Risk factors for mesothelioma

A risk factor is something that increases the risk of developing cancer. It could be a behaviour, substance or condition. Most cancers are the result of many risk factors. Exposure to asbestos is the most important risk factor for mesothelioma.

Mesothelioma affects men much more often than women. This is probably because men are more likely to be exposed to asbestos at work.

Mesothelioma develops 15–40 years after someone is exposed to asbestos. As a result, it is uncommon in people under the age of 50 and the incidence of mesothelioma increases with age.

Risk factors are generally listed in order from most to least important. But in most cases, it is impossible to rank them with absolute certainty. Research shows that there is no link between smoking and a higher risk for mesothelioma.

There is convincing evidence that the following factors increase your risk for mesothelioma.

Asbestos is the name of a group of minerals that occur naturally. It can be separated into long, thin fibres that are very fine. When someone breathes in these fibres, they can make their way to the smallest airways of the lung and into the mesothelium. The fibres get into the pleura, where they can eventually cause pleural mesothelioma. If they are coughed up and then swallowed, asbestos fibres can also settle in the peritoneum. This is the most likely cause of peritoneal mesothelioma.

The link between asbestos and mesothelioma has been well known for many years. According to the International Agency for Research on Cancer (IARC) and the US National Toxicology Program, all forms of asbestos are known to cause cancer. Most people with mesothelioma have a history of asbestos exposure.

Occupational exposure to asbestos is the strongest and most common risk factor for mesothelioma. The risk is related to how much asbestos you were exposed to and how long the exposure lasted. People exposed at an early age, for a long period of time and to greater amounts of asbestos are more likely to develop mesothelioma.

Asbestos has been widely used in building materials and many industries. People who may come into contact with asbestos while working include:

• workers in asbestos mines or mills
• construction workers, carpenters and painters
• shipyard workers
• cement plant workers
• insulation workers
• electricians
• plumbing and heating tradespeople
• demolition workers
• automotive industry workers, including brake and clutch repair workers
• people who work in buildings where asbestos was present and was disturbed during renovations

People who live near an asbestos mine or mill are also exposed to asbestos or asbestos dust in the air. Family members may also be exposed to asbestos from fibres that are brought home on a worker’s clothing.

Occasionally, mesothelioma develops in people who have never been exposed to asbestos.

Erionite is known to cause cancer in people, and it is linked to pleural and peritoneal mesothelioma. It is a naturally occurring mineral that belongs to a group of minerals called zeolites. Zeolites are chemically related to asbestos and erionite has asbestos-like fibres.

Erionite is common in the soil in parts of Turkey. Materials made with erionite are used in construction in these regions. As a result, there are high rates of mesothelioma in these areas due to exposure to erionite.

Fluoro-edenite fibrous amphibole is a naturally occurring mineral that is similar to asbestos, with asbestos-like fibres. It is found in lava flows on the sides of volcanos, especially on Mount Etna in Italy. Exposure to this mineral increases the risk of mesothelioma.

People given radiation therapy to the chest or abdomen to treat lymphoma, breast, lung or other types of cancer have a higher risk for mesothelioma.

Thorium dioxide (Thorotrast) is a radioactive contrast medium that was once used for imaging tests. People who were given thorium dioxide have a higher risk of developing mesothelioma many years after being exposed to it. Because it was found to increase the risk of some cancers, thorium dioxide is no longer used.

The BAP1 gene is also called the BRCA1 associated protein 1 gene. It is a type of gene that helps control cell growth and may limit the growth of cancer cells (called a tumour suppressor gene). A rare mutation in the BAP1 gene may increase the risk for mesothelioma and melanoma of the skin and eye. Healthcare professionals may refer to people who have the BAP1 gene mutation as having BAP1 cancer syndrome.

People who are exposed to asbestos and have the BAP1 gene mutation are at an even higher risk of developing mesothelioma.

It isn’t known whether or not the following risk factors are linked with mesothelioma. It may be that researchers can’t show a definite link or that studies have had different results. More research is needed to see if these are risk factors for mesothelioma:

• simian virus 40 (SV40)
• carbon nanoparticles

To make the decisions that are right for you, ask your healthcare team questions about risks.