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Exposure to asbestos is the only known cause of mesothelioma. Inhaling or ingesting asbestos causes these microscopic fibers to get lodged in the lining of the chest or abdomen. Over time, the fibers cause tumor development because the body is incapable of expelling the fibers.

Mesothelioma Asbestos ExposureAsbestos is a naturally occurring mineral used for centuries in products ranging from textiles to insulation. Asbestos usage increased throughout the world in the first half of the 20th century and peaked in the United States during the 1970's. Asbestos continued to be used in a wide variety of industries in the 1980’s and later. To date, roughly 30 million tons have been used in the United States alone.

There are several ways people are exposed to asbestos.


Types of Asbestos Exposure

Occupational: Some people were directly exposed to asbestos at their jobs or from performing tasks such as home or car repairs. Asbestos products were widely used in construction and industrial trades. This is called first-hand exposure.

Secondhand: Other people were exposed to asbestos found on the clothes, skin or hair of someone working with or near the mineral. This is known as secondhand exposure.

Environmental: As a mineral, asbestos can be found in nature. Traditionally, asbestos mines that operated in the past released fibers into the air.

Asbestos: A Cancer-Causing Mineral

Asbestos is made up of flexible, microscopic fibers that are lighter than air and have high tensile strength. Each fiber is hundreds of times thinner than the average human hair. Asbestos is also highly resistant to heat, water, and corrosive damage. These natural properties made asbestos an ideal material for a variety of applications ranging from building insulation to gaskets to brake pads in cars.

There are two main categories of asbestos: serpentine and amphibole.

These categories are characterized according to the shape of the asbestos fibers.

Serpentine: These wavy fibers are found in approximately 95 percent of commercially developed asbestos products in the United States.

Amphibole: These spindle-shaped fibers are sharp, rigid, and more capable of lodging themselves in body tissue. This characteristic increases the risk of developing mesothelioma.

There are six types of asbestos. The four types that can be found in a wide range of materials and products are:


  • White
  • Only form of serpentine asbestos
  • Accounts for the vast majority of asbestos used commercially
  • Curled fibers
  • Chrysotile fibers are more easily removed from the body than other forms of asbestos

Crocidolite and Amosite:

  • Crocidolite is blue in appearance while amosite is brown
  • Used on ships and spray-on insulation products
  • Both form a brittle, needle-like structure, whose fibers are difficult to dislodge from the respiratory tract


  • Gray
  • Used in a variety of commercial applications

Asbestos and Mesothelioma

Asbestos is not an automatic threat. Before it can do damage to your body, asbestos must be inhaled or ingested. Organizations, such as the Environmental Health Agency (EPA), do not acknowledge any safe level of asbestos exposure.

Asbestos is categorized as a carcinogen by the following health organizations:

  • US Department of Health and Services
  • EPA
  • International Agency for Research on Cancer

Generally speaking, asbestos enters the body as follows:

  • Microscopic asbestos fibers are inhaled and travel through the airways
  • After inhalation, roughly two-thirds of the fibers are breathed out from the body. Some fibers remain and become lodged in the lining of the lungs (the pleura), abdominal cavity (the peritoneum) or heart (pericardium)
  • Over time, the tiny fibers cause scarring, inflammation, and genetic changes that develop into mesothelioma

Current Theories Linking Asbestos Fibers and Tumor Growth

Research has not yet shown how exactly mesothelioma causes the genetic changes leading to the development of a tumor. There are a number of theories concerning this process, such as:

  • The microscopic size and needle-like shape of asbestos could prevent cells in the immune system from clearing the fibers out. Cells in the mesothelial lining then absorb the fibers, which in turn interfere with normal cellular division.
  • Inhaled fibers irritate mesothelial cells, causing them to swell. This results in cellular damage and tumor development.
  • Asbestos fibers may influence the production of molecules that damage DNA and disrupt cellular reproduction. This damage leads to the production of tumors.
  • Asbestos fibers may also influence the production of proteins that can mutate regular mesothelial cells into tumor cells.

Regardless of how asbestos fibers cause mesothelioma, symptoms do not usually present themselves until 10 to 60 years after the initial exposure to asbestos occurred. Mesothelioma symptoms are often mistaken for those of other ailments.

You can learn more about the causes of mesothelioma and how this disease is treated in our free Patient Help Guide.

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Types of Asbestos Exposure

Exposure to asbestos can occur in a number of ways. The four most common methods that people come into contact with asbestos are at work (occupational), in the military, at home, and through secondhand exposure.

The most common type of asbestos exposure occurs at work. About 70 to 80 percent of all mesothelioma cases are work-related. Workers dealing directly with the manufacture and installation of asbestos-containing products, such as insulation, have the highest risk of developing mesothelioma. Manufacturers stopped mass producing some asbestos products in the 1980's, so workers today have less risk. However, people exposed to asbestos in the 1980's and 90's may still be at risk because it takes up to 60 years for mesothelioma to develop after exposure.

Many large companies who knowingly exposed their employees and others to asbestos have set up asbestos trust funds to help victims pay for treatment.

A few of the occupations presenting the most risk for asbestos exposure are:

  • Drywall installers
  • Demolition specialists
  • Firefighters
  • Mill workers
  • Power and chemical plant operators
  • Automobile and airplane mechanics
  • Shipbuilders

Veterans. All branches of the military used asbestos-containing materials between the 1930's and 1980's. As a result, veterans are the group most at risk for developing mesothelioma. They account for nearly a third of all mesothelioma diagnoses.

Secondary Exposure

Mesothelioma can also develop in people who have not worked directly with asbestos-containing materials. Asbestos workers would often unknowingly expose their families to asbestos after work. Family members were exposed via clothes or hair or skin with dust containing tiny asbestos fibers. The slightest movement released fibers into the air, increasing each family member's risk of developing mesothelioma. Unfortunately, few people knew the risks related to asbestos until the 1980s.

Survivor Profile: Louise W.

Lou Williams

Louise was first diagnosed with peritoneal mesothelioma in 2003 and again in 2009 with pleural mesothelioma.

She attributes her diagnosis to the frequent secondary asbestos exposure she endured as a child. Her father worked with asbestos and would unknowingly expose her and her siblings to asbestos dust on his work clothes.

Environmental Exposure

Asbestos is a naturally-occurring mineral, and people had to mine it to make asbestos-containing products. Environmental exposure to asbestos often occurs near mines that produce or process asbestos. The daily operation of these mines may have released microscopic fibers into surrounding area. In the past, airborne asbestos fibers could float into nearby communities.

Asbestos is a mineral that gathers natural deposits, some of which occur very near the surface. When these deposits are disturbed, they can release fibers into the air, contaminating the surrounding area. Sometimes asbestos deposits are disturbed by cars or trucks.

Mesothelioma Risk Factors

Asbestos exposure is the only known cause of mesothelioma. There are factors, however, that may increase the risk of developing mesothelioma.

Age: Older people are more likely to be diagnosed with mesothelioma due to the amount of time symptoms associated with the disease take to appear. Two out of three people diagnosed with mesothelioma are older than 65.

Gender: Mesothelioma is more common in men than women. Though research has not determined the exact reason why, the increased risk may be connected to the type of labor traditionally occupied by men. These jobs are most likely to involve exposure to asbestos.

Taking Action

If you or a loved one have been exposed to asbestos, it is important to visit a doctor for a check up. Symptoms of mesothelioma can take decades to appear after the initial exposure to asbestos occurred. Those experiencing symptoms should seek help from a mesothelioma specialist as soon as possible.

Our Patient Help Team has access to a network of experienced mesothelioma specialists and can help you get treatment. Contact a member of our Patient Help Team for more information on getting treatment from an experienced mesothelioma specialist.