Asbestos Exposure and Cancer
Asbestos is a naturally occurring group of heat-resistant minerals which has been widely used in various industries such as construction, automotive and shipbuilding until the late 1970s.
Due to its durability, resistance to heat and chemicals and inability to conduct electricity, asbestos has represented a convenient and accessible raw material for numerous manufacturers after the Industrial Revolution in the US.
It was commonly used for strengthening cement and plastic, fireproofing and insulation, as well as for ceiling and floor tiles, roofing, paint, adhesives, vehicle brake shoes, and clutch pads. Until the early 1970s, the health risks associated with asbestos exposure were unknown.
It was during the 1970s that asbestos use became more strictly regulated and subsequently banned in the US, as multiple government organizations, including the U.S. Consumer Product Safety Commission (CPSC) and the US Environmental Protection Agency (EPA), started raising awareness regarding the dangers of prolonged exposure to asbestos in the workplace.
Consequently, asbestos use has decreased to a great extent throughout the following decades, being replaced with safer materials such as cellulose fibers, flour fillers, and polyurethane foams. Additionally, 55 countries completely banned the use of asbestos in any form, excluding the US. Because of poor regulation, negligence and a large number of companies turning a blind eye to imported asbestos-containing or asbestos-tainted materials due to their low cost, these toxic minerals, however, continue to be present in numerous products nowadays.
Although it has been demonstrated that exposure to asbestos can lead to the development of conditions such as asbestosis, pleural effusion, and pleural thickening, it can also cause a series of malignant diseases, including lung cancer, mesothelioma, and laryngeal cancer, as well as ovarian, gastrointestinal and colorectal cancer. Exposure occurs when asbestos particles released into the air due to friction are inhaled or swallowed.
The accumulation of fibers within the body can determine the appearance of various types of malignant diseases, as asbestos tends to cause severe inflammation of the affected organ or region which can subsequently lead to the growth of a cancerous tumor. Nevertheless, there are several factors which significantly increase the risk of developing a form of asbestos-related cancer:
- Duration of exposure: Frequent exposure entails the inhalation or swallowing of larger amounts of asbestos fibers, thus heightening the risk of developing a malignant disease within the following decades.
- Quantity of asbestos fibers accumulated within the body: The chances of being affected by a form of cancer are higher when one has inhaled or swallowed a large dose of fibers.
- Type, size and structure of fibers: There are six types of asbestos, of which crocidolite (blue asbestos) and amosite (brown asbestos) were deemed particularly more hazardous by certain agencies. The dimension of the inhaled or swallowed asbestos can increase the risk as well, as larger fibers tend to produce more severe inflammation. Moreover, several studies have shown that the amphibole type may be more dangerous than chrysotile.
- Smoking: Smoking can also increase the risk of lung cancer or mesothelioma in conjunction with exposure to asbestos since it causes great deterioration of the lungs' health and function.
- Preexistent lung conditions and diseases: When the lungs are already affected by other conditions or diseases unrelated to asbestos exposure, the risk of developing lung cancer or pleural mesothelioma becomes greater as well, due to the weakened state of the organs.
Lung cancer is the most commonly encountered malignant disease affecting the lungs. Despite the fact that only 10% of diagnosed lung cancer cases are directly caused by exposure to asbestos, the rest having occurred as a result of long-term tobacco use, research has demonstrated that a combination of habitual smoking and exposure to asbestos highly increases the risk of developing it. When it occurs exclusively due to asbestos, lung cancer tends to develop within approximately 15 years following exposure. Some of the most commonly experienced symptoms of lung cancer include:
- chest pain which intensifies with breathing or coughing
- shortness of breath or difficulty breathing
- chronic cough which does not improve regardless of treatment
- unintentional weight loss
- frequent or recurring respiratory infections such as bronchitis or pneumonia
Depending on the type, as well as on its ongoing stage, life expectancy for lung cancer varies between several months and over 5 years. If the disease has been detected in its early phases, a larger number of treatment options are available, and their effectiveness is also significantly increased in this case. On the other hand, if lung cancer has been diagnosed in its advanced stages, the survival rates dramatically decrease. Moreover, the number of treatments which the patient can undergo without any additional complications will also be limited.
Pleural mesothelioma is a very rare and aggressive form of cancer which occurs on the outer lining of the lungs (pleura). Unlike lung cancer, it is primarily associated with prolonged or frequent asbestos exposure, with approximately 80% of the diagnosed cases being caused by the presence of asbestos fibers within the lungs. It is different from the previous disease in terms of the lung region affected, latency period, as well as the structure of the malignant tumors.
While lung cancer develops inside the lungs, mesothelioma occurs on the outer surface of the organs. Pleural mesothelioma also entails a longer latency period (up to 50 years following exposure to asbestos) than lung cancer, which typically appears after 10-30 years of exposure, particularly when long-term tobacco use is involved as well. However, symptoms of pleural mesothelioma tend to be very similar to those caused by lung cancer, some of the most common signs of the disease being:
- chest pain
- shortness of breath and difficulty breathing
- persistent cough
- swollen face or arms
- unintentional weight loss
- sweating or fever
- accumulation of fluid within the lungs
- coughing up blood
Prognosis of pleural mesothelioma also depends greatly on the stage of the disease, the type of cancerous cells within the tumor, as well as on the age and general health of the patient. Thus, if pleural mesothelioma has been discovered in its early phases, the numerous treatment options available may increase life expectancy as well as improve one's prognosis. The general prognosis for this malignant disease is quite negative, with a life expectancy of approximately one year. However, by opting for a multi-modal treatment approach involving standard procedures such as chemotherapy, radiotherapy, and surgery in conjunction with alternative treatments available in clinical trials, one might survive for up to 20 years.
Although asbestos exposure does not represent the primary cause for laryngeal cancer, which most commonly develops due to excessive alcohol consumption and long-term tobacco use, a 2006 report sponsored by the National Institutes of Health revealed that it is, indeed, a significant risk factor. The study discovered that exposure to asbestos in the workplace can increase the chances of developing laryngeal cancer by over 40%.
Due to the fact that inhaled asbestos fibers can become embedded in the inner lining of the larynx and subsequently cause severe inflammation, this type of cancer is more likely to occur following exposure to asbestos. Additionally, it has been found that the risk increases with the amount of fibers which have accumulated within the body. The following symptoms are often encountered with laryngeal cancer:
- painful or difficult swallowing
- a lump in the neck
- hoarseness or a change in your voice
- persistent cough
- ear pain
- chronic halitosis (foul-smelling breath)
- sore throat which does not improve over time
- difficulty breathing (particularly in severe cases)
When laryngeal cancer is detected in its early phases, the prognosis is generally positive, with a life expectancy of over 5 years for 80-95% of the diagnosed patients. However, if the malignant tumor has entered its advanced stages, survival rates decrease dramatically. Thus, only between 20 and 25 percent of patients suffering from severe cancer of the larynx will survive for over 5 years following diagnosis.
Ovarian cancer is another type of malignant disease which can also be caused by asbestos. In this case, exposure may occur due to the use of asbestos-containing talcum powder by women as a hygiene product. Fibers can travel through the vagina and uterus, ultimately reaching the ovaries where they can produce severe inflammation, subsequently leading to the development of cancerous tumors. Even though the link between asbestos exposure and ovarian cancer has not been conclusively demonstrated, most oncology specialists agree that the toxic minerals represent a risk factor for this disease. The most common symptoms of ovarian cancer include:
- persistent bloating in the abdominal region
- changes in appetite
- pressure in the pelvis or lower back
- frequent need to urinate
- menstrual irregularities
- painful intercourse
The average prognosis for ovarian cancer entails a life expectancy of approximately 5 years for 45% of the diagnosed women. Nevertheless, the prognosis can be significantly improved by undergoing appropriate and prompt treatment and is also dependent on the stage of the disease, as well as on its type. The sooner ovarian cancer is discovered, the more increased are the patient's chances of survival.
Gastrointestinal cancer refers to a group of malignant diseases which affect organs within the digestive system and intestinal tract, such as the liver, gallbladder, stomach, colon, pancreas, and rectum. Despite the lack of conclusive evidence in this respect, the causes of gastrointestinal cancer might include asbestos exposure as well. A 2005 study revealed a concrete correlation between this group of cancers and asbestos. Researchers estimated that the risk of developing gastrointestinal cancer increased by up to 450% in the case of people who consumed asbestos-contaminated water. Similarly to mesothelioma, certain types of gastrointestinal cancer may not cause any noticeable discomfort during their initial stages. However, some of the most commonly experienced symptoms are:
- blood in vomit or stool
- difficulty swallowing
- unintentional weight loss
- abdominal discomfort or pain
- loss of appetite or feeling full after eating small amounts of food
- a lump in the abdominal region
- constipation or diarrhea
The prognosis for gastrointestinal cancer is relatively poor, particularly due to the fact that this group of diseases tends to be detected in their advanced phases, as the patient does not initially experience any distressing symptoms. Life expectancy also varies greatly depending on the cancer affected organ. Thus, for stomach cancer, the five-year survival rate is 27%, while only 7% of the patients diagnosed with pancreatic cancer will survive for more than five years.
The results of research focused on discovering a connection between exposure to asbestos and colorectal cancer have also been generally inconclusive. However, numerous studies suggested that a causal relation might indeed exist, as asbestos fibers have been found embedded in malignant tumors of the colon. Additionally, it has been observed that colorectal cancer caused by exposure to asbestos tends to occur preponderantly on the right region of the organ. The main symptoms of colorectal cancer include:
- persistent abdominal discomfort or pain
- diarrhea or constipation
- blood-tainted stools
- unintentional weight loss
- frequent need to defecate
The prognosis of colorectal cancer is highly dependant on the stage of the disease. Thus, the survival rate is 80-90% for the incipient phase and 55-80% for stage II tumors. Patients diagnosed with stage III colorectal cancer have a life expectancy of over 5 years in approximately 40% of cases, which decreases dramatically when stage IV occurs, with a survival rate of only 10%.
While prolonged or frequent exposure to asbestos is certainly known to represent a major risk factor for mesothelioma and lung cancer, additional research is required in order for asbestos to be listed among the main causes for other forms of cancer such as ovarian, gastrointestinal and colorectal. Despite the fact that the results of certain studies have suggested a strong correlation between asbestos exposure and the previously mentioned diseases, evidence in this respect cannot be yet deemed conclusive. Moreover, research focusing on the link between these toxic minerals and other malignant diseases such as kidney cancer, leukemia, Hodgkin's lymphoma, and breast cancer are even fewer and their findings are quite ambiguous as well.