers have been studying the environments of these individuals who have mesothelioma but have never worked with asbestos, and have made some interesting discoveries.
The ultimate cause of any type of cancer is mutations in DNA. DNA is the large molecule that contains all of the genes a person has. These can become mutated, or changed, sometimes randomly, other times triggered by things like radiation or asbestos fibers. Asbestos is thought to cause mutations in the DNA of the cells in the mesothelium, and this is what most likely leads to the development of cancer.
On the other hand, not everyone who inhales asbestos fibers will end up with mesothelioma or any type of cancer. This may mean that some people have genes that make them more susceptible to the damage and the mutations caused by asbestos. Research has found that people at high risk for mesothelioma have mutations in a gene called BAP1. This gene, when not changed, is responsible for helping cell growth remain under control. If that gene is damaged it could cause uncontrolled cell growth, or cancer.
There have also been a few published cases of patients who developed mesothelioma after receiving considerable doses of radiation to the chest or abdomen, as part of treatment for another form of cancer. While the chances of a cancer patient developing mesothelioma after receiving radiation treatment are somewhat elevated, still these cases are rare. The reason that radiation can contribute to mesothelioma is that it mutates DNA.
The SV40 Virus
Simian virus 40, also known as SV40, is a virus that is found in both humans and other primates. Infection with the virus may not produce symptoms and may simply stay in the body for a long period of time. However, studies have found that it can also cause cancer in humans and animals. SV40 has been implicated as a possible risk factor for mesothelioma, although evidence is limited.
Between 1955 and 1963 some people who received the polio vaccine were accidentally given SV40. The vaccines had inadvertently been contaminated with the virus. Nearly 30 million people were exposed and some experts think this may have increased the risk of developing mesothelioma within this group.
Carbon Nanotube Inhalation
Carbon nanotubes are an up-and-coming molecule being used more and more often in the manufacture of goods that need to be simultaneously lightweight and strong (such as electronics, automotive parts, and sports equipment). Because the use of carbon nanotube technology is relatively new, little is known about the risks involved with long-term exposure to them. However, recent mesothelioma cases have developed in people who have worked in labs developing carbon nanotubes, and on production floors where items containing carbon nanotubes are manufactured, suggesting a link between carbon nanotube exposure and mesothelioma.
Other Risk Factors
Other risk factors should also be taken into account when considering the causes of mesothelioma. These factors may not directly cause mesothelioma, but they do seem to contribute to it. For example, people who smoke and who are exposed to asbestos are more likely to develop mesothelioma than non-smokers exposed to asbestos. Other risk factors include being male and being over the age of 45. Men in this age group are overwhelmingly the majority of mesothelioma patients.
Contact with a group of minerals called zeolites may also contribute to mesothelioma. These are minerals that, like asbestos, are naturally found in the earth. They are similar in chemical composition and structure to asbestos. Zeolites are more common in the soil of certain locations, including areas of Turkey. Higher incidences of mesothelioma in these areas are attributed to the presence of zeolites.
What Does this Mean?
Until recently, occupational asbestos exposure over the long term was thought to be the sole cause of malignant mesothelioma cancer. These recent findings suggest that there are other factors that can influence the development of mesothelioma, and possibly other causes of this form of cancer lurking in the environment, far removed from vinyl flooring or insulation fibers laden with asbestos.
Since this form of cancer is so aggressive in its ability to grow and spread, knowing other risk factors for its development is incredibly important in terms of not only prevention, but also early diagnosis—something which is crucial in order for treatment to be the most effective.
More Research is Needed
These recent findings suggest that more research should be conducted in order to investigate other potential causes of mesothelioma, beyond asbestos exposure. If research focused on determining environmentally-based (rather than vocationally-based) causes of mesothelioma is successful, it could lead to precautionary measures being suggested and taken—measures that could potentially save lives by preventing unwitting exposure to carcinogenic substances apart from asbestos.
Being conscious of mesothelioma’s primary causes and risk factors increases a patient’s probability of catching the disease in its early stages. If you suspect that you or someone you know is at risk of developing mesothelioma based on their history, please seek medical attention as soon as possible. Symptoms and warning signs may be undetectable for many years and the sooner a doctor is able to make a diagnosis, the sooner the patient can begin seeking treatment.
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