Asbestosis · What Is It, Causes, Signs and Symptoms, and More

Asbestosis is a type of pneumoconiosis, a group of chronic interstitial lung diseases caused by the inhalation of mineral dusts (e.g., silica, coal dust, talc dust), which are most commonly encountered in occupational settings.  

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 a wide range of products, including roofing tiles, water supply lines, fire blankets, automobile parts, paint, and cement.  

Asbestosis is caused by exposure to asbestos. Because asbestos fibers are extremely small (around 500 times finer than human hair), 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 (i.e., fibrotic thickenings of the parietal pleura). These fibers are then 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 an attempt to repair the damage, the interstitial lung tissue is substituted with collagen fibers, leading to thickening of the alveolar walls. The overall result is a fibrotic, rigid lung that cannot expand properly during inhalation, leading to impaired air inflow and reduced lung volume. 

Today, most individuals with asbestosis have a history of occupational or secondhand exposure to asbestos. The risk of developing asbestosis depends on the duration and intensity of exposure, and on the characteristics of inhaled fibers (i.e., type, length, and thickness). Historically, high-risk jobs include builders, plumbers, electricians, and shipyard workers, as well as individuals working in asbestos mining facilities and the military. Additionally, family members living with asbestos workers could also develop the disease from fibers carried on their clothes, skin, or hair. 

Currently, many industrialized countries have either banned or restricted the use of asbestos; however, the World Health Organization (WHO) estimates that exposure to asbestos at the workplace causes more than 200,000 deaths worldwide every year. Additionally, asbestos can still be found enclosed in elements like electrical parts, water pipes, or floor tiles of many old buildings. Whenever these are demolished or undergo structural damage, 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 20-30 years, symptoms like progressive shortness of breath, nonproductive cough, and fatigue may appear. 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 lead to cor pulmonale, 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, an aggressive cancer originating from the mesothelium (i.e., the thin membrane that lines the pleural cavity). Symptoms of mesothelioma include chest pain, shortness of breath, pleural effusions, and hemoptysis (i.e., coughing up blood) if the tumor invades a blood vessel. Additionally, tobacco smoking has a synergistic effect with asbestos and can further increase the risk of lung cancer. 

Diagnosis of asbestosis is suspected in individuals with respiratory symptoms and a history of exposure to asbestos. The diagnostic work-up typically begins with imaging techniques such as chest X-ray or lung CT scan, which may show bilateral opacities in the lower lobes and pleural plaques if the pleura is already affected.  

Next, pulmonary function tests such as spirometry and plethysmography may be performed to assess lung function. If the diagnosis remains uncertain, bronchoalveolar lavage may be carried out to examine the sputum for asbestos bodies, which appear under the microscope as gold or brown dumbbell-shaped rods. 

As no specific treatment is currently available for asbestosis, its management focuses on measures to reduce symptom severity.  

In order to prevent further damage to the lungs and progression of the disease, cessation of asbestos exposure and smoking are recommended. 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.