Orientation notes for study. Check Kenyan occupational health law and local guidelines for notification and compensation.
Definition
Occupational lung diseases are lung conditions caused or made worse by exposure to dusts, fumes, gases, vapours or biological agents at work. They are largely preventable and are often missed because nobody asks about work.
Main groups
- Pneumoconioses: fibrosis from inorganic dust (silica, asbestos, coal).
- Occupational asthma: asthma caused by a workplace agent.
- Hypersensitivity pneumonitis: immune reaction to organic dusts (see also the ILD note).
- Occupational COPD and chronic bronchitis: dusts and fumes.
- Occupational cancers: lung cancer and mesothelioma.
- Acute toxic inhalation: chlorine, ammonia, smoke, nitrogen oxides.
- Infection risk: TB in miners and health workers, anthrax and brucellosis (animal workers).
The pneumoconioses
| Disease | Agent | Typical workers | Features |
|---|---|---|---|
| Silicosis | Silica (quartz) dust | Miners, quarry and stone workers, sandblasters, tunnellers, ceramics, masons | Upper-zone nodules, eggshell calcification of hilar nodes, progressive massive fibrosis; high risk of TB (silico-tuberculosis), lung cancer, COPD, autoimmune disease |
| Asbestosis | Asbestos fibres (roofing, insulation, brakes, shipbuilding, demolition) | Construction and building workers, mechanics, insulators | Lower-zone fibrosis, pleural plaques (calcified, marker of exposure), diffuse pleural thickening, benign pleural effusion; risk of mesothelioma and lung cancer (especially with smoking) |
| Coal worker's pneumoconiosis | Coal dust | Coal miners | Small upper-zone nodules, progressive massive fibrosis, Caplan syndrome (rheumatoid arthritis + nodules) |
| Berylliosis | Beryllium | Aerospace, electronics, nuclear | Granulomas that look like sarcoid |
| Siderosis, stannosis, baritosis | Iron, tin, barium | Welders, miners | Radiological change with little functional impairment |
Occupational asthma
- Agents: isocyanates (spray painting), flour and grain dust (bakers), latex (health workers), wood dust, solder flux, animal proteins, enzymes, pesticides.
- Clue: symptoms improve at weekends and holidays and worsen at work; serial peak flow records at work and off work show the pattern.
- Management: early diagnosis, remove from exposure (earlier removal gives a better outcome), usual asthma treatment.
Organic dust diseases
- Byssinosis: cotton, flax, hemp workers; "Monday morning" chest tightness that eases later in the week; progresses to chronic obstruction.
- Farmer's lung: mouldy hay (Saccharopolyspora rectivirgula, Thermoactinomyces); acute flu-like illness 4–8 hours after exposure, chronic fibrosis.
- Bagassosis: mouldy sugar cane waste (relevant to sugar-belt workers in western Kenya).
- Bird fancier's lung, mushroom worker's lung, malt worker's lung.
- Grain and cotton dust also cause chronic bronchitis and organic dust toxic syndrome (non-immune fever).
Occupational cancers
- Asbestos → mesothelioma (latency 20–40 years, pleural, poor prognosis), lung cancer.
- Silica, arsenic, chromium, nickel, radon, diesel fumes → lung cancer.
Clinical approach
- Always take an occupational history: every job ever held, duties, dust and fume exposure, protection used, latency (often many years), symptoms relating to work, coworkers affected, hobbies.
- Examination: clubbing, crackles, wheeze, pleural signs.
- Investigations: chest X-ray (use ILO classification for pneumoconioses), HRCT, spirometry and DLCO, serial peak flow (occupational asthma), TB screening in silica-exposed workers, specific IgE or challenge tests, biopsy if needed, mineral analysis.
Management and prevention
- No cure for established pneumoconiosis: stop or reduce exposure, stop smoking, treat complications (TB, COPD, cancer), vaccinations, oxygen and rehabilitation, palliative care.
- Prevention is the key:
- Hierarchy of control: eliminate or substitute the hazard → engineering controls (wet drilling, dust extraction, enclosure, ventilation) → administrative controls (limit exposure time) → personal protective equipment (respirators/masks) last.
- Pre-employment and regular medical surveillance, air monitoring, worker education.
- Ban or restrict hazardous substances (asbestos).
- Notification and compensation (in Kenya, the Occupational Safety and Health Act 2007 and the Work Injury Benefits Act 2007 provide for notification of occupational disease and compensation).
Exam points
- Always ask about work.
- Silica = upper zones, eggshell calcification, TB risk; asbestos = lower zones, pleural plaques, mesothelioma.
- Occupational asthma: better on days off.
- Prevention is by controlling exposure at source.
- Silicosis and TB often occur together in miners.
Practice questions
1. A 55-year-old retired stone-quarry worker has upper-zone nodules and eggshell calcification of hilar nodes on chest X-ray. The disease with the highest associated risk of infection is: A. Pneumococcal pneumonia · B. Tuberculosis · C. Candida · D. PCP · E. Histoplasmosis Answer: B.
2. A bakery worker wheezes at work, improving on holidays. The most likely cause is: A. COPD · B. Occupational asthma (flour dust) · C. Silicosis · D. Asbestosis · E. Heart failure Answer: B.
3. Calcified pleural plaques on the chest X-ray of a retired roofer suggest exposure to: A. Silica · B. Coal · C. Asbestos · D. Cotton · E. Beryllium Answer: C.