Asbestos cancers are caused by inhalation or ingestion of large amounts of toxic asbestos fibers. Besides mesothelioma and lung cancer, asbestos exposure can lead to other serious, potentially fatal diseases.
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While the term “asbestos cancer” most often refers to mesothelioma, a number of other cancers are associated with asbestos exposure. Lung cancer can be directly caused by asbestos exposure, and some studies have suggested a link between exposure and other types of cancer. Elevated risks for a number of other cancers continue to be investigated. According to the World Health Organization, approximately half of all deaths from occupational cancer are caused by asbestos.
In a large study of 1,047 asbestos industry employees, a malignant neoplasm was listed as the official cause of death for 208 workers. Respiratory cancers (primarily in the bronchus, trachea or lung) made up the majority of the cancer deaths, followed by cancers of the digestive organs and peritoneum.
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Causes, Risk Factors and Incidence
As its name suggests, asbestos cancers are caused by the inhalation or ingestion of asbestos. When these toxic fibers enter the body, they can cause genetic changes in healthy mesothelial cells. Over time, healthy mesothelial cells die and tumors grow in their place. Asbestos exposure is practically the only cause and risk factor for mesothelioma, while lung cancer can be caused by smoking cigarettes or exposure to radon.
Although smoking exacerbates any potential symptoms that asbestos-related diseases may display, it does not increase your risk of developing mesothelioma if you've been exposed to the toxic mineral. Smoking combined with asbestos exposure does greatly increase the risk of developing lung cancer. Other factors that may affect a person's overall health and risk of developing cancer following exposure may include a lifestyle low in exercise, high in stress and poor dietary choices.
Inhaled asbestos can lodge in the lining of organs, causing cells to mutate and become cancerous
EWG estimated yearly asbestos related deaths
The Environmental Working Group (EWG) states that mesothelioma, asbestosis and asbestos-related lung and gastrointestinal cancers claimed as many as 230,000 lives between 1979 and 2001. The following chart reflects the EWG's yearly morbidity estimates for three primary asbestos-associated cancers as well as asbestosis, a noncancerous condition that is commonly diagnosed in asbestos cancer patients.
The majority of references to asbestos cancer speak to mesothelioma because it is the only one that is almost exclusively caused by the mineral. Mesothelioma can develop after someone inhales or ingests large amounts of asbestos over time.
The inflammation and DNA damage that can result from exposure may eventually lead to the formation of tumors in the lining of the lungs (pleura) or abdominal cavity (peritoneum). In rare cases, the lining of the heart or testicles can be affected.
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Lung cancer is the second most common cancer in the U.S., and the Occupational Safety and Health Administration calls it “the greatest health risk for American asbestos workers.” One study shows asbestos kills at least twice as many people through lung cancer than mesothelioma.
Occupational asbestos exposure accounts for 5 to 7 percent of all lung cancer cases in the U.S.
Unlike mesothelioma, the risk of lung cancer is greater among smokers exposed to asbestos. The effect of smoke and asbestos drastically weakens the lungs and makes smokers with past exposure more likely to develop lung cancer.
Aside from mesothelioma and lung cancer, asbestos has been associated with a number of other cancers. Research is still determining the extent to which asbestos can cause other types.
Other Cancers Potentially Associated with Asbestos Exposure
Facts about Laryngeal Cancer
- Incidence rates are more than four times higher in men
- Risk increases with tobacco use or excessive alcohol use
- Symptoms include abnormal breathing, cough and neck pain
Although older studies conflict, a 2006 report sponsored by the National Institutes of Health indicated sufficient scientific evidence linking asbestos exposure to the development of laryngeal cancer. Cancer of the larynx, known as the voice box, is rare. The American Cancer Society estimates more than 12,000 cases will be diagnosed in 2012, the majority of which will be caused by smoking and heavy alcohol consumption.
Comparing the results of more than 50 epidemiological studies, the Institute of Medicine found that asbestos exposure significantly increases incidences of laryngeal cancer. There is also evidence that the risk increases with the intensity and duration of exposure. In addition, the study found that smoking, either alone or in combination with drinking, may contribute to the accumulation of asbestos fibers in the larynx.
Because the larynx lies directly in the path of an inhaled air stream, asbestos fibers can easily become lodged in the laryngeal mucosa. Other studies have suggested that asbestos-containing sputum can land on the larynx after being coughed up from the lungs.
Facts about Ovarian Cancer
- Fifth most common cancer among women
- Causes more deaths than other female reproductive cancers
- Asbestos-contaminated talc has caused some cases
A study by the International Agency for Research on Cancer (IARC) confirmed a causal relationship between asbestos exposure and ovarian cancer. Despite few documented cases of women exposed to asbestos and the misclassification of peritoneal mesothelioma as ovarian cancer on many death certificates, researchers found that exposure notably increases the likelihood of developing ovarian malignancies.
Occupational studies show excess mortality from reproductive cancers, yet there are inconsistencies between levels of exposure and incidences of ovarian cancer. Research showed that the toxic fibers can accumulate in the ovaries of exposed women, but the process of how they get there is under debate. Researchers suspect the use of talc on the genitals might be to blame. (Asbestos was a known ingredient in talc.) Evidence also showed that a father or husband who works with the mineral is a common denominator in many cases of this disease.
Facts about Gastrointestinal Cancer
- Average age at the time of diagnosis is 61.4 years old
- Can arise in either the midgut, foregut or hindgut
- One study found that between 15,524 cases among 12 different occupations associated with mesothelioma
The World Health Organization already associates gastrointestinal cancers with asbestos exposure, and numerous studies have reported increased incidence of the cancers in exposed populations. Gastrointestinal cancers can involve tumors in a number of locations along the gastrointestinal tract. According to one major study of asbestos installation workers, the fibers are more likely to get trapped in the upper gastrointestinal tract (esophagus and stomach) than the lower sites (colon and the rectum).
Asbestos-related gastrointestinal cancers are predominantly caused by chronic oral exposure to the mineral rather than short-term inhalation. Ingesting contaminated drinking water is thought to be one of the primary routes for fibers to reach gastrointestinal sites. Studies show fewer positive associations between asbestos and gastrointestinal cancers in regions of Utah and Connecticut, where community drinking water sources contained much lower concentrations of the mineral.
Facts about Colorectal Cancer
- Colon and rectal cancers caused 51,690 deaths in 2012
- Surgery can cure approximately half of all patients
- A study found asbestos-related cases developed more often cancers in the right part of the colon
In 1986, the Occupational Safety and Health Administration added colorectal cancer to the list of illnesses to be screened for during asbestos surveillance examinations. While there is still no conclusive ruling on the link between colorectal cancer and exposure, many studies suggest that the two may be related. Fibers have been found in the colonic tissue of asbestos workers with colon cancer.
In one British study of asbestos cement workers, colorectal cancer had a clear relation to the cumulative dose of exposure. The duration of exposure was not found to impact the risk, but as the cumulative amount increased through the years, so did the risk. Colorectal cancer risk was found similar to the risk for respiratory cancers.
Facts about Kidney Cancer
- Most common in men between the ages of 50 and 70
- Drinking asbestos-tainted water may affect cancer risk
- Renal cell carcinoma accounts for 90 percent of cases
The first correlation between excess mortality from kidney cancer and asbestos was made in 1979. Asbestos has been found in human kidneys and in urine, leading to the belief that the fibers can cause cancerous changes in this organ. However, since the occurrence is rare, only a few studies have been able to explore the correlation.
Two out of three occupational studies revealed strong, direct evidence for an excess of kidney cancer mortality in exposed workers. A separate study found that kidney cancer was one of two cancers found more frequently among Utah residents whose water supply was funneled through asbestos-sided pipes. Despite these studies, others have provided inconclusive data to draw an official correlation.
Facts about Gallbladder Cancer
- Incidence higher in ethnic populations.
- More common in women between the ages of 50 and 60
- A study found a connection between asbestos-tainted drinking water and female gall bladder cancers
The National Cancer Institute has determined that asbestos exposure can lead to an elevated risk of gallbladder cancer, but evidence for the correlation is still inconclusive. A positive correlation between asbestos and the disease in white females was found in two of seven studies, yet few others have been able to support the association.
Several other malignancies have been examined with weak or inconclusive results.
Cancers with Weak or Inconclusive Relationships to Asbestos Exposure
Studies on breast cancer and its correlation with asbestos have not found a significant link between the two. While one study revealed an excess of asbestos bodies in the tissue of 82 women with breast carcinomas, there was no way to link the presence of the fibers with their diagnosis.
Of five studies that considered the link between ingested asbestos and prostate cancer, three studies found no association between the two factors. A few studies have pointed out a slightly elevated rate of prostate cancer diagnoses, yet none has illustrated a concrete correlation.
Some studies vaguely linked leukemia to occupational exposures such as asbestos. One study detected multiple B-Cell neoplasms (including chronic lymphocytic leukemia) in three patients with a heavy history of occupational exposure, however the results supported the idea that exposure may predispose a person to the illness rather than cause it.
As with leukemia, lymphoma has been diagnosed in slight excess in asbestos-exposed persons. However, studies do not show a clear correlation between this cancer of the immune system and exposure.