Industrial production of asbestos began in the 1850s, but by the middle of the 20th century, it was evident that asbestos exposure increased the risk for non-malignant inflammatory (pleural effusions, pleural plaques, rounded atelectasis, and asbestosis) and malignant (mesothelioma and bronchogenic carcinoma) pulmonary diseases. The first cases of asbestos-associated fibrosis were described in the early 1900s, and the term “asbestosis” was coined by Cooke in 1927. Asbestos-associated bronchogenic carcinoma was established by the mid-1950s, whereas the association between asbestos and malignant mesothelioma (MM) was recognized by the 1960s. In the early 1970s, the United States placed a moratorium on asbestos use, and at least 40 other countries have banned or severely restricted asbestos use.
Asbestos fibers have been historically chosen for construction, shipping, mining, and aerospace engineering commercial use because of its high electrical and thermal resistance and low-cost.
Asbestos:Group of naturally occurring hydrated silicate fibers whose tensile strength and resilience are ideal for a variety of construction and insulation purposes.
- Serpentine fibers (chrysolite): Curly and flexible and are less pathogenic than amphibole fibers
- Amphibole fibres (crocidolite, amosite, tremolite, and anthophyllite): Straight, stiff, more brittle fibers that are are more toxic than serpentine fibers as they are less soluble and straight, and they usually align along the airstream and reach deeper into the lungs and the interstitium by penetrating the epithelium
- Direct work-related environmental exposure: Common among workers at shipyard, mining, aerospace, etc.
- Bystander exposure: Commonly seen in certain professionals like electricians, mason, and painters
- General community exposure (M/C form): Due to use of asbestos road surface, playground material, landfills, and chemical paints
Asbestos exposure increases the risk for:
- Non-malignant inflammatory diseases:
- Pleural effusions
- Pleural plaques
- Rounded atelectasis
- Malignant diseases:
- Bronchogenic carcinoma
Interstitial fibrosis is regarded as the principal pathogenic mechanism of asbestosis. It is believed that after deposition and transmigration of asbestos fibers in the lung, there is an accumulation of macrophages followed by fibroblasts that lay the foundation for fibrosis.
Usually, there is a history of 10 to 20 years of exposure to asbestos and progressively worsening dyspnea.
- Progressive dyspnea (esp on exertion)
- Cough with sputum and wheezing (mainly associated with smoking)
- Clubbing (32-42% cases)
- Asbestos warts
- Reduced chest expansion due to restrictive lung disease (38% cases)
- Bibasilar rales (best auscultated at lower lateral and basal areas)
Right-sided heart failure:Right-sided heart failure from pulmonary vascular remodeling and subsequent pulmomary hypertension
- Chest discomfort
- Cor pulmonale signs (advanced cases): Pedal edema, jugular venous distension, right ventricular heave, hepatojugular reflux, cyanosis
Lung cancer:M/C cancer associated with asbestosis
- Loss of appetite & weight
Pleural mesotheliomaM/specific cancer associated with asbestosis
- Gradual onset of localized pain or breathlessness and then radiating to the shoulder
- ↑ CRP, ESR, RF, and ANA
Pulmonary function tests (PFT):
- Spirometry: Restrictive pattern
- ↓ DLCO
- Interstitial fibrosis
High-resolution computed tomography (HRCT)
- Pleural thickening and calcified pleural plaques (HALLMARK)
- Ground-glass opacities, along with diffuse interstitial fibrosis in asbestosis (in idiopathic pulmonary fibrosis, there is evidence of patches of opacities)
- Interstitial fibrosis with characteristically peribronchial fibrosis
Asbestosis has no specific treatment, so supportive care is the only available option. Therefore, prevention is the best management. Monitoring of the occupational environment and minimizing asbestos exposure has a significant role in asbestosis control.
Corticosteroid therapy:Suppress the acute and chronic inflammatory process, thereby further reducing lung damage
Antibiotics therapy:For superimposed respiratory infections
- Immunization against pneumococcus and Haemophilus influenza
Oxygen supplementation:Patients with hypoxemia (PaO2< 55 mmHg) at rest or with exertion should be supplemented with oxygen
- Decortication of subpleural fibrosis by thoracotomy (improves atelectasis)
- Pleurectomy (pleural fibrosis)
- Palliative removal of fluids to relieve breathlessness (rapid collection of pleural fluid)
Lung transplantation:Ultimate treatment in severe asbestosis, where all other therapies have failed in case of chronic and irreversible fibrosis.