Describe the occupational lung diseases with their prevention.

The Pneumoconioses

• The critical particle size is 0.5 to 5 micrometres, which is the respirable fraction
• The reasoning behind that range is worth giving — particles larger than about 5 micrometres are trapped in the upper airway and removed by the mucociliary escalator, while particles smaller than about 0.5 micrometres behave like a gas and are largely breathed out again
• Only the intermediate size reaches and remains in the alveoli — which means that visible dust is not necessarily the dangerous dust, and the most hazardous particles are those too small to see
• The classification of dusts by tissue response:
• Fibrogenic (fibrosis-producing) — silica, asbestos, coal and beryllium
• Non-fibrogenic (inert) — iron (siderosis), tin (stannosis) and barium (baritosis), which produce striking radiographic changes with little or NO functional impairment
• That dissociation is worth noting — a dramatic chest radiograph in a worker with normal lung function should raise the possibility of an inert dust rather than a fibrogenic one
• Organic dusts — causing hypersensitivity reactions rather than simple deposition: byssinosis, bagassosis, farmer’S lung
• Carcinogenic — asbestos, arsenic, chromium and nickel
• Asbestosis — caused by asbestos fibres, encountered in mining and milling, asbestos-cement sheet manufacture, insulation, brake linings, shipbuilding and demolition
• It produces diffuse interstitial fibrosis, predominantly in the lower zones — which contrasts with silicosis, which affects the upper zones, and that contrast is a favourite examination point
• Its features — progressive dyspnoea, dry cough, fine end-inspiratory crackles, clubbing, and a restrictive pattern on spirometry; with pleural plaques, which indicate exposure rather than disease
• Asbestos bodies (ferruginous bodies) in sputum or tissue indicate exposure, not necessarily disease
• The malignant complications are what make asbestos exceptional — bronchogenic carcinoma and mesothelioma of the pleura or peritoneum
• Mesothelioma is virtually specific to asbestos, has a latency of 20 to 40 years, and may follow brief or low-level exposure — including para-occupational exposure of family members from dust carried home on clothing
• The synergism between asbestos and smoking for lung cancer is multiplicative rather than additive, so an asbestos worker who smokes has a risk far exceeding the sum of the two separately — which makes smoking cessation an especially high-value intervention in this group
• India has not banned asbestos, unlike many countries, and continues to use chrysotile, which is a live public health controversy worth acknowledging
• Coal worker’S pneumoconiosis — from coal dust, progressing from simple pneumoconiosis with small opacities to progressive massive fibrosis
• CAPLAN syndrome is the combination of pneumoconiosis with rheumatoid arthritis, producing large rounded nodules

Organic Dusts, Occupational Asthma and Management

• Byssinosis — caused by cotton, flax and hemp dust, in textile mills, particularly in the blowing, carding and spinning departments
• Its characteristic feature is the MONDAY morning pattern — chest tightness and dyspnoea on the first day back after a break, improving over the following days of the week
• The graded classification runs from grade 0 through half, 1, 2 and 3, depending on whether symptoms occur on the first day only, on other days also, or with permanent disability
• The Monday pattern is diagnostically valuable, since it points immediately to an occupational cause and to tolerance developing over the week
• Bagassosis — from bagasse, the dry fibrous residue of sugar cane after the juice is extracted, when it is stored damp and becomes mouldy with thermophilic actinomycetes
• It is an extrinsic allergic alveolitis, presenting with fever, cough and dyspnoea a few hours after exposure
• Its prevention is entirely practical — keeping the moisture content of stored bagasse below about 20%, spraying with propionic acid, and wetting during handling, which is an agricultural and storage measure rather than a medical one
• Farmer’S lung — from mouldy hay containing thermophilic actinomycetes, with the same hypersensitivity mechanism
• Other organic dust conditions — bird fancier’s lung; mushroom worker’s lung; and grain dust exposure
• Occupational asthma is now the commonest occupational lung disease in industrialised settings, caused by isocyanates, flour and grain, wood dusts, latex, animal proteins, colophony and epoxy resins
• Its diagnosis rests on the temporal relationship to work — symptoms improving on days away and on holidays and returning on return, documented by serial peak flow measurements recorded at work and away over several weeks
• Serial peak flow is the practical diagnostic tool, and is cheap and available anywhere
• The critical management point is that once sensitisation has occurred, even very low exposure will provoke attacks, so the worker must be removed from exposure rather than merely given protective equipment or treatment
• The earlier the removal, the greater the chance of complete recovery; continued exposure leads to permanent impairment
• Diagnosis of the pneumoconioses generally — occupational history, which is the foundation; chest radiograph classified by the ILO system for profusion, size and shape of opacities and zones affected; high-resolution CT, which is more sensitive; spirometry showing a restrictive pattern in most; and rarely, biopsy
• The uncomfortable truth about management is that there is NO specific treatment for established pneumoconiosis — the fibrosis does not regress, and may progress even after exposure ceases
• Management is therefore — removal from further exposure; treatment of complications, particularly tuberculosis, respiratory infection and cor pulmonale; smoking cessation; vaccination against influenza and pneumococcus; pulmonary rehabilitation and oxygen; and compensation
• The conclusion that every answer on this topic should reach — since there is no cure, prevention by dust control is the only effective measure, and every case of pneumoconiosis represents a preventive failure years earlier
• The dangerous dust is the one you cannot see, since only particles of half to five micrometres reach and stay in the alveoli
• Larger particles are cleared by the escalator and smaller ones are breathed out again, which defines the respirable range
• Asbestosis affects lower zones, silicosis upper, which is the contrast examiners most reliably ask for
• Byssinosis is worst on Monday, improving through the week, which points immediately to an occupational cause
• Remove a sensitised worker from exposure, since even trace amounts provoke attacks once occupational asthma is established
• Serial peak flow diagnoses occupational asthma, recorded at work and away over several weeks, and costs almost nothing
• Earlier removal gives better recovery, while continued exposure leads to permanent impairment
• Mesothelioma is virtually specific to asbestos, with latency of twenty to forty years and may follow brief exposure
• Asbestos and smoking multiply rather than add, which makes cessation especially valuable in exposed workers
• Family members are exposed through clothing, which is para-occupational exposure and a real cause of mesothelioma
• Pleural plaques indicate exposure, not disease, and should be explained as such to an anxious worker
• Inert dusts give dramatic films and normal function, which is a dissociation worth recognising before alarming anyone
• Caplan syndrome is pneumoconiosis with rheumatoid arthritis, producing large rounded nodules
• Bagassosis is prevented by keeping bagasse dry, which is a storage measure rather than a medical one
• Farmer lung comes from mouldy hay, through the same thermophilic actinomycetes as bagassosis
• The ILO classification grades the chest film by profusion, size and shape of opacities and the zones involved
• Fibrosis does not regress and may progress even after exposure ceases, which is the hard truth about management
• Prevention by dust control is the only cure, since no treatment reverses established pneumoconiosis
• Every case represents a failure years earlier, which is the sentence to close a pneumoconiosis answer with
• Treat tuberculosis and infection aggressively in these patients, since complications determine the outcome
• India has not banned asbestos, unlike many countries, which is a live controversy worth acknowledging
• Occupational asthma is now the commonest occupational lung disease in industrialised settings, ahead of the pneumoconioses