Environmental Health
For Health Loksewa exam
Environmental Health
An in-depth exploration of sanitation, waste management, medical entomology, occupational hazards, disaster management, and climate impacts on health.
8.1 Management of Basic Factors: Water, Air, Lighting, Noise, Housing
Environmental health focuses on the physical, chemical, and biological factors external to a person. Managing these fundamental components is the primary barrier against disease transmission and the promotion of community well-being.
Municipal Water Purification Process
Water
Safe yield, chlorination, coliform testing.
Air
Ventilation, PM2.5, biomass smoke.
Lighting
Daylight factor, glare prevention.
Noise
Decibel limits, auditory fatigue.
Housing
Space standards, dampness, cross-ventilation.
25 Key Points on Basic Factors
1. Safe water must be free from pathogenic agents, harmful chemicals, and pleasant to taste.
2. Water hardness is caused by calcium and magnesium bicarbonates/sulfates; temporary hardness is removed by boiling.
3. Chlorination is the most common water disinfection method; it requires a contact time of 30-60 minutes.
4. Free residual chlorine of 0.5 mg/L is recommended for safe drinking water at the consumer end.
5. E. coli (Thermotolerant coliforms) is the primary indicator of recent fecal contamination in water.
6. Air pollution is measured by Air Quality Index (AQI); PM2.5 particles are small enough to enter the bloodstream.
7. Indoor air pollution in Nepal is largely driven by burning biomass fuels (wood, dung) in unventilated kitchens.
8. Cross-ventilation requires windows/doors on opposite walls to ensure effective indoor air exchange.
9. Overcrowding increases the transmission of airborne diseases like TB, Measles, and ARI.
10. Floor space requirements dictate at least 50-100 sq. ft. per person to prevent overcrowding.
11. Good lighting prevents eye strain and accidents; Daylight Factor is the ratio of indoor to outdoor illumination.
12. Glare occurs when the light source is too bright compared to the background, causing visual discomfort.
13. Noise is defined as unwanted sound, measured in decibels (dB).
14. Prolonged exposure to noise >85-90 dB can cause Noise-Induced Hearing Loss (NIHL).
15. The permissible noise level in hospital zones is generally 45 dB during the day and 35 dB at night.
16. Healthy housing must provide physical protection, thermal comfort, and psychological well-being.
17. Dampness in housing promotes the growth of molds and dust mites, strongly linked to asthma and allergies.
18. Rapid Sand Filters are used in modern municipal water treatment to remove suspended impurities quickly.
19. Slow Sand Filters (Biological filters) form a “Schmutzdecke” (vital layer) that digests biological contaminants.
20. Carbon monoxide (CO) from incomplete combustion binds to hemoglobin 200x stronger than oxygen, causing asphyxiation.
21. Auditory fatigue is a temporary threshold shift in hearing after exposure to loud noise.
22. Setback rules in housing construction ensure adequate light and ventilation between buildings.
23. Biological Oxygen Demand (BOD) measures the amount of oxygen bacteria require to break down organic matter in water.
24. Sick Building Syndrome refers to acute health effects linked directly to time spent in a poorly ventilated building.
25. Vector-proofing (screens on windows, sealing cracks) is a core component of hygienic housing.
8.2 & 8.3 Solid & Health Care Waste Management
Waste management involves the collection, transport, treatment, and disposal of waste materials. Health Care Waste Management (HCWM) requires specific, highly regulated protocols due to the infectious and hazardous nature of medical waste.
Health Care Waste Color Coding (WHO Standards)
YELLOW
Infectious Waste
Anatomical parts, blood, body fluids, placenta.
Incineration / Deep Burial
RED
Infected Plastics
IV sets, tubing, catheters, urine bags, gloves.
Autoclaving / Microwaving
BLUE / WHITE
Sharps & Glass
Needles, scalpels, broken ampoules, glass slides.
Puncture-proof / Encapsulation
BLACK
General Waste
Paper, food wrappers, office waste, non-infected.
Municipal Landfill
25 Key Points on Solid & HCWM
26. Refuse is a general term for solid waste, excluding human excreta.
27. Garbage specifically refers to putrescible (decaying) organic food waste.
28. Rubbish refers to non-putrescible combustible (paper, wood) and non-combustible (glass, metal) waste.
29. The 3 R’s of waste management are Reduce, Reuse, and Recycle.
30. Uncontrolled dumping is unhygienic, breeds flies/rats, and contaminates groundwater via leachate.
31. Sanitary Landfilling (Controlled Tipping) buries waste under layers of earth, managing gas and leachate.
32. Composting is the biological decomposition of organic waste into humus (fertilizer).
33. The Bangalore method of composting is anaerobic (without oxygen), taking several months.
34. The Indore method of composting is aerobic, requiring turning of the waste, making it faster and less smelly.
35. Incineration burns waste at high temperatures, reducing volume by up to 90%, but can release toxic dioxins if poorly managed.
36. E-waste (electronic waste) contains heavy metals (lead, mercury, cadmium) requiring specialized recycling.
37. Source segregation (separating wet and dry waste at the household) is the most critical step for municipal waste management.
38. Leachate is the toxic liquid that drains from a landfill, requiring a geomembrane liner to protect aquifers.
39. Health Care Waste (HCW) includes all waste generated by medical, dental, and veterinary facilities.
40. About 75-90% of HCW is general, non-hazardous waste (Black bin).
41. The remaining 10-25% is hazardous (infectious, toxic, radioactive) and requires special treatment.
42. Segregation of medical waste at the point of generation is the absolute most important principle of HCWM.
43. Yellow bags are for highly infectious waste: human tissues, organs, placenta, and blood-soaked items.
44. Red bags are for infected recyclable plastics: IV lines, catheters, syringes (without needles), and gloves.
45. White translucent/Blue puncture-proof containers are strictly for Sharps (needles, scalpels, glass).
46. Needles should never be recapped manually to prevent needlestick injuries (the primary cause of occupational HIV/Hep B/C transmission).
47. Pharmaceutical waste (expired drugs) requires safe chemical disposal or incineration, not general landfills.
48. Cytotoxic/Genotoxic waste (from cancer chemotherapy) is highly hazardous and requires high-temperature incineration (>1200°C).
49. Autoclaving uses high-pressure steam (121°C for 20 mins) to sterilize infectious waste.
50. Encapsulation involves filling containers of sharps/chemicals with cement or clay before burying, sealing the hazard permanently.
8.4 Excreta Disposal and Control
Safe disposal of human excreta is the most critical intervention for preventing enteric diseases (cholera, typhoid, dysentery, helminths). The “F-Diagram” illustrates how pathogens from feces reach a new host, and how sanitation blocks these pathways.
The F-Diagram of Fecal-Oral Transmission
25 Key Points on Excreta Disposal
51. Open Defecation Free (ODF) status is a primary public health goal for Nepal and global sanitation initiatives.
52. Trench latrines are temporary, shallow trenches used primarily in camps or emergency disaster settings.
53. A standard Pit Latrine must be at least 50 feet (15m) away from water sources to prevent contamination.
54. The depth of a standard pit latrine is usually 1.5 to 3 meters.
55. VIP (Ventilated Improved Pit) latrines have a tall vent pipe with a fly screen, eliminating odors and trapping flies.
56. Water-seal latrines (Pour-flush) use a U-shaped trap filled with water to completely block gases and insects.
57. A Septic Tank is an unsewered, anaerobic digestion chamber for water-carriage waste.
58. Septic tanks require a retention time of 24-48 hours for solids to settle as sludge and grease to rise as scum.
59. The effluent (liquid output) from a septic tank is highly infectious and must be dispersed into a soakage pit or dispersion trench.
60. Desludging (emptying the accumulated solid sludge) of a septic tank is required every 2 to 5 years.
61. Sewered systems transport wastewater via underground pipes to a municipal sewage treatment plant.
62. Primary sewage treatment relies on physical processes: screening out large debris and gravity sedimentation of grit/sludge.
63. Secondary sewage treatment is a biological process where aerobic bacteria digest organic matter.
64. Activated Sludge Process heavily aerates wastewater, mixing it with microbe-rich sludge to rapidly oxidize organic waste.
65. Tertiary treatment is chemical or physical (chlorination, UV, reverse osmosis) to kill remaining pathogens before discharging.
66. COD (Chemical Oxygen Demand) measures the total amount of oxygen required to chemically oxidize all organic/inorganic matter in water.
67. BOD (Biochemical Oxygen Demand) measures only the oxygen used by microorganisms; therefore, COD is always higher than BOD.
68. Sulabh Shauchalaya is an Indian twin-pit pour-flush toilet model highly suitable and popular in South Asia.
69. In a twin-pit system, one pit is used while the other rests for 1.5-2 years, allowing the contents to become safe, pathogen-free compost.
70. Eco-san (Ecological Sanitation) toilets separate urine and feces at the source, treating both as resources for agriculture rather than waste.
71. The “Primary Barrier” in the F-diagram is the toilet itself, preventing feces from entering the environment.
72. The “Secondary Barrier” includes handwashing with soap and protecting water/food, stopping transmission even if feces are in the environment.
73. Feces can contain viruses (polio), bacteria (cholera), protozoa (amoeba), and helminths (hookworm).
74. Night soil refers to human feces historically collected manually at night for disposal or agricultural use.
75. A soakage pit is filled with stones/brickbats to allow septic tank effluent to percolate harmlessly into the surrounding soil.
8.5 – 8.7 Medical Entomology, Insecticides & Rodents
Arthropods and rodents are significant vectors and reservoirs of human disease. Understanding their biology, life cycles, and the safe application of chemical controls is central to environmental health.
Mosquito Life Cycle & Control Points
| Vector / Pest | Key Identifying Trait / Breeding | Primary Diseases Transmitted |
|---|---|---|
| Anopheles Mosquito | Rests at an angle (45°). Clean, stagnant water. | Malaria |
| Culex Mosquito | Hunchback posture. Polluted, dirty water. | Lymphatic Filariasis, Japanese Encephalitis |
| Aedes Mosquito | Tiger-striped legs. Clean artificial containers, daytime biter. | Dengue, Chikungunya, Zika, Yellow Fever |
| Sandfly (Phlebotomus) | Hairy wings, hops instead of flying. Cracks/crevices. | Kala-azar (Leishmaniasis) |
| Rat Flea (Xenopsylla) | Wingless, powerful jumpers. Lives on rodents. | Bubonic Plague, Murine Typhus |
| Body Louse (Pediculus) | Lives in seams of clothing. Associated with overcrowding/poor hygiene. | Epidemic Typhus, Relapsing Fever |
25 Key Points on Vectors, Insecticides & Rodents
76. Biological transmission implies the pathogen multiplies or develops inside the vector (e.g., Malaria in Anopheles).
77. Mechanical transmission implies the vector simply carries the pathogen on its body/legs (e.g., Housefly carrying Cholera).
78. Mansonia mosquitoes transmit specific types of filariasis and their larvae attach to aquatic plants (like water hyacinth) to breathe.
79. The Tse-Tse fly transmits African Trypanosomiasis (Sleeping Sickness).
80. Hard Ticks transmit diseases like Lyme disease and Kyasanur Forest Disease (KFD).
81. The Itch Mite (Sarcoptes scabiei) burrows into the human epidermis causing Scabies.
82. Reduviid bugs (Kissing bugs) bite near the mouth/eyes at night, transmitting Chagas disease in the Americas.
83. Organochlorines (like DDT) are highly persistent in the environment and bioaccumulate in the food chain.
84. Due to toxicity and environmental persistence, DDT is banned for agriculture but still used in strictly controlled IRS for malaria in some countries.
85. Organophosphates (like Malathion, Temephos) are less persistent but highly toxic to humans, inhibiting acetylcholinesterase.
86. Pyrethroids (like Deltamethrin) are the *only* class of insecticides approved for treating Long-Lasting Insecticidal Nets (LLINs) due to their safety profile for humans.
87. Paris Green is a highly toxic, arsenic-based stomach poison historically used as a mosquito larvicide.
88. Indoor Residual Spraying (IRS) coats walls with insecticide; mosquitoes absorb it when they rest on the wall after a blood meal.
89. Target-site resistance (like the *kdr* mutation) genetically alters the insect’s nervous system so the insecticide can no longer bind.
90. Behavioral resistance occurs when vectors change their habits (e.g., biting outdoors or earlier in the evening) to avoid IRS or bed nets.
91. Symptoms of organophosphate poisoning include pinpoint pupils, excessive salivation, sweating, and muscle twitching (SLUDGE syndrome).
92. Atropine is the specific antidote for organophosphate and carbamate poisoning.
93. Biolarvicides like Bti (Bacillus thuringiensis israelensis) are toxic to mosquito larvae but completely harmless to humans and fish.
94. Rattus norvegicus (Sewer rat/Brown rat) is larger, burrows in the ground, and is associated with Leptospirosis.
95. Rodent control must *always* be preceded by flea control during a plague outbreak, otherwise, fleas leave dead rats to bite humans.
96. Acute (single-dose) rodenticides, like Zinc Phosphide, act rapidly but induce “bait shyness” if the rat survives an initial small dose.
97. Chronic (multiple-dose) rodenticides are anti-coagulants (like Warfarin or Bromadiolone).
98. Anti-coagulants cause fatal internal bleeding after a few days; rats do not associate the bait with the slow death, preventing bait shyness.
99. Vitamin K is the antidote for accidental human or pet poisoning with anti-coagulant rodenticides.
100. Fumigation using Cyanogas (calcium cyanide dust) is pumped directly into rat burrows to kill both rats and their fleas simultaneously.
8.8 Climate Change and its Impact on Health
Climate change is the greatest global health threat of the 21st century. Rising temperatures, shifting rainfall patterns, and extreme weather events directly and indirectly impact human survival, infectious disease spread, and food security.
15 Key Points on Climate Change Impacts
101. Greenhouse Gases (GHGs) like Carbon Dioxide, Methane, and Nitrous Oxide trap solar radiation, causing the Earth to warm.
102. Direct health impacts include morbidities and mortalities from extreme weather (cyclones, floods, wildfires, heatwaves).
103. Global warming is expanding the geographic range of vectors. Mosquitoes can now survive at higher altitudes (e.g., Dengue reaching Kathmandu/Mountains).
104. Warmer temperatures shorten the extrinsic incubation period of pathogens inside vectors, accelerating transmission cycles.
105. Increased flooding overwhelms sanitation systems, mixing sewage with drinking water, leading to Cholera and Typhoid outbreaks.
106. Prolonged droughts cause severe water scarcity, compromising WASH practices and increasing diarrheal and skin diseases (Trachoma, Scabies).
107. Rising CO2 levels actually decrease the nutritional density (protein, zinc, iron) of staple crops like wheat and rice.
108. Glacial lake outburst floods (GLOFs) are a specific, severe climate hazard in the Himalayas (Nepal), causing massive downstream devastation.
109. Climate-induced migration creates “Climate Refugees,” leading to overcrowding, stress on urban infrastructure, and mental health crises.
110. Mitigation refers to actions taken to reduce GHG emissions (e.g., switching to solar energy, active transport).
111. Adaptation refers to actions taken to manage the impacts of climate change (e.g., building flood defenses, developing heat-action plans).
112. The healthcare sector itself is a major emitter of GHGs; transitioning to “Green Hospitals” is a mitigation priority.
113. Early Warning Systems (EWS) for floods and heatwaves are highly cost-effective adaptation tools to save lives.
114. “Co-benefits” occur when climate mitigation also improves immediate health (e.g., reducing coal use lowers GHGs *and* reduces local asthma rates).
115. Deforestation contributes to climate change and simultaneously pushes wildlife closer to humans, increasing Zoonotic spillover risk.
8.9 – 8.10 Occupational Health & Food Sanitation
Occupational health ensures the physical, mental, and social well-being of workers in all occupations. Managing workplace hazards relies on the Hierarchy of Controls. Food sanitation ensures that food is handled, prepared, and stored in ways that prevent foodborne illness.
Hierarchy of Hazard Controls
25 Key Points on Occupational Health & Food Sanitation
116. Ergonomics is the science of designing the workplace to fit the worker, preventing musculoskeletal disorders.
117. Pneumoconiosis is a group of occupational lung diseases caused by inhaling inorganic dust.
118. Anthracosis (Black Lung Disease) is caused by inhaling coal dust.
119. Silicosis is caused by inhaling silica dust (common in mining, quarrying, and sandblasting).
120. Asbestosis is caused by inhaling asbestos fibers and is strongly linked to Mesothelioma (pleural cancer).
121. Byssinosis is caused by inhaling cotton dust, common in the textile industry.
122. Bagassosis is caused by inhaling sugar cane dust.
123. Farmer’s Lung is caused by inhaling moldy hay or grain dust.
124. Lead poisoning (Plumbism) causes anemia, abdominal colic, and severe neurological damage (wrist drop).
125. The Hierarchy of Controls is the framework for occupational safety; Elimination is the most effective, PPE is the least effective.
126. Pre-placement medical examinations ensure a worker is physically and mentally fit for a specific job role.
127. Food hygiene encompasses all conditions and measures necessary to ensure the safety and suitability of food at all stages of the food chain.
128. Pasteurization of milk (heating to 72°C for 15 seconds) kills pathogens like Brucella, Salmonella, and Mycobacterium bovis.
129. Abattoir (slaughterhouse) sanitation requires strict antemortem and postmortem inspection of animals to prevent zoonoses like Anthrax and Tapeworms.
130. Cross-contamination occurs when pathogens from raw food (e.g., raw chicken) are transferred to ready-to-eat food via hands or cutting boards.
131. The “Danger Zone” for food bacterial growth is between 5°C and 60°C. Food must be kept outside this range.
132. HACCP (Hazard Analysis Critical Control Point) is a systematic preventive approach to food safety from biological, chemical, and physical hazards.
133. Food fortification adds micronutrients to staple foods to improve public health (e.g., iodine in salt).
134. Food adulteration is the illegal, intentional addition of inferior/harmful substances (e.g., water in milk, brick powder in spices) for profit.
135. FIFO (First In, First Out) is a fundamental food storage principle to ensure older stock is used before newer stock.
8.11 Environmental Health in Disasters
Disasters, whether natural (earthquakes, floods) or man-made, cause sudden, massive disruptions to environmental health infrastructure. Managing water, sanitation, and disease surveillance during the Disaster Cycle is critical to preventing post-disaster epidemics.
The Disaster Management Cycle
25 Key Points on Disaster Management
136. A disaster is a sudden, calamitous event that seriously disrupts the functioning of a community or society and exceeds its ability to cope using its own resources.
137. The Disaster Management Cycle consists of four phases: Mitigation, Preparedness, Response, and Recovery.
138. Mitigation involves structural (building earthquake-resistant hospitals) and non-structural (zoning laws) measures to minimize disaster impact.
139. Preparedness involves developing emergency action plans, stockpiling medical supplies, and conducting community drills.
140. Response is the immediate post-disaster phase focused on saving lives, search and rescue, and providing basic needs (water, shelter, medical care).
141. Triage is the process of rapidly sorting patients based on the severity of their injuries to maximize the number of survivors in mass-casualty events.
142. Red tag in triage indicates immediate, life-threatening injuries requiring urgent surgery or intervention.
143. Black tag in triage indicates the patient is deceased or their injuries are so severe that survival is unlikely given the available resources.
144. Water supply is the absolute highest priority environmental health intervention immediately following a disaster.
145. Minimum water requirement in an emergency camp is 15-20 liters per person per day for drinking, cooking, and basic hygiene.
146. High-dose chlorination is the most practical and effective method for mass water purification in disaster camps.
147. Excreta disposal must be rapidly organized using trench latrines to prevent devastating outbreaks of Cholera and Typhoid.
148. Overcrowding in temporary shelters rapidly facilitates the spread of respiratory infections (ARI, TB, Measles) and skin infections (Scabies).
149. Measles vaccination combined with Vitamin A supplementation is a top priority intervention for children in disaster camps due to high mortality risk.
150. Dead bodies rarely cause epidemics following natural disasters, contrary to popular myth; the primary risk is contaminated water.
151. Nutritional relief in disasters often utilizes High Energy Biscuits (HEB) and Ready-to-Use Therapeutic Foods (RUTF).
152. Floods specifically increase the risk of waterborne diseases and Leptospirosis (due to rodent urine in floodwaters).
153. Earthquakes cause massive crush injuries leading to Crush Syndrome, releasing myoglobin which causes acute kidney failure.
154. Post-Traumatic Stress Disorder (PTSD) is a profound, long-term health impact requiring psychosocial support during the recovery phase.
155. Vector control (fogging and distributing LLINs) is critical if disaster camps are in endemic malaria or dengue zones.
156. An Early Warning System (EWS) is a crucial preparedness tool for hydro-meteorological disasters like floods and cyclones.
157. Recovery (Rehabilitation and Reconstruction) focuses on restoring the community to normal and “building back better” to withstand future hazards.
158. Nepal is highly vulnerable to disasters, particularly earthquakes due to active fault lines, and landslides/floods during the monsoon.
159. The SPHERE Standards define the minimum humanitarian standards in vital areas like water supply, sanitation, and food aid during disaster response.
160. Rapid Health Assessment must be conducted within the first 48-72 hours to identify immediate health risks and resource needs.
Knowledge Check: 125 MCQs
Test your knowledge on Environmental Health. Click an option to see if you’re correct.
Basic Factors
Waste Mgmt
Excreta
Vectors
Occ Health & Disasters