Occupational Health
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Direct answer
An occupational disease is one contracted primarily by exposure at work to a physical, chemical, biological or ergonomic hazard — the definition demands an exposure-response link, not merely a disease in a worker. India's framework rests on the Factories Act 1948 (health, safety and welfare provisions), the Employees' State Insurance Act 1948 (medical care and cash benefits, funded by employer 3.25% and employee 0.75% contributions) and the Employees' Compensation Act 1923, while the examinable clinical core is a set of dust-disease pairs (silicosis, asbestosis, byssinosis), metal poisonings (lead, mercury), organophosphate poisoning and noise-induced hearing loss with its 4 kHz dip.
What you must remember
- The joint ILO/WHO definition emphasises the highest degree of physical, mental and social well-being of workers in all occupations — prevention, not just treatment.
- Factories Act 1948: applies to factories with 10 or more workers using power (20 without power); mandates cleanliness, ventilation, guarding of machinery, and a creche where 30 or more women are employed.
- ESI Act 1948: comprehensive social security — sickness, maternity, employment injury, disablement, dependants' and funeral benefits plus full medical care — for employees earning up to the wage ceiling, run through ESI hospitals and dispensaries.
- Pneumoconioses: silicosis from free silica (mining, grinding, quarrying; egg-shell calcification, restrictive defect, no cure); asbestosis (pleural plaques, mesothelioma risk); coal workers' pneumoconiosis; byssinosis from cotton dust with "Monday fever" graded by Schilling; hypersensitivity pneumonitis — farmers' lung from mouldy hay, bagassosis from sugarcane bagasse.
- Lead poisoning: Burtonian line, basophilic stippling, wrist drop (radial nerve), anaemia and colic; mercury gives erethism and intention tremor ("hatter's shakes"); cadmium causes itai-itai; chromium erodes the nasal septum.
- Organophosphate pesticides: muscarinic DUMBELLS effects (diarrhoea, urination, miosis, bronchorrhoea and bronchospasm, emesis, lacrimation, lethargy, salivation and sweating), nicotinic fasciculations and weakness; treat with atropine for muscarinic effects plus pralidoxime for the nicotinic; beware the intermediate syndrome at 24-96 hours.
- Noise-induced hearing loss begins at the 4 kHz notch on audiometry; exposure above 85-90 dB over 8 hours is the risk benchmark; prevention is engineering control then ear protection.
- Prevention hierarchy: substitution first, engineering controls (enclosure, ventilation, wet methods), administrative controls, and personal protective equipment last; pre-employment and periodic examinations and disease notification are statutory duties.
A welder with breathlessness: occupational history first
A 45-year-old construction welder reports progressive breathlessness and a dry cough. Before ordering a single test, take the occupational history in three layers: job tasks across his working life (welding, grinding concrete, demolishing old buildings), exposure specifics (duration, dust clouds, respirator provided or not), and symptom timing relative to shifts and holidays. Chest X-ray shows small rounded opacities in the upper zones with egg-shell calcification of hilar nodes; spirometry is restrictive. The diagnosis is silicosis from silica in concrete dust — notifiable and compensable. Contrast the case next door: a mill worker whose chest tightness peaks every Monday and eases by Thursday — byssinosis, grade I by Schilling. The welder needs removal from exposure, supportive care and ESI compensation support; the mill needs dust extraction. Both diagnoses came from the history, not the X-ray — the occupational history is the highest-yield instrument in this field.
Pairs the exam loves
Matching questions dominate: silica to silicosis (egg-shell calcification), asbestos to mesothelioma and pleural plaques, cotton to byssinosis (Monday fever), mouldy hay to farmers' lung, bagasse to bagassosis — and the metals: lead to wrist drop and Burtonian line, mercury to erethism and hatter's shakes, cadmium to itai-itai, manganese to parkinsonism, chromium to septal perforation. Second favourite: organophosphate management — atropine is dosed to dry secretions, and oximes must be given early before the enzyme ages; atropine alone does not reverse the nicotinic fasciculations that pralidoxime addresses. Third: the 4 kHz dip — the early audiometric signature of noise damage. Do not forget the creche threshold (30 women workers) and the ESI contribution split.
Frequently asked questions
What is byssinosis and what is the Monday phenomenon?
An airway disease of raw cotton dust exposure characterised by chest tightness and cough worst on the first day back at work after a weekend (Monday fever), improving over the week; graded clinically by Schilling into grades I, II and III.
What are the classic clinical features of lead poisoning?
Burtonian blue line on the gums, basophilic stippling of erythrocytes, microcytic anaemia, abdominal colic, constipation, and peripheral neuropathy classically causing wrist drop; children risk encephalopathy.
How is organophosphate poisoning managed?
Decontamination, airway support, generous atropine titrated to drying of secretions, and pralidoxime given early to reactivate acetylcholinesterase for nicotinic effects; watch for the intermediate syndrome of proximal weakness and respiratory failure at 24 to 96 hours.
Which hearing frequency is affected earliest by noise exposure?
The 4 kHz region shows the earliest notch on pure-tone audiometry — the diagnostic signature of noise-induced hearing loss — before deficits spread to speech frequencies.
What social security does the ESI Act 1948 provide?
Full medical care through ESI facilities plus cash benefits for sickness, maternity, employment injury, temporary or permanent disablement, dependants of deceased insured persons and funeral expenses, financed by employer and employee contributions.