Mesothelioma is a rare and deadly cancer caused by the inhalation of asbestos fibers. When these tiny asbestos fibers lodge in the lining of the lungs, they can cause cellular changes that lead to the development of cancer. Any workplace or household exposure to asbestos leads to a greater risk of developing mesothelioma.
Asbestos is the only definitive cause of mesothelioma, accounting for at least 90% of mesothelioma cases. However, researchers have identified a variety of other risk factors that can increase the risk of developing mesotehlioma, like a history of smoking. Better understanding the cause of mesothelioma can help prevent the disease, promote awareness and improve detection and treatments.
Mesothelioma and Asbestos
Mesothelioma develops in the mesothelium, a thin membrane encompassing the body’s internal organs and cavities. It often takes 10 to 50 years for symptoms to manifest, making it difficult to pinpoint the cause and challenging the possibility for early detection. In the majority of cases, the cause is exposure to asbestos.
Where Does Asbestos Exposure Occur
Asbestos exposure is most common in a workplace environment, though exposure can also happen through secondary exposure in homes, in schools, at construction sites, and many other locations.
- Asbestos mines
- Auto shops and car dealerships
- Construction and demolition
- Insulation installation
- Oil refineries
- Power plants
- Roofing, carpentry and floor installation
With occupational exposure there have been many cases of secondhand exposure as well, such as family members coming into contact with clothing and materials that have collected microscopic asbestos fibers. Asbestos has also been found in common household items, such as talcum powder, potting soils, and paint. It’s important to be aware of all asbestos products and understand when you might be at high risk for exposure.
How Asbestos Causes Cancer
In the most common scenario, asbestos fibers are inhaled and eventually become embedded in the lining of the lungs, abdomen, or heart, causing harmful inflammation that eventually leads to the formation of mesothelioma tumors. Peritoneal mesothelioma is associated with the abdomen, pleural mesothelioma with the lungs, and pericardial mesothelioma with the heart.
As generally understood by researchers, asbestos can cause DNA damage both directly and indirectly. Directly, asbestos interferes with the mitosis process in cell division, which can cause cellular damage and mutation. Indirectly, asbestos can cause mesothelial cells to release mutagenic reactive oxygen and nitrogen, which also causes mutation.
Other Potential Causes of Mesothelioma
Around 90% of all mesothelioma cases are tied to known asbestos exposure. However, there are other factors that patients claim could be a potential cause or influencing factor to their malignant mesothelioma cancer.
Zeolites and Mesothelioma
Asbestos-like materials are thought to be another cause of mesothelioma. Zeolites are absorbent minerals that contain silicone and aluminum. Erionite is a certain type of zeolite that has drawn a large amount of attention with its relation to cancer. The fibrous material is naturally occurring and often found in volcanic ash. Evidence has shown a connection with the development of cancer, especially in regions where populations are exposed to erionite in their natural environment, such as Turkey.
Radiation Exposure and Mesothelioma
Some malignant mesothelioma patients claim that they were never exposed to asbestos and instead believe that the cause of their cancer was radiation exposure. While radiation is a potential secondary factor for mesothelioma, there are limited reports in establishing this connection.
Simian Virus 40 and Mesothelioma
Some mesothelioma cases show a possible connection between mesothelioma and simian virus 40 (SV40). Studies have shown a strong correlation between those that have the virus and a development of mesothelioma, though further investigation is needed.
High Aspect Ratio Nanoparticles and Mesothelioma
Commonly referenced as HARNs, high aspect ratio nanoparticles also have a suggested link with mesothelioma. HARNs are nanoparticles that have a length that is multiple times the width. Particles of this nature have been proven to be harmful to human health. Like other non-asbestos causes of mesothelioma, evidence is lacking and more research is needed.
Pre-Existing Factors in Malignant Mesothelioma
Aside from asbestos exposure and other potential causes and contributors to the development of mesothelioma, there are a variety of pre-existing factors that play a role in mesothelioma.
Age: Elderly and Mesothelioma
One common misconception of mesothelioma is that it occurs only in the elderly. 91% of those diagnosed are 55 years old, or older. However, it’s important to note the long latency period before mesothelioma symptoms emerge. Though many are diagnosed at an older age, younger adults are also being diagnosed. Studies are continuing to look at a potential link between young adults, their genetics and mesothelioma, which could change age-related statistics for the disease.
Gender: Men and Mesothelioma
Some cancers are gender-specific, such as ovarian cancer and breast cancer, affecting one gender more than the other. Mesothelioma is not gender-specific, but has been seen in higher rates in men. One potential reason for this correlation is that occupations that exposed workers to asbestos years ago were male-dominated. For example, with more men working in mining and oil refineries, more men are now developing symptoms of mesothelioma. However, in recent years, research has shown that mesothelioma rates among women are also on the rise as they are increasingly exposed on the job and through secondhand exposure.
Genetics: BAP1 and Mesothelioma
BAP1 is a tumor-suppressing gene, and if there is a mutation of the gene, tumors are more likely to develop. Individuals in families with a genetic mutation of the BAP1 gene may be more susceptible to developing mesothelioma as their tumor-suppressing capabilities are hindered.
Health: Illness and Mesothelioma
Poor health means an increased risk for developing any kind of disease, not just mesothelioma. When the body’s immune system and defenses are down, it makes it harder to fight off foreign substances. For those that have already been diagnosed with mesothelioma, poor health can also complicate treatment options and the body’s ability to respond.
Currently, there is no proof that smoking is directly linked to mesothelioma. However, many studies have shown that smokers are 50 – 90% more likely to develop asbestos-related lung cancer. Similarly, smokers exposed to asbestos are twice as likely to develop mesothelioma.
The relationship between smoking, lung disease, and various forms of cancer – especially lung cancer – is well established. There is little evidence that smoking alone increases a person’s chance of developing mesothelioma, but it is possible that smoking can cause conditions in the lungs that make it easier for asbestos to become embedded and cause inflammation, leading to cancer. These include:
- Weakening of lung tissue: Asbestos fibers can more easily become lodged in the linings of the lungs.
- Decrease in overall health: Smoking can cause a host of other medical problems, and can significantly reduce a patient’s mesothelioma treatment options and life expectancy.
- Increased mucus production: Irritation of the air passages causes them to produce more mucus. This blocks the passage of air and affects the lungs’ ability to cleanse themselves.
Cigarette Filters and Asbestos
By themselves, cigarettes contain thousands of chemicals, at least several dozen of which are classified by the International Agency for Research of Cancer as carcinogens. To supposedly make cigarettes “healthier,” some brands have filters intended to remove some of these substances, but their effectiveness is much disputed.
In fact, filters have presented their own dangers. Studies have shown that at least one brand of cigarettes – Kent, manufactured by Lorillard Company – was composed of as much as 25% asbestos. These cigarettes were sold in the United States between 1952 and 1956, with up to a half million packs being sold each day. While Kent is the only brand known to have contained asbestos, it is possible that other cigarette brands have also contained asbestos at various times.
Mesothelioma and Asbestos Awareness
Asbestos is not yet completely banned. With a mission to protect the health of both humans and the environment, the Environmental Protection Agency (EPA) has put many rules and regulations in place in regard to asbestos, though much work still has to be done to identify asbestos products. Organizations such as the National Cancer Institute have also helped by spreading awareness of asbestos and related cancer risks.
If you suspect that you’ve been exposed to asbestos, it’s important to get help immediately. Seek professional care as soon as you recognize symptoms of the asbestos-related disease, as early detection is a key factor to life expectancy. In the event that you come into contact with asbestos, don’t disturb the substance; instead contact a removal professional.
Author: Linda Molinari
Editor in Chief, Mesothelioma Cancer AllianceRead about Linda
Reviewer: Dr. James Stevenson
Medical Reviewer and Thoracic Medical OncologistRead about Dr. Stevenson
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