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    Abestosis

    Asbestosis is widespread scarring of lung tissue caused by
    breathing asbestos dust.

    Asbestos is composed of fibrous mineral silicates of different chemical
    compositions. When inhaled, asbestos fibers settle deep in the lungs,
    causing scaring. Asbestos inhalation also can cause the two layers of
    membrane covering the lungs (pleural space) to thicken; these thickenings
    are called pleural plaques. These plaques do not become cancerous.

    Inhaling asbestos fibers can occasionally cause fluid to accumulate in the
    space between the two pleural layers of the lungs (pleural space); this is
    called a noncancerous (benign) asbestos effusion.

    Asbestos also causes cancer in the pleura, called mesothelioma, or in the
    membranes of the abdomen, called peritoneal mesothelioma. In the United States,
    asbestos is the only known cause of cancerous (malignant) mesothelioma.
    Smoking is not a cause of cancerous mesothelioma. Mesotheliomas most
    commonly appear after exposure to crocidolite, one
    of four types of asbestos. Amosite, another type, also causes mesotheliomas.
    Chrysotile probably causes fewer cases of mesothemliomas than other types,
    but chrysotile is often contaminated with tremolite, which does. Mesotheliomas
    usually develop 30 to 40 years after exposure and can occur after low exposure.

    Asbestos can also cause lung cancer. Lung cancer from asbestos is related in
    part to the level of exposure to asbestos fibers; however, among people with
    asbestosis, lung cancer occurs most commonly in those who also smoke
    cigarettes, principally in those who smoke more than a pack a day.

    Although the general public has become anxious about the risks of asbestos,
    most non-occupationally exposed people are at extremely low risk of developing
    asbestos related lung disease. The asbestos must be broken into tiny pieces
    to be inhaled into the lungs. Workers who demolish buildings that have
    insulation containing asbestos are at increased risk. People who frequently
    work with asbestos are at the greatest risk of developing lung disease. The
    more a person is exposed to asbestos fibers, the greater the risk of developing
    an asbestos related disease.

    Symptoms

    Symptoms of asbestosis appear gradually only after large areas of the lung
    become scarred. The scarring causes the lungs to lose their elasticity. The
    first symptoms are a mild shortness of breath and a decreased ability to
    exercise. Smokers who have chronic bronchitis along with asbestosis may
    cough and wheeze. Gradually, breathing becomes more and more difficult.
    In about 15% of people with asbestosis, severe shortness of breath and
    respiratory failure develop.

    A person with noncancerous asbestos effusion may have trouble breathing
    because of fluid accumulation. Pleural plaques cause only a mild breathing
    difficulty that results from stiffness of the chest wall. Persistent pain in the
    chest and shortness of breath are the most common symptoms caused by
    mesothelioma.

    Diagnosis

    Usually the person with asbestosis has abnormal lung function, and a doctor
    listening with a stethoscope placed over the lungs can hear abnormal sounds
    called crackles. In a person who has a history of exposure to asbestos, a
    doctor sometimes can diagnose asbestosis with a chest x-ray or a chest
    computed tomography (CT) that shoes characteristic changes. Pleural
    plaques that develop in many people with exposure to asbestos often
    contain calcium, which makes them easy to see on chest x-rays and CT.
    A lung biopsy is rarely needed to make the diagnosis.

    If a tumor of the pleura is found on x-ray, a doctor must perform a biopsy
    (remove a small piece of pleura and examine it under a microscope) to
    determine if it is cancerous. Fluid around the lungs may be removed with
    a needle and analyzed for cancer cells (a procedure called thoracentesis).
    However, throracentesis is not usually as accurate as performing a pleural biopsy.
    If a chest x-ray reveals something that looks like a tumor, there is
    a good possibility that the area is a primary lung cancer and should be
    evaluated completely.

    Prevention and Treatment

    Diseases caused by asbestos inhalation can be prevented by minimizing asbestos
    dust and fibers in the workplace. Because industries that use
    asbestos have improved dust control, fewer people develop asbestosis
    today, but mesotheliomas are still occurring in people who were exposed
    as many as 40 years ago. Asbestos in the home should be removed by
    workers trained in safe removal techniques. Smokers who have been in
    contract with asbestos can decrease their risk of lung cancer by giving up
    smoking and should almost certainly have a chest x-ray annually.

    Most treatments for asbestosis ease symptoms – for example, oxygen therapy
    relieves shortness of breath. Draining fluid from around the lungs using a
    procedure called thoracentesis also may make breathing easier. Occasionally,
    lung transplantation has been successful in treating asbestosis.

    Mesotheliomas are invariably fatal; sadly, most people with mesotheliomas die
    within 1 to 4 years of diagnosis. Chemotherapy and radiation therapy do not
    work well, and surgical removal of the tumor does not cure the cancer. Other
    treatment is focused on controlling pain and shortness of breath, in an effort
    to preserve as much quality or life as possible.


    Source: Merck Manual of Medical Information
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