Mesothelioma Risk

Asbestos exposure plays a role in 70 percent to 80 percent of mesothelioma cases, though the actual percentage could be higher. Asbestos is a mineral that is found naturally in the environment. Asbestos fibers are strong and resistant to heat, making them useful in a wide variety of applications. Asbestos fibers have been used to make insulation, cement, brakes, shingles, flooring and many other products.
People who work around asbestos fibers are thought to have the greatest risk of mesothelioma. When asbestos is broken up — for instance, in the mining process or in removing asbestos insulation from a building — dust may be created. If the dust is inhaled or swallowed, the asbestos fibers may settle in the lungs or in the stomach, where they can cause irritation that may lead to mesothelioma, though how exactly this happens isn't understood. Although asbestos is still used in a limited number of industries, the federal government limits the amount of asbestos fibers workers may be exposed to and sets rules to protect workers.
Mesothelioma risk is believed to be increased in people who are exposed to high levels of asbestos, in people who are exposed to asbestos over a long period of time and in people exposed to asbestos at a young age. It can take 30 to 40 years or more for mesothelioma to develop as a result of asbestos exposure.
People who live with workers exposed to asbestos may also have an increased risk of mesothelioma. Asbestos dust is thought to have been carried home on workers' clothes. Today workers are required to shower and change clothes after working with asbestos to protect their families.
Some people with years of asbestos exposure never develop mesothelioma. Researchers estimate only about 5 percent of the people with the highest exposure to asbestos will develop mesothelioma. And yet, others with very brief exposure develop the disease. This indicates that other factors may be involved in determining whether someone gets mesothelioma or doesn't. For instance, you could inherit a predisposition to cancer or some other condition could increase your risk. Risk of mesothelioma is increased greatly in smokers who are exposed to asbestos.
Other possible risk factorsResearchers have identified other factors that may increase the risk of mesothelioma, including:
SV40. Some research indicates a link between mesothelioma and simian virus 40 (SV40), a virus originally found in monkeys. Millions of people may have been exposed to SV40 when receiving polio vaccinations between 1955 and 1963, because the vaccine was developed using monkey cells. Once it was discovered that SV40 was linked to certain cancers, the virus was removed from the polio vaccine. There is some evidence that SV40 may also be passed between people, though it isn't clear how. Whether SV40 increases the risk of mesothelioma is a point of contention, and more research is needed.
Radiation. The radioactive substance thorium dioxide was used along with X-rays to diagnose various health conditions from the 1920s to the 1950s. Thorium dioxide was later found to cause cancer and was no longer used. Some research links thorium dioxide to mesothelioma.
Asbestos-like minerals. A naturally occurring asbestos-like mineral called zeolite has been linked to mesothelioma cases in Turkey, where the mineral is used to construct homes.
Family history. Research into the same region of Turkey where zeolite is used reveals that family history may play a role in mesothelioma there. More research is needed to determine whether family history may predispose some people to mesothelioma.