Exposure to asbestos can be deadly and can cause a number of serious diseases including pleural thickening, asbestosis, lung cancer and mesothelioma.
Asbestos is a naturally-occurring mineral that was widely used in many industries for its heat-insulating properties. Mining, manufacturing and use of products containing asbestos can produce dust, made from the needle-like fibers of the mineral. These fibers may lodge in body tissues such as the lungs, abdomen or heart and over time, cause cancer to develop.
Basics of Cancer
Cancer begins when cells of a particular tissue type begin dividing uncontrollably. This may be influenced by a person’s cellular DNA but may also be a result of toxic exposure. In some cases, exposure to toxic agents may increase the likelihood that mutation of the DNA will occur, resulting in uncontrolled cell division and the formation of tumor(s).
- Each Cancer is Different
Not every person that is exposed to a toxic substance like asbestos will develop cancer. In addition, asbestos may cause different types of cancer. Due to individual characteristics, asbestos may cause a number of serious diseases including lung cancer, mesothelioma, asbestosis and others.
There are many substances that, like asbestos, can be carcinogenic. These toxic chemicals lead to cellular changes which cause rapid cell division and the development of cancer.
- DNA Mutations
One of the ways that carcinogens cause cancer is through mutations of cellular DNA. These mutations can alter the appearance and behavior of cells. They can also turn the cell division “switch” to an “on” position so that the cells begin dividing uncontrollably.
Within the body, each type of tissue is composed of cells that are designed to perform certain functions. The DNA of a cell provides a set of “instructions” that tells the cell how to behave, including when to reproduce. Cellular reproduction is done through a process known as mitosis or cell division.
The frequency of normal cell division is determined by the DNA and varies from tissue to tissue. Skin cells and the lining of the intestinal tract are known as epithelial type cells which divide frequently, to replace cells lost through erosion. Bone cells divide rarely after a patient has stopped growing taller. Brain cells are not thought to divide regularly at all.
Cells are also programmed to divide only a certain number of times before “apoptosis” occurs. This is essentially cellular suicide which ensures that old cells, which may have become damaged, do not continue to reproduce. In most tissues, non-reproductive cells are programmed to divide only 50 or so times before apoptosis.
Cell division is often driven by chemical messengers from the immune system. These chemical messengers known as cytokines, tell cells to divide when cell replacement is needed and to stop dividing when there are enough cells. If cellular DNA is damaged, the cell may not follow cytokine instructions correctly.
Cancer occurs when healthy cells divide uncontrollably. These cells have become unresponsive to apoptosis and/or cytokine messaging. They do not “hear” the body’s messaging and do not follow preprogrammed instructions.
Cancer cells may have lost the sensitivity to anti-growth messengers and may no longer undergo apoptosis as they should. This uncontrolled division may result in the growth of cancerous tumors. It may also explain why some cancers recur after the disease has gone into remission.
Mutations in cellular DNA are responsible for formation of cancer. Mutations can be a natural occurrence of aging, related to the genetic makeup of certain people but in many cases, mutations are caused by carcinogens.
Once mutations occur, the cell no longer responds to anti-growth messaging and fails to undergo apoptosis, resulting in continuing, uncontrolled cell division and tumor growth.
Asbestos is a needle-like fibrous mineral which can be inhaled or ingested as dust particles. Even though asbestos dust may appear to be a powder, microscopic examination will show its dangerous shape. Asbestos that is inhaled or ingested will become lodged in body tissues, similar to a needle.
Because of its shape, the body cannot easily dislodge the fiber and over a period of time, other cells, often mesothelial cells will try to surround or engulf the fibers to protect the rest of the body. In most cases, a process like this involves bacteria, other cells or foreign material which will be destroyed by the engulfing cells.
In the case of asbestos, the mineral cannot be destroyed and will remain lodged in the area. Over a period of time, the tissue will become inflamed and the immune system may attempt to destroy the inflammatory tissue. This may ultimately lead to tissue scarring and genetic mutations at the site of asbestos.
As the DNA is mutated, uncontrolled cell growth may begin. Scar tissue may also prevent proper functioning of the organ, such as pleural thickening which leads to difficulty breathing from lung restriction.
Mesothelioma is an asbestos-related cancer that can affect the lungs, abdomen, heart or testicles. Fibers of asbestos have been inhaled or ingested and lodged in the mesothelial layers of tissue surrounding those organs. Mesothelioma cancer caused by asbestos can occur as pleural mesothelioma, peritoneal mesothelioma, pericardial mesothelioma or testicular mesothelioma.
No matter where the mesothelioma occurs, it usually takes 20 to 50 years for cancer to develop after asbestos exposure.
Non-Small Cell Lung Cancer
Asbestos can also lead to “lung cancer”. It is different than mesothelioma cancer as it emerges from the lung tissue and not the mesothelial tissue. However, it is caused in the same way. Asbestos fibers lodge in the lung tissue, causing inflammation and cellular mutations. These DNA mutations ultimately lead to uncontrolled cell division in lung tissue cells.
Asbestos is responsible for about 4 percent of “regular” lung cancer cases. Even though it is different from mesothelioma, it also has a long latency period and may take 20 or more years after exposure to develop. People who have other risk factors like smoking are more likely to get mesothelioma lung cancer.
Within the non-small cell lung cancer diagnosis, there are different types:
- Squamous cell carcinoma – begins in the squamous cells of the larger bronchii
- Large cell carcinoma – begins in the large cells in the outer lung area, most common in smokers
- Adenocarcinoma – begins in the glandular cells of outer regions of the lungs, most common in non-smokers
Mesothelioma and non-small cell carcinoma may be treated differently from one another, though some treatments will be the same. A mesothelioma specialist will be able to differentiate and provide the most appropriate options for treatment.
- Other Asbestos Cancers
Asbestos exposure has been linked to cancer of the larynx (voice box) and ovarian cancer. Some studies have suggested that asbestos exposure may also cause other cancers. These may include throat cancer affecting the pharynx, cancers of the gastrointestinal tract including the stomach, colon and rectum. Each type of cancer will be treated differently according to the tissue type.
Asbestos may also be linked to kidney, gall bladder, prostate and breast cancer and to leukemia and lymphoma though clear evidence has not been shown.
Asbestosis is a long-term illness caused by exposure to asbestos. It results in thickening and scarring or fibrosis in the lungs. This makes lung expansion difficult and leads to shortness of breath, chronic cough and general breathing difficulties. Asbestosis usually takes 10 to 20 years to develop and may get worse over time.
Symptoms for Asbestosis may include:
- Chest pain
- Shortness of breath
- Persistent cough
- Congestive cough (with mucus)
- Loss of appetite
- Lung sounds
Asbestosis may be mild to moderate in some people but in others can be severely disabling. There is no effective treatment for asbestosis as it is not a “cancer” but in some cases, certain types of surgery may reduce symptoms and medications may make breathing easier. Asbestosis also increases the chance of developing asbestos lung cancer, therefor, medical attention is essential.
- Pleural thickening
Asbestos inhalation can cause pleural thickening due to scar tissue that builds on the pleural lining surrounding the lungs. This may result in systemic or body-wide inflammation which may appear to be similar to rheumatoid arthritis, psoriasis or other auto-immune disease. Pleural thickening can also result in pleuritic or pleurisy, which is severe inflammation of the lungs.
In severe cases, pleurectomy may be considered while in other cases, medical management may be the best option.
Most disease caused by asbestos exposure takes 10, 20 or more years to develop. It is essential that anyone with symptoms of mesothelioma, lung cancer, asbestos or other disease seek medical treatment. Mesothelioma is a very rare type of cancer, affecting only about 3,000 new patients per year, that is optimally treated by a mesothelioma specialist.
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American Cancer Society, (18 May 2015), Asbestos and Cancer Risk, ACS Cancer.org, Accessed on 02 February 2016 http://www.cancer.org/cancer/cancercauses/othercarcinogens/intheworkplace/asbestos
EWG, (04 March 2004), Asbestos: Think again, Environmental Working Group, Accessed on 02 February 2016 http://www.ewg.org/research/asbestos-think-again
National Cancer Institute, (01 May 2009), Asbestos exposure and cancer risk, National Institutes of Health, Accessed on 02 February 2016 http://www.cancer.gov/cancertopics/factsheet/Risk/asbestos
National Cancer Institute, (2016), Malignant Mesothelioma – Health Professional Version, National Institutes of Health, Accessed on 02 February 2016 http://www.cancer.gov/types/mesothelioma/hp