Mesothelioma Causes

Asbestos Exposure Causes Mesothelioma

Experts established decades ago that there is a close association between long-term exposure to asbestos and a diagnosis of malignant mesothelioma. Most mesothelioma patients worked in jobs with repeated exposure to asbestos-containing materials over an extended period of time.[2]

Some of the most common workplaces and jobs that put people at risk of asbestos exposure include:[3]

• Demolition and construction
• Shipyards and on ships, including in the U.S. Navy
• HVAC and other building maintenance work
• Manufacturing facilities and plants
• Other industrial settings

In most cases of malignant mesothelioma, there is 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. It consists of tiny fibers, over a thousand times thinner than the average human hair. Bundled together, these fibers make asbestos strong and durable.[4]

How Does Asbestos Cause Mesothelioma?

Several things happen when asbestos fibers come loose from a material and a person inhales or ingests them:

• The fibers embed in the mesothelium, a thin membrane lining that covers several of the body’s organs.
• The embedded asbestos fibers trigger inflammation and damage to the tissue.
• In some people, this damage leads to the formation of cancerous tumors.[4]
• Pleural mesothelioma, cancer in the tissue around the lungs and chest cavity, is caused by inhaling asbestos fibers.
• Peritoneal mesothelioma, in the abdominal cavity, may result from ingesting asbestos fibers or from inhaled fibers migrating to the abdomen.
• Pericardial mesothelioma, in the lining of the heart, and testicular mesothelioma, are also likely caused by asbestos fibers migrating through the body.[5]

Primary Asbestos Exposure

The first and most common mode of exposure to asbestos is primary occupational exposure, which can happen at many different workplaces.

Primary exposure on the job occurs in any industry that uses asbestos materials. Asbestos was once common in insulation, fireproofing, and several construction and shipbuilding materials.

Secondary Asbestos Exposure

Secondary exposure to asbestos is less common. It occurs when a person is in contact with someone primarily exposed to asbestos. Family members of workers exposed to asbestos may experience secondary exposure from their clothing, for instance.

Second-hand asbestos exposure can also result from living in an area where asbestos air pollution is an issue. This may occur in neighborhoods close to factories, industrial shipyards, mines, mills, and construction demolitions.[3]

Natural Asbestos Exposure

The third, and least common, mode of exposure is contact with asbestos that naturally occurs in the ground and in rocks and minerals.

This may occur when asbestos-containing earth or rocks are disturbed during mining, construction, or road building.[3]

Other Types of Exposure

Some people may have been exposed to asbestos through contamination of other materials. Several lawsuits are currently under way against manufacturers of talcum powder products that may have contained asbestos.

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 ovarian cancer or mesothelioma in regular users.[6]

Does Anything Else Cause Mesothelioma?

Although asbestos exposure is the most common cause of this rare cancer, research indicates this is not the only factor.[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 one or more mutations in an individual’s 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.

Research continues to identify several ways genes play a role in mesothelioma:

• 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.
• Not everyone who inhales asbestos fibers develops mesothelioma or any type of cancer.
• This means that some people have genes that make them more susceptible to the damage and the mutations caused by asbestos.
• Research shows that people at high risk for mesothelioma have mutations in a gene called BAP1.[8] This gene, when not changed, is responsible for preventing cell growth from getting out of control. If that gene is damaged it could cause uncontrolled cell growth, or cancer.
• BAP1 may also confer a less aggressive form of the disease in those who have certain changes in the gene and develop mesothelioma.
• 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

Researchers have described a few 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]

The reason that radiation can contribute to mesothelioma is that it mutates DNA. This is possible but still rare.

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.

Studies have found that it can cause cancer in some humans and animals exposed to the virus. SV40 has been implicated as a possible risk factor for mesothelioma, but evidence is limited.

Between 1955 and 1963 some people who received the polio vaccine mistakenly received doses of SV40. Nearly thirty million people were exposed and some experts think this may have increased the risk of developing mesothelioma within this group. Exposure to SV40 today is unlikely.[10]

Carbon Nanotubes

Carbon nanotubes are increasingly important in research and manufacturing. They help to make products, like electronics and automotive parts, lighter and stronger. 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 may not directly cause mesothelioma, but they may 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:[12]

• Being male
• Being over the age of forty-five
• Exposure to a mineral group known as zeolites

Knowing 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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