Mesothelioma Causes

Asbestos Exposure Causes Mesothelioma

In recent decades, the association between long-term exposure to asbestos and the development of malignant mesothelioma has become well-established. The majority of mesothelioma patients are people whose vocations involved repeated exposure to asbestos-containing materials over a lengthy time period.[2]

Some of the common jobs or workplaces of people with mesothelioma included construction, shipyards, HVAC, manufacturing facilities and plants, and other industrial settings. These are all work environments and occupations which frequently involve working with materials that contain asbestos.[3] 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 it is often used in industrial products and factories. Asbestos fibers exist in 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.[4]

How Asbestos Can Cause Mesothelioma

When asbestos fibers are swallowed or inhaled through the mouth or nose – often without a person realizing it’s happening – the fibers become embedded in the mesothelium, a thin membrane lining that covers several of the body’s organs.

Mesothelial cells are responsible for producing a kind of natural lubrication that coats 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 cause harmful internal inflammation and damage to the tissue and ultimately lead to cancerous tumors.[4]

Pleural mesothelioma, in which the cancer forms on the membrane surrounding the lung and chest cavity, is caused by inhaling asbestos fibers. Peritoneal mesothelioma, in which the membrane surrounding the abdominal cavity is affected, may result from ingesting asbestos fibers or from inhaled fibers migrating to the abdomen. This helps to explain pericardial mesothelioma, the cancer of the lining of the heart, and testicular mesothelioma.[5]

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.

Secondary Asbestos Exposure

The second most common means of asbestos exposure is secondary exposure. This occurs when there is regular contact with someone who works in a high risk industry such as those previously mentioned. Family members, such as children and spouses, can be 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.[3]

Natural Asbestos Exposure

The third, and least common, mode of exposure results from people coming into contact with asbestos that naturally occurs in the ground and in rocks and minerals. For instance, an individual may 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.[3]

Other Types of Exposure

Some people may have been exposed to asbestos through contamination of other materials. There are currently several lawsuits against manufacturers of talcum powder products over cases of ovarian cancer and mesothelioma. Studies have found that these products can be contaminated with asbestos because talc is also a natural mineral. If it is not purified after mining, contaminants can remain and cause harm to those who use talcum powder regularly.[6]

Factors That Add to the Risk Posed by Asbestos Exposure

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.[7] Other things may predispose a person to the cancer, especially if combined with asbestos exposure.

Genetics

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.[8] 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.

In addition to mesothelioma, BAP1 is a hereditary cancer predisposition syndrome associated with an increased risk for certain forms of melanoma and renal cell carcinoma. This is considered an autosomal dominant mutation, meaning parents have a 50% chance of passing on to their offspring. Although many genetic mutations tend to have more aggressive cancers that occur earlier in life, BAP1 associated mesothelioma is different. These patients may have a more favorable outcome with less aggressive disease. Be sure to discuss all family history of cancer with your care team to determine if genetic testing is appropriate. This information may be helpful to your disease management and overall prognosis.

Radiation Exposure

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.[9] 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 thirty million people were exposed and some experts think this may have increased the risk of developing mesothelioma within this group. Current exposure is unlikely.[10]

Carbon Nanotubes

Carbon nanotubes are increasingly being researched and used in manufacturing. They help to make products, like electronics and automotive parts lighter and stronger, but not a lot is currently known about any potential health risks of these molecules. A few recent cases of mesothelioma developed in people who worked with carbon nanotubes.[11] More study is needed, but there may be a link between inhaling these tiny fibers and developing cancer.

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 forty-five. Men in this age group are overwhelmingly the majority of mesothelioma patients.[12]

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.[12]

These recent findings suggest that more research should be conducted in order to investigate all the contributing factors to mesothelioma. This extended research could lead to precautionary measures being suggested and taken—measures that could potentially save lives by preventing unwitting exposure to asbestos, especially in those with other risk factors.

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.

Page Medically Reviewed and Edited by
Luis Argote-Greene, M.D.

Luis Argote-Greene is an internationally recognized thoracic surgeon. He has trained and worked with some of the most prominently known thoracic surgeons in the United States and Mexico, including pioneering mesothelioma surgeon Dr. David Sugarbaker. He is professionally affiliated with University Hospitals (UH). His areas of interest and expertise are mesothelioma, mediastinal tumors, thoracic malignancies, lung cancer, lung transplantation, esophageal cancer, experimental surgery, and lung volume reduction. Dr. Argote-Greene has also done pioneering work with video-assisted thoracoscopic surgery (VATS), as well as robotic assisted minimally invasive surgery. He has taught the procedures to other surgeons both nationally and internationally.

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