Asbestosis, Asbestos Pleural Diseases, Limit Lung Function
Pleural Plaques and Pleural Thickening Part of Asbestosis Disease
Asbestosis and asbestos pleural disease are nonmalignant asbestos diseases that are slowly progressive. They can be severely disabling and potentially fatal. These asbestos diseases cause impairment of pulmonary function, including small airway obstruction, a reduction in lung capacity, breathing restriction, and a reduction in the ability to transfer oxygen from air into the blood. Approximately one in seven people who suffer from asbestosis eventually develop asbestos lung cancer (Asbestos Fact Sheet, Lung Cancer, American Cancer Society).
Asbestosis and asbestos pleural disease are the result of cumulative exposure to asbestos. In individuals who develop these asbestos diseases, every nontrivial occupational exposure to asbestos is significant.
Asbestos Diseases: Asbestosis
Asbestosis is a scarring of lung tissue caused by the inhalation of asbestos fibers. A portion of the fibers reach the alveoli (air sacs) where oxygen is transferred into the blood. Asbestos activates the lung’s immune system and starts a reaction best described as an inflammatory process. Scavenger white blood cells (macrophages) try to break down the asbestos (phagocytosis) but are not successful, causing other cells (fibroblasts) to grow and form connective–tissue–based scars.
The formation of scar tissue or collagen in the lungs is known as fibrosis. The scar tissue slowly builds up, often reducing the lung’s ability to deliver oxygen to the blood and remove carbon dioxide (reduced diffusion capacity). The total lung capacity or TLC may also be reduced. In severe cases, the impairment of lung function can strain the heart, or even result in heart disease, such as right–sided heart failure or “cor pulmonale.”
Asbestosis and the Inflammatory Process
The inflammatory process starts within hours or days after inhalation of asbestos and injury at the cellular level begins shortly thereafter. In people who develop asbestosis, the inflammatory process continues to progress, fueled by indestructible asbestos fibers, even long after exposure to asbestos ceases.
This asbestosis inflammatory process may continue undetected for decades causing no pain or respiratory symptoms. In many people, the process eventually produces symptoms—breathing abnormalities and radiographic changes. Usually, the first symptoms are shortness of breath and a dry cough. These symptoms often precede abnormalities on chest x–ray or pulmonary function tests. The period between exposure and diagnosis is called “latency” and may range from 10 to 50 years. See Asbestosis Diagnosis for more details.
Asbestos Diseases: Asbestos Pleural Disease
Asbestos pleural disease is a nonmalignant disease caused by inhalation of asbestos fibers that scar the pleura. The pleura is the thin membrane lining the lung and chest cavity. If the scarring is diffuse and extends along the chest wall, it is called pleural thickening. If the scarring is more focused and well–defined, it is called pleural plaques.
Asbestos pleural disease results in a similar scarring process as the one that occurs inside the lung with asbestosis; however, it occurs in the lining of the lungs rather than in the lungs. Pleural thickening and pleural plaques can cause shortness of breath and impair lung function. Although its symptoms may be treated, asbestos pleural disease is permanent and progressive with no cure. Even after exposure to asbestos has ceased, scarring continues due to the body’s interaction with retained asbestos fibers.
Pleural scarring, which is often seen in conjunction with asbestosis, can be detected on chest x–rays and CT scans and usually reflects a significant history of exposure to asbestos. It normally takes at least 10 years after the first exposure to asbestos for asbestos pleural disease to develop.