What Is It, Causes, Signs and Symptoms, and More
Author: Anna Hernández, MD
Editors: Alyssa Haag, Józia McGowan, DO, Kelsey LaFayette, DNP
Illustrator: Jessica Reynolds, MS
Copyeditor: David G. Walker
What is asbestosis?
Asbestosis is a type of pneumoconiosis, which is a chronic lung disease caused by the inhalation of small airborne particles like dust, pollen grains, or ash. As the name suggests, asbestosis occurs from exposure to asbestos, a family of minerals that were widely used as construction materials for many years due to their heat-resistant and insulating properties. Because of these characteristics, asbestos was used in many different products, ranging from roofing tiles and water supply lines to fire blankets, automobile parts, paint, and cement.
What causes asbestosis?
Asbestosis is caused by exposure to asbestos. Asbestos fibers are extremely small, around 500 times finer than human hair, and as such, they can be inhaled easily without one noticing. Once in the respiratory tract, asbestos fibers tend to settle in the lower lobes of the lungs and on the pleural membrane, forming thick white patches called pleural plaques. These fibers are ingested by alveolar macrophages, which normally clear the lungs by eliminating all foreign particles in a process called phagocytosis. In asbestosis, however, macrophages are unable to digest asbestos fibers, triggering an inflammatory reaction that damages the lungs. In order to repair the damage, the interstitial lung tissue is substituted with collagen fibers, thereby resulting in the thickening of the alveolar walls. The overall result is a fibrotic, rigid lung that doesn’t allow air to easily enter during inhalation, reducing the total volume of air in the lungs.
Today, most individuals with asbestosis have a history of occupational or secondhand exposure to asbestos. The risk of getting asbestosis depends on the duration and intensity of exposure as well as the type, length, and thickness of inhaled fibers. Historically, high-risk jobs included builders, plumbers, electricians, and shipyard workers as well as individuals working in asbestos mining facilities and in the military. Additionally, family members who lived with asbestos workers could also develop the disease from fibers found on the clothes, skin, or hair of the exposed individual.
Currently, many industrialized countries have either banned or restricted the use of asbestos; however, the World Health Organization (WHO) estimates about 125 million individuals in the world are still exposed to asbestos at their workplace. Additionally, in many old buildings, asbestos can still be found enclosed in elements like electrical parts, water pipes, or flooring tiles. If these old buildings get demolished or become structurally damaged over time, asbestos fibers can be released into the air, posing a health risk to exposed individuals.
What are the signs and symptoms of asbestosis?
Initially, asbestosis is asymptomatic, however; after a latency period of 10 to 15 years, it can begin to cause symptoms like progressive shortness of breath, nonproductive cough, and fatigue. Advanced asbestosis may cause low oxygen blood levels (i.e., hypoxemia), nail clubbing, and dry (i.e., fine) crackles at the base of the lungs upon respiratory auscultation. In late stages, asbestosis can cause cor pulmonale; this is a condition where lung disease causes enlargement of the right ventricle of the heart, resulting in heart failure over time.Individuals exposed to asbestos also have an increased risk of developing lung cancer and mesothelioma, which is a type of aggressive cancer that originates from the mesothelium: a thin membrane that lines the pleural cavity. Symptoms of mesothelioma include chest pain, shortness of breath, pleural effusions, and bloody sputum if the tumor invades a blood vessel. Additionally, tobacco smoking has a synergistic effect with asbestos, which can further increase the risk of lung cancer.
How is asbestosis diagnosed?
Diagnosis of asbestosis is suspected in individuals with respiratory symptoms and a past history of exposure to asbestos. The diagnostic work-up typically begins with imaging techniques, like a chest X-ray or CT scan of the lungs, which may show bilateral opacities in the lower lobes of the lungs as well as pleural plaques if the pleura is already affected. Next, pulmonary function tests, like spirometry and plethysmography, may be performed to assess lung function. In cases where the diagnosis is uncertain, bronchoalveolar lavage may be conducted to analyze the sputum for asbestos bodies, which can be seen as gold or brown dumbbell-shaped rods under a microscope.
How is asbestosis treated?
There is currently no specific treatment available for asbestosis, and therefore, management focuses on measures to reduce symptom severity. Cessation of asbestos exposure is recommended to prevent further damage to the lungs. Smoking cessation is also recommended as tobacco can increase the damage and accelerate the progression of the disease. Because individuals diagnosed with asbestosis are more likely to develop severe respiratory infections, influenza and pneumococcal vaccination are recommended to reduce the risk of complications. Oxygen therapy may be prescribed for individuals who have hypoxemia at rest or during mild physical activity. Finally, individuals may undergo pulmonary rehabilitation consisting of exercise training, health education, and breathing techniques to improve their exercise capacity and quality of life.
The prognosis of asbestosis is highly variable amongst individuals and depends on the extent of lung damage and the severity of other coexisting lung disorders, such as chronic obstructive pulmonary disease (COPD). In those who smoke, the disease progresses more rapidly as the clearance mechanisms of the respiratory tract are impaired.
What are the most important facts to know about asbestosis?
Asbestosis is a type of lung disease that occurs from breathing in asbestos, typically from occupational exposure (e.g., construction workers, plumbers, electricians, shipyard workers, military service, etc.). Inhalation of asbestos causes pulmonary fibrosis, resulting in coughing, shortness of breath, and low blood oxygen levels. Diagnosis is based on a history of exposure to asbestos, a restrictive pattern on pulmonary function tests, and chest X-ray or high-resolution CT with compatible findings. There is currently no curative treatment for asbestosis, and management focuses on cessation of exposure and modifiable risk factors, oxygen therapy, and pulmonary rehabilitation. In addition to asbestosis, other asbestos-related diseases include pleural effusions and pleural plaques and increased risk of lung cancer and mesothelioma.
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Resources for research and reference
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Balmes JR. Occupational and Environmental Lung Disease. In: Jameson J, Fauci AS, Kasper DL, Hauser SL, Longo DL, Loscalzo J. eds. Harrison's Principles of Internal Medicine, 20e. McGraw Hill; 2018.
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