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Tuesday 16 July 2013

How Much Exposure To Asbestos Mesothelioma Lawyers 2013

How Much Exposure To Asbestos Biogarphy About

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Asbestos exposure becomes a health concern when relatively high concentrations of asbestos fibers are inhaled over a long time period. People who become ill from asbestos are almost always those who are exposed on a day-to-day basis in a job where they work directly with the material. As a person's exposure to fibers increases, either by breathing large amounts of fibers or by breathing fibers for a longer time, the risk of disease also increases. It can take anywhere from 10 to 40 years after exposure for an asbestos-related illness to develop. There is no known safe level of asbestos exposure. Great care should be exercised when asbestos exposure is likely. The following government offices and regulatory agencies have deemed asbestos a known human carcinogen based on extensive review of the data and of the evidence regarding the carcinogenicity of asbestos.

The U.S. Department of Health and Human Services (DHHS).
The U.S. Environmental Protection Agency (EPA).
The International Agency for Research on Cancer (IARC).

Potential Exposure
Asbestos minerals are widespread in the environment. They may occur in large natural deposits or as contaminants in other minerals. For example, tremolite asbestos may occur in deposits of vermiculite and talc. Asbestos may also be found in soil formed from the erosion of asbestos-bearing rock. You are most likely to be exposed to asbestos by breathing in fibers that are suspended in air. These fibers can come from naturally occurring sources of asbestos, or from the wearing down or disturbance of asbestos-containing manufactured products including insulation, automotive brakes and clutches, ceiling and floor tiles, dry wall, roof shingles, and cement. Low levels of asbestos that present little, if any, risk to your health can be detected in almost any air sample. For example, 10 fibers are typically present in a cubic meter (fibers/m3) of outdoor air in rural areas. (A cubic meter is about the amount of air that you breathe in 1 hour.) Health professionals often report the number of fibers in a milliliter (mL) (equivalent to a cubic centimeter [cm3]) of air rather than in a cubic meter of air. Typical levels found in cities are about 10-fold higher than in rural areas. Levels may reach 10,000 fibers/m3 or higher near an asbestos factory or mine. Above average levels may also occur near a building containing asbestos products that is being torn down or renovated, or near a waste site where asbestos is not properly covered up or stored. The concentration of asbestos in indoor air depends on whether asbestos is present (for example, insulation, ceiling or floor tiles) and whether these asbestos-containing materials are in good condition, or are deteriorated and easily crumbled. People who work with asbestos or asbestos-containing products (for example, miners, insulation workers, asbestos abatement workers, and automobile brake mechanics) without proper protection are likely to be exposed to much higher levels of asbestos fibers in air. In addition, custodial and maintenance workers in buildings with asbestos-containing materials may be exposed to higher levels of asbestos. Since vermiculite and talc may contain asbestos, both workers and the general population may be exposed to asbestos when using these products. You can also be exposed to asbestos by ingesting asbestos fibers present in drinking w ater. Even though asbestos does not dissolve in water the small fibers can be suspended in water like dust particles. The fibers can enter water through erosion from natural deposits or piles of waste asbestos, from asbestos-containing cement pipes used to carry drinking water, or from filtration through asbestos-containing filters. Most drinking water supplies in the United States have concentrations of less than 1 million fibers per liter (MFL), even in areas with asbestos deposits or with asbestos-cement water supply pipes. However, in some locations, water samples may contain 10-300 million fibers per liter or even higher. The average person drinks about 2 liters of water per day. The health effects of swallowing small amounts of asbestos are unclear. Some groups of people exposed to asbestos fibers in their drinking water have higher-than-average death rates from cancer of the esophagus, stomach, and intestines; however, it is very difficult to tell whether this is caused by asbestos or by something else. Animals given very high doses of asbestos in food did not get more fatal cancers than usual, although a higher than normal rate of nonfatal tumors did occur in the intestines of rats in one study. Asbestos does not pass through the skin.

Entering and Leaving Body
If you breathe asbestos fibers into your lungs, some of the fibers will be deposited in the air passages and on the cells that make up your lungs. Most fibers are removed from your lungs by the natural process of coughing up mucus that is then swallowed and carried into the stomach. This process usually takes place within a few hours. Fibers deposited in the deepest parts of the lung are removed more slowly. In fact, some fibers may remain in place for many years and may never be eliminated from your body. Amphibole asbestos fibers are retained in the lung longer than chrysotile asbestos fibers. If you swallow asbestos fibers (either those present in water or those that are moved to your throat from your lungs), nearly all of the fibers pass through your digestive system and are excreted in the feces within a few days. A small number of fibers may penetrate the cells that line the stomach and intestines, and a few may penetrate and enter the blood. Asbestos fibers in the bloodstream may become trapped in other tissues or eliminated in urine. Asbestos fibers do not pass through the skin.
Treatment

A chest x-ray is the most common test used to determine if you have received sustained exposure to asbestos. A chest x-ray is recommended only for persons who have sustained relatively heavy exposure to asbestos. A chest x-ray is of no value for the detection of asbestos exposure in a person whose exposure to asbestos has been only brief (industrial or occupational) or transient (environmental). The x-ray cannot detect the asbestos fibers themselves, but it can detect the early signs of lung damage caused by asbestos. While substances other than asbestos can sometimes produce similar changes in the lungs, a chest x-ray is usually reliable for detecting asbestos-related effects produced by long-term exposures at relatively high concentrations of asbestos fibers. Other tests, such as gallium-67 lung scanning and high-resolution computer tomography, are also useful in detecting changes in the lungs; however, no currently available test can detect exposure-related effects from normal environmental exposures. The most reliable test to determine exposure to asbestos is a biopsy. In this test small pieces of lung tissue are removed surgically and examined for the presence of microscopic asbestos fibers. Another direct test involves determining the presence of asbestos fibers in material rinsed out of the lung through lavage. Both biopsy and lavage are invasive and uncomfortable. Asbestos fibers can also be detected in mucus (sputum), urine, or feces, but these tests are not reliable for determining how much asbestos may be in your lungs since nearly all people show low levels of asbestos fibers in body waste products. Higher-than-average levels in mucus, urine, or feces can indicate exposure to asbestos, but it is not yet possible to use the results of these tests to estimate how much asbestos you have been exposed to, or to predict whether you are likely to suffer any health effects. Individuals who have been exposed (or suspect they have been exposed) to asbestos fibers on the job or at home should inform their physician of their exposure history and any symptoms. Asbestos fibers can be measured in urine, feces, mucus or material rinsed out of the lungs, although these tests do not indicate the actual amount of asbestos in the lungs. Your doctor may recommend a thorough physical examination, including a chest x-ray and lung function tests. It is important to note that chest x-rays cannot detect asbestos fibers in the lungs, but they can help identify any lung changes resulting from asbestos exposure. Interpretation of the chest x-ray may require the help of a specialist experienced in reading x-rays for asbestos-related diseases. Other tests may also be necessary. The symptoms of asbestos-related diseases may not become apparent for many decades after exposure. If any of the following symptoms develop, a physical examination should be scheduled without delay:
Shortness of breath.
A cough or a change in cough pattern.
Blood in the sputum (mucus) coughed up from the lungs.
Pain in the chest or abdomen.
Difficulty in swallowing or prolonged hoarseness.
Significant weight loss.
Prevention
The most important way that families can lower their exposures to asbestos is to be aware of the sources of asbestos in their homes and avoid exposure to these sources. The most important source of asbestos in a home is damaged or deteriorating asbestos-containing insulation, ceiling tiles, or floor tiles. Should you suspect that your house contains asbestos, you may wish to use this website to locate a company that is trained to abate the asbestos. Prior to disturbance or when damaged, contact a professional to identify asbestos-containing materials in the home and take appropriate action to control release of asbestos fibers. If you live close to locations where asbestos and certain other ores are mined or processed, where a building that contains asbestos products is being torn down or renovated, or a waste site where asbestos is not properly covered, then the levels of asbestos in dust and wind-blown soil may be higher. Keep windows shut to avoid dust accumulation inside your home. Be sure to clean dust from your shoes or remove your shoes upon entry into the house. Pets can also bring asbestos into the home by carrying dust or dirt on their fur or feet if they spend time in places that have high levels of asbestos in the soil. Ingesting asbestos in house dust or soil by hand-to-mouth activities (like thumb sucking or mouthing toys) is a significant exposure pathway for children that can be reduced in many ways. Regular hand and face washing to remove asbestos-containing dusts and soil, especially before meals, can lower the possibility of asbestos fibers on the skin being accidentally ingested while eating. Families can lower exposures to potential household hazards, such as asbestos, by using a high efficiency particulate air (HEPA)-equipped vacuum cleaner during regularly cleaning the home. By doing this settled fibers on the floors and horizontal surfaces are picked up along with the normal dust and tracked in soil. Residents should not attempt to clean-up asbestos fiber contamination from releases from damaged asbestos in the home, but should seek professional assistance to determine the extent of hazard and to remove contamination. Planting grass and shrubs over bare soil areas in the yard can lower the contact that children and pets may have with soil, and reduce the tracking of soil into the home. You can also bring asbestos into your home in the dust on your hands or clothes if you work in mine or are involved with the processing of minerals that contain asbestos, in asbestos removal, or in buildings with damaged or deteriorating asbestos. (Federal law regulates work practices to limit the possibility of asbestos being brought home in this way. Your occupational health and safety officer at work can tell you whether materials you work with contain asbestos and what measures you must take to avoid exposures to yourself and your family as a result of you work.)

How Much Exposure To Asbestos Mesothelioma Lawyers 2013

How Much Asbestos Exposure Mesothelioma Lawyers 2013

How Much Asbestos Exposure About Biogarphy

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Your doctor will diagnose an asbestos-related lung disease based on your past exposure to asbestos, your symptoms, a physical exam, and test results.

Specialists Involved
Your primary care doctor, such as a family doctor or internist, may provide ongoing care if you have an asbestos-related lung disease. Other specialists also may be involved in your care, including a:
Pulmonologist. This is a doctor who specializes in diagnosing and treating lung diseases.
Radiologist. This is a doctor who is specially trained to supervise x-ray tests and look at x-ray pictures.
Surgeon or oncologist. An oncologist is a doctor who specializes in diagnosing and treating cancer. The surgeon or oncologist may take a tissue sample from your lungs to study under a microscope.
Pathologist. A pathologist is a doctor who specializes in identifying diseases by studying cells and tissues under a microscope. A pathologist may study your tissue sample.

Exposure to Asbestos
Your doctor will want to know about your history of asbestos exposure. He or she may ask about your work history and your spouse's or other family members’ work histories.
Your doctor also may ask about your location and surroundings. For example, he or she may ask about areas of the country where you've lived.
If you know you were exposed to asbestos, your doctor may ask questions to find out:
How much asbestos you were exposed to. For example, were you surrounded by visible asbestos dust?
How long you were exposed to asbestos and how often during that time you were in direct contact with it.

Symptoms
Your doctor may ask whether you have any symptoms, such as shortness of breath or coughing. The symptoms of asbestos-related lung diseases vary. They depend on which disease you have and how much it has damaged your lungs.
Your doctor also may ask whether you smoke. Smoking, along with asbestos exposure, raises your risk for lung cancer.

Physical Exam
Your doctor will listen to your breathing with a stethoscope to find out whether your lungs are making any strange sounds.
If you have a pleural effusion with a lot of fluid buildup, your doctor might hear a dull sound when he or she taps on your chest. Or, he or she might have trouble hearing any breathing sounds. If you have asbestosis, your doctor may hear a crackling sound when you breathe in.
Your doctor will check your legs for swelling, which may be a sign of lung-related problems. He or she also will check your fingers and toes for clubbing.
Clubbing is the widening and rounding of the fingertips and toes. Clubbing most often is linked to heart and lung diseases that cause lower-than-normal blood oxygen levels.
Chest X RayA chest x ray is the most common test for detecting asbestos-related lung diseases. This painless test creates pictures of the structures inside your chest, such as the lungs
A chest x ray can’t detect asbestos fibers in the lungs. However, it can show asbestos-related diseases, such as pleural plaque and pleural effusion. Pleural effusion also can be a sign of a more severe disease, such as mesothelioma.

A chest x ray also can show asbestosis. Often the lung tissue will appear very white on the x-ray pictures. The size, shape, location, and degree of whiteness can help your doctor figure out how much lung damage you have. Severe asbestosis may affect the whole lung and have a honeycomb look on the x-ray pictures.
If you have lung cancer, a chest x ray may show masses or abnormal fluid.
If you have mesothelioma, a chest x ray will show thickening of the pleura. The pleura is the tissue around the lungs and diaphragm (the muscle below your lungs). The chest x ray also will usually show signs of pleural effusion in people who have mesothelioma.

Other Diagnostic Tests
To help confirm a chest x-ray finding, or to find out how much lung damage you have, you may have more tests.Chest Computed Tomography Scan
A chest computed tomography (to-MOG-ra-fee) scan, or chest CT scan, is a painless test that creates precise pictures of the structures inside your chest, such as your lungs. A CT scan is a type of x ray, but its pictures show more detail than standard chest x-ray pictures.
A chest CT scan may be very helpful for finding asbestosis in its earliest stages, before a standard chest x ray can detect it.Lung Function Tests
Lung function tests measure how much air you can breathe in and out, how fast you can breathe air out, and how well your lungs deliver oxygen to your blood.
These tests can show whether your lung function is impaired. They also can help your doctor track your disease over time.

Biopsy
The only way to confirm a diagnosis of lung cancer or mesothelioma is for a pathologist to check samples of your lung cells or tissues. A pathologist is a doctor who identifies diseases by studying cells and tissues under a microscope.
Doctors have many ways to collect tissue samples. One way is through bronchoscopy (bron-KOS-ko-pee). For this procedure, your doctor will pass a thin, flexible tube through your nose (or sometimes your mouth), down your throat, and into your airways. He or she will then take a sample of tissue from your lungs.

If your doctor thinks you have mesothelioma, you may have a thoracoscopy (thor-ah-KOS-ko-pee). For this procedure, you'll be given medicine so you don't feel any pain.
Your doctor will make a small cut through your chest wall. He or she will put a thin tube with a light on it into your chest between two ribs. This allows your doctor to see inside your chest and get tissue

Asbestos exposure has been attributed as a root cause for many types of health complications, with some being more serious than others. Many of these complications affect the respiratory system and can impact breathing and lung function. Because mesothelioma symptoms may be similar (i.e. chronic cough, chest pain, or difficulty breathing) to other respiratory ailments, it is important to discuss specific situations with mesothelioma doctors, especially for those who have a known asbestos-exposure history. Specialists like Dr. Sugarbaker and others can help make an accurate mesothelioma diagnosis.

Though asbestos was once considered a “miracle mineral”, since the days of the Holy Roman Empire it has been apparent that asbestos causes severe pulmonary problems. Even centuries ago, naturalists like Pliny the Elder noted that the slaves who mined asbestos suffered from “sickness of the lungs” and died at an early age.

However, asbestos diseases really didn’t garner attention until the early to mid 1900s, when asbestos use was at its peak and more and more individuals were getting sick due to exposure to this toxic mineral, which was primarily used as insulation but was also added to myriad other manufactured goods including a wide variety of building products.

Though researchers don’t fully understand why some individuals develop asbestos diseases and others do not, evidence points to the fact that length and intensity of exposure may have something to do with it. However, experts agree that no amount of asbestos exposure is safe

Life with an Asbestos Disease
Because they affect the lungs and inhibit breathing, living with an asbestos disease can be quite difficult. Both asbestosis and mesothelioma patients will require certain procedures or treatments that serve to lessen symptoms of the disease and aim to improve quality of life. Unfortunately, however, both diseases eventually claim the lives of their victims.
Most individuals who’ve developed asbestos diseases were exposed to the mineral without knowing it was toxic. Though many employers knew of the dangers of asbestos, many continued to use it without regard for employees’ health and never provided masks or other gear that may have prevented inhalation of asbestos fibers. This negligence has negatively impacted not only the lives of thousands of victims but their loved ones as well.

Mesothelioma
Mesothelioma is a rare but aggressive form of asbestos cancer for which the only known cause is exposure to asbestos. It affects about 2,000 to 3,000 Americans each year. Like asbestosis, it can take as much as 50 years to be diagnosed because it has a long latency period. That means it remains silent in the body for decades, finally appearing via symptoms like cough, shortness of breath, difficulty breathing, chest pain, and fatigue.

Because asbestos exposure is the only cause of mesothelioma cancer, those individuals who exhibit these symptoms must be sure to inform their doctor of their past exposure. He will most likely order x-rays, MRIs, or CT scans to determine the presence of a tumor, which usually appears in the pleura – the lining of the lungs. The imaging tests will be followed by a biopsy, which can determine whether or not the tumor is malignant. Once a definitive diagnosis is made, the patient will meet with an oncologist or medical team to determine the best course of treatment.

Mesothelioma Lung Cancer
Lung cancer, which is different than mesothelioma because it actually occurs in the lung tissue as opposed to the mesothelium, can also be attributed to asbestos exposure. There are general sub-classifications of lung cancer. These are small cell and non-small cell which are assigned based on how the cancer cells appear within the lung tissue. Each of these types has appeared in those exposed to asbestos.

Asbestos Lung Cancer
Mesothelioma, while extremely rare, is still the most common malignancy associated with asbestos exposure. Pure lung cancers have also been connected with asbestos exposure, though it is also possible for mesothelioma to spread into the affected lung from the pleura or peritoneum. Lung cancers caused by asbestos exposure are known to be more common in those with other mitigating risk factors, including smoking.

Asbestosis, also known as diffuse pulmonary fibrosis, can take anywhere from 10-30 years to develop. That means those who are diagnosed with asbestosis may have been exposed to asbestos as much as 30 years before the disease is diagnosed.

Asbestosis is characterized by severe shortness of breath, which is generally the first symptom to appear. At first, this is only evident after exertion but may eventually happen even during rest. Other symptoms include tightness in the chest, dry cough, loss of appetite, fatigue, and – when the disease reaches an advanced stage – clubbing of the fingers.

This disease is generally diagnosed by means of a chest x-ray which can show scarring, as well as testing with more sophisticated imaging including MRIs or CT scans. If asbestosis is suspected, an open lung biopsy will most likely be performed.

If you are experiencing such symptoms and have worked with asbestos in the past, it is essential that you inform your doctor as to your history with this toxic mineral. It may help speed a diagnosis.
There is currently no cure for asbestosis but doctors can suggest treatments and other procedures that can serve to lessen its symptoms and make patients more comfortable. It is also essential that those who have asbestosis stop smoking immediately. Smokers with asbestosis are much more likely to develop mesothelioma – asbestos-caused cancer.

How Much Asbestos Exposure Mesothelioma Lawyers 2013

What Is Asbestos Exposure Mesothelioma Lawyers 2013

What Is Asbestos Exposure About Biogarphy

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Asbestos is a mineral that is made up of silicon, oxygen, hydrogen and other metal ions. These needle shaped fibers are so small that they cannot be seen unless the concentration in the air is very heavy. Asbestos is an excellent material for insulation because the fibers are strong, flexible and will not burn. The three most common forms of asbestos fibers are chrysolite, amosite and crocidolite. Because asbestos is such a tiny fiber, it needs to be attached to something. When asbestos fibers are mixed with other materials, it produces what is called an asbestos containing material.
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Many industrial products are made of asbestos, including thermal insulation (pipe, block & cement); fireproofing acoustical texture products; textile and cloth products (asbestos gloves, blanket, etc.); spackling, patching & taping compounds; gaskets and packing, asbestos-cement pipe and sheet material, ceiling tiles, wall board, siding and roofing; friction materials (brakes & clutches). Asbestos materials had been used by the automotive industry, shipping industry and NASA for insulating the Space Shuttle.

The dust that is created from the manufacture, installation and eventual deterioration of asbestos materials releases asbestos in the air. Asbestos becomes a health hazard only when these materials crumble, fall apart, are damaged or ripped. When asbestos materials are damaged, fibers are released into the air, where they may stay suspended for long periods of time. Asbestos can then be inhaled and the fibers can lodge deeply in the lungs.

The Federal government placed a moratorium on the production of most asbestos products in the early 1970's, but these products continued to be installed through the late 1970's and even into the early 1980's. Asbestos cement pipe which would need to be cut, beveled, and grinded by pipe fitters had continued well into the late 1980s and sometimes the 1990s.

Commercial production of asbestos insulation began in 1879, and the first case of asbestos-related disease, described as "curious bodies" in the lungs was detected in 1899. The first cases of asbestosis and lung cancer attributable to asbestos exposure were diagnosed in the United States in 1935. The Congressional Library of Congress has had a book on the harmful effects of asbestos and its link to cancer causation as it discusses the analysis of work place illnesses on its shelves since it was published in 1939.

Most health information on asbestos has been derived from studies of workers who have been exposed to asbestos in the course of their occupation. Asbestos fiber concentrations for these workers were many times higher than those encountered by the general public. Although the risks associated with low-level non-occupational exposure are not as well established, the Environmental Protection Agency (EPA) concludes that there is no safe level of exposure to asbestos fibers.

This commentary reviews the research of Dr. Le Roy Upson Gardner conducted in 1942 that inhaled chrysotile fibers could induce malignant neoplasia in mice; and between 1951 and 1954, using cancer-insusceptible mice, yielded neoplasia risk ratio of 5.7 compared with control animals. The studies also showed that the primary effect of chrysotile is to cause epithelial proliferation in alveoli adjacent to bronchioles. Gardner had written letters and reports designating some of the mouse tumors as malignant and he attributed the tumors to inhaled chrysotile asbestos fibers, even though the mice had not developed asbestosis. Gardner had found in 1942 that the majority of the mouse tumors were truly malignant. Details are provided in a manuscript on the "Thirty Years of Asbestos Research of the Saranac Laboratory between the years 1928 and 1958" by Gerrit Schepers. These details are fairly clearly recorded in Dr. Gardner's handwritten notes (cited in the book noted above) because he did not publish these research findings in technical journals, for his work was performed on behalf of industrial sponsors, from whom he did not have permission to publish.

Asbestos in automobile brake linings may be a potential cause of cancer, a Wayne State University School of Medicine research team fears. Dr. Andrew Reeves, chief of the research team, said yesterday that overexposure to asbestos particles is known to be the cause of a number of lung diseases, including cancer. But what isn't known, he said, is whether use of the brakes releases harmful particles into the air.

ASBESTOS is used in brake linings, building materials and, to some extent, in the clothing industry. In addition to lung cancer, overexposure to asbestos may lead to asbestosis, a degenerative type of lung disease, and possibly to mesothelioma, a tumor of the lining of the chest cavity, or pleura.
Dr. Reeves said the asbestos industry denies, on good evidence, that asbestos released into the air from automobile brakes poses a health hazard because the high temperatures incurred in braking mean the asbestos has taken another form. "But the final word is not known," Dr. Reeves said, nothing that is not known yet what that form is and whether it presents any hazard to humans.

Seeking "the final word," Dr. Reeves and his research team are planning an experimental system that will simulate the mechanical action of brakes, heat the asbestos to 1,500 degrees Fahrenheit and blow the dust into chambers for inhalation by guinea pigs. The guinea pigs will then be
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The study investigates mortality from cancer and other diseases in a cohort of wives of asbestos cement workers in Casale Monferrato (northern Italy). The cohort comprised of 1,964 women after the exclusion of those with an occupational record in the asbestos cement industry. A woman's domestic exposure to asbestos was estimated according to their husbands' periods of employment in the asbestos plant. The occurrence of malignant mesotheliomas after domestic exposure to asbestos has been shown. Despite the well known association between asbestos and malignancies and the suggestions from case reports and case-control studies of mesotheliomas due to domestic exposure to asbestos only one cohort study has been published so far on mortality among family contacts of asbestos workers. In this study, except for pleural neoplasms, mortality among women with the opportunity for exposure to domestic asbestos was not statistically different from that expected for any of the causes of death considered.

All women reported to have a pleural cancer and all but two of those dying from lung cancer had been exposed for at least 10 years. In conclusion this study found a clear excess of mesotheliomas among wives of workers in the asbestos cement production industry. Our results are in agreement with the only similar study published before and confirm the importance of avoiding contamination of asbestos workers' homes

LIBBY, Mont. -- Yvonne Resch remembers thinking as a child that the vermiculite mine only added to the area's natural beauty -- its lights on Zonolite Mountain looked like a castle.
But the mine and its processing plants spewed asbestos over her town for more than 70 years, coating homes, schools and ball fields. Now her father, mother and two brothers are among many residents who suffer the coughing, hacking and wheezing of asbestos-related diseases, which have been blamed in more than 200 deaths since the late 1990s.

The Environmental Protection Agency took the unprecedented step this week of declaring Libby a federal public health emergency, vowing to finish a cleanup that has languished for nearly a decade.
The agency pledged at least $125 million to speed the work of going door-to-door, raising tents over contaminated homes, removing contaminated soil and vacuuming out attics and any other surface once contaminated by miners returning from work.

This article presents a historical analysis of published data regarding the exposure of brake mechanics to asbestos as a result of doing brake work. Concerns about this possible hazard were first raised in the late 1960s. This analysis focuses on 30 years of data collected during the brake repair event (e.g., a brake job) and 8-hour time-weighted average (TWA) personal samples. A brake job TWA represents the average concentration a mechanic experienced during brake servicing, rather than throughout the workday, and an 8-hour TWA represents the average airborne concentration of asbestos for the entire workday (which would involve brake work and other activities). Nearly 200 brake job and 8-hour TWA airborne asbestos samples were analyzed to assess how asbestos concentrations varied by type of vehicle serviced, country in which mechanics worked, time period, and brake-cleaning method. To facilitate comparisons, brake job TWAs were converted to estimated 8-hour TWAs using the durations and number of brake jobs performed per mechanic each day. Estimated and measured 8-hour TWAs for mechanics servicing automobiles and light trucks ranged from <0.002 to 0.68 f/cc, with a mean of 0.04 f/cc. In contrast, the 8-hour TWAs for mechanics servicing heavy trucks and buses ranged from 0.002 to 1.75 f/cc, with a mean of 0.2 f/cc, suggesting that these mechanics experienced higher daily asbestos exposures than automobile and light truck mechanics. Brake job and 8-hour TWAs for brake mechanics worldwide were found to be similar during the same time periods, and they were consistently below contemporaneous occupational health standards in the United States. The increased use of brake-dust control measures in some garages resulted in at least a 10-fold decrease in the TWA airborne concentrations of asbestos from the 1970s to the late 1980s.

Our goal in this brief and limited historical summary of asbestos-related diseases has been to bring the clinician up to date with the current status of this important medical and public health issue. The references will provide an information source for those who require more comprehensive knowledge.

What Is Asbestos Exposure Mesothelioma Lawyers 2013

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The story of asbestos is an all to familiar one, "A miraculous, do anything chemical substance is identified as a serious health hazard" - except for one thing. Unlike many of its doomed chemical contemporaries, asbestos is not a product of modern technology. Its use predates history, and the recognition of health hazards associated with asbestos is recorded in writings from the first century.
The word asbestos comes from the Greek word meaning "inextinguishable" or "indestructible." However, asbestos has been known by many other names including: "mountain leather," "incombustible linen," and "rock floss." The name of chrysotile, one of the most common forms of asbestos, is derived from the Greek words "chrysos" (gold) and "tilos" (fiber) or "gold fiber."

It is possible to trace written documentation of the use of asbestos back to the days of the Roman Empire. However, evidence of the use of asbestos in pottery and chinking of log homes dating back 3000 BC has been found archeological digs in Scandinavia.

The geographer in the first century identified what was believed to be the first asbestos quarry on the Greek island of Evvoia. In early Greek and Roman times, it was used for flame retardant cloth, building materials and women's clothing. Roman restaurants used tablecloths made of asbestos. These tablecloths were flame retardant and could be thrown into the fire to remove food and other debris, and placed back on the table for the next customer. Romans also used asbestos in their building materials. Historian Pliny the Elder went so far as to note that asbestos "affords protection against all spells, particularly that of the Magi."

Asbestos was used by many different cultures for hundreds of purposes purposes. The Egyptians embalmed pharos with asbestos, and the Persians imported asbestos from India for wrapping their dead. They thought it was hair from a small animal that lived by fire and died by water.
In medieval times Asbestos was used extensively as insulation in suits of armor. And unscrupulous merchants made it into crosses that they advertised as having been made from "the true cross." Some forms of asbestos look like old wood, and merchants claimed that their resistance to fire was proof that these "wooden crosses" came from cross on which Christ was hung. .

Near the end of the 19th century, the use asbestos became even more widespread as a result of the industrial revolution. Asbestos was used in the manufacture of more than 3000 products including textiles, building materials, insulation and brake linings. Its use continued to increase through the 1970s. At that time the evidence against asbestos as a health hazard (it was found to cause asbestosis and mesothelioma) could no longer be denied, and its use fell into sudden decline.

Interestingly enough, the hazards of asbestos were recorded as early as Roman times. Both Pliny the Elder and the first century geographer Strabo noted that workers exposed to asbestos had many health problems. Pliny the Elder recommended that quarry slaves from asbestos mines not be purchased because "they die young." Lung ailments were common to anyone who worked with asbestos fibers. Pliny the Elder suggested the use of a respirator made of transparent bladder skin to protect workers from asbestos dust.

In 1897 a Viennese physician attributed emaciation and pulmonary problems to (asbestos) dust inhalation. The first documented case of an asbestos-related death was reported in 1906 when the autopsy of an asbestos worker revealed lung fibrosis. As early as 1908 insurance companies began decreasing policies and benefits for asbestos workers. Metropolitan Life increased the premiums for such workers. In 1928 Cook identified the effects of asbestos in the lungs as asbestosis. He pointed out that this fibrotic scarring of lungs resulting from prolonged exposure to asbestos dust could have a latency period of 15 years. Others have suggested that the latency period can be much longer. In 1929 a coroner called for public enquiry after the death of an employee. By 1935 physicians were beginning to notice that some patients who had asbestosis also were victims of lung cancer.
By 1978 documented studies were beginning to demonstrate the extent to which asbestos workers had been affected. In one study asbestosis was detected in 10% of asbestos workers who had been employed in the industry for 10-19 years, in 73% of workers who had been employees 20-29 years and in 92% of workers who had been employed for more than 40 years.

It is interesting that despite the evidence of severe health risks related to exposure to asbestos dating as far back as the first century, the production of products containing asbestos continued to grow until the mid 1970s. Documents reveal that asbestos manufacturers were aware of the health risks related to exposure to asbestos from the 1940s and 1950s, but chose to conceal this information from their employees. In the 1970s, the Environmental Protection Agency (EPA) and Occupational Safety and Health Administration (OSHA) began to regulate asbestos. Today workers are protected from exposure to asbestos as a result of very strict regulations and enforcement. Unfortunately, legislation cannot undo the damage that was done to those who worked in asbestos related jobs prior to 1980s.

Because of its fiber strength and heat resistance asbestos has been used in a variety of building construction materials for insulation and as a fire retardant. Asbestos has also been used in a wide range of manufactured goods, mostly in building materials (roofing shingles, ceiling and floor tiles, paper products, and asbestos cement products), friction products (automobile clutch, brake, and transmission parts), heat-resistant fabrics, packaging, gaskets, and coatings.

Asbestiform tremolite, CaliforniaAsbestiform tremolite, California
Most uses of asbestos are not banned. A few are banned under existing regulations.
Where asbestos may be found:
Attic and wall insulation produced containing vermiculite
Vinyl floor tiles and the backing on vinyl sheet flooring and adhesives
Roofing and siding shingles
Textured paint and patching compounds used on wall and ceilings
Walls and floors around wood-burning stoves protected with asbestos paper, millboard, or cement sheets
Hot water and steam pipes coated with asbestos material or covered with an asbestos blanket or tape
Oil and coal furnaces and door gaskets with asbestos insulation
Heat-resistant fabrics

Automobile clutches and brakes
A very simplistic visualization of an atom includes a dense nucleus comprised of a specific number of positively charged protons and uncharged neutrons surrounded by orbits of negatively charged electrons. One might be tempted to envision a configuration similar to a solar system with the nucleus representing the sun and the electrons representing planets. While this is a good starting point, you will soon discover that the solar system model does not provide a true representation of the atom.

Atomic Number
The number of protons always equals the number of electrons in an atom, and that number is equal to the atomic number. For instance, carbon has an atomic number of six and therefore has six protons and six electrons.

Atomic Mass
The weight of an atom is determined by the number of neutrons and protons that are present in the nucleus. The proton and neutron, which are similar in mass, each weighs approximately 1,836 times greater than a single electron, thus the mass contributed by electrons is insignificant when determining atomic weight or atomic mass. The atomic mass is the sum of the protons and neutrons in the nucleus. Carbon has an atomic mass of twelve. Since there are six protons in carbon (remember, it has an atomic number of six and, therefore, must have six protons), it must have six neutrons:

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While the number of protons and electrons remain constant in the neutral atom, the number of neutrons may vary within different atom species of the same element. As a result, the atomic mass for one atom may be different from another atom of the same element if the number of neutrons varies. Atomic mass must account for all possible species or nuclides (isotopes), of an atom. Carbon 12 with its 6 neutrons is by far the most common isotope of carbon. In reality, there is a carbon 14 which has eight neutrons and an atomic mass of 14. There is also a carbon 11 which has only five neutrons.
The Atomic Mass Average

This is the sum of all nuclide (isotope), masses multiplied by their natural abundance. This weighted average is the relative mass listed in the Periodic Table. The relative percentage of each nuclide (isotope), appears to be similar throughout the world.

The Charge of an Atom
Since the number of protons (positive charges) always equals the number of electrons (negative charges) in an atom, positive charges equal negative charges and atoms in the elemental state have no charge. Only when an atom takes an electron from another atom does the particle become charged. This charged form of the atom is known as an ion. Positively charged ions are called cations, and negatively charged ions are called anions. For instance, when chlorine accepts an electron from sodium, the sodium ion that is formed will have one more proton than electrons. It will therefore have a positive charge and be called a cation. The chlorine (or chloride) ion will have one more electron than protons. It will take on a negative charge and be called an anion. The compound formed by this transfer of electrons is sodium chloride or table salt, which is nothing like the highly reactive sodium or extremely poisonous chlorine from which it was formed.

Energy Levels
Until now we have focused on the nucleus. Lets turn our attention to the electrons, which surround the nucleus of the atom. Electrons are located in energy levels a term which has replaced the word shells, which was once used to describe the location of electrons. The word shell suggests a fixed position, which is far from reality. We will use energy level to describe the possible location of electrons.
There are seven energy levels. Each has a specific maximum number of electrons that can exist in it. The number of electrons, which an energy level can hold is equal to 2n2 where n = energy level. The letter n represents the principal quantum number that specifies the energy level of the atom in which an electron is located. The chart below identifies the various energy levels and maximum number of electrons possible. The energy level closest to the nucleus is represented by energy level 1.

Within each principal energy level is one or more energy sublevels (Orbitals) or subshells. The number of sublevels possible for any one principal energy level is equal to the value of the quantum number (n) for that energy level. Note that I have purposely introduced the reader to the term quantum number quite early in this discussion. The idea is not to scare the reader, but rather to begin building up a certain comfort level with a term that may invoke a certain fear of the unreachable to the new chemist. While there are theoretically 7 possible sublevels, only four are actually used for the known elements. The others are not currently needed. Sublevels are numbered with consecutive whole numbers. The first sublevel is 0 followed by numbers 1 through 6. These numbers are the azimuthat quantum numbers, ohm. The value of l can never be greater than n-1. Based on the 112 known and verified elements, the following table represents possible sublevels in the atom (Jespersen, 1997)

Marco Polo encountered asbestos in China where it was called salamander’s wool. The ancients had many names for asbestos, calling it "mountain leather," "incombustible linen," "rock floss," and “lapis asbestos”. Defined by its uses, the strange material could be braided into rope or used as insulation. The use of oil lamps for illumination was a major application before the invention of the incandescent light bulb. Once braided, asbestos could be turned into a wick that was both indestructible and cheap. Charlemagne had a napkin made from asbestos that he would purify by throwing into a fire.

At the dawning of the industrial age, machinery, steam, and fire became catalysts for the more widespread use of asbestos. By the 1860’s asbestos began appearing as insulation in the United States and Canada. Thousands of different uses for asbestos appeared by the middle of the 20th century. These included fire retardant coatings, concrete, bricks, pipes and fireplace cement, heat, fire, and acid resistant gaskets, pipe insulation, ceiling insulation, fireproof drywall, flooring, roofing, lawn furniture, drywall joint compound and on and on.

Timeline Linking Asbestos Use and Respiratory Diseases
For all its wonderful properties, early asbestos research also proved that this naturally occurring material could be linked to a number of respiratory diseases. Early citings linking asbestos to respiratory disease, mesothelioma and other cancers included:
The Roman historian Pliny the Elder noted that the slaves who worked in the asbestos mines were less healthy than other slaves. He recommended that such slaves not be purchased since they would “die young”.

Strabo, a 1st century geographer, also observed the rise of health problems among asbestos workers. Since it was noted that asbestos exposure caused primarily a respiratory disease, Pliny the Elder suggested the use of a respirator made of transparent bladder skin to protect workers from asbestos dust.

Modern medicine first documented an asbestos-related death in 1906. Soon afterwards medical reports began to identify a mystery tumors, and insurance companies began to cut their coverage of asbestos workers.

The term mesothelioma entered the medical literature in 1931 when it was identified by Klemperer and Rabin.
By the 1940’s mesothelioma was being associated with asbestos exposure. Still, at the urging of industry, public authorities and the medical establishment continued to resist recognizing the connection between mesothelioma and asbestos.
Finally, the link became incontrovertible with a 1960 article published in Lancet entitled "Primary Malignant Mesothelioma of the Pleura."

During this time, the growing awareness of the connection between asbestos exposure [New Page http://www.curemeso.org/site/Asbestos_Information/who-is-at-risk.htm] and asbestosis and mesothelioma eventually brought some government regulation. (Contrary to popular belief, to this day asbestos has not been banned in the U.S., though it has in numerous other countries.) It also brought litigation. During trial discovery proceedings it became clear that the asbestos industry had known about the hazards of the product for decades. Moreover, they had conspired to hide the facts from both their workers and the consumers of their products. This disregard for the health and safety of both employees and consumers led to thousands of successful lawsuits and settlements against asbestos vendors. Over time this led to over sixty companies seeking refuge in Chapter 11 bankruptcy protection.

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The chances of developing lung cancer associated with asbestos exposure, asbestosis and smoking are dramatically increased when these three risk factors are combined, and quitting smoking significantly reduces the risk of developing lung cancer after long-term asbestos exposure, according to a new study.\

Share This"The interactions between asbestos exposure, asbestosis and smoking, and their influence on lung cancer risk are incompletely understood," said lead author Steven B. Markowitz, MD DrPH, professor of occupational and environmental medicine at the School of Earth & Environmental Sciences at Queens College in New York. "In our study of a large cohort of asbestos-exposed insulators and more than 50,000 non-exposed controls, we found that each individual risk factor was associated with increased risk of developing lung cancer, while the combination of two risk factors further increased the risk and the combination of all three risk factors increased the risk of developing lung cancer almost 37-fold."

The findings were published online ahead of print publication in the American Thoracic Society's American Journal of Respiratory and Critical Care Medicine.

The study included 2,377 long-term North American insulators and 54,243 male blue collar workers with no history of exposure to asbestos from the Cancer Prevention Study II. Causes of death were determined from the National Death Index.

Among non-smokers, asbestos exposure increased the rate of dying from lung cancer 5.2-fold, while the combination of smoking and asbestos exposure increased the death rate more than 28-fold. Asbestosis increased the risk of developing lung cancer among asbestos-exposed subjects in both smokers and non-smokers, with the death rate from lung cancer increasing 36.8-fold among asbestos-exposed smokers with asbestosis.

Among insulators who quit smoking, lung cancer morality dropped in the 10 years following smoking cessation from 177 deaths per 10,000 among current smokers to 90 per 10,000 among those who quit. Lung cancer rates among insulators who had stopped smoking more than 30 years earlier were similar to those among insulators who had never smoked.

There were a few limitations to the study, including the fact that smoking status and asbestosis were evaluated only once and that some members of the control group could have been exposed to relatively brief periods of asbestos.

"Our study provides strong evidence that asbestos exposure causes lung cancer through multiple mechanisms," said Dr. Markowitz. "Importantly, we also show that quitting smoking greatly reduces the increased lung cancer risk seen in this population."

The International Expert Meeting on Asbestos, Asbestosis, and Cancer was convened in Helsinki on 20--22 January 1997 to discuss disorders of the lung and pleura in association with asbestos and to agree upon state-of-the-art criteria for their diagnosis and attribution with respect to asbestos. The group decided to name this document The Helsinki Criteria.

The requirement for diagnostic criteria was perceived in part because of new developments in diagnostic methods, with better identification of asbestos-related disorders. Such developments enhance awareness of health hazards imposed by asbestos, lead to practical prevention and appropriate compensation, and also provide opportunity to carry out international comparisons. They also provide possible models for the risk assessment of other mineral dusts. The meeting was attended by 19 participants from 8 countries not producing asbestos. The chairmen were Professor Douglas W Henderson (Flinders Medical Centre, Australia) and Professor Jorma Rantanen (Finnish Institute of Occupational Health, Finland). The group was a multidisciplinary gathering of pathologists, radiologists, occupational and pulmonary physicians, epidemiologists, toxicologists, industrial hygienists, and clinical and laboratory scientists specializing in tissue fiber analysis. Collectively, the group has published over 1000 articles on asbestos and associated disorders. This document is based on a more comprehensive report providing scientific evidence for the conclusions and recommendations (People and Work Research Reports, no 14, Finnish Institute of Occupational Health, Helsinki, 1997).

The meeting was scientifically supported by leading institutions in the field of asbestos research, and it was funded by the Ministry of Social Affairs and Health and the Finnish Work Environment Fund
General considerations
Occupational exposures to asbestos dust have been widespread in all industrial countries and continue as a consequence of "in-place" materials. In detailed interviews about 20% to 40% of adult men report some past occupations and jobs that may have entailed asbestos exposure at work. In Western Europe, North America, Japan, and Australia the use of asbestos peaked in the 1970s, and currently about 10 000 mesotheliomas and 20 000 asbestos-induced lung cancers are estimated to occur annually in the population of approximately 800 million people.

In general, reliable work histories provide the most practical and useful measure of occupational asbestos exposure. Using structured questionnaires and checklists, trained interviewers can identify persons who have a work history compatible with significant asbestos exposure. Dust measurements can be used in the estimation of past fiber levels at typical workplaces and in the use of asbestos-containing materials. A cumulative fiber dose, as expressed in fiber-years per cubic centimeter, is an important parameter of asbestos exposure.

The clinical diagnosis of asbestos-related diseases is based on a detailed interview of the patient and occupational data on asbestos exposure and appropriate latency, signs and symptoms, radiological and lung physiology findings, and selected cytological, histological and other laboratory studies. Histopathological confirmation is required for suspected asbestos-related malignancies and for the resolution of differential diagnoses. A multidisciplinary approach is suggested for the evaluation of problem cases.

The chest radiograph is the basic tool for identifying asbestos-related diseases such as asbestosis, pleural abnormalities, lung cancer, and mesothelioma. The limitation of the chest radiograph in the detection of asbestosis and asbestos-associated pleural abnormalities is widely recognized. Computed tomography (CT) and high resolution computed tomography (HRCT) can facilitate the detection of asbestosis and asbestos-related pleural abnormalities, as well as asbestos-related malignancies; they are not recommended as a screening tool but may be invaluable for individual clinical evaluation and research purposes. Examples are the detection of pleural abnormalities in suspected cases of asbestosis and the detection of parenchymal disease obscured on the chest film and also use as an aid to differential diagnosis. As new imaging techniques such as digital radiography are evolving, standard images and interpretations must be developed. The place of other imaging techniques (ultrasound, magnetic resonance imaging, gallium scanning, ventilation-perfusion studies, positron-emission tomography) has yet to be established, and they are not currently recommended for the clinical diagnosis of asbestos-related disorders.

Analysis of lung tissue for asbestos fibers and asbestos bodies can provide data to supplement the occupational history. For clinical purposes, the following guidelines are recommended to identify persons with a high probability of exposure to asbestos dust at work: over 0.1 million amphibole fibers (>5 µm) per gram of dry lung tissue or over 1 million amphibole fibers (>1 µm) per gram of dry lung tissue as measured by electron microscopy in a qualified laboratory or over 1000 asbestos bodies/g dry tissue (100 asbestos bodies per gram of wet tissue) or over 1 asbestos body per milliliter of bronchoalveolar lavage fluid, as measured by light microscopy in a qualified laboratory. Each laboratory should establish its own reference values. The median values for occupationally exposed populations should be substantially above the reference values. Efforts to standardize analytical methods for fiber burden analyses by different laboratories are recommended

Asbestosis
Asbestosis is defined as diffuse interstitial fibrosis of the lung as a consequence of exposure to asbestos dust. Neither the clinical features nor the architectual tissue abnormalities sufficiently differ from those of other causes of interstitial fibrosis to allow confident diagnosis without a history of significant exposure to asbestos dust in the past or the detection of asbestos fibers or bodies in the lung tissue greatly in excess of that commonly seen in the general population. Symptoms of asbestosis include dyspnea, and cough. Common findings are inspiratory basilar crackles and, less commonly, clubbing of the fingers. Functional disturbances can include gas exchange abnormalities, a restrictive pattern, and obstructive features due to small airway disease.

Asbestosis is generally associated with relatively high exposure levels with radiological signs of parenchymal fibrosis. However, it is possible that mild fibrosis may occur at lower exposure levels, and the radiological criteria need not always be fulfilled in cases of histologically detectable parenchymal fibrosis. The recognition of asbestosis by chest radiography is best guided by standardized methods such as the classification of the International Labour Organisation (ILO) and its modifications. Standard films must always be used. For research and screening purposes, radiological findings of small opacities, grade 1/0, are usually regarded as an early stage of asbestosis. Inspiratory basilar rales, restrictive impairment, small airway obstruction, and gas exchange disturbances in pulmonary function are considered valuable information for clinical diagnosis, for occupational health practice, and for attribution purposes. HRCT can confirm radiological findings of asbestosis and show early changes not seen on chest X rays, but should be performed only in selected cases.

Smoking effects should be considered in the evaluation of early asbestosis, lung function tests, and respiratory symptoms. A histological diagnosis of asbestosis requires the identification of diffuse interstitial fibrosis in well inflated lung tissue remote from a lung cancer or other mass lesion, plus the presence of either 2 or more asbestos bodies in tissue with a section area of 1 cm2 or a count of uncoated asbestos fibers that falls into the range recorded for asbestosis by the same laboratory.
In order to achieve reasonable comparability between different studies, a standardized system for the histological diagnosis and grading of asbestosis is required. The Roggli-Pratt modification of the CAP-NIOSH system is recommended as a reasonably simple and reproducible scheme for this purpose.
There is evidence that rare cases of asbestosis occur without significant numbers of asbestos bodies. These cases are recognizable—and distinguishable from idiopathic pulmonary fibrosis—only by analysis of the uncoated fiber burden. Rare cases of asbestosis in relation to the inhalation of pure chrysotile can occur, with a prolonged interval between the last exposure and the diagnosis and few or no detectable asbestos bodies and a low fiber burden. The existence of such cases is speculative and, if the diagnosis can be made, it must be done from other compelling clinical or radiological grounds combined with exposure data.

Fibro-inflammatory patterns other than conventional asbestosi
s have also been described for workers with occupational exposure to asbestos, including a pattern resembling desquamative interstitial pneumonia (DIP), the occurrence of granulomatous inflammation, a picture that resembles lymphocytic interstitial pneumonia, and organizing pneumonia with bronchiolitis obliterans. Although the DIP-like picture with asbestos bodies is probably asbestos-related, the other patterns have not yet been shown to be so related

Pleural disorders
Asbestos-related pleural abnormalities are divided into pleural plaques, mainly involving the parietal pleura, sometimes with calcification, and diffuse pleural thickening, which is a collective name for pleural reactions involving mainly the visceral pleura. These include benign asbestos-related pleural effusion, blunted costophrenic angle, crow`s feet or pleuroparenchymal fibrous strands, and rounded atelectasis. Avoidance of the term "pleural asbestosis" is recommended. Pleural plaques are usually asymptomatic, and without clinically important findings.

The specificity of pleural plaques according to the ILO 1980 Classification of Radiographs of Pneumoconioses is low unless the plaques are radiographically well defined. The most common differential diagnosis is subpleural fat. Radiographic findings are reliable for the diagnosis of asbestos-related pleural plaques when they are characteristic (eg, bilateral circumscribed plaques, bilateral calcification, diaphragmatic plaques). Pleural plaques represent circumscribed areas of fibrous thickening, typically of the parietal pleura, due to the deposition of paucicellular collagenous tissue with a laminar or basket-weave pattern; they may or may not calcify. In regions where plaques are not endemic, 80–90% of the plaques that are radiologically well defined are attributable to occupational asbestos exposure. The presence of pleural plaques may justify follow-up among occupationally exposed groups.

Diffuse pleural fibrosis designates noncircumscribed fibrous thickening of variable cellularity, which usually affects the parietal, but mainly the visceral, layers. In the setting of occupational asbestos exposure, such diffuse fibrosis is probably a result of benign asbestos pleuritis with effusion. It may or may not be associated with rounded atelectasis. Diffuse pleural thickening can be associated with mild, or rarely moderate or severe, restrictive pulmonary function defects.

Low exposures from work-related, household, and natural sources may induce pleural plaques. For diffuse pleural thickening, higher exposure levels may be required

Mesothelioma
Malignant mesothelioma affecting any serosal membrane may be induced by asbestos inhalation. The histological, immunohistochemical and ultrastructural markers for the diagnosis of mesothelioma are well established. Expert opinion should be sought on atypical cases, or on those in which the diagnosis is uncertain because of discordant findings or in which the amount of material available is insufficient for definite diagnosis. Mesothelioma is frequently presented with pleural effusion, dyspnea and chest pain.

With the exception of certain histological types of mesothelioma that are benign or of uncertain or borderline malignant potential (eg, multicystic mesothelioma, benign papillary mesothelioma), all types of malignant mesothelioma can be induced by asbestos, with the amphiboles showing greater carcinogenic potency than chrysotile.

A lung fiber count exceeding the background range for the laboratory in question or the presence of radiographic or pathological evidence of asbestos-related tissue injury (eg, asbestosis or pleural plaques) or histopathologic evidence of abnormal asbestos content (eg, asbestos bodies in histologic sections of lung) should be sufficient to relate a case of pleural mesothelioma to asbestos exposure on a probability basis. In the absence of such markers, a history of significant occupational, domestic, or environmental exposure to asbestos will suffice for attribution. There is evidence that peritoneal mesotheliomas are associated with higher levels of asbestos exposure than pleural mesotheliomas are. In some circumstances, exposures such as those occurring among household members may approach occupational levels.

The question in unresolved of whether or not a case of mesothelioma for which the lung fiber count falls within the range recorded for unexposed urban dwellers is related to asbestos. More information is needed regarding the interpretation of fiber burdens in the pleura or samples of tumor tissue before these measures can be used for the purposes of attribution.

The following points need to be considered in the assessment of occupational etiology:
• The great majority of mesotheliomas are due to asbestos exposure.
• Mesothelioma can occur in cases with low asbestos exposure. However, very low background environmental exposures carry only an extremely low risk.

• About 80% of mesothelioma patients have had some occupational exposure to asbestos, and therefore a careful occupational and environmental history should be taken.
• An occupational history of brief or low-level exposure should be considered sufficient for mesothelioma to be designated as occupationally related.
• A minimum of 10 years from the first exposure is required to attribute the mesothelioma to asbestos exposure, though in most cases the latency interval is longer (eg, on the order of 30 to 40 years).
• Smoking has no influence on the risk of mesothelioma
Lung cancer

All 4 major histological types (squamous, adeno-, large-cell and small-cell carcinoma) can be related to asbestos. The histological type of a lung cancer and its anatomic location (central or peripheral, upper lobe versus lower lobe) are of no significant value in deciding whether or not an individual lung cancer is attributable to asbestos. Clinical signs and symptoms of asbestos-related cancer do not differ from those of lung cancer of other causes.

As examples, 1 year of heavy exposure (eg, manufacture of asbestos products, asbestos spraying, insulation work with asbestos materials, demolition of old buildings) or 5–10 years of moderate exposure (eg, construction, shipbuilding) may increase the lung cancer risk 2-fold or more. In some circumstances of extremely high asbestos exposure, a 2-fold risk of lung cancer can be achieved with exposure of less than 1 year.

The relative risk of lung cancer is estimated to increase 0.5–4% for each fiber per cubic centimeter per year (fiber-years) of cumulative exposure. With the use of the upper boundary of this range, a cumulative exposure of 25 fiber-years is estimated to increase the risk of lung cancer 2-fold. Clinical cases of asbestosis may occur at comparable cumulative exposures.

A 2-fold risk of lung cancer is related to retained fiber levels of 2 million amphibole fibers (>5 µm) per gram of dry lung tissue or 5 million amphibole fibers (>1µm) per gram of dry lung tissue. This lung fiber concentration is approximately equal to 5000 to 15 000 asbestos bodies per gram of dry tissue, or 5 to 15 asbestos bodies per milliliter of bronchoalveolar lavage fluid. When asbestos body concentrations are less than 10 000 asbestos bodies per gram of dry tissue, electron microscopic fiber analyses are recommended.

Chrysotile fibers do not accumulate within lung tissue to the same extent as amphiboles because of faster clearance rates; therefore, occupational histories (fiber-years of exposure) are probably a better indicator of lung cancer risk from chrysotile than fiber burden analysis is.

A lung fiber burden within the range recorded for asbestosis in the same laboratory should be assigned a significance similar to that of asbestosis. For a patient with lung cancer and a fiber count that falls within the range recorded for unexposed urban dwellers, the relationship of the tumor to amphibole asbestos is doubtful at most.

Estimates of the relative risk for asbestos-associated lung cancer are based on different-sized populations. Because of the high incidence of lung cancer in the general population, it is not possible to prove in precise deterministic terms that asbestos is the causative factor for an individual patient, even when asbestosis is present. However, attribution of causation requires reasonable medical certainty on a probability basis that the agent (asbestos) has caused or contributed materially to the disease. The likelihood that asbestos exposure has made a substantial contribution increases when the exposure increases. Cumulative exposure, on a probability basis, should thus be considered the main criterion for the attribution of a substantial contribution by asbestos to lung cancer risk. For example, relative risk is roughly doubled for cohorts exposed to asbestos fibers at a cumulative exposure of 25 fiber-years or with an equivalent occupational history, at which level asbestosis may or may not be present or detectable. Heavy exposure, in the absence of radiologically diagnosed asbestosis, is sufficient to increase the risk of lung cancer. Cumulative exposures below 25 fiber-years are also associated with an increased risk of lung cancer, but to a less extent.

The presence of asbestosis is an indicator of high exposure. Asbestosis may also contribute some additional risk of lung cancer beyond that conferred by asbestos exposure alone. Asbestosis diagnosed clinically, radiologically (including HRCT), or histologically can be used to attribute a substantial causal or contributory role to asbestos for an associated lung cancer.

Pleural plaques are an indicator of exposure to asbestos fibers. Because pleural plaques may be associated with low levels of asbestos exposure, the attribution of lung cancer to asbestos exposure must be supported by an occupational history of substantial asbestos exposure or measures of asbestos fiber burden. Bilateral diffuse pleural thickening is often associated with moderate or heavy exposures, as seen in cases with asbestosis, and should be considered accordingly in terms of attribution.
A minimum lag-time of 10 years from the first asbestos exposure is required to attribute the lung cancer to asbestos.

Not all exposure criteria need to be fulfilled for the purposes of attribution. For example, the following can be considered: (i) significant occupational exposure history with low fiber burdens (eg, long exposure to chrysotile and long lag-time between the end of exposure and mineralogical analysis) and (ii) high fiber counts in lung or broncholavage fluid with an uncertain history or without long-term duration (short exposures can be very intense).

At very low levels of asbestos exposure, the risk of lung cancer appears to be undetectably low.

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