Causes, Risk Factors, and Prevention of Mesothelioma

Asbestos is a group of minerals that occur naturally as bundles of tiny fibers. These fibers are found in soil and rocks in many parts of the world. In the past, asbestos was used in many products, such as building materials, because it was heat and fire-resistant.

Most of its use in the US stopped several decades ago, but it's still used in some products. People can still be exposed to asbestos in other ways, such as in building materials that were installed decades ago.

When asbestos fibers in the air are inhaled, they can get into the lungs. Fibers that stay in the lungs can travel to the ends of the small airways and enter the pleural lining of the lung and chest wall.

These fibers can injure the cells of the pleura, and, over time, cause mesothelioma. Asbestos fibers can also damage cells of the lung and result in asbestosis (scar tissue in the lung) or lung cancer.

Peritoneal mesothelioma (mesothelioma in the abdomen) can form when inhaled asbestos fibers are coughed up and then swallowed.

Mesotheliomas related to asbestos exposure take a long time to develop. The time between the first asbestos exposure and diagnosis of mesothelioma is usually between 20 and 50 years. The risk does not go down over time after the exposure to asbestos stops.

Workplace exposure

Most pleural mesotheliomas are linked to exposure to high levels of asbestos in the workplace. People at risk include some miners, factory workers, insulation manufacturers and installers, railroad and automotive workers, shipyard workers, plumbers, and construction workers. Family members of people exposed at work can also be exposed because the workers can carry home asbestos fibers on their clothes.

Exposure at home or in other buildings

Asbestos was used to insulate many older homes and buildings around the country, including some schools. Because these particles are contained within the building materials, they're not likely to be found in the air in large numbers.

The risk of exposure is likely to be very low unless the particles somehow escape into the air, such as when building materials begin to decompose over time, or during remodeling or removal.

Naturally occurring asbestos

Many people are exposed to very low levels of naturally occurring asbestos in outdoor air. It's in dust that comes from rocks and soil containing asbestos. This is more likely to happen in areas where rocks have more asbestos in them. In some areas, asbestos can be found in the water supply as well as in the air.

Most people exposed to asbestos do not get mesothelioma

The risk of developing mesothelioma is loosely related to how much asbestos a person is exposed to and how long exposure lasts. People exposed at an earlier age, for a longer time, and at higher levels are more likely to develop this cancer.

Still, most people exposed to asbestos, even in large amounts, do not get mesothelioma. Other factors, such as a person’s genes or having had radiation treatments in the past, might make them more likely to develop mesothelioma when exposed to asbestos.

For more information, see Asbestos and Cancer Risk.

Zeolites are minerals chemically related to asbestos. An example is erionite, which is common in the rocks and soil in parts of Turkey. High mesothelioma rates in these areas are believed to be caused by exposure to this mineral.

In the US, erionite deposits have been detected in several western states, including Nevada, Oregon, Utah, and Arizona.

Some studies have suggested that the risk of mesothelioma might be higher in people who have been exposed to high doses of radiation to the chest or abdomen as treatment for another cancer. Still, this cancer is still rare in these people.

The risk of mesothelioma increases with age. Mesothelioma can occur in young people and children, but it's rare in people under age 45.

Mesothelioma, especially pleural mesothelioma, is much more common in men than in women. This is probably because men have been more likely to work in jobs with heavy exposure to asbestos.

In rare cases, mesotheliomas run in families because of a common gene change (mutation) among family members.

For example, in BAP1 tumor predisposition syndrome, family members have a change in the BAP1 gene. Most often, but not always, this gene change is inherited from a parent.

People with this gene change are at higher risk for mesothelioma when exposed to asbestos, as well as some other cancers.

SV40 is a virus that usually infects monkeys. Some polio vaccines prepared between 1955 and 1963 were made from monkey cells and were later found to be contaminated with SV40.

Some older studies suggested that infection with SV40 might increase the risk of developing mesothelioma and some other cancers. Larger studies looking at this issue have not found an increased risk for mesothelioma or other cancers among people who got the contaminated polio vaccines as children.