Asbestos Lung Disease - A Primer for Patients, Physicians and Lawyers - part 1 Lawrence Martin, M.D., FACP, FCCP A NOTE FROM THE AUTHOR:
I am a pulmonary physician with experience in diagnosing asbestosis and other asbestos-related lung diseases. Because most cases of alleged asbestos lung disease end up as legal claims, I also have experience working with lawyers involved in asbestos litigation. While the majority of my legal work has been in defense of companies sued by workers, I have also been on the side of patients making asbestos-related claims. This web site has been created without help (financial or otherwise) from any attorneys or attorney advocates, and the views expressed are my own. To illustrate both valid and invalid asbestos claims, I have included several cases evaluated over the years. This Primer is written in lay language so as to reach the widest possible audience. Many web links are included and, for some topics, medical references for those who wish to research the topics further. Plaintiff's lawyers may take umbrage at some of my comments, mistaking my answers as "pro-industry." However, I am neither "pro-industry" nor "pro-plaintiff." I offer this Asbestos Primer with only one bias -- on the side of consistency and rationality in diagnosis, and toward expediting the thousands of extant asbestos claims. (A plea for objectivity in analysis of occupational cases can also be found in my on-line paper Pitfalls in Diagnosis of Occupational Lung Disease For Purposes of Compensation -- One Physician's Perspective.)
What is asbestos? Asbestos is a naturally occurring mineral that was long ago found to have fire retardant properties. Since 1879 asbestos has been used in production of fire-retardant products such as bricks, pipe coverings, brake linings, ceiling tiles, floor tiles, fire-resistant work clothes and many others. Because in its raw state asbestos is friable - meaning easily broken into microscopically small pieces by ordinary hand action - asbestos can be inhaled into the lungs and cause damage. Individual asbestos fibers are very small, with a width much smaller than a human hair. When asbestos is not friable - such as when embedded in ceiling tiles or completely encased in pipe coverings - it cannot be inhaled and cause damage. Asbestos-containing materials are known as ACMs. ACMs, when broken up by machines, cut, scraped, or sanded, can release friable asbestos into the air. Six naturally occurring minerals are considered "asbestos". Three were commonly used in various products (chrysotile, amosite and crocidolite). Three other asbestos minerals were uncommonly used (tremolite, actinolite, anthophyllite) and are rarely found today. COMMON FORMS OF ASBESTOS | | Form | Chemical Formula | Shape | chrysotile
(accounts for 90% of asbestos in products) | 3MgO-2SiO2-2H20 | white, curly (serpentine family) | | amosite | (FeMg)SiO3 | brown or gray, straight (amphibole family) | | crocidolite | Na2O-Fe2O3-3FeO-8SiO2-H2O | blue, straight
(amphibole family) |
Today only chrysotile - so called "white asbestos" - is mined and incorporated into products. However, since asbestos is indestructible, older buildings and products (pre-dating 1970s) may also contain some amosite (brown/off-white) or crocidolite (blue) asbestos.
What are ferruginous bodies? Individual asbestos fibers cannot be seen under the ordinary (light) microscope. However, once in the lungs, a portion of asbestos fibers usually becomes coated with material that contains iron. The scientific name for things containing iron is "ferrous"; hence these coated fibers are called ferruginous bodies. An individual ferruginous body has a much greater mass than the uncoated fiber, and as a result can be seen under the light microscope. Ferruginous bodies are often looked for in lung tissue to prove asbestos exposure, and when found are sometimes referred to as "asbestos bodies." However, asbestos is not the only fiber that may be coated with iron; glass and cotton fibers, talc and graphite can also become coated with iron, and when this happens they are indistinguishable (under the light microscope) from true asbestos bodies. Some asbestos claims revolve around the presence or absence of asbestos bodies in lung tissue. Any interpretation of this finding (presence or absence) must be balanced with the claimant's exposure history and associated lung pathology.
What is the harm from inhaling asbestos? Because friable asbestos can be inhaled, the main medical concern is lung or respiratory disease. Disease can come about because of the body's reaction to the inhaled asbestos, which can be the formation of scar tissue. When scar tissue forms it replaces normal lung tissue; extensive amounts of scar tissue in the lungs can interfere with breathing. In addition, asbestos scar tissue in the lungs can lead to lung cancer. Generally, asbestos respiratory diseases take two or more decades to develop from the time of exposure, and then only after extensive and long term exposure to friable asbestos. The more extensive and longer the exposure, the more risk an individual has for developing asbestos-related disease years later.
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Who is at risk for asbestos-related disease? Asbestos is so ubiquitous we are all exposed to it in minute quantities. However, to develop disease one must have substantial exposure to friable asbestos. Usually, such exposure requires working with the friable product over a long period of time. At risk are workers in various occupations that exposed them to friable asbestos, in most cases, over many years. Examples of workers at risk are listed in the box. - Miners of asbestos
- Shipyard workers
- Powerplant workers
- Brake lining workers
- Pipe fitters
- Insulators
- Boiler makers and repairers
- Maintenance workers (sometimes called millwrights) who worked in areas of the factory where friable asbestos was present
- Workers in the production of fire bricks, fire-retardant paints, asbestos cement, and other asbestos-containing products
It should be noted that, while asbestos exposure occurs almost exclusively in the work place, it also may occur outside the workplace, such as in neighborhoods near asbestos mines. There are also several instances of worker's wives developing asbestos disease because they cleaned their husbands' asbestos-covered work clothes.
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What are the asbestos-related lung and respiratory diseases? Five main respiratory diseases or conditions may occur from asbestos exposure (see Table). All of these diseases or conditions also have other causes; the patient's asbestos exposure history and specific features of the diagnosis often suffice to implicate asbestos as a cause. In many cases however, the role of asbestos in causing the problem may be in doubt and will be disputed. Asbestos-related diseases or conditions | | Disease or condition | Other causes besides asbestos | Comment | | Interstitial fibrosis | Over 100 | Called asbestosis when cause is asbestos | | Pleural plaques/fibrosis | Several | Best visualized on a chest CT scan. | | Benign pleural effusion | Many | Rarely from asbestos | | Lung cancer | Cigarettes alone in >90% of cases | Asbestos synergistic with cigarettes | | Malignant mesothelioma | About half the cases are of unknown cause | Asbestos assumed cause if there has been documented remote exposure |
Interstitial fibrosis.Lung tissue is very thin, delicate tissue that consists of millions of air sacs surrounded by blood vessels and connective tissue; that portion of the lungs surrounding the air sacs is collectively called the "interstitium." If scarring occurs in the interstitium it is called interstitial fibrosis. Now if thin asbestos fibers are inhaled and get into the interstitium they can be a cause of this fibrosis. When this occurs the patient has asbestosis, i.e., intersititial fibrosis from inhaled asbestos. Interstitial fibrosis can actually occur from many products and diseases (well over 100), and is by itself a non-specific disorder; other causes include drug reactions, infections, arthritis-related diseases, and chronic heart failure. Again, asbestosis is interstitial fibrosis specifically due to inhaled asbestos. Like any case of interstitial fibrosis, asbestosis can lead to shortness of breath and ultimately be fatal.
References for this condition Pleural plaques and pleural fibrosis. Sometimes the scarring is not in the lung tissue itself, but in the outside linings of the lung, called the pleura or pleural membranes. These are thin, glistening membranes that completely cover the lungs. When visible on a chest x-ray, this scarring is termed pleural plaques or pleural fibrosis. However, they are often difficult to discern on plain chest x-ray, and are much better vizualized on a chest CT scan. Disease confined to the pleural membranes is not asbestosis, a mistake in diagnosis frequently made by physicians reading chest x-rays. Unlike asbestosis, pleural plaques and fibrosis rarely cause symptoms or any discomfort. Sometimes calcium is deposited into these plaques, and then they are much more easily seen on chest x-ray (because calcium is so dense). Several other conditions can cause pleural scarring and calcium deposits, such as healed tuberculosis and other infections. However, a particular distribution of pleural plaques/fibrosis on the chest x-ray (for example, covering both diaphragm muscles, especially if calcified) can be attributed to asbestos, if there is a history of exposure and no other cause is evident.
References for this condition Benign Pleural effusion. Pleural effusion - a collection of fluid around the lung - is a very common medical problem; like interstitial fibrosis, there are many potential causes (e.g., pneumonia, congestive heart failure, cancer, kidney disease, rheumatoid arthritis, tuberculosis). Asbestos can cause two very different types of pleural effusion - benign and malignant. Benign pleural effusion is a frequent condition, but is only rarely from asbestos. Malignant pleural effusion can be due to either lung cancer or mesothelioma, conditions which are discussed separately. Benign pleural effusion, when attributable to asbestos, is presumably due to inflammation generated by reaction to asbestos fibers. When the pleural fluid becomes substantial (usually over a pint or 500 cc's) the patient may have symptoms (usually shortness of breath) and the chest x-ray will show the fluid collection. Asbestos is actually a rare cause of pleural effusion (pleural scarring and pleural plaques are a much more common result of asbestos inhalation). The only way to to reliably diagnose most causes of pleural effusion is to sample the fluid via a needle in the pleural space, and examine it in the lab. This is an invasive procedure (because it involves a needle) called 'thoracentesis', and is routinely performed in hospitals.
References for this condition Lung cancer. Lung cancer is the most difficult disease to attribute to asbestos for one principal reason: Over 90% of lung cancers are due to cigarette smoking and virtually all lung cancer patients with asbestos exposure also have a strong smoking history. (In over two decades I have come across only one case of lung cancer in an asbestos worker who never smoked.) Lung cancer is common, with about 180,000 new cases a year in the U.S. Since we know asbestos is potentially carcinogenic, every patient with lung cancer and a history of friable asbestos exposure should be evaluated to see what role, if any, asbestos played. Lung cancer in patients with a history of asbestos exposure frequently leads to litigation. The litigation often ends up pitting expert against expert, all quoting from the abundant literature on the subject (see references). This point is discussed further in What is the Browne Hypothesis?
References for this condition Malignant Mesothelioma. This is cancer of the thin membranes that surround the lungs and abdominal organs. Malignant mesothelioma occurs much more commmonly in the chest than in the abdomen. Asbestos-caused mesothelioma in the abdomen is thought to arise from fibers entering the lungs and then penetrating through the diaphragm muscles. Fortunately, mesothelioma is a rare cancer, affecting only about 2000 people a year in the U.S. Unlike lung cancer, it is not due to smoking; in fact, the only known cause of mesothelioma in this country is remote asbestos exposure (there are other, rare causes of mesothelioma, such as the fibrous material "erionite," mined in Turkey). The lag time from first exposure to diagnosis is 20 to 40 years. However, in about half the cases there is no history of asbestos exposure, and the cause is unknown. A documented history of asbestos exposure and the diagnosis of malignant mesothelioma will invariably be linked, so in the area of asbestos litigation these cases are straightforward -- medically, at least.
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Are asbestos-related diseases treatable? Asbestosis is not treatable, although symptoms in the worst cases can be ameliorated with oxygen, steroids and other measures. Pleural plaques and pleural fibrosis are also not treatable, but they generally cause no symptoms or discomfort. Pleural effusion is treatable with removal of the fluid; if the fluid comes back, there are procedures that can be taken to keep this from happening. Lung cancer is curable only by removing the cancer through surgery; however, at the time of diagnosis most lung cancers can't be removed, and then treatment will be with radiation or (less commonly) chemotherapy. Radiation and chemotherapy are considered palliative, as they rarely will cure lung cancer, only slow it down. Mesothelioma is not resectable, since it involves the lining of the lung and the adjacent chest wall. Rarely, in highly selected cases, a few surgeons will attempt to remove the entire lung with its lining and parts of the chest wall; this procedure, called "radical pneumonectomy", might prolong survival in a few individuals but is not an option for most patients. Radiation and chemotherapy are not effective for mesothelioma, and most patients succumb within 12 months of the diagnosis.
What are the symptoms of asbestos-related lung disease? The symptoms are the same as would be seen in any cause of interstitial fibrosis, pleural plaques/fibrosis, benign pleural effusion, lung cancer or mesothelioma, and generally depend on two factors: - extent of the disease, both within the chest (usually determined from the chest x-ray or CT scan) and, for cancer, spread to other parts of the body;
- co-existing conditions, such as smoking-related lung disease.
In early interstitial fibrosis there are usually no symptoms, but as the disease advances shortness of breath is the principal complaint. Benign pleural effusion is asymptomatic when the amount of fluid is small, but in moderate to large effusions shortness of breath is common; sometimes patients can also complain of chest pain worse with a full breath (so-called pleuritic pain). Lung cancer causes no symptoms in the early stages, even though it may be seen on chest X-ray. In fact, by the time the cancer does cause symptoms it is usually far advanced. Symptoms from lung cancer can include shortness of breath, coughing up blood, and chest pain. (If lung cancer has spread outside the chest it can cause other symptoms, depending on location.) Mesothelioma generally causes symptoms earlier than lung cancer, because it grows between the lung and the chest wall, an area more sensitive to pain than inside the lung (where lung cancer starts). As a mesothelioma grows it can cause shortness of breath, chest pain, decreased appetite and weight loss. Pleural plaques/pleural fibrosis cause no symptoms unless the amount of scarring is very extensive, over both lungs; then it can cause shortness of breath. However, extensive scarring of the pleura from asbestos is rare, so the vast majority of workers with pleural plaques/pleural fibrosis have no symptoms. In summary, the main symptom from asbestos-related lung conditions is either "none" or "shortness of breath." The medical term for shortness of breath is dyspnea. Dyspnea is such a common symptom, with so many causes, that it has no specificity by itself. Given a randomly-chosen, middle-aged man who was exposed to asbestos in the past, any shortness of breath he has is statistically most likely from a non-asbestos-related condition. The most common causes of dyspnea in this population: poor physical fitness with or without obesity; smoking-related lung disease; and heart disease.
How does smoking affect asbestos diseases? Smoking does not cause asbestosis, pleural scarring, pleural effusion or mesothelioma. However, there is some evidence that smoking - since it affects the lungs' natural protective mechanisms - makes people more vulnerable to inhaled asbestos and more likely to develop asbestosis. Also, a patient with any asbestos-related disease might have shortness of breath due to mainly or exclusively from his smoking-related disease. Many workers who were exposed to asbestos were also heavy cigarette smokers. Because the latency of asbestos-related diseases is 20 years or more, by the time these workers are checked for asbestos diseases they often have a very long smoking history and therefore smoking-related disease -- principally chronic obstructive pulmonary disease (COPD). COPD includes two separate pulmonary diseases, which commonly overlap in a given patient - chronic bronchitis and emphysema. Chronic bronchitis and emphysema are just different manifestations of lung damage from smoking. Smoking is also the major cause of lung cancer. Since both asbestos and smoking can independently cause lung cancer, it is obviously important that anyone who might have been exposed to friable asbestos never smoke. Smoking not only adds to lung cancer risk in some asbestos workers, it can heighten the risk -- a process known as synergism. This has been demonstrated with certainty only if the worker has lung scarring from asbestosis. Synergism means that if, for example, the risk of developing lung cancer from asbestosis is 1% and the risk from smoking is 2%, that the risk in the smoking asbestosis patient is significantly higher than 3%. One of the most contentious areas in asbestos claims is whether mere asbestos exposure -- without any apparent scarring in the lungs -- also acts synergistically with smoking to increase lung cancer risk. The published evidence suggests that it does not. This point is discussed extensively in What is the Browne Hypothesis?
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What other diseases can occur from asbestos? Rarely, patients can get mesothelioma in the abdomen from inhaled asbestos. Other conditions often attributed to asbestos, like colon cancer and throat cancer, are unproven and so are often the subject of litigation when they occur. Common respiratory illnesses like asthma, sinusitis, bronchitis, emphysema and pneumonia are not due to asbestos.
How is asbestos lung disease diagnosed? There must be a history of substantial exposure to friable asbestos AND a lung condition that could be related to asbestos exposure AND no evidence for another cause. For example, a positive exposure history plus interstitial lung disease on chest x-ray plus the absence of any other cause, would be a presumptive diagnosis of asbestosis. However, note that: - A history of asbestos exposure, without a documented lung condition related to asbestos exposure = no diagnosis of asbestos-related disease. Example: A 65-year-old man with a history of asbestos exposure and a previously clear chest x-ray suddenly develops pulmonary edema (water in the lungs); his pulmonary condition is not one related to asbestos exposure.
- No history of asbestos exposure, with a condition that could otherwise be due to inhaled asbestos = no diagnosis of asbestos-related disease. Example: A 45-year-old woman with no history of asbestos exposure develops malignant mesothelioma. This pulmonary condition is commonly linked to asbestos exposure, but absent such history the cause in her case remains unknown.
The vast majority of asbestos lung diseases occur from remote exposure at the workplace. Given a documented history of asbestos exposure, there are three ways to diagnose asbestos lung disease: - A chest x-ray or chest CT scan (more detailed than a regular chest x-ray) diagnostic of or consistent with an asbestos-related condition.
- A lung biopsy diagnostic of an asbestos-related condition.
- An autopsy diagnostic of an asbestos-related condition.
Well over 95% of cases can be diagnosed with just the history of friable asbestos exposure and an abnormal chest x-ray or chest CT scan. It is rare to make the diagnosis using lung tissue or autopsy, because these exams are rarely obtained. Obtaining a portion of lung tissue usually requires surgery. While tiny pieces of lung tissue can be obtained without surgery (through an instrument called a bronchoscope), they are usually too small to diagnose asbestos-related diseases. When lung tissue is available the pathologist will look for ferruginous bodies (see What are ferruginous bodies?) as well as other signs of asbestos-related pathology. Surgical removal of lung tissue obviously presents some risk to the patient, and won't be attempted unless there is perceived benefit. For example, since asbestosis is not treatable, physicians won't recommend an operation if they strongly suspect only this condition. On the other hand, a patient may have surgery to remove a lung cancer, and then there will be sufficient lung tissue to also look for asbestosis. Autopsy is even rarer than operation for lung tissue, because most diagnoses are made while the patient is living. Also, the vast majority of deaths are no longer autopsied in this country. In fact, most families of asbestos-exposed workers refuse permission, even though an autopsy, because it allows for complete examination of both lungs, would definitively make the diagnosis if the disease is present.
Why is there so much argument over asbestos? "Asbestos" is a term fraught with dispute. Decades ago it was a widely-used mineral in thousands of manufacturing processes, with no hint of the dangers it might impose. Today its use is highly constricted, in this country only to chrysotile, and then only in selected products. There are few parallels to the changed perception of asbestos in just a few short decades. (The closest parallel is cigarettes; another might be nuclear power plants.) Like tobacco companies, asbestos manufacturers knew more about the harm of their product than they admitted, and they did not take proper safeguards to protect the people most exposed (in this case blue collar workers, not consumers of the product). Then, when workers started developing disease years after exposure, numerous law suits ensued, eventually putting many companies out of business. (See also Kook Sim, 2001). When all or virtually all people truly sick with asbestos disease either died or were compensated, attorneys sought out workers not sick but who might become ill from remote asbestos exposure; this has generated the tens of thousands of claims extant today. A result of all this activity is tremendous polarization on the subject. On the web you will find (as expected) widely divergent viewpoints, from "The Asbestos Institute" to the "Coalition for Asbestos Resolution" to the "Association of American Trial Lawyers". Underlying disputes in each claim (see next two questions) are fundamental philosophical differences between plaintiff lawyers and defendants. Plaintiff lawyers believe the asbestos industry -- companies engaged in mining, manufacturing or supplying the product -- should pay every worker ever exposed to asbestos, irrespective of the worker's medical condition (in other words, pay the lawyers who solicited these workers to file claims). To this end the plaintiff's bar conducts seminars on how to file claims when there is no demonstrable medical condition (Schmitt 2001). The defendants of asbestos claims -- as well as many judges, congressmen and physicians - feel this is an illogical position, self-serving only for the lawyers, and that only workers who have actually have demonstrable asbestos-related disease should be compensated. Anyone involved or who plans to become involved in asbestos disease evaluation should understand this fundamental philosophical rift, as it helps explain claims that seem preposterous in the light of medical science. For plaintiffs' lawyers, the reports their physician experts provide -- all too often medically bogus -- are merely a means to one of two ends. First, and preferable, is to obtain mass settlements; a few legitimate cases are bundled with the bogus claims, and defending companies often settle the whole lot without investigating the merits of individual cases. (For a discussion of how this works, see Asbestos Litigation 101.) Second, if a defending company chooses to fight a case to trial, the plaintiff's lawyers are then fully prepared to proclaim the sins of asbestos suppliers, and argue that these sins justify compensation for any worker exposed to asbestos in the past regardless of the medical condition. In other words, Doctor A may say asbestos disease and Doctor B may say there is none, but the "sins" and the "worker's exposure" will be argued as equally (if not more) important issues.
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