Community medicine chapters
Occupational health and ergonomics
The hazards workers face (physical, chemical, biological, mechanical and psychosocial), the classic occupational diseases including the pneumoconioses and lead poisoning, how they are prevented, and what ergonomics means.
- Occupational hazards are physical (noise, heat, radiation), chemical (dusts, gases, metals, solvents), biological, mechanical (accidents, ergonomic strain) and psychosocial (stress).
- Pneumoconioses come from inhaled dust: silicosis (quartz; mining, stone cutting; raises TB risk), asbestosis (mesothelioma), anthracosis (coal), byssinosis (cotton), bagassosis (sugar cane), farmer's lung (mouldy hay).
- Ergonomics fits the job to the worker; prevention runs from engineering controls to pre-placement and periodic medical examinations and personal protective equipment.
On this page
Overview
Occupational health aims to promote the physical, mental and social well-being of workers, prevent ill health caused by working conditions, protect workers from hazards, and place them in jobs suited to their abilities (WHO and ILO).
In Pakistan, large numbers of people work in agriculture, brick kilns, textiles, stone crushing, mining, leather tanning and construction, often in the informal sector with little protection.
Occupational hazards
| Type | Examples |
|---|---|
| Physical | Heat (heat stroke, cramps), cold, light, noise, vibration, ionising and non-ionising radiation, high or low atmospheric pressure |
| Chemical | Dusts (silica, asbestos, coal, cotton), gases (carbon monoxide), metals (lead, mercury, cadmium, chromium), solvents (benzene), pesticides |
| Biological | Infections from work: brucellosis and anthrax (animal handlers, wool and hide workers), tetanus, leptospirosis, hepatitis B and HIV (health workers), TB |
| Mechanical | Machinery injuries, falls, accidents; poor posture and repetitive strain (see ergonomics) |
| Psychosocial | Stress, shift work, job insecurity, harassment, monotony |
Pneumoconioses (dust diseases of the lungs)
| Disease | Dust | Occupations | Key points |
|---|---|---|---|
| Silicosis | Free silica (quartz) | Mining, quarrying, stone crushing, sandblasting, glass and pottery, construction | Most common and serious; raises the risk of TB (silicotuberculosis); "eggshell" calcification of hilar nodes; nodular fibrosis of upper lobes |
| Asbestosis | Asbestos fibres | Asbestos mining, insulation, brake linings, shipbreaking, construction | Lower-lobe fibrosis; pleural plaques; mesothelioma and lung cancer (risk multiplied by smoking) |
| Anthracosis (coal workers' pneumoconiosis) | Coal dust | Coal mining | Black lung; progressive massive fibrosis |
| Byssinosis | Cotton dust (also flax, hemp) | Textile mills | Chest tightness and breathlessness on the first day back at work after the weekend: "Monday fever" |
| Bagassosis | Bagasse (sugar cane fibre) | Sugar industry, paper and board made from bagasse | Hypersensitivity pneumonitis |
| Farmer's lung | Mouldy hay (thermophilic actinomycetes) | Farmers | Hypersensitivity pneumonitis |
| Siderosis | Iron oxide | Welders, iron workers | Benign |
Silicosis predisposes to tuberculosis. Asbestos causes mesothelioma.
Dust particles of about 0.5–3 µm (respirable dust) reach the alveoli and are the most dangerous.
Lead poisoning (plumbism)
Sources: battery manufacture and recycling, smelting, paints, printing, pottery glazes, petrol (historically), and in Pakistan some traditional cosmetics (surma).
How it enters: mainly inhalation of fumes and dust in industry; ingestion in children.
Features:
- Burton's line (blue line on the gums).
- Anaemia with basophilic stippling of red cells (lead blocks haem synthesis).
- Abdominal colic and constipation.
- Wrist drop and foot drop (motor neuropathy).
- Encephalopathy, especially in children (learning problems).
- Raised urinary coproporphyrin and aminolaevulinic acid (ALA); blood lead level for diagnosis.
Treatment: remove from exposure; chelation (for example calcium EDTA, DMSA).
Occupational cancers
| Exposure | Cancer |
|---|---|
| Asbestos | Mesothelioma, lung |
| Aniline (aromatic amine) dyes, rubber industry | Bladder |
| Benzene | Leukaemia |
| Vinyl chloride | Angiosarcoma of the liver |
| Chromium, nickel, arsenic, radon | Lung |
| Soot, tar, mineral oils | Skin (scrotal cancer in chimney sweeps, first described by Percivall Pott) |
| Ionising radiation | Leukaemia, skin, thyroid |
| Ultraviolet light | Skin |
Other occupational problems
- Noise-induced hearing loss: sensorineural; an early dip at about 4,000 Hz on the audiogram; prevented by noise control and ear protection.
- Heat disorders: heat cramps, heat exhaustion, heat stroke (in furnace workers, labourers in summer).
- Caisson disease (decompression sickness): divers and tunnel workers who return to normal pressure too quickly.
- Occupational dermatitis: cement (chromium), detergents, rubber.
- Pesticide poisoning: organophosphates in agriculture.
- Musculoskeletal disorders: back pain, repetitive strain injuries.
Prevention
Medical measures
- Pre-placement examination: before employment, to place the worker in a suitable job and record a baseline (chest X-ray, hearing, lung function).
- Periodic examination: at regular intervals to detect early disease.
- Immunisation, health education, first aid, treatment and rehabilitation; notification of occupational diseases.
Engineering and environmental measures (most effective)
In order of preference (hierarchy of control):
- Elimination or substitution of the hazard (replace asbestos; use a less toxic chemical).
- Engineering controls: enclosure, isolation, wet methods to suppress dust, local exhaust ventilation.
- Administrative controls: shorter exposure time, job rotation, training.
- Personal protective equipment (PPE): masks and respirators, ear plugs, gloves, goggles. The last line of defence.
PPE is the least effective control on its own; removing or substituting the hazard and engineering controls come first.
Legislation
Pakistan's Factories Act 1934, provincial occupational safety and health laws, and ILO conventions set duties for employers.
Ergonomics
Ergonomics is the science of fitting the job to the worker (and the worker to the job): designing tools, workstations, tasks and environment to suit human capabilities and limits.
Poor ergonomics causes:
- Low back pain (lifting and bending).
- Neck and shoulder pain (computer work, poor posture).
- Repetitive strain injuries and carpal tunnel syndrome.
- Fatigue, accidents and lower productivity.
Good ergonomics includes adjustable chairs and desks, screens at eye level, safe lifting techniques (bend knees, keep the load close), regular breaks and job rotation, and tools designed for the hand.
Ergonomics = fitting the job to the worker.
Expect: the types of hazard, matching each pneumoconiosis to its dust and occupation (silicosis and TB, asbestos and mesothelioma, cotton and byssinosis, bagasse, mouldy hay), lead poisoning signs, occupational cancers, noise-induced hearing loss at 4,000 Hz, pre-placement vs periodic examination, the hierarchy of control and the definition of ergonomics.
Quick revision
- Hazards: physical, chemical, biological, mechanical, psychosocial.
- Silicosis (stone crushing) → TB; asbestos → mesothelioma; cotton → byssinosis ("Monday fever").
- Bagasse → bagassosis; mouldy hay → farmer's lung.
- Lead: Burton's line, basophilic stippling, wrist drop, anaemia.
- Aniline dyes → bladder; benzene → leukaemia; vinyl chloride → liver angiosarcoma.
- Hierarchy: eliminate, substitute, engineer, administrate, PPE last.
- Ergonomics: fit the job to the worker.
Written by The House Job from Excel Community Medicine and Park's Textbook of Preventive and Social Medicine (named in the UHS PGET syllabus).
FAQ
Which pneumoconiosis increases the risk of tuberculosis?
Silicosis.
What is byssinosis?
A lung disease of cotton textile workers, with chest tightness that is typically worst on the first day back at work after a break ("Monday fever").
What are the signs of lead poisoning?
A blue line on the gums, anaemia with basophilic stippling, abdominal colic, wrist and foot drop, and encephalopathy in children.
What is ergonomics?
The science of designing work, equipment and the workplace to fit the worker's abilities and limits.