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Asbestosis

Asbestos is a naturally occurring mineral widely used in commercial and industrial construction between 1930-1970 for its durable, heat resistant properties. Inhalation of microscopic asbestos fibers deep into the lungs may lead to inflammation and scarring, causing a number of medical conditions. Asbestosis is a diffuse scarring of lung (pulmonary) tissue leading to loss of lung capacity, low oxygen levels, and progressive impairment from shortness of breath. Typically, individuals must be exposed to high levels of microscopic, airborne asbestos fibers over several years to accumulate enough of a "fiber burden" in the lungs to cause asbestosis, a type of diffuse interstitial pulmonary fibrosis (A number of other diseases besides asbestos inhalation may lead to similar lung changes). A long latent period between onset of exposure and disease is required for the diagnosis, usually measured in decades. The diffuse lung injury in asbestosis can progress long after exposure ceases. Pleural plaques are localized scars of the pleural tissue lining the inside of the chest walls, next to the outer edges of the lung. They are more common than pulmonary asbestosis, occurring at lower exposure levels, and the potential health effects are less serious. Plaques also require a long latency period to appear, usually causing no symptoms or loss of lung capacity. They most commonly are discovered on routine x-rays of asbestos-exposed workers. Less commonly, pleural scarring can lead to diffuse pleural fibrosis, a generalized thickening of the linings of chest wall and lung, sometimes leading to loss of lung capacity and symptoms of breathlessness. Rarely, benign areas of diffuse pleural scarring may trap a small piece of lung, giving rise to an unusual x-ray shadow mistaken for a lung mass, called rounded atelectasis, or "pleural pseudotumor", which can lead to additional tests (CAT scan of the lungs, biopsy) to confirm the benign diagnosis. Malignant mesothelioma is a rare cancer of the pleura lining the lung and chest wall caused by asbestos exposure that can occur 20-40 years after initial exposure. Progressive and difficult to control with surgery or chemotherapy, mesotheliomamay be fatal within several years of diagnosis. Carcinoma of the lung occurs with increased frequency in asbestos-exposed individuals who have also been heavy smokers.

Diagnosis of asbestos-related disorders is made by a pulmonary or occupational disease specialist. A careful work history must establish exposure and latency. Complete medical history and physical examination are required to exclude other diseases of the heart and lungs that can mimic the findings of asbestosis. Chest x-rays demonstrate typical findings in the lungs and/or pleural surfaces. Pulmonary function tests, or "breathing tests" are mandatory to document any lung impairment. Lung biopsy is rarely needed for diagnosis of benign conditions (asbestosis, pleural plaques and fibrosis), and always necessary to confirm a malignant diagnosis of mesothelioma or lung cancer. Fortunately, elimination of asbestos from the workplace in the United States and most industrialized countries in the 1970's and 80's has greatly reduced the exposed population at risk for development of pulmonary asbestosis, mesothelioma and other asbestos-related disorders.

In addition to being a risk for developing asbestosis, asbestos exposure is a risk factor for pleural tumors (mesothelioma), lung cancer, abdominal lining cancer (peritoneal mesothelioma), and benign fluid collections around the lung (benign asbestos effusion). The risk of developing lung cancer after asbestos exposure is greatly magnified in smokers.

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