What Causes Mesothelioma?

A risk factor is anything that affects a person's chance of getting a disease such as cancer. Different cancers have different risk factors. Some risk factors, such as smoking, can be controlled. Others, like a person's age or family history, can't be changed. But risk factors don't tell us everything. Having a risk factor, or even several risk factors, does not mean that you will get the disease. And some people who get the disease may not have had any risk factors.

Researchers have found some risk factors that increase a person's risk of mesothelioma. 

Asbestos

The main risk factor for mesothelioma is contact with asbestos. In fact, most cases of mesothelioma have been linked to asbestos in the workplace. In the past, asbestos was used in insulation, and in other things like floor tiles, door gaskets, roofing, patching compounds, and more. Since asbestos is a natural mineral, it can also be found in dust and rocks in certain parts of the United States. Most asbestos use stopped after 1989, but it is still used in some products.

When asbestos fibers are breathed in, some can travel to the ends of the small air passages and reach the lining of the lungs. There they can damage the cells lining the lungs, and with time lead to pleural mesothelioma. If swallowed, these fibers can also reach the lining of the abdominal cavity (belly) where they play a part in causing peritoneal mesothelioma.

People who may be at risk for asbestos exposure include some miners, factory workers, makers of insulation, railroad workers, ship builders, gas mask makers, and construction workers. Studies have shown that family members of people exposed to asbestos at work have an increased risk of mesothelioma, too, because asbestos fibers are carried home on the clothes of the workers.

Asbestos was used in the insulation of many older homes and public buildings around the country, including some schools. Because the asbestos is contained within the building materials, a large amount is not likely to be found in the air. The risk is thought to be much less unless the asbestos is somehow released into the air, such as when building materials begin to rot over time, or during remodeling or removal. 

The risk of getting mesothelioma depends on how much asbestos a person was exposed to and for how long. Mesotheliomas take a long time to develop. The time between the first exposure and finding the disease is often between 20 and 50 years. Also, once you have been exposed to asbestos, the risk of mesothelioma appears to be lifelong and it does not go down over time.

To learn more, see our document called Asbestos.

Other risk factors

Radiation: There is some evidence linking thorium dioxide (Thorotrast) to mesothelioma. Thorotrast was once used in certain x-rays. It has not been used for many years.

SV40 virus: Some studies have suggested that infection with simian virus 40 (SV40) might increase the risk of mesothelioma. Some polio vaccines made between 1955 and 1963 were contaminated with SV40. Research into this is still going on.

Age: Mesothelioma is rare in people under age 45. The chance of having it goes up with age. About 3 out of 4 people with mesothelioma are over 65 years old.

Sex: The disease affects men about 4 times more often than women.