Virtually all cases of mesothelioma are linked to one specific risk factor: exposure to asbestos. Beginning in the later parts of the 1800s, asbestos became commercially popular for use in construction products like insulation, concrete, and flooring.  As the dangers of asbestos became clear in the late 20^th century, many countries took efforts to ban or reduce asbestos use. Even though asbestos use has been virtually eliminated in most modernized countries, many buildings still contain asbestos which can result in exposure. According to the EPA, there are more than 733,000 public buildings and approximately 107,000 schools which contain asbestos.¹

There is a possibility for asbestos to be found in virtually every type of building – including homes, schools and office buildings – especially if built or remodeled before the 1990s when asbestos use was very common.  Asbestos exposure can also occur environmentally if a person lives near an asbestos mine.  The groups of people who are most at-risk of mesothelioma are military veterans, shipyard workers, miners, construction workers, demolition workers, railroad workers, and factory workers as asbestos exposure is likely to be found at these work sites.  The family members of these people can also be at risk because the asbestos fibers may be carried home on clothing.

Mesothelioma most often results from prolonged, repeated exposure to asbestos.  However, any asbestos exposure can result in mesothelioma or other asbestos diseases such as pleural thickening, asbestosis, or lung cancer.

Other Mesothelioma Risk Factors

Virtually all cases of mesothelioma are linked to asbestos.  However, there are some uncommon cases of mesothelioma which have been caused by other factors.  These include:

• Radiation: There is ample evidence that radiation exposure, alone or in conjunction with viral infections or a genetic predisposition, can lead to mesothelioma.² Some experts also believe that a radioactive substance called thorium dioxide which was frequently used during x-rays in the first half of the 20^th century can cause mesothelioma. Research also shows that people exposed to radiation, whether through their occupations or environmentally, are at higher risk of mesothelioma.  Note that radiation exposure increases the risk of other cancers and is not just linked to mesothelioma.
• Zeolite: Zeolites are a type of mineral which have various commercial uses, including as laundry detergents and for purifying water, among others. There is ample evidence that these minerals can cause mesothelioma which has led them to be labeled as a Group 1 Carcinogen by the International Agency for Research on Cancer.  People who live in areas with high amounts of zeolites – such as those in the Cappadocia region of Turkey – are at very high risk of getting mesothelioma. In the United States, zeolites can be found in some western states including Arizona, North Dakota, South Dakota, Utah, Nevada, Oregon, and Montana. People living in these areas may be at a higher risk of getting mesothelioma due to zeolite exposure.
• Simian Virus 40: Though inconclusive, there is a possibility that people exposed to Simian Virus 40 (SV40) are at risk for mesothelioma.  SV40 is a virus that is found in the cells of rhesus monkeys.  In the late 1950s to early 1960s, the kidney cells of rhesus monkeys were used to manufacture polio vaccines. Some of these vaccines contained SV40 and it is estimated that 10 to 30 million Americans may have received the contaminated vaccines.

In a study of mesothelioma in the US, approximately 54% of the cases had SV40 in the cancer cells, but SV40 was not present in the cells of other lung cancers.  Thus, researchers believe that exposure to SV40 is a risk factor for mesothelioma.  However, they are uncertain about the exact role SV40 has in causing mesothelioma. As of right now the SV40 is considered to be a probable cofactor in tumor generation and is not solely responsible for causing human malignancy.³ Because the infected polio vaccines were given primarily to children from 1955-1963 and mesothelioma has a long latency period, the exact role of SV40 in mesothelioma will not likely be discovered for another couple decades when people exposed to the virus reach the peak age for mesothelioma to become diagnosable.

• Carbon Nanotubes: Nanotubes are a material made from carbon which is used in the construction of various products such as car parts, electronics, medical instruments, and sporting gear.  Nanotubes are incredibly durable and strong yet very lightweight. Because of these qualities, they are becoming increasingly popular for use in many items.  Like asbestos, nanotubes are comprised of very small fibers which could be inhaled.  There is mounting evidence that inhaled nanotubes could lead to mesothelioma.

There are other contributors to mesothelioma but they are usually co-factors and not fully responsible for a person developing mesothelioma. However, factors like smoking and genetics may increase the risk of developing mesothelioma.

Despite these factors, microscopic asbestos fibers account for most cases of mesothelioma and should be avoided as much as possible.

References 

¹ The Asbestos Informer. (9 February 2011) Retrieved from Environmental Protection Agency at: http://www.epa.gov/region4/air/asbestos/inform.htm

² Carbone, M., Ly, B. H., Dodson, R. F., Pagano, I., Morris, P. T., Dogan, U. A., Gazdar, A. F., Pass, H. I. and Yang, H. (2012), Malignant mesothelioma: Facts, Myths, and Hypotheses. Journal of Cellular Physiology, 227: 44–58.

doi: 10.1002/jcp.22724

³ Qu F., Carbone M., Yang H. and Gaudino G. (Oct 2011)  Simian virus 40 transformation, malignant mesothelioma and brain tumors. Expert Rev Respiratory Medicine, V5; 683-697.