Environmental and Occupational Health

Community Medicine — Environmental and Occupational Health, NMC MBBS licence examination syllabus (Nepal Medical Council).

Environmental and occupational health

Two questions that are almost never asked, and frequently explain the diagnosis.

A great deal of disease is caused by where people live and what they do for a living, and almost none of it is recorded that way. A woman with chronic cough who has never smoked is investigated for everything except the open cooking fire she has spent four hours a day beside for thirty years. A man with progressive breathlessness is treated for asthma without anyone asking what he cuts stone with.

The two questions in this chapter — what fuel do you cook with? and what does your work actually involve? — cost nothing and change the diagnosis often enough to be worth asking routinely.

🩺 Where this lives: Household air pollution from solid cooking fuel is one of the largest environmental causes of disease worldwide, and its burden falls almost entirely on women and young children. The exposure is concentrated by gender and by age: the person cooking, and the infant carried on her back or playing beside the stove. It produces chronic obstructive lung disease in people who have never smoked a cigarette — which means a clinician who equates COPD with smoking will systematically misdiagnose exactly the group most affected.

💡 A note on numbers. This chapter gives no exposure limits, no arsenic or fluoride concentration thresholds and no air quality figures. These are set by national standards and WHO guideline values and are revised over time. It also gives no Nepal-specific prevalence figures, which come from national survey data. Water and sanitation microbiology is covered in the Enteric Infections chapter, pesticide poisoning management in the Poisoning chapter, and heat illness in the Snakebite and Environmental Emergencies chapter.

Household air pollution

The clinical instruction that follows is simple: ask about cooking fuel in any patient with chronic respiratory symptoms, and treat a never-smoking woman with COPD as an entirely expected presentation rather than a puzzle. The same exposure contributes to childhood pneumonia, low birth weight, cardiovascular disease and lung cancer. The interventions — improved stoves, better ventilation, cleaner fuels — sit outside the clinic, which is exactly why they need clinicians to point at the problem.

Water: the chemical hazards

WHY A SAFE WELL CAN STILL BE UNSAFE Water programmes have historically focused on microbiological safety — and rightly, since faecal contamination causes cholera, typhoid and childhood diarrhoea (see the Enteric Infections chapter). But moving a community from contaminated surface water to groundwater can substitute one hazard for another. ARSENIC Occurs naturally in groundwater in parts of South Asia. It is TASTELESS, ODOURLESS and COLOURLESS — so it cannot be detected without testing. Chronic exposure causes characteristic SKIN changes: pigmentation alteration and KERATOSES on palms and soles, which are often the first clinical sign. Later: skin, bladder and lung CANCER, and peripheral vascular and neurological effects. THE DIAGNOSIS IS MADE BY THINKING OF IT — the skin findings are easy to dismiss as a dermatosis unless you ask where the drinking water comes from. FLUORIDE A U-shaped relationship: too little causes dental caries, too much causes DENTAL FLUOROSIS (mottled, discoloured enamel) and, with heavy chronic exposure, SKELETAL FLUOROSIS with bone and joint changes. Both are addressed by testing the source and providing an alternative supply or treatment. Concentration limits come from national standards and WHO guideline values.

Taking an occupational history

💡 Exam angle: the highest-yield single question is "are your symptoms better when you are away from work?" — improvement at weekends or on holiday, with recurrence on return, is close to diagnostic of an occupational cause and is the classic stem for occupational asthma. Two further habits matter: a job title is not an exposure history (ask what they actually handle and breathe), and previous jobs count, because latency for dust diseases and occupational cancers can be decades.

Controlling the hazard

The hierarchy of control is examined because the instinctive answer is the wrong one. Faced with a hazard, most people reach first for personal protective equipment — and PPE is the last resort, not the first. It protects one person at a time, only while worn correctly, and fails silently when it is not fitted or maintained. Eliminating or substituting the hazard protects everyone permanently and depends on nobody's behaviour, which is why it sits at the top.

Specific hazards

A FEW EXPOSURES WORTH KNOWING BY NAME SILICA — stone cutting, quarrying, mining, construction Causes SILICOSIS, a progressive fibrotic lung disease. IMPORTANTLY, it also substantially increases the risk of TUBERCULOSIS — so a silica-exposed worker with a chronic cough needs TB actively excluded, and the two diagnoses can coexist. ASBESTOS — long latency, mesothelioma and lung cancer. Past exposure matters decades later. PESTICIDES — acute poisoning in agricultural work, covered in the Poisoning chapter. Note the public health angle: pesticides stored in the home are a common means of self-harm in rural communities, and restricting access to means is an evidence-based suicide prevention measure (see the Risk Assessment chapter). NOISE — causes IRREVERSIBLE sensorineural hearing loss. Prevention is the only effective intervention. ERGONOMIC hazards — back and upper limb disorders from lifting, repetition and posture. Enormously common and rarely recorded as occupational. HEAT, HEIGHTS AND MACHINERY — injury and heat illness in construction and agriculture. THE STRUCTURAL PROBLEM: most workers in this region are in the INFORMAL SECTOR — agriculture, construction, small workshops, domestic work. They have no occupational health surveillance, no protective equipment, no compensation scheme, and often no alternative employment. Recognising occupational disease in that setting means the clinician is frequently the only surveillance system there is.

Clinical reasoning: four presentations

🔍 Case 1 — COPD in a woman who has never smoked

PresentationA 55-year-old woman has years of cough and progressive breathlessness with obstructive spirometry. She has never smoked. She is labelled as having "asthma of unclear cause" and no further history is taken.

Question not askedWhat does she cook with?

ReasoningHousehold air pollution from solid fuel is a major cause of COPD in never-smoking women, who spend hours daily beside an unvented stove. Equating COPD with smoking systematically misses this group.

AnswerTake a cooking fuel and ventilation history, manage the lung disease appropriately, and advise on improved stoves, ventilation and cleaner fuel where possible. Consider the children exposed in the same room.

🔍 Case 2 — better on Sundays

PresentationA factory worker has wheeze and cough that improve markedly on his day off and during a week away, returning within a day of going back. He is treated with inhalers and told to continue working.

The diagnostic clueImprovement away from work.

ReasoningThis temporal pattern is close to diagnostic of occupational asthma. Continuing exposure risks permanent fixed airflow obstruction, so treating symptomatically without addressing the exposure is inadequate.

AnswerTake a detailed exposure history, ask about affected colleagues, and pursue removal from exposure per occupational health pathways. Ask the same question of anyone with adult-onset asthma.

🔍 Case 3 — patches on the palms

PresentationA man from a village that changed to tubewell water years ago has pigmentation changes on his trunk and thickened keratotic lesions on his palms and soles. He is treated with topical preparations for a presumed dermatosis.

Question not askedWhere does the drinking water come from?

ReasoningPigmentation change with palmar and plantar keratoses is the characteristic cutaneous picture of chronic arsenic exposure, and arsenic in groundwater is tasteless and undetectable without testing.

AnswerTake a water source history, arrange testing of the supply, and consider the whole community — others will be exposed. Chronic arsenic exposure also carries a long-term cancer risk requiring follow-up.

🔍 Case 4 — masks for the stone cutters

ScenarioSeveral workers at a stone-cutting yard have developed breathlessness. The employer's response is to buy cloth masks and require workers to wear them.

ProblemStarting at the bottom of the hierarchy of control.

ReasoningPPE is the last resort: it protects one person at a time, only while correctly worn and maintained, and cloth masks do not protect against respirable silica. Elimination, substitution and engineering controls such as wet cutting and extraction protect everyone.

AnswerApply the hierarchy: dust suppression and extraction first, then administrative measures, with appropriate respiratory protection as an addition rather than the plan. Also actively exclude tuberculosis — silica exposure substantially raises TB risk.

Commonly confused

Confusion	The distinction	Why it matters
COPD vs smoking	Solid fuel smoke causes it in never-smokers	Misses the most affected group.
Safe water vs tested water	Arsenic is tasteless and odourless	A clean-looking well can be unsafe.
Microbiological vs chemical safety	A tubewell fixes one and may add the other	Both must be considered.
Job title vs exposure history	Ask what they actually handle and breathe	Titles conceal the exposure.
Current vs previous jobs	Latency can be decades	Asbestos and occupational cancers.
PPE vs the hierarchy	PPE is the LAST resort	It protects one person, only while worn.
Silicosis vs tuberculosis	Silica raises TB risk, and both can coexist	TB must be actively excluded.
Fluoride deficiency vs excess	Caries versus fluorosis	Both ends of the curve cause harm.

Rapid revision

MUST-KNOW FACTS 1. HOUSEHOLD AIR POLLUTION is a leading environmental cause of disease. 2. Solid fuel: wood, dung, crop residue, coal, burned indoors. 3. Exposure falls on WOMEN who cook and YOUNG CHILDREN nearby. 4. It causes COPD IN NEVER-SMOKERS. 5. Also childhood pneumonia, low birth weight, cardiovascular disease, lung cancer. 6. ASK ABOUT COOKING FUEL in any chronic respiratory presentation. 7. Interventions: improved stoves, ventilation, cleaner fuels. 8. ARSENIC occurs naturally in some groundwater. 9. It is TASTELESS, ODOURLESS and COLOURLESS — testing is the only detection. 10. Chronic arsenic: PIGMENTATION change and palmar/plantar KERATOSES. 11. Later: skin, bladder and lung CANCER. 12. Ask about the WATER SOURCE in unexplained pigmented or keratotic skin. 13. FLUORIDE: too little causes caries, too much causes FLUOROSIS. 14. Dental fluorosis, and skeletal fluorosis with heavy exposure. 15. A tubewell may fix microbiology and introduce chemistry. 16. THE OCCUPATIONAL QUESTION: are symptoms BETTER AWAY FROM WORK? 17. Improvement at weekends with recurrence on return suggests occupational cause. 18. A JOB TITLE IS NOT AN EXPOSURE HISTORY. 19. Ask about PREVIOUS jobs — latency may be decades. 20. If one worker is affected, ASK ABOUT COLLEAGUES. 21. HIERARCHY OF CONTROL: eliminate, substitute, engineering, administrative, PPE. 22. PPE IS THE LAST RESORT, NOT THE FIRST. 23. PPE protects one person, only while correctly worn and maintained. 24. SILICA causes SILICOSIS — stone cutting, quarrying, mining. 25. SILICA EXPOSURE SUBSTANTIALLY INCREASES TUBERCULOSIS RISK. 26. Silicosis and TB can coexist — exclude TB actively. 27. ASBESTOS: long latency, mesothelioma and lung cancer. 28. PESTICIDES: acute poisoning, and a common means of self-harm at home. 29. Restricting access to means is evidence-based suicide prevention. 30. NOISE causes IRREVERSIBLE hearing loss — prevention only. 31. ERGONOMIC hazards cause back and limb disorders. 32. Most workers here are INFORMAL — no surveillance, no protection. 33. Take exposure limits and water thresholds from national standards.

💡 Exam angle: two questions carry this whole chapter. "What do you cook with?" turns an unexplained COPD into a diagnosis. "Are you better away from work?" turns adult-onset asthma into an occupational disease. Both take seconds, and neither is asked routinely.

Syllabus points

Household air pollution and solid fuel
Why women and children bear the exposure
COPD in never-smokers
Arsenic in groundwater
The cutaneous signs of chronic arsenic exposure
Fluoride deficiency and excess
Taking an occupational history
The symptoms-away-from-work question
Why previous jobs matter
The hierarchy of control
Why PPE is the last resort
Silica, silicosis and tuberculosis risk
The informal sector problem

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