Mesothelioma is an aggressive type of cancer that typically affects the lungs and abdomen, but can also affect the heart and testicles. It develops in the thin tissue (the mesothelium) that lines and covers these organs (and other organs), and the four types of mesothelioma are defined based on the part of the body affected (pleural, peritoneal, pericardial, and tunica vaginalis). There is currently no cure for the disease, but there are treatments to help ease the symptoms and prolong a patient’s lifespan.
Mesothelioma was particularly rare before the wide use of asbestos in industrial and commercial construction that took place during the 20th century, especially after World War II. Research conducted on mesothelioma and its causes has consistently pointed to asbestos exposure in the development of most cases. In 2009, the International Agency for Research on Cancer (IARC), a branch of the World Health Organization, classified asbestos as “carcinogenic” based on it being a leading cause of mesothelioma, and a cause of lung, larynx, and ovarian cancer.
Asbestos as Primary Cause of Mesothelioma
Asbestos is a group of minerals, naturally occurring as fiber bundles in soil and rocks worldwide, that were widely used in construction due to their versatility, heat resistance, strength, and insulating properties. Asbestos has been used in hundreds of products, as insulation in factories, schools, homes, and ships, and included in automobile brake and clutch parts, roofing shingles, ceiling and floor tiles, cement, and, even, textiles. Most exposure leading to mesothelioma has been seen to occur in the workplace, and the latency period between exposure and mesothelioma development can be long, often 20 to 50 years. Thirty years is typical, the American Cancer Society, says, and the risk of exposure leading to this cancer does not diminish with time. It is lifelong.
People are typically exposed to asbestos by inhaling its fibers, whether during making products that contain asbestos, mining asbestos, or breathing in or swallowing tiny particles of asbestos as dust (in air or liquids) that are released during the renovation or demolition of older buildings, or the breakdown of asbestos-containing materials, like insulation. (It’s also possible to breath in asbestos fibers, cough them up, and then swallow them in saliva.)
Most mesothelioma case are related to heavy and long-term exposure, such as by industrial workers or miners, but exposure that’s short-term or even one-time can also be dangerous. Fibers that become trapped in the body can inflame and irritate cells, beginning a process that includes genetic changes to cells that might lead to mesothelioma or another cancer. There are two main types of asbestos, chrysotile (also known as white asbestos) and amphibole, and both are considered carcinogenic.
According to The Mesothelioma Center, about 20 percent of people regularly exposed to asbestos end up developing a health condition related to it. Exposure can take many forms, but occupational exposure is the most common, spanning work in shipyards, construction, power plants, chemical plants, and industrial work like insulators, boiler workers, and auto mechanics. Secondary exposure can occur when a worker carries home fibers on the hair, clothes or tools, or by living or working in an older building. Environmental exposure most often affects people who live near large deposits, like asbestos mines.
Other Risk Factors Related to Mesothelioma
While asbestos is known to be the main risk factor for mesothelioma, others factors can contribute to its development or affect its severity. Among them is exposure to a class of fibrous minerals chemically equivalent to asbestos, called zeolites, commonly found in rocks and soil in Turkey. An example is erionite, found in some commercial zeolite products. Exposure to high doses of radiation, perhaps as a treatment for another cancer, is also thought to be a mesothelioma risk factor.
Research has suggested that people vaccinated for polio between 1955 and 1963 may have an increased risk of developing mesothelioma, because some polio vaccines in that period were infected by the simian virus 40 (SV40). A correlation, however, has not been fully established and remains controversial. Smoking is not a direct risk factor for mesothelioma, but smokers are more likely to suffer lung and respiratory diseases. According to The Mesothelioma Center, smoking can be a contributing causal factor when paired with asbestos exposure.
Mesothelioma is more common in older people because of its long latency period, and is thought very rare in people under age 45. It is also more common in men than women, likely because of its connection to workplace asbestos exposure and the labor-intensive nature of those jobs.
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