Environmental Lung Diseases

Exposure to various dusts, gases, vapours and fumes can cause several types of lung diseases:

1) Acute bronchitis and pulmonary oedema
caused by irritants (eg. sulphur dioxide, chlorine, ammonia, nitrogen oxides)

2) Pulmonary fibrosis
caused by mineral dust

3) Asthma
caused by isocyanates (eg. polyurethane varnishes, industrial coatings, spray painting), colophony fumes (eg. soldering/welding, electronics), allergens (eg. animals, insects, antibiotics, flour, grain, latex), proteolytic enzymes in biological washing powders, complex salts of platinum in metal refineries and acid anhydrides and polyamine hardening agents in industrial coatings.

4) Extrinsic allergic alveolitis
caused by mouldy hay and vegetable material, handling of birds, turning of germinating barley, contaminated humidifying systems in air conditioners or humidifiers in factories, turning of mushroom compost, mouldy cheese and mouldy grapes.

5) Bronchial carcinoma
caused by industrial agents (eg. asbestos, polycyclic hydrocarbons, radon in mines)


Coal-worker's pneumoconiosis
Caused by dust particles being retained in small airways and alveoli of the lung. 2-stage disease:

Simple pneumoconiosis - reflects deposition of coal dust in the lung. Produces fine micronodular shadowing on CXR. May lead to development of progressive massive fibrosis.

Progressive massive fibrosis (PMF)- patients develop round fibrotic masses in upper lobes, sometimes having necrotic central cavities. Fibrosis likely due to immune responses. Apical destruction and disruption of lung results in emphysema and airway damage. Lung function tests show mixed restrictive and obstructive ventilatory defect with loss of lung volume, irreversible ariflow limitation and reduced gas transfer. Patient suffers considerable effort dyspnoea, usually with cough and sputum may be black. May progress to respiratory failure.

Silicosis
Caused by inhalation of silica (silicon dioxide). Dust is highly fibrogenic - silica is toxic to alveolar macrophages and readily initiates fibrogenesis. CXR and clinical features largely similar to PMF distinctive thin streaks of calcification may be seen around hilar lymph nodes ('eggshell' calcification).

Asbestosis
Defined as fibrosis of the lungs caused by asbestos dust, may or may not be associated with fibrosis of the parietal or visceral layers of pleura. Progressive disease characterised by breathlessness and accompanied by finger clubbing and bilateral basal end-inspiratory crackles. Mesothelioma often results, with patient presenting with pleural effusions, typically with persistent chest wall pain.

Byssinosis
Cotton mill workers present with symptoms starting on the first day at work with improvement as week progresses. Symptoms include chest tightness, cough and breathlessness. Cotton dust causes airflow limitations. Asthmatics are particularly affected. Endotoxins from the bacteria present in the raw cotton causes constriction of lung airways.

Berylliosis
When beryllium is inhaled, it can cause a systemic illness with clinical presentation similar to sarcoidosis. Due to progressive dyspnoea with pulmonary fibrosis.

Reference: Kumar and Clark (Clinical Medicine 6e)