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. 

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. 

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.