The only confirmed cause of mesothelioma is asbestos exposure. However, some people develop mesothelioma without any known exposure to asbestos. The most likely explanation in these cases is unknown asbestos exposure. While many risk factors increase the risk of mesothelioma, there are few, if any, proven mesothelioma causes outside of asbestos exposure.
Medically Reviewed By:
Patricia Shelton, M.D.
Medically Reviewed By:Patricia Shelton, M.D.
Asbestos exposure occurs without immediate symptoms or warning signs that exposure has occurred. Instead, the asbestos fibers quietly damage the tissues in the body until mesothelioma develops years later. However, only a small percentage of people exposed to asbestos develop mesothelioma.
While no other cause of mesothelioma has been definitively identified, some mesothelioma cases have occurred without a known history of asbestos exposure. While heavy exposure to asbestos over a long period is associated with a higher risk of developing asbestos, some people with heavy exposures never develop it, while others with light exposures do.
This raises questions about the real causes of mesothelioma and the role asbestos exposure actually plays in its development. Despite these concerns, asbestos exposure is the only proven cause of mesothelioma. However, asbestos exposure can work with other factors to increase the risk of developing mesothelioma.
How Does Asbestos Cause Mesothelioma?
When asbestos enters the body, it stimulates an inflammatory process that can cause swelling, scarring, and DNA damage, according to a study published by Clinical Cancer Research. DNA damage may occur as a result of the following mechanisms:
- Long-term inflammation caused by the asbestos fibers
- Asbestos fibers physically separating chromosomes during cell division
- Asbestos fibers triggering cells to release free radicals and nitric oxide synthase, which alter the DNA
In addition, as the body attempts to break down the fibers, cancer-causing chemicals may be released. This process occurs when asbestos is present but not when other mineral fibers are present.
According to Cureus, asbestos exposure causes chronic inflammation leading to cell death. However, some cells that should die actually survive and undergo mutations. This occurs repeatedly over decades until mesothelioma develops.
How Much Asbestos Does It Take to Cause Mesothelioma?
The people with the highest risk of developing mesothelioma are those who experience heavy levels of daily exposure over an extended period. However, there is no safe level of asbestos, and people have developed mesothelioma after a single exposure.
The Occupational Health and Safety Administration limits the amount of asbestos permitted in occupational settings to a weighted average of one fiber per cubic centimeter over an eight-hour workday. This is known as the permissible exposure limit or PEL. However, OSHA acknowledges that even at this level, workers may develop mesothelioma.
Does Anything Other than Asbestos Cause Mesothelioma?
Potential causative factors outside of asbestos exposure are controversial. When considering this question, it is important to understand the difference between a risk factor and a cause.
- Risk factor – a condition or circumstance that increases the risk of developing mesothelioma after asbestos exposure has occurred
- Cause – a circumstance that results in mesothelioma without asbestos exposure having occurred
While scientists agree many risk factors work in tandem with asbestos exposure to increase the risk of developing mesothelioma, they disagree about whether mesothelioma can occur in humans independent of asbestos exposure.
Some researchers have identified the following risk factors as potential causes of mesothelioma in the absence of asbestos exposure:
- The SV-40 virus
- Ionizing radiation
- The BAP-1 Germline Mutation
- Unclassified asbestiform minerals
Attorneys representing asbestos companies will sometimes attribute mesothelioma to these factors to avoid liability, but the current data suggests that even these factors are more likely to be risk factors than causes.
According to Translational Lung Cancer Research, the Simian Virus 40 was transmitted to humans through the polio vaccine, which contained material from Rhesus monkey kidney cell cultures from 1954 to 1963 in the United States. Also known as SV-40, Simian Virus 40 is a DNA tumor virus that causes a variety of tumors in species other than the Rhesus monkey.
According to the study, 60 percent of hamsters injected with SV-40 directly into the pericardium, the thin lining around the heart, developed mesothelioma. In addition, 100 percent of the hamsters who received injections directly into the pleura, the membranes surrounding the lungs, developed mesothelioma.
This shocked researchers because the hamsters had no historical asbestos exposure. However, these findings have not been duplicated in humans, and the virus would never be injected directly into the human pericardium or pleura anyway.
A 1997 study by Nature Medicine found that 60 percent of human mesotheliomas tested contained the SV-40 virus—a finding that other studies have confirmed.
According to the study, at least 20 percent of mesothelioma in the United States is not associated with asbestos exposure, or at least with known asbestos exposure, and only a small percentage of people exposed to high concentrations of asbestos later develop the disease.
According to Expert Review of Respiratory Medicine, a 2011 review of the literature found some studies with a 100 percent co-occurrence of SV-40 with mesothelioma and other studies with a 0 percent occurrence. Researchers concluded that it seems unlikely that SV-40 is a cause of mesothelioma in humans by itself, but it may be a cofactor.
The following people may be exposed to ionizing radiation:
- Patients exposed to the contrast dye Thorotrast during diagnostic X-rays
- Patients who undergo radiation therapy to treat cancer
- Atomic energy workers exposed to small amounts of radiation over time
According to Cancer Causes & Control, a review of the current studies concluded that ionizing radiation may be a causative factor in the development of mesothelioma, but the current body of literature is insufficient to firmly establish this.
A 2022 study published in Cancer Medicine led to similar findings, and the data supported a strong link between ionizing radiation and mesothelioma, whether exposure occurred in short-term high doses, such as during radiotherapy, or in low doses over time, such as in an occupation.
This study found an increase in mesotheliomas among individuals exposed to radiation but noted the following hurdles in arriving at a conclusive determination of a causative link:
- Frequent misdiagnosis and misclassification of mesothelioma
- Rarity of mesothelioma
- Lack of standardization and reporting of mesothelioma diagnoses
Limited data supports the conclusion that radiation applied to areas near the abdominal area is associated with peritoneal mesothelioma. The data shows a slightly stronger association between radiation for lymphomas and pleural mesothelioma.
While scientists have not ruled out the possibility that ionizing radiation may cause mesothelioma without asbestos exposure, they also have not identified sufficient data to conclude that it does.
BAP-1 Germline Mutation
The BAP-1 germline mutation is also known as the cancer gene, and it makes some families especially susceptible to developing a variety of cancers, including mesothelioma. The Journal of Translational Medicine published a case study of a mesothelioma patient with the BAP-1 germline mutation and no known history of asbestos exposure.
The researchers found that mesothelioma may run in families and observed that mesothelioma tends to occur in this population differently from the regular population, with the following unusual variances:
- Higher incidence of peritoneal mesothelioma
- Younger age at diagnosis, with many patients younger than 55
- Longer overall survival
The average age of diagnosis of pleural mesothelioma in the general population is 72. Approximately one percent of mesothelioma occurs in people with the BAP-1 germline mutation. It was apparent in this study that people with the mutation were highly susceptible to mesothelioma.
However, susceptibility does not equal causation. According to the Annals of Translational Medicine, the development of mesothelioma in people with the BAP-1 germline mutation requires at least some asbestos exposure, even if it is a very small amount.
This is an example where a risk factor explains why some people can develop mesothelioma with only minor asbestos exposure.
Unclassified Asbestiform Minerals
Asbestos is defined as a group of six naturally-occurring silicate minerals, including the following:
However, there are several other types of silicate minerals, some of which bear striking similarities to those classified as asbestos. These minerals were never classified because they were not used commercially. There is some evidence that they may cause mesothelioma and perhaps should be classified as asbestos.
These minerals include the following:
- Some forms of talc
According to the International Association for the Study of Lung Cancer, Clark and Nye Counties in southern Nevada have naturally-occurring asbestos deposits, including actinolite, erionite, winchite, magnesio-riebeckite, and richterite. Women and individuals younger than 55 have been diagnosed with malignant mesothelioma at higher-than-expected levels in these areas.
The infamous vermiculite mine in Libby, Montana, turned out to be contaminated with asbestos. This mine was the largest source of vermiculite in the world. It was contaminated with tremolite asbestos, an amphibole form of asbestos considered more dangerous than the more common serpentine type, chrysotile.
While the Libby mesothelioma cases have been attributed to tremolite asbestos, the vermiculite was also contaminated with erionite and winchite, according to Current Opinion in Pulmonary Medicine.
Erionite has also been found in natural deposits in the following states, according to the American Cancer Society:
- South Dakota
Another mineral commonly contaminated with asbestos is talc. While talc is not considered dangerous, according to a study published in Electron Microscopy, it can take on a fibrous form leading to scar tissue in humans and animals. While it can be differentiated from asbestos analytically, it bears some similarities.
The researchers believe the current literature and ongoing studies point to talc being carcinogenic on its own and in conjunction with asbestos based on its proven ability to produce an inflammatory response.
Known Mesothelioma Risk Factors
The known risk factors for mesothelioma include details and circumstances surrounding the asbestos exposure and personal characteristics. Risk factors cannot cause mesothelioma by themselves. Instead, they increase the risk of developing mesothelioma when asbestos exposure occurs.
These risk factors may increase the risk of the following in relation to mesothelioma:
- The likelihood of contracting mesothelioma
- A worsened prognosis if mesothelioma develops, resulting in a shorter life expectancy
- A shorter latency period, meaning diagnosis at a younger age
Occupational Asbestos Exposure
Workers exposed to asbestos in the workplace are most likely to develop mesothelioma. The workers with the highest risks are those who handled asbestos directly or were otherwise exposed to heavy asbestos concentrations regularly over an extended period.
The occupations with the highest risks of asbestos exposure include the following:
Living with Someone with Occupational Asbestos Exposure
Living with a worker exposed to asbestos occupationally has been shown to increase the risk of developing mesothelioma. This occurs because workers may bring asbestos fibers home on their clothing, which may expose other family members. This is known as secondary asbestos exposure.
Living in an Older Home
Homes were commonly built with asbestos materials from the 1930s until approximately 1980. Living in a home with asbestos may increase your risk of developing mesothelioma.
Asbestos was used in nearly every component of home construction, from the roof to the foundation, including in the following:
Having asbestos in your home is not always hazardous if the asbestos and the containing material are undisturbed and undamaged. However, some asbestos, such as the asbestos in popcorn ceilings, can be easily disturbed and are almost always hazardous. In addition, cutting or drilling into a wall or other structure containing asbestos can release it, making it hazardous.
If your house contains loose-fill vermiculite insulation and was built before 1990, this insulation may have come from an asbestos-contaminated mine in Libby, Montana. This product was sold under the brand name Zonolite.
Several states have naturally-occurring asbestos deposits, some of which were commercially mined. If you live near these sites, whether or not the area was mined, the asbestos may be disturbed through erosion, storms, animal activity, and human activity.
This could increase your risk of exposure, which increases your risk of developing mesothelioma. The states with naturally-occurring asbestos deposits include the following:
Living or Working Near the World Trade Center After the 9/11 Terrorist Attacks
During the terrorist attack on the World Trade Center in New York City on September 11, 2001, a plume of dust containing numerous toxic chemicals, which included 400 tons of asbestos. People exposed to this toxic plume have an increased risk of developing mesothelioma and other related illnesses. Mesothelioma cases have only recently begun to emerge.
Demographics with Higher Mesothelioma Incidence
Certain inborn characteristics statistically increase your odds of being diagnosed with mesothelioma. They include the following:
- Mature age
Mesothelioma can occur in nearly any demographic, but it is most common in older white males. Mesothelioma in people under the age of 50 is rare.
Does Smoking Increase the Risk of Mesothelioma?
There is no connection between smoking and mesothelioma. Smoking neither causes nor increases the risk of developing mesothelioma. However, if you have been exposed to asbestos and smoke, these two factors create a synergistic effect resulting in a 50-fold increase in the risk of developing lung cancer.
How Can I Reduce the Risk of Developing Mesothelioma?
Avoiding asbestos is the only proven way to eliminate the risk of developing asbestos. If you have already been exposed to asbestos, you may be able to slightly reduce your risk of developing mesothelioma by avoiding additional asbestos exposure.
How to Avoid Asbestos Exposure
Avoiding asbestos exposure can be challenging because it was widely used before 1980. It was and may still be present in nearly every pre-1980 building, including homes, schools, government buildings, and commercial buildings. It may also still be used in some occupations without your knowledge.
However, the following tips can help you minimize the likelihood of asbestos exposure:
- Avoid working in professions with a known history of asbestos exposure.
- Before purchasing a home built before 1980, have it inspected by a state-certified asbestos inspector.
- Be aware of the locations of asbestos deposits in your state and avoid living near them.
- Avoid buildings damaged by demolitions, fires, and natural disasters, especially if built before 1990.
Unfortunately, it is not always possible to avoid being exposed to asbestos. The good news is that asbestos is no longer in popular use today, and the likelihood of experiencing long-term, cumulative asbestos exposure is low.
We Are Here to Help If You or Your Loved One Has Contracted Mesothelioma
If you have contracted mesothelioma, the Lanier Law Firm may be able to help you recover substantial compensation. Contact us today for a free consultation.