Causes of Mesothelioma

Asbestos is the only confirmed cause of mesothelioma. When inhaled or ingested, asbestos fibers become lodged in the linings of the lungs, abdomen or heart and may eventually lead to tumors.

Key Points

  • 1

    Asbestos exposure is the only proven cause of mesothelioma.

  • 2

    A number of factors can increase the risk of developing mesothelioma.

  • 3

    Most asbestos exposure occurs on the job, with certain occupations more at risk.

  • 4

    Men over the age of 65 who worked in the military are considered the most at risk.

When asbestos is disturbed, the fibers become airborne and may be swallowed or inhaled, eventually becoming lodged in the delicate lining of the lungs, abdomen, or heart. The fibers cause irritation and scarring, which can mutate, inhibiting the body’s natural cancer defenses. Eventually, this scar tissue may develop into tumorous growths.

Symptoms of mesothelioma may appear anywhere from 10 – 50 years after exposure. While the connection between asbestos and deadly lung diseases was known prior to the 1900s in asbestos mine workers, it wasn’t until the 1960s that an official study linked asbestos exposure with incidents of mesothelioma and other related diseases.

Occupational Risk of Mesothelioma

Asbestos exposure often happens as a result of certain occupations, the environment, or secondhand from clothing and other materials brought into the home. Men over the age of 65 who worked in the military are most at risk of contracting mesothelioma. More than 75% of patients who die from mesothelioma are men.

Most high risk trades are related to construction. Because asbestos is strong and water, fire, and chemical resistant, it was used extensively in manufacturing everything from insulation to cement. Machine shops added it to steel to make their equipment heat resistant. It was even added to household drapes to prevent the risk of fire.

Common industrial materials containing asbestos include

  • Insulation
  • Piping materials
  • Roofing and flooring
  • Electrical wiring
  • Paint
  • Vehicular materials like brake pads

People who have worked the following trades are at an increased risk for asbestos exposure and mesothelioma:

High-risk occupations

  • Firefighters
  • Construction workers
  • Demolition crews
  • Mechanics
  • Machine workers
  • Pipefitters
  • Shipyard workers
  • Boiler workers

Certain job sites left their workers especially vulnerable to asbestos exposure:

Common workplace sources of asbestos exposure

  • Shipyards
  • Railroads
  • Auto shops
  • Construction sites
  • Power plants
  • Oil refineries
  • Steel mills
  • Asbestos product manufacturers
  • Mines

According to the US government, veterans who performed the following tasks were likely exposed to asbestos:


  • Mining
  • Milling
  • Shipyard work
  • Insulation work
  • Demolition of old buildings
  • Carpentry
  • Construction
  • Flooring
  • Roofing
  • Working with cement sheets
  • Installing pipes
  • Servicing clutch facings and brake linings

Additional causes and contributing factors to mesothelioma

A number of additional factors can increase the risk of developing mesothelioma, including:

Duration, amount, and frequency of asbestos exposure

Generally, the more asbestos a person is exposed to, the higher the risk of mesothelioma, as more asbestos fibers lead to increased irritation, scarring, and mutation. In rare cases, a single instance of exposure is enough to cause mesothelioma.

Type of asbestos

Exposure to amphibole asbestos (which is more durable and tends to travel more deeply into the lung) and in particular blue and brown asbestos (which may increase the risk of cellular genetic mutation due to increased oxidation) is more risky than other types of asbestos. In general, shorter and wider asbestos fibers are more likely to be trapped reaching the lining of the lung. Longer, sharper fibers can more easily work their way through lung tissue into the mesothelium because they are less likely to be expelled by the body’s natural defenses.


The BAP1 gene, a tumor suppressor, helps keep cancer from metastasizing or spreading. A mutation that neuters the BAP1 gene’s ability to fight cancer leaves affected people more vulnerable to mesothelioma. One symptom of this mutation is the presence of epithelioid atypical Spitz tumours, which look like a beauty mark or mole, but are usually neutral or red in color. Ask your doctor if you should be screened for the BAP1 gene mutation.

Is smoking a risk factor?

There is no evidence of a relationship between smoking and developing mesothelioma specifically. However, studies have shown that asbestos-exposed smokers are 50 – 84 times more likely to contract lung cancer.


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Sources [+]
  • 1 Medline Medical Encyclopedia:
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  • 4 Environmental Protection Agency:
  • 5 Agency for Toxic Substances and Disease Registry: