Side B: The biggest risk factor by far of developing mesothelioma is exposure to asbestos particles, often at work. Asbestos exposure occurred in 70-80 percent of people with mesothelioma. Diagnosis usually occurs 20 to 50 years after exposure, and even low levels of exposure can be carcinogenic to some. Family members of exposed people have higher rates of occurrence as well, due to particles brought into the home from work. Mesothelioma is more common in men, people over 65 and white people.
Other theorized risk factors include exposure to simian virus 40 through old polio vaccines, radioactive thorium dioxide and the asbestos-like mineral zeolite.
Mesothelioma is relatively rare. About 2,000 to 3,000 people are diagnosed in the U.S. each year, but these rates seem to be going down. The average life expectancy after diagnosis is one year. The 5-year relative survival rate for mesothelioma is about 10 percent, but new treatments offered today may improve survival rates for those recently diagnosed.
Exposure to asbestos is the greatest risk factor for the development of mesothelioma, causing 80% of all cases, but it can also occur in the absence of exposure. Heavy concentrations and longer duration of exposure results in a greater risk for the disease, but shorter exposure times have also caused the disease. Men and women seem to be affected equally, but since more men work with asbestos, they have a higher incidence. Smoking AND asbestos exposure greatly multiplies the risk.
The U.S. Occupational Safety and Health Administration (OSHA) is responsible for setting the limits of asbestos exposure. Those who work with asbestos must wear equipment that reduces the risk of exposure. Workers should shower and change clothes at work to avoid bringing asbestos home with them, since family members have been known to contract the disease in this way.
Mesothelioma is a rare cancer, representing less than 1% of all cancers. In the United States in 2000, there were only 2300 cases of mesothelioma diagnosed. The single, greatest risk for developing mesothelioma is exposure to asbestos, either in the workplace or at home. Typically patients who have had a long-term exposure to asbestos are at the highest risk of developing mesothelioma. However, some cases have been documented when patients have only been exposed to asbestos for a short time, such as one to two months. Other risk factors involve living with a person who was exposed to asbestos in their work environment, due to the fact that asbestos could be embedded in a worker’s clothing or hair. The combination of tobacco use and asbestos also greatly increases the risk of developing mesothelioma in the lung lining. Often, it takes 20-50 years after the asbestos exposure before mesothelioma is detected.
People who have been exposed to asbestos are at high risk for mesothelioma. Although the duration of exposure is directly related to the incidence of development of the disease, people with only casual exposure have developed mesothelioma. There are also people who have been exposed who do not develop the disease.
Asbestos is a fibrous substance used in the construction of buildings prior to 1989, when the EPA banned it for all new uses. Asbestos was used for insulation, for strengthening substances used in construction, such as cements and adhesives, and in the manufacture of fire-retardant materials. The dust and fibers from these products, when inhaled or digested, can cause the disease.
Construction workers have traditionally been the most at risk group, as have their families when the fiber or dust was brought home on clothing. Symptoms often do not appear for over twenty years after exposure.
One of the major risk factors for mesothelioma is asbestos exposure. The disease has a long latency phase and may present 40 years after exposure. The mechanism of action of asbestos causing mesotheliomas is not clearly known but may be related to prolonged exposure of the serous membranes to a foreign body. The fibers may be inhaled or ingested and remain in the body. There are two types of fibers associated with asbestos; Crocidolite, which is the most carcinogenic, and Chrysotile. Tumor growth usually begins in the inferior chest wall. Eventually mesothelioma will grow and encase the chest wall causing lung restriction. Typically mesothelioma does not metastases distantly, but remains confined to the chest cavity.
• The main risk factor is exposure to asbestos. In fact, about 70% to 80% of patients with malignant mesothelioma report a history of asbestos exposure.
• Occupational asbestos exposure includes miners, ship builders, automobile manufacturing, insulation manufacturing, railroad workers or construction workers.
• Exposure can also occur in household environments from exposure to asbestos containing products including insulation materials, brake linings, roof shingles, flooring products, cement, textiles, and paint.
• There is an estimated 8% lifetime risk of asbestos workers developing mesothelioma. In a study conducted on asbestos insulation workers, the death rate from mesothelioma was 344 times higher than in the general population.
• Family members of asbestos workers have an increased risk of mesothelioma because asbestos dust is carried home on clothing.
• There is no association between mesothelioma and smoking.
Mesothelioma may occur in men and women of any age. The most common risk factor is a history of asbestos exposure. As asbestos particle separate, they float in the air and may be inhaled or swallowed by a person. This is the main reason why the most common asbestos exposure causing mesothelioma is in the pleura. Smoking has not been proven to cause mesothelioma. However, if a person has a history of asbestos exposure it is very important to educate a person about cessation of smoking due to the increased risk of lung cancer. Today, the United States Occupational Safety and Health Administration (OSHA) have set limits for the acceptable levels of asbestos exposure. People that have occupations in which they may come in contact with asbestos are required to wear protective equipment to decrease their exposure levels.
The typical patient with mesothelioma will be a male in his 50s to 70s with a history of working in a profession where there is a high risk of exposure to asbestos.
Professions with a high risk of asbestos exposure include construction workers, railroad workers, naval mechanics, bakers, automobile mechanics and explosive workers.
Women also do develop mesothelioma, but it is more common in men at a ratio of 3:1.
Women who develop mesothelioma also have a history of working in high risk professions for asbestos exposure or may have been exposed to asbestos secondary to inhaling fibers off of the clothing of a person who has been exposed to asbestos.
The period between exposure to asbestos and developing symptoms of malignant mesothelioma can range from 20-40 years.
Survival rate after the onset of symptoms can be as little as five months in extensive disease and sixteen months in localized disease.
Majority of patients die within a year after diagnosis.
Those who have come in contact with asbestos have the greatest risk of developing mesothelioma. Over 50 percent of those with mesothelioma have had some type of contact with asbestos. This includes shipyard workers, construction workers, roofers, insulation installers and miners. Due to the majority of males in these professions, it is seen more often in males than females. The family members of those exposed to asbestos at work are also at risk because of the exposure to secondary asbestos in the air or on clothes worn home from work. Exposure to asbestos in tiles or ceilings at home is also a risk factor. The addition of smoking to asbestos exposure greatly increases the risk of developing mesothelioma. Among those exposed to asbestos, smokers were 55 percent more likely to get cancer as opposed to the normal population. In Turkey, exposure to erionite has also shown an increased risk of development of mesothelioma.
Exposure to asbestos in certain occupations places patients at risk for mesothelioma. Workers in the field of insulation, fireproofing, plumbing, pipe fitting, plastering, cement production, shipyard construction, boiler making and the automotive brake and clutch industry. Environmental hazards such as joint compound, transite siding, gunnite, roof, floor and ceiling tiles, wall plasters and insulation all pose a threat to patients.
Other rare causes are irradiation of the chest wall, intrapleural thorium dioxide and inhalation of fibrous silicate.
There may be a viral connection to mesothelioma. The Simian Virus 40 (SV40) may be a cofactor in the development of mesothelioma.
Additionally, others living with asbestos workers are at risk of developing this disease. It is thought that exposed workers bring home fibers of asbestos in their clothing and hair which in turn expose their families. Mandatory showering before leaving the workplace is felt to decrease this risk.