There are several factors that have been found to increase a person's risk of developing mesothelioma.

Asbestos

Exposure to asbestos, a naturally-occurring mineral fiber, accounts for at least 70 to 80% of all mesothelioma cases. As many as 8 million Americans may already have been exposed to this dangerous substance through swallowing or inhaling it. Those most vulnerable to mesothelioma are people exposed to high levels of asbestos, those exposed to asbestos at a very young age, or individuals who are exposed to the fibers for an extended period of time. Second-hand asbestos exposure has also been found to be a mesothelioma risk factor. For example, a person that works with asbestos can carry the fibers home on their clothing, where a family member unknowingly comes into contact with it.

However, not everyone who comes into contact with asbestos will develop mesothelioma. In fact, only about 5% of those exposed to high levels of asbestos will contract the disease, while others with only brief exposure will become seriously ill. This suggests that some individuals may have a pre-existing condition that increases their risk of developing mesothelioma or were born with a predisposition to the disease.

Radiation

Thorotrast (thorium dioxide), a radioactive substance used in x-rays from the 1920s to the 1950s, was found to cause cancer. Some research establishes a link between Thorotrast and malignant mesothelioma. Fortunately, it is no longer being used today and is no longer considered a mesothelioma risk factor.

Simian Virus 40 (SV40)

There is some evidence to suggest a link between malignant mesothelioma and SV40, a disease originally found in monkeys. Since the polio vaccine was developed using monkey cells, millions were exposed to this virus between 1955 and 1963 when they received polio vaccinations. More research is needed to confirm this link as one of the mesothelioma risk factors.

Genetics

Some studies suggest that family history may play a role in whether or not a person develops mesothelioma. However, there is no conclusive evidence yet to support this theory.

Zeolite

Zeolite is a naturally occurring mineral that is found in the soil, with properties similar to asbestos. It has been linked to cases of mesothelioma in Turkey, where zeolite is used in the construction of houses.

Smoking

Smoking tobacco itself does not cause malignant mesothelioma and thus, is not a mesothelioma risk factor. However, people who smoke and are exposed to asbestos appear to have a greatly increased risk of developing mesothelioma in the lungs and air passageways (pleural mesothelioma).