Risk Factors of Mesothelioma

The predominant cause of mesothelioma is exposure to asbestos - according to some estimations cancer of mesothelium is caused by asbestos exposure in about 80% of all patient. For that reason the greatest risk factor of mesothelioma is direct or indirect contact with asbestos and asbestos products although mesothelioma has been also reported in people without known exposure to asbestos. However, some experts are convinced that the percentage of people who suffer from mesothelioma because of exposure to asbestos would be a lot higher if their contact with asbestos would be better researched. Asbestos was not only used in construction and building industries but in variety of other industries and manufacture of products such as automobile brake pads and even textiles, and thus many people could be exposed to asbestos without even being aware of it.

The risk of mesothelioma, like other asbestos related diseases, is the greatest in people who worked with asbestos such as people who worked in asbestos mines and mills, workers who manufactured asbestos products, workers in the construction industry, shipbuilders, demolition workers as well as all who lived near asbestos mines, mills and factories. In greater risk of developing mesothelioma are also family members and others living with asbestos workers who could have brought asbestos fibers home on their clothes or hair. However, all who had been heavily exposed to asbestos do not develop mesothelioma or any other asbestos related disease, while asbestos fibers were fatal for many people who were exposed to asbestos only for a sort period. The amount of asbestos fibers that needs to be inhaled to cause mesothelioma is unknown but in theory already one asbestos fiber is potentially carcinogen. Either way, incidence of mesothelioma is higher in people who have been heavily exposed to asbestos.

There is no association between smoking and mesothelioma but experts assume that a combination of smoking and asbestos exposure greatly increases the risk of developing mesothelioma.

Who are at high risk for development of mesothelioma?

Asbestos is mined, milled and used in a variety of industrial and commercial products. Asbestos was used in insulations, textile industry, heat protectors, filters, and construction industry. Occupational exposure to asbestos may have occurred to asbestos miners, millers and producers of asbestos products, and workers who install plumbing, boilers and heating equipment in ships factories and homes. It is not necessary for the worker to handle the asbestos products directly to have a higher risk of developing mesothelioma, but working in the environment in proximity to asbestos may be sufficient. Carpenters, electricians, welders and many other workers who may have worked in the shipyard may have been exposed to asbestos and could be in the high-risk category for mesothelioma.

Mesothelioma exposure puts grave risk to the workers. One study has suggested that up to 10% asbestos workers may have died as the direct result of mesothelioma development. The time period between the initial exposure to a disease causing agent and development of disease known as lag period. Mesothelioma is a disease with a very long lag period. Average lag period associated with the development of mesothelioma is around 30 to 40 years and it could be as long as 65 years or more. Different subtypes of asbestos are associated with varying risk of development of mesothelioma. A subtype of asbestos, namely crocidolite is shown to be associated with higher risk of mesothelioma in miners, manufacturers and workers who install asbestos products. Another subgroup, amosite is associated with intermediate risk of development of mesothelioma. Chrysolite, which is currently the major form of asbestos in production, probably has the weakest association with the development of mesothelioma. Prior to restrictions imposed on asbestos use, a variety of workers were exposed to asbestos. The high-risk workers included asbestos minors, insulators, asbestos producers and asbestos manufacturers. Heating and construction workers also had very high risk of exposure to asbestos. People in this occupation with history of exposure to asbestos during early adulthood have a very high risk of development of mesothelioma. It is estimated that such workers have a lifetime risk of about 20 percent for the development of mesothelioma. The risk of mesothelioma development is not confined to workers who directly handle asbestos products as in the case of workers mentioned above. Other workers who work in close proximity to these occupational groups in construction sites, but had no direct contact with asbestos, have a high risk of development of mesothelioma. Workers who had no direct contact with asbestos have a relatively lower risk of development of mesothelioma compared to those who worked in direct contact. Exposure to asbestos may also increase the risk of other cancers. These cancers include lung cancer (about 4 to 5 fold increase) and pancreatic cancer.

People At Risk for Mesothelioma

Unfortunately, there are numerous people at risk for Mesothelioma based on the types of jobs they have had. For example, the following trades or occupations are considered as high risk: oil refinery workers, people working in factories that manufacture asbestos, mechanics, tile contractors, rail yard and power plant workers, shipyard workers, construction workers, brick layers, ship builders, welders, electricians, sand blasters, plumbers, and sheet metal workers.

Individuals At Risk For Developing Mesothelioma

The following represents some of the individuals who are at risk for developing mesothelioma or asbestosis.

• Brick layers, plumbers, sand blasters, sheet metal workers, millwrights, welders, painters, longshoremen, merchant marines, grinders, electricians, drywall contractors, miners, drillers, building inspectors and maintenance personnel.

• Any job that includes the manufacturing of asbestos, for example: insulation, fireproofing, plumbing supplies, roofing components, or other building materials and supplies such as cement, pipe coverings, refractory materials, gaskets, floor tiles and joint compounds.

• Individuals employed in the railroad, factory, shipyard, automobile, and construction and building industries during the last six decades.
  

• People working in factories that manufacture asbestos.

• Mechanics are at risk due to asbestos that is used in brake and clutch linings.

• Tile contractors are at risk due to the dust from cutting some types of tile.

There is strong evidence in the medical literature that the dangers of asbestos exposure were known long before millions of American workers were exposed.

• Oil refinery workers, rail yard and power plant workers can be at risk from various sources of asbestos.

• Shipyard and/or ship builders are at risk due to the asbestos in pipe insulation and other sources.

What type of jobs are at risk for developing asbestosis or mesothelioma? Any job that includes the manufacturing of asbestos, for example: insulation, fireproofing, plumbing supplies, roofing components, or other building materials and supplies such as cement, pipe coverings, refractory materials, gaskets, floor tiles and joint compounds.

• Steel mill workers can come into contact with asbestos from a variety sources due to the fact that steel mills frequently use asbestos as an insulator (especially when employees are required to work in high-temperature areas).

• Navy veterans and maritime workers.
  
• Construction workers can be at risk, especially those who do demolition of older buildings

Individuals employed in the railroad, factory, shipyard, automobile, and construction and building industries during the last six decades are at the risk of developing asbestosis or mesothelioma symptoms.

People At Risk for Mesothelioma: Conclusion

Regrettably, there are many people at risk for Mesothelioma due to the types of employment they have had.

For instance, the following trades or occupations are considered as high risk: rail yard and power plant workers, mechanics, oil refinery workers, shipyard workers, construction workers, sand blasters, brick layers, sheet metal workers, people working in factories that manufacture asbestos, ship builders, electricians, tile contractors, welders, and plumbers.

Mesothelioma Risk Factors

Risk factors are environmental, hereditary, or behavioral conditions that increase a person’s chances of getting a disease. Risk factors do not control whether someone gets a disease or not; they are simply the statistically-associated factors that seem to indicate that the development of a disease is more likely. For example, the primary risk factor for developing lung cancer is whether a person smokes tobacco or not. Other factors such as diet, hereditary predisposition to cancer, and so forth also affect the odds, and are also considered risk factors in assessing the chances that someone will develop the disease.

For malignant mesothelioma, the primary risk factor is absolutely clear: exposure to asbestos. Approximately 90 percent of malignant mesothelioma cases are in individuals who have had major occupational or environmental exposure to asbestos. At least eight million Americans have had sufficient exposure to asbestos, either in their jobs, through exposure to friable asbestos in commercial products or in homes or schools, or through secondary exposure to someone who worked in asbestos-using industries, to be considered at risk for malignant mesothelioma.

There are three primary factors in determining the risk posed to an individual by asbestos exposure: the time of the exposure, the duration of the exposure, and the level of the exposure. Malignant mesothelioma has a very long latency period – from 20 to 50 years in the majority of cases. Exposure to asbestos at young ages is therefore worse than exposure at an older age; asbestos exposure at age 70, for example, is unlikely to develop into malignant mesothelioma since the exposed person is likely to die of other causes long before the mesothelioma has a chance to form.

Exposure to high levels of asbestos is worse than exposure to modest levels; it is better to have gone to school in a building with some crumbling asbestos tiles than to have worked in an asbestos mine. Exposure over a long period of time is worse than exposure for brief periods. One grim fact of asbestos exposure and mesothelioma risk is that the passage of time without exposure does not reduce the risk; the body does not repair or recover from asbestos exposure the way it can from things like tobacco smoking.

Although asbestos exposure is the primary risk factor for mesothelioma, there are some other risk factors which can contribute to the disease.

Radiation, specifically exposure to thorium dioxide, has been linked to at least a few cases of mesothelioma.

Zeolite, a silicate mineral found mainly in Turkey, is similar to asbestos and is thought to have a similar ability to cause malignant mesothelioma.

Tobacco smoking, although not a direct risk factor, has been found to increase the incidence of mesothelioma in patients who also were exposed to asbestos.

The SV40 virus, a simian virus which some 10 to 30 million Americans were exposed to during the early days of the polio vaccine, is thought by some researchers to contribute to the development of malignant mesothelioma.

Risk Factors for Malignant Mesothelioma

A risk factor is anything that affects your chance of getting a disease such as cancer. Different cancers have different risk factors. For example, exposing skin to strong sunlight is a risk factor for skin cancer. Smoking is a risk factor for cancers of the lung, mouth, larynx (voice box), bladder, kidney, and several other organs. But risk factors don't tell us everything. Having a known risk factor, or even several risk factors, does not mean that you will get the disease. And some people who get the disease may not have had any known risk factors. Researchers have found some factors that increase a person's risk of mesothelioma. Asbestos The main risk factor for developing mesothelioma is exposure to asbestos. In fact, most cases of mesothelioma have been linked to asbestos exposure in the workplace. Asbestos refers to a family of fibrous minerals made of silicate. It is a naturally occurring mineral that can be found in dust and rocks in certain parts of the United States and other parts of the world. There are 2 main forms of asbestos: Serpentine (curly) fibers include chrysotile, the most widely used form of asbestos. Amphiboles are thin, rod-like fibers. There are 5 main types -- crocidolite, amosite, anthrophylite, tremolite, and actinolyte. Amphiboles (particularly crocidolite) are considered to be more likely to cause cancer. However, even the more commonly used chrysotile fibers are linked with mesotheliomas. When chrysotile fibers in the air are inhaled, they tend to stick to mucus in the throat, trachea (windpipe), or bronchi (large breathing tubes of the lungs) and are then cleared by being coughed up or swallowed. But the long, thin amphibole fibers are less readily cleared, and they may reach the ends of the small airways and penetrate into the pleural lining of the lung and chest wall. These fibers may then injure mesothelial cells of the pleura, and eventually cause mesothelioma. Asbestos fibers can also damage cells of the lung and result in asbestosis (formation of scar tissue in the lung) and/or lung cancer. Indeed, asbestosis, mesothelioma, and lung cancer are the 3 most frequent causes of death and disease among people with heavy asbestos exposure. Peritoneal mesothelioma, which forms in the abdomen, may result from coughing up and swallowing inhaled asbestos fibers. Because of its heat and fire resistant properties, asbestos was once used in many products such as insulation, floor tiles, door gaskets, soundproofing, roofing, patching compounds, fireproof gloves, ironing board covers, and brake pads. The link between asbestos and mesothelioma has become well known, so its use in the United States has decreased dramatically. Most use stopped after 1989, but it is still used in some products. Still, millions of Americans may already have been exposed to asbestos. People at risk for workplace asbestos exposure include some miners, factory workers, insulation manufacturers and installers, railroad and automotive workers, ship builders, gas mask manufacturers, and construction workers. Family members of people exposed to asbestos at work also have an increased risk of developing mesothelioma because asbestos fibers can be carried home on the clothes of the workers. The incidence rate for mesothelioma in men appears to be dropping, probably because there is now much less direct exposure to asbestos in industrial workplaces. Asbestos was also used in the insulation of many older homes, as well as commercial and public buildings around the country, including some schools. Because these particles are contained within the building materials, they are not likely to be found in the air in large numbers. The risk of exposure is thought to be much less hazardous unless the particles are somehow escaping into the air, such as when building materials begin to decompose over time, or during remodeling or removal. The risk of developing mesothelioma is related to how much asbestos a person was exposed to and how long this exposure lasted. People exposed at an early age, for a long period of time, and at higher levels are more likely to develop this cancer. Mesotheliomas take a long time to develop. The time between first exposure to asbestos and diagnosis of mesothelioma is usually between 20 and 50 years. Unfortunately, the risk of mesothelioma does not drop with time after exposure to asbestos. The risk appears to be lifelong and undiminished. For more detailed information on asbestos, see our document, Asbestos. Zeolites Zeolites are silicate minerals that are chemically related to asbestos. An example is erionite, which is common in the soil in parts of Turkey. High mesothelioma rates in these areas are believed to be due to exposure to this mineral. Radiation There have been a few published reports of mesotheliomas that developed following exposure to high doses of radiation to the chest or abdomen or after injections of thorium dioxide (Thorotrast). This material was used by doctors for certain x-ray tests until the 1950s. Thorotrast was found to cause cancers, so it has not been used for many years. SV40 virus Some studies have raised the possibility that infection with simian virus 40 (SV40) might increase the risk of developing mesothelioma. Some injectable polio vaccines given between 1955 and 1963 were contaminated with SV40. As many as 30 million people in the United States may have been exposed to the virus. Some lab studies have suggested that SV40 infection may cause mesothelioma. For example, intentional infection with SV40 of some lab animals, such as hamsters, causes mesotheliomas to develop. Researchers also have noticed that SV40 can cause mouse cells grown in dishes to become cancerous, and that asbestos increases the cancer-causing effect of SV40 on these cells. Other researchers have found SV40 DNA in some biopsy specimens of human mesotheliomas. But fragments of SV40 DNA can also be found in some non-cancerous human tissues. So far, the largest studies addressing this issue in humans have not found an increased risk for mesothelioma or other cancers among people who received the contaminated vaccines as children. But the peak age range for diagnosis of mesothelioma is 50 to 70 years. Some researchers have pointed out that this issue may remain unresolved until more of the people accidentally exposed to SV40 between 1955 and 1963 reach that age range. Most experts have concluded that at this time we still don't know whether SV40 is responsible for some mesotheliomas. Research into this important topic is still under way.

Mesothelioma Risk Factors

There are several risk factors for mesothelioma. A risk factor is something that increases the chance that a person may develop a disease. Having a risk factor does not guarantee a person will develop mesothelioma, it only increases the risk of developing it.

Mesothelioma Risk Factors

Asbestos Exposure
Asbestos exposure is the primary risk factor for mesothelioma. Asbestos is a group of minerals once used in industrial and construction materials, but is now produced in small quantities. Asbestos was once found in products like:

tile and flooring

insulation

door gaskets

roofing materials

cement

plaster of paris

joint compound

textured paint

It is estimated that about 8 million Americans have been exposed to asbestos. It generally takes 20-50 years for mesothelioma symptoms to present themselves after a person is exposed to asbestos.

Smoking and Asbestos Exposure
The combination of tobacco smoking and exposure to asbestos can greatly increase the risk factor for developing mesothelioma. According to the American Cancer Society, no studies currently link smoking alone to mesothelioma.

Radiation

In the past, certain x-rays used a material called thorium doxide. It was later to have been found to cause mesothelioma. Fortunately, it is no longer in use.

Zeolite
Zeolite is a natural occurring mineral in the Turkish region, Anatoli. Zeolite is found in the soil and is very similar to asbestos.

If You Think You're at Risk for Mesothelioma...

Talk to you doctor, if you feel you are at risk for developing mesothelioma. Together you can monitor your health and decide a course of action for possible screening methods.

Keep in mind that mesothelioma is a very slow moving disease. People usually do not develop symptoms for decades after being exposed to asbestos.

Mesothelioma

Diagnosing mesothelioma is often difficult, because the symptoms are similar to those of a number of other conditions. Diagnosis begins with a review of the patient's medical history. A history of exposure to asbestos may increase clinical suspicion for mesothelioma. A physical examination is performed, followed by chest X-ray and often lung function tests. The X-ray may reveal pleural thickening commonly seen after asbestos exposure and increases suspicion of mesothelioma. A CT (or CAT) scan or an MRI is usually performed. If a large amount of fluid is present, abnormal cells may be detected by cytology if this fluid is aspirated with a syringe. For pleural fluid this is done by a pleural tap or chest drain, in ascites with an paracentesis or ascitic drain and in a pericardial effusion with pericardiocentesis. While absence of malignant cells on cytology does not completely exclude mesothelioma, it makes it much more unlikely, especially if an alternative diagnosis can be made (e.g. tuberculosis, heart failure).

If cytology is positive or a plaque is regarded as suspicious, a biopsy is needed to confirm a diagnosis of mesothelioma. A doctor removes a sample of tissue for examination under a microscope by a pathologist. A biopsy may be done in different ways, depending on where the abnormal area is located. If the cancer is in the chest, the doctor may perform a thoracoscopy. In this procedure, the doctor makes a small cut through the chest wall and puts a thin, lighted tube called a thoracoscope into the chest between two ribs. Thoracoscopy allows the doctor to look inside the chest and obtain tissue samples.

If the cancer is in the abdomen, the doctor may perform a laparoscopy. To obtain tissue for examination, the doctor makes a small incision in the abdomen and inserts a special instrument into the abdominal cavity. If these procedures do not yield enough tissue, more extensive diagnostic surgery may be necessary.

Typical immunohistochemistry results

Positive	Negative
EMA (epithelial membrane antigen) in a membranous distribution	CEA (carcinoembryonic antigen)
WT1 (Wilms' tumour 1)	B72.3
Calretinin	MOC-3 1
Mesothelin-1	CD15
Cytokeratin 5/6	Ber-EP4
HBME-1 (human mesothelial cell 1)	TTF-1 (thyroid transcription factor-1)

Mesothelioma

Symptoms of mesothelioma may not appear until 20 to 50 years after exposure to asbestos. Shortness of breath, cough, and pain in the chest due to an accumulation of fluid in the pleural space are often symptoms of pleural mesothelioma.

Symptoms of peritoneal mesothelioma include weight loss and cachexia, abdominal swelling and pain due to ascites (a buildup of fluid in the abdominal cavity). Other symptoms of peritoneal mesothelioma may include bowel obstruction, blood clotting abnormalities, anemia, and fever. If the cancer has spread beyond the mesothelium to other parts of the body, symptoms may include pain, trouble swallowing, or swelling of the neck or face.

These symptoms may be caused by mesothelioma or by other, less serious conditions.

Mesothelioma that affects the pleura can cause these signs and symptoms:

• Chest wall pain
• Pleural effusion, or fluid surrounding the lung
• Shortness of breath
• Fatigue or anemia
• Wheezing, hoarseness, or cough
• Blood in the sputum (fluid) coughed up (hemoptysis)

In severe cases, the person may have many tumor masses. The individual may develop a pneumothorax, or collapse of the lung. The disease may metastasize, or spread, to other parts of the body.

Tumors that affect the abdominal cavity often do not cause symptoms until they are at a late stage. Symptoms include:

• Abdominal pain
• Ascites, or an abnormal buildup of fluid in the abdomen
• A mass in the abdomen
• Problems with bowel function
• Weight loss

In severe cases of the disease, the following signs and symptoms may be present:

• Blood clots in the veins, which may cause thrombophlebitis
• Disseminated intravascular coagulation, a disorder causing severe bleeding in many body organs
• Jaundice, or yellowing of the eyes and skin
• Low blood sugar level
• Pleural effusion
• Pulmonary emboli, or blood clots in the arteries of the lungs
• Severe ascites

A mesothelioma does not usually spread to the bone, brain, or adrenal glands. Pleural tumors are usually found only on one side of the lungs.

Mesothelioma

Mesothelioma is a form of cancer that is almost always caused by exposure to asbestos. In this disease, malignantcells develop in the mesothelium, a protective lining that covers most of the body's internal organs. Its most common site is the pleura (outer lining of the lungs and internal chest wall), but it may also occur in the peritoneum (the lining of the abdominal cavity), the heart,^[1] the pericardium (a sac that surrounds the heart) or tunica vaginalis.

Most people who develop mesothelioma have worked on jobs where they inhaled asbestos particles, or they have been exposed to asbestos dust and fiber in other ways. Washing the clothes of a family member who worked with asbestos can also put a person at risk for developing mesothelioma.^[2] Unlike lung cancer, there is no association between mesothelioma and smoking, but smoking greatly increases risk of other asbestos-induced cancer.^[3] Compensation via asbestos funds or lawsuits is an important issue in mesothelioma (see asbestos and the law).

The symptoms of mesothelioma include shortness of breath due to pleural effusion (fluid between the lung and the chest wall) or chest wall pain, and general symptoms such as weight loss. The diagnosis may be suspected with chest X-rayand CT scan, and is confirmed with a biopsy (tissue sample) and microscopic examination. A thoracoscopy (inserting a tube with a camera into the chest) can be used to take biopsies. It allows the introduction of substances such as talc to obliterate the pleural space (called pleurodesis), which prevents more fluid from accumulating and pressing on the lung. Despite treatment with chemotherapy, radiation therapy or sometimes surgery, the disease carries a poor prognosis. Research about screening tests for the early detection of mesothelioma is ongoing.

Mesothelioma Risk Factors

In as many as 75-85% of mesothelioma cases, there is a history ofexposure to asbestos. The material was used extensively in numerous industries from the early 1900’s through the 1960’s. Through the World War II era, over 8 million workers were exposed to asbestos. Evidence that serious health problems were related to asbestos began to mount, and in 1999, a conclusive link between asbestos exposure andmesothelioma was made.

Because it can take as long as 50 years for mesothelioma to develop, anyone who has been exposed should be evaluated by a physician experienced in this form of cancer. Even if you are not ill, you should learn about your legal rights in case mesothelioma is found in the future.

Asbestos is a broad term which refers to a collection of minerals know as asbestiform. It is a small mineral comprised of tiny fibers. Asbestos fibers exist in two forms; they can be either amphibole or serpentine (chrysotile). Several studies suggest that the amphibole form of asbestos is more dangerous than the chrysotile form, especially in mesothelioma.

These small particles float in the air, in an exposed environment and they may be inhaled or swallowed. Asbestos fibers breathed into the lungs cannot be expelled; they become embedded in the thin lining of the lungs, the mesothelium. Over the period of many years, cells in the mesothelium can become cancerous. In most cases of mesothelioma, it takes decades for the disease to cause symptoms.

Although a serious hazard to your health, asbestos is an excellent insulating material. It is used in many products that need to withstand high heat such as home insulation and construction, brake pads, electrical equipment, hot water piping, boilers, ship engines, and welding supplies. People who have worked in these industries should be screened regularly for the development of lung disease.

When the asbestos is contained within finished products such as walls and tiles, it does not appear to pose a health as long as it is not damaged or disturbed. However, damage or inadvertent destruction can release dangerous fibers into the air. When asbestos fibers are set free and inhaled, however, exposed individuals are at risk of developing an asbestos-related disease.

While smoking has not been found to cause mesothelioma, smoking has been linked to an increased incidence in mesothelioma in asbestos exposed workers. Therefore, if you have had occupational e exposure to asbestos, smoking could raise the risk of developing mesothelioma.

Asbestos exposure

The most common way in which people are exposed to asbestos is through their work. There are a number of jobs in which exposure to asbestos may have occurred. Asbestos has been extensively used in industrial products, including cement, brake linings, roof shingles, flooring products, textiles, and insulation as well as shipbuilding and other forms of construction. The risk of developing Mesothelioma increases according to the length and level of exposure to asbestos.

The number of workers exposed to asbestos far exceeds the number of documented cases. The reasons why some people who are exposed to asbestos do not develop the disease are not well understood.

The risk of developing asbestos-related diseases varies with the type of industry in which the exposure occurred and with the extent of the exposure. According to the Environmental Protection Agency (EPA) there is no safe level of exposure to asbestos fibers. The Occupational Safety and Health Administration (OSHA), however, has set a Permissible Exposure Limit (PEL) of 0.1 fibers per cubic centimeter (f/cc) for an 8 hour time weighted average. The safest course of action is to limit exposure and always wear protective gear when dealing with any type of suspected asbestos.

Hidden asbestos risks

The risk of developing mesothelioma is not just confined to the person directly exposed but may extend to family members and friends of those directly exposed. Even someone who has not been directly exposed or has been exposed at very low levels is at risk may develop the disease.

An increasing incidence of mesothelioma in spouses and children whose only to asbestos was from the dust laden work clothes of a family member is being reported. People who were in contact with workers in asbestos related injuries should also be vigilant for symptoms and be screened for lung disorders regularly.