Occupational Health & Hazards

Occupational health links the workplace to disease — dusts, gases, metals, radiation, noise and ergonomic stress. For NEET PG, the highest-yield zone is the pneumoconioses (dust–disease pairs), the byssinosis "Monday fever" story, threshold/permissible exposure limits, and the Factories Act, 1948 welfare/safety provisions. This page is built around the exact associations examiners love to swap and trap.

Definition & scope

Occupational disease = a disease arising specifically out of, and in the course of, employment, caused by exposure to a physical, chemical, biological or ergonomic agent at work. Contrast with work-related disease (multifactorial, work is one contributor, e.g. hypertension, IHD aggravated by shift work).

The classic occupational health triad / objectives (ILO–WHO, 1950, revised 1995):

1. Promotion & maintenance of physical, mental and social well-being of workers.
2. Prevention of departures from health caused by working conditions.
3. Protection from risk factors adverse to health.
4. Placing & maintaining the worker in an environment adapted to their capabilities — i.e. "adapt the job to the man and each man to his job."

High-yield: The guiding ILO/WHO principle is "adapting work to man and man to his job." This phrase is a frequent single-best-answer.

Classification of occupational hazards

Type	Examples
Physical	Heat (heat stroke, cataract in glass workers), cold, noise (NIHL), vibration (Raynaud's/"white finger"), radiation, abnormal pressure (caisson disease)
Chemical	Dusts → pneumoconioses; metals (lead, mercury, arsenic, cadmium, manganese); gases (CO, H₂S); solvents (benzene → aplastic anaemia/leukaemia)
Biological	Anthrax (wool-sorter's disease), brucellosis, leptospirosis, viral hepatitis, TB (health workers)
Mechanical	Injuries, repetitive strain
Psychosocial	Stress, burnout, shift work

Pneumoconioses — the core of the topic

Pneumoconiosis = permanent deposition of inhaled dust in the lungs (alveolar/interstitial) with the tissue reaction to its presence. The most dangerous particle size is 0.5–3 (up to 5) microns — these reach the alveoli; larger particles are filtered out, much smaller ones are breathed back out.

High-yield: Respirable, fibrogenic dust = 0.5–5 µm, most dangerous around 1–3 µm. Particles >10 µm impacted in upper airways; <0.5 µm exhaled.

Silicosis

• Agent: free crystalline silica (SiO₂) — quartz.
• Occupations: mining (gold, coal, lead), quarrying, sandblasting, pottery/ceramics, glass, foundry, stone-cutting, slate-pencil industry (classic Indian exam example: Mandsaur, MP slate-pencil workers).
• Pathology: nodular fibrosis; silicotic nodules with concentric "onion-skin" hyalinised collagen, upper-zone predominance. Eggshell calcification of hilar lymph nodes on chest X-ray is characteristic.
• Progressive massive fibrosis (PMF) when nodules coalesce.
• Silicosis + active TB = Silico-tuberculosis — silica impairs macrophage function, hugely raising TB risk.

High-yield: Silicosis → nodular fibrosis, upper lobe, eggshell calcification of hilar nodes, strong association with tuberculosis. Most prevalent and most serious pneumoconiosis in India.

Asbestosis

• Agent: asbestos fibres (chrysotile = white, most used; crocidolite = blue, most carcinogenic for mesothelioma).
• Occupations: insulation, shipbuilding, brake-lining, roofing, cement-asbestos sheets.
• Pathology: diffuse interstitial fibrosis, lower zone predominance, pleural plaques (often calcified), ferruginous (asbestos) bodies, and honeycombing.
• Cancers: Bronchogenic carcinoma (commonest cancer in asbestosis, synergistic and multiplicative with smoking) and malignant mesothelioma of pleura/peritoneum (no smoking link; latency 20–40 yrs).

High-yield: Asbestos → diffuse lower-zone fibrosis + pleural plaques. Crocidolite (blue) → mesothelioma. Smoking + asbestos → multiplicative lung-cancer risk.

Coal Worker's Pneumoconiosis (CWP) / Anthracosis

• Agent: coal dust (carbon).
• Simple CWP → coal macules around respiratory bronchioles.
• Complicated CWP → PMF.
• Caplan syndrome = CWP (or silicosis) + rheumatoid arthritis → multiple large nodules + rapidly developing pulmonary fibrosis.

High-yield: Caplan syndrome = pneumoconiosis (coal/silica) + rheumatoid nodules in lung.

Byssinosis ("Brown lung" / "Monday fever")

• Agent: cotton, flax, hemp dust (textile/cotton-ginning mills).
• Mechanism: endotoxin/histamine-releasing reaction in airways (not classic fibrosis).
• Hallmark — Monday fever / Monday morning tightness: chest tightness and dyspnoea on the first day back after a break/weekend, improving as the week proceeds (tachyphylaxis), recurring after the next break. This temporal pattern is THE exam clue.

High-yield: Byssinosis = chest tightness on the FIRST working day after a holiday ("Monday fever"), cotton-mill worker. Grading uses the Schilling classification.

Other named dust diseases

Disease	Dust / agent	Occupation
Bagassosis	mouldy sugarcane bagasse (thermophilic actinomycetes)	sugarcane/paper, "extrinsic allergic alveolitis"
Berylliosis	beryllium	aerospace, fluorescent lamps, electronics; granulomatous (mimics sarcoid)
Siderosis	iron oxide	arc welders; benign
Stannosis	tin oxide	tin workers; benign
Baritosis	barium	benign
Farmer's lung	mouldy hay (Saccharopolyspora/thermophilic actinomycetes)	farmers (hypersensitivity pneumonitis)
Anthracosis	carbon/soot	urban dwellers, coal

High-yield: Bagassosis (sugarcane), berylliosis (granuloma, sarcoid-like), siderosis/stannosis/baritosis = benign/inert pneumoconioses (radio-opaque but no fibrosis).

Mnemonic — dust to disease: "SILica → Stone/Sandblast; ASBestos → ASBuilding/ships; BYSsinosis → cotton on monday; BAGassosis → sugarcane BAG; BERyllium → BRight bulbs."

Occupational disease – causative agent pairs (high-frequency MCQ table)

Disease / effect	Agent	Setting / clue
Wool-sorter's disease	Anthrax (B. anthracis)	wool, hides, hair
Aplastic anaemia / leukaemia	Benzene	paint, rubber, petrochemicals
Peripheral neuropathy, wrist/foot drop, basophilic stippling, blue gum line (Burton's line)	Lead	battery, paint, smelting
Mad-hatter / erethism, tremor, gingivitis	Mercury	thermometer, chlor-alkali
Itai-itai (osteomalacia), proteinuria	Cadmium	smelting, batteries
Manganism (parkinsonism)	Manganese	mining, welding
Cancer scrotum (Pott's)	Soot / PAH	chimney sweeps
Bladder cancer	β-naphthylamine / aniline dyes	dye, rubber industry
Angiosarcoma of liver	Vinyl chloride monomer	PVC plastics
Hatter's / nasal septum perforation	Chromium / nickel	electroplating
Phossy jaw (mandibular necrosis)	Yellow phosphorus	match industry
Caisson disease (dysbarism, bends)	Nitrogen at high pressure	divers, tunnel workers
Cataract	Infrared / heat / microwave	glass-blowers, furnace

High-yield: Burton's line + basophilic stippling + wrist drop = lead. Itai-itai = cadmium. Angiosarcoma liver = vinyl chloride. Bladder cancer = β-naphthylamine.

Pathophysiology in brief

Inhaled respirable particles (1–3 µm) bypass mucociliary clearance and reach alveoli, where alveolar macrophages phagocytose them. Cytotoxic dusts (silica, asbestos) kill macrophages, releasing lysosomal enzymes, ROS and fibrogenic cytokines (TNF-α, IL-1, TGF-β) → recruitment of fibroblasts → collagen deposition and fibrosis. Silica is directly cytotoxic (membrane lysis), explaining its severity and the impaired anti-TB defence. Inert dusts (iron, tin, barium) are merely stored → radio-opacity without fibrosis (benign pneumoconioses).

Clinical features (common thread)

• Insidious exertional dyspnoea, dry cough, reduced exercise tolerance.
• Restrictive lung disease pattern on spirometry (↓ FVC, ↓ TLC, normal/↑ FEV₁/FVC ratio, ↓ DLCO).
• Late: cor pulmonale, type-1 then type-2 respiratory failure.
• Byssinosis is the exception — airway tightness with a Monday pattern (more obstructive/reactive).

Diagnosis & investigation of choice

Stepwise approach: Occupational history → Chest X-ray (ILO classification) → Spirometry/PFT (restrictive) → HRCT (best imaging) → biopsy if doubtful.

• Occupational history is the single most important diagnostic step (the "what do you do / did you do for a living" question). Use the WHEN framework: What exactly, How long/intensity, Exposures (substances), Now vs past, plus protective measures and co-workers' health.
• Chest X-ray: graded by the ILO International Classification of Radiographs of Pneumoconioses — small rounded opacities p, q, r; irregular opacities s, t, u; profusion 0–3.
• HRCT = most sensitive imaging.
• PFT: restrictive defect with reduced DLCO.
• Lung biopsy (asbestos bodies / silicotic nodules) only when diagnosis is unclear.

High-yield: Occupational history is the key to diagnosis; ILO classification standardises chest-X-ray reporting of pneumoconioses.

Management / "drug of choice"

There is no specific cure for established pneumoconiosis — fibrosis is irreversible. Management = prevention + supportive care.

• Primary prevention (most important): dust suppression (wet drilling, water sprays), enclosure/ventilation (engineering control > PPE), substitution (e.g. ban crocidolite), exposure-limit enforcement, respirators/PPE (last resort), pre-placement and periodic medical examination.
• Stop further exposure; smoking cessation (critical in asbestos).
• Supportive: oxygen, bronchodilators (esp. byssinosis), pulmonary rehab, vaccination (influenza, pneumococcus).
• Silico-tuberculosis: treat TB with standard ATT; high index of suspicion and screening.
• Berylliosis: corticosteroids help (granulomatous, immune-mediated).
• Mesothelioma: poor prognosis, palliative + chemo (pemetrexed-cisplatin).

High-yield: Hierarchy of control = Elimination → Substitution → Engineering controls → Administrative controls → PPE. Engineering control (ventilation/enclosure) is preferred over personal protective equipment.

Permissible exposure limits (cut-offs)

• Threshold Limit Value (TLV): airborne concentration of a substance to which nearly all workers may be repeatedly exposed (8 h/day, 40 h/week) without adverse effect (ACGIH).
  • TLV-TWA (time-weighted average, 8 h).
  • TLV-STEL (short-term, 15 min).
  • TLV-C (ceiling, never to be exceeded).
• MAC (Maximum Allowable Concentration) and PEL (Permissible Exposure Limit, OSHA) are related regulatory limits.
• Noise: permissible 90 dB(A) for 8 hours (some texts 85 dB); each 5 dB rise halves permissible exposure time. >85 dB sustained → noise-induced hearing loss (NIHL), classically a notch at 4000 Hz (4 kHz dip), bilateral sensorineural.

High-yield: TLV-TWA = 8 h/day, 40 h/week safe limit. NIHL = 4000 Hz notch, permissible noise ≈ 90 dB(A)/8 h.

Factories Act, 1948 — welfare, safety & health provisions

A factory = premises where ≥10 workers with power, or ≥20 workers without power, are engaged in a manufacturing process.

Domain	Key statutory provisions
Health	cleanliness, disposal of waste, ventilation & temperature, dust & fume control, overcrowding (≥14.2 m³ / 500 cu ft air space per worker), lighting, drinking water, latrines/urinals, spittoons
Safety	fencing of machinery, work on/near machinery in motion, protection of eyes, precautions against fire, safe means of access
Welfare	washing facilities, first-aid (≥1 box per 150 workers), canteen if >250 workers, shelters/rest rooms if >150, crèche if >30 women workers, welfare officer if ≥500 workers
Working hours	≤48 h/week, ≤9 h/day, weekly holiday; spread-over ≤10.5 h; rest interval after 5 h
Employment of young persons	no child <14 yrs; adolescent (15–18) with fitness certificate; no women/young persons in night shifts (traditional provision)

High-yield numbers: Factory = 10 (with power)/20 (without power); air space 14.2 m³/worker; crèche if >30 women; canteen if >250 workers; first-aid box per 150; 48 h/week; no child below 14.

Other legislation worth knowing: Employees' State Insurance (ESI) Act, 1948 (medical + cash benefits, sickness/maternity/disablement/dependant's benefit; contributory; covers factories & establishments); Workmen's/Employees' Compensation Act, 1923 (no-fault compensation for employment injury); Mines Act, 1952; Maternity Benefit Act, 1961 (26 weeks).

Complications

• Progressive massive fibrosis (silicosis, CWP).
• Silico-tuberculosis.
• Cor pulmonale and right heart failure.
• Bronchogenic carcinoma & mesothelioma (asbestos).
• Respiratory failure, recurrent infection, pneumothorax (honeycomb lung).
• Caplan syndrome with RA.

Key differentials

• Idiopathic pulmonary fibrosis (no exposure history; lower-zone, but no plaques/macules).
• Sarcoidosis (vs berylliosis — beryllium lymphocyte proliferation test distinguishes; both non-caseating granulomas).
• Hypersensitivity pneumonitis (bagassosis, farmer's lung — these are HP variants; acute/subacute with antigen exposure).
• Tuberculosis (must always exclude in silicosis).
• Sarcoid vs silicosis on eggshell calcification (both can show it, but silica history decides).

Recently asked / exam angle

• Byssinosis "Monday morning chest tightness" in a cotton-mill worker — repeatedly the stem; answer = byssinosis.
• Eggshell calcification of hilar nodes → silicosis (occasionally sarcoidosis as distractor).
• Most common / most serious pneumoconiosis in India → silicosis.
• Caplan syndrome definition (pneumoconiosis + rheumatoid arthritis).
• Crocidolite (blue asbestos) → mesothelioma; chrysotile most common type used.
• Most dangerous particle size 1–5 µm; particles >10 µm filtered.
• TLV-TWA definition (8 h/day, 40 h/week).
• Factories Act numbers — crèche >30 women workers; child labour ban <14 yrs; 14.2 m³ air space.
• Itai-itai (cadmium), Burton's line (lead), angiosarcoma liver (vinyl chloride), bladder cancer (β-naphthylamine) — agent–disease matching.
• NIHL 4000 Hz notch; permissible noise 90 dB(A)/8 h.
• "Adapt work to man and man to job" — ILO/WHO occupational health aim.
• Hierarchy of control / engineering control over PPE.

Rapid revision

1. Most dangerous respirable dust particle size = 1–5 µm (peak 1–3 µm); >10 µm filtered, <0.5 µm exhaled.
2. Silicosis = nodular, upper-zone, eggshell calcification, slate-pencil/sandblasting; strongly predisposes to TB (silico-TB).
3. Asbestosis = diffuse lower-zone fibrosis + pleural plaques; crocidolite → mesothelioma; smoking multiplies lung-cancer risk.
4. Byssinosis = cotton dust, "Monday fever" (tightness first day back), graded by Schilling classification.
5. Caplan syndrome = coal/silica pneumoconiosis + rheumatoid arthritis.
6. Bagassosis = mouldy sugarcane; berylliosis mimics sarcoid; siderosis/stannosis/baritosis = benign inert dusts.
7. Burton's line + basophilic stippling + wrist-drop = lead; Itai-itai = cadmium; manganism = parkinsonism.
8. Angiosarcoma of liver = vinyl chloride; bladder cancer = β-naphthylamine; scrotal cancer = soot (Pott).
9. Occupational history = single most important diagnostic tool; ILO classification for chest X-ray; HRCT most sensitive imaging.
10. TLV-TWA = safe 8 h/day, 40 h/week exposure (ACGIH); noise ≤ 90 dB(A)/8 h, NIHL = 4 kHz notch.
11. Factories Act 1948: factory = 10 (power)/20 (no power) workers; air space 14.2 m³; crèche >30 women; canteen >250; child <14 barred; ≤48 h/week.
12. Control hierarchy: Elimination → Substitution → Engineering controls → Administrative → PPE; pneumoconiosis is preventable, not curable.