Mesothelioma causes and risk factors

This page was reviewed under our medical and editorial policy by

Maurie Markman, MD, President, Medicine & Science

This page was updated on June 6, 2022.

About 3,000 people are expected to be diagnosed with mesothelioma in the United States this year, representing a decline in the prevalence of this disease compared to the 1970s through the 1990s.

What causes mesothelioma?

While the exact cause of mesothelioma may not be known, about 80 percent of patients diagnosed with pleural mesothelioma were exposed to asbestos.

Asbestos is a major risk factor for mesothelioma. Asbestos is a naturally occurring fibrous mineral that was found to have many useful industrial applications because of the fiber’s strength and resistance to fire and heat, as well as its low electrical conductivity. It’s now known that asbestos exposure is harmful and linked to several types of cancer, most commonly mesothelioma.

Exposure to asbestos is a major risk factor for mesothelioma. The risk from long-term asbestos exposure doesn’t decrease over time. Rather, it may take more than 20 years from the last exposure before cancer develops. People with a history of asbestos exposure should talk to a doctor. Today, the risk of exposure for workers in the manufacturing industry is much lower because asbestos, by and large, is no longer used in the United States. Although the use of asbestos has decreased dramatically since the late 1980s, it may still be found in older buildings or products.

Mesothelioma causes other than asbestos

Knowing the risk factors for mesothelioma may help people take preventative measures to reduce the likelihood of developing the disease. Some common risk factors are listed below.

Smoking: Although smoking alone is not a risk factor for mesothelioma, some think that smoking in combination with asbestos exposure may increase a person’s risk of mesothelioma.

SV40: Between 1955 and 1963, some polio vaccinations were infected with SV40 (simian virus 40). There is ongoing research exploring the possibility that SV40 infections may have an effect on the development of mesothelioma. Although there is no conclusive evidence, there may be an overlap in the peak age range of those who are diagnosed with mesothelioma (ages 50 to 70) and the timing of the exposure to SV40.

Thorium dioxide: Up until the 1950s, thorium dioxide was injected into the chest or abdomen before an X-ray was taken to create contrast in the image. There may be a link between the thorium dioxide, followed by a high dose of radiation, and mesothelioma.

Next topic: What are the symptoms of mesothelioma?

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