Whether you are experiencing symptoms of mesothelioma or were recently diagnosed, have a loved one with symptoms or a recent diagnosis, or want to take steps to prevent mesothelioma, it is important to understand what causes mesothelioma. In many cases of malignant mesothelioma, exposure to asbestos can cause this specific type of cancer, but it is essential to understand that a person can develop mesothelioma without exposure to asbestos, and many people are exposed to asbestos who never develop mesothelioma. Researchers, scientists, and medical doctors also have not yet been able to determine with specificity the amount of asbestos exposure that is necessary to cause malignant mesothelioma, so it is possible that a single, minimal, one-time exposure could cause mesothelioma, yet it is more likely that mesothelioma is caused by prolonged exposure to asbestos.
What ultimately causes mesothelioma? Asbestos is known to cause mesothelioma, but other factors can play a role in malignant mesothelioma causation.
Research Shows That Asbestos Exposure Causes Malignant Mesothelioma
Various types of research have shown that asbestos exposure can cause mesothelioma. In the twentieth and twenty-first centuries, research has been conducted on animals and humans, including autopsy studies, to determine the ways in which asbestos can cause mesothelioma. A specific study conducted on autopsies from Mount Sinai between 1883-1910, in which researchers examined more than 2,000 patient autopsies, showed that malignant mesothelioma was not present in patients at this point in time. That finding was particularly significant because asbestos was not in common use in the late nineteenth century or early part of the twentieth century. That study was published in the American Journal of Industrial Medicine in June 2011, entitled, “Rarity of Malignant Mesothelioma Prior to the Widespread Commercial Introduction of Asbestos: The Mount Sinai Autopsy Experience 1883-1910.”
According to the authors of that study: “Most malignant mesotheliomas are related to asbestos exposure. Whether malignant mesothelioma occurs in the absence of asbestos exposure remains unsettled. To address this question we reviewed a series of 2,025 autopsies performed at Mount Sinai Hospital between 1883 and 1910, prior to the widespread commercial introduction of asbestos . . . . No cases of malignant mesothelioma were identified in 2,025 autopsies performed between 1883 and 1910. Malignant mesothelioma was rare prior to the widespread commercial introduction of asbestos.”
How Much Asbestos Exposure is Necessary to Cause Malignant Mesothelioma?
Unfortunately, researchers do not yet have sufficient evidence to determine how much exposure to asbestos is necessary to cause mesothelioma. It is under what level of asbestos must be inhaled or ingested to cause mesothelioma, and it is not fully understood if one-time asbestos exposure is sufficient to cause mesothelioma, or whether a person would need multiple exposures over a period of time for the asbestos to cause mesothelioma.
According to the National Cancer Institute, “everyone is exposed to asbestos at some time during their life” because “low levels of asbestos are present in the air, water, and soil.” Yet these types of exposures do not typically cause malignant mesothelioma. Indeed, the National Cancer Institute clarifies, “people who become ill from asbestos are usually those who are exposed to it on a regular basis, most often in a job where they work directly with the material or through substantial environmental contact.”
How Asbestos Exposure Causes Malignant Mesothelioma
How does exposure to asbestos ultimately cause malignant mesothelioma for some people? The answer to that question depends upon the type of malignant mesothelioma and how the asbestos exposure occurs. When a person inhales asbestos, the asbestos fibers can travel through that person’s airways and become lodged in that person’s tissue. That initial type of exposure itself can result in irritation or tissue inflammation. Researchers believe it is possible that asbestos fibers becoming lodged in a person’s tissue can lead cells to release something known as “cytokines.” According to the National Cancer Institute, a cytokine is “a type of protein that is made by certain immune and non-immune cells and has an effect on the immune system.” Researchers do not yet fully understand whether cytokines are released as a result of the presence of the asbestos fibers in the body, or whether cytokines are released by the inflamed or damaged tissue that results initially from asbestos fibers.
How can cytokines lead to cancer, and to malignant mesothelioma in particular? It is possible, as noted above, that the inhalation or ingestion of asbestos fibers can lead the body to make cytokines. The National Cancer Institute clarifies that certain cytokines can “stimulate the immune system” while “others slow it down” and can play a role in cancer growth. In other words, cytokines can direct a person’s cells to reproduce in a particular way that results in cancerous growth.
Understanding How Asbestos Enters the Body and Causes Mesothelioma
How do asbestos fibers get lodged in the body and ultimately lead to the release of cytokines and the development of malignant mesothelioma? Asbestos fibers can either be inhaled when they are in the air, or they can be ingested if a person coughs them up and swallows them. The way in which asbestos fibers are introduced into the body is a major factor in the type of mesothelioma a person develops—either pleural mesothelioma when the asbestos fibers are inhaled or peritoneal mesothelioma when they are ingested. When asbestos fibers are inhaled, they typically travel through a person’s air passages—including the throat, the windpipe, and the bronchi—before reaching the lungs. If the body detects asbestos fibers, it might lead the person who inhaled the fibers to cough, and that person might cough up the fibers and then swallow them in the secretion that is coughed up. Yet in many circumstances, the body does not immediately recognize asbestos fibers because of how small and thin they are, so they travel into the area of the lungs.
Pleural Embedding of Asbestos Fibers Can Cause Mesothelioma
Once asbestos fibers reach a person’s lungs, they can become embedded in the pleura. When this happens, something known as pleural plaques can develop. Pleural plaques are essentially scar tissue areas in the pleura that are signs of asbestos exposure. Pleural plaques are often identified as thicker areas of tissue, and they tend to appear anywhere from 10 to 30 years after a person has been exposed to asbestos. Pleural plaques themselves do not usually require any kind of medical attention or treatment, but they can help doctors to know whether a person’s malignant mesothelioma likely results from asbestos exposure. Fibrosis can also occur when asbestos fibers become lodged, which is another form of thickening or scarring in the tissue. When a person’s tissue has become scarred or thickened due to asbestos exposure, that tissue may be described as fibrotic. When the asbestos fibers injure a person’s lungs, asbestosis can occur.
Asbestosis is a chronic condition of the lungs, according to the American Lung Association, that typically results from prolonged exposure to high amounts of asbestos that is in the air. While secondhand exposure can occur through dust and by bringing asbestos home on clothing, most people who develop asbestosis have been exposed through occupational work. Asbestosis can be linked to both malignant mesothelioma diagnoses and to lung cancer.
Abdominal Embedding of Asbestos Fibers Can Cause Mesothelioma
Asbestos fibers can also end up traveling through a person’s body through the lymph, or through the bloodstream when they are swallowed. Ultimately, these asbestos fibers find their way to a person’s abdomen, where they can also become lodged in the tissue. When asbestos fibers lodge in the abdomen, they can lead to peritoneal mesothelioma in a manner similar to how asbestos fibers lodged in the pleura ultimately result in pleural mesothelioma. It is important to know that it is often more difficult for doctors to see asbestos fibers in the abdomen, but many patients who have peritoneal mesothelioma will also have pleural plaques. The presence of such pleural plaques can serve as clear evidence of earlier asbestos exposure and the likely cause of mesothelioma.
Other Causes of Malignant Mesothelioma
While as many as 80 percent or more of malignant mesothelioma diagnoses are linked to asbestos exposure, it is important to know that there are other causes of mesothelioma, as well. According to the Mayo Clinic, the two other primary causes of malignant mesothelioma outside asbestos exposure include genetics and a history of radiation therapy to your chest for previous cancer.
Genetics can play a role in causing mesothelioma, although this is relatively rare. Genetics could be the cause of a mesothelioma diagnosis if you have a parent, a child, or a sibling who has been diagnosed with mesothelioma. A mutation in the BAP1 gene has been potentially linked to some cases of mesothelioma, and this type of mutation is passed on among family members. If you had radiation therapy to your chest to treat cancer in the past, that radiation exposure also may cause malignant mesothelioma.
There are some other potential causes for malignant mesothelioma, but they are much rarer. For example, infection with the SV40 virus may cause mesothelioma in rare cases, although this connection is still being researched. Exposure to certain zeolites also may cause mesothelioma, but this is significantly rarer than asbestos exposure causing mesothelioma.
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