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Make it little concise as per wbuhs mbbs 2026 exam oriented answers

Here is the concise, WBUHS MBBS 2026 exam-oriented version of Chapter 3 - Environmental Health Problems:

CHAPTER 3: ENVIRONMENTAL HEALTH PROBLEMS

Group A - Long Answer Questions

Q.1. Define 'Safe and Wholesome Water'. Discuss bacteriological surveillance of drinking water. (WBUHS 2013)

Safe and Wholesome Water is water which is:

Free from pathogenic agents
Free from harmful chemical substances
Pleasant to taste (free from colour and odour)
Usable for domestic purposes

Tests for Bacteriological Surveillance:

1. Presumptive Coliform Test (two methods):

Multiple Tube Method (MPN): Sample water (0.1, 1.0, 10, 50 ml) inoculated into McConkey's Lactose Bile Salt Broth with bromocresol purple; incubated at 37°C for 48 hrs. Tubes showing acid + gas = positive. Result = MPN of coliform organisms per 100 ml.
Confirmatory Test: Subculture positive tubes in brilliant green bile broth at 44°C - gas = confirmed coliforms; also test for indole at 44°C.
Membrane Filtration Technique: Water filtered through cellulose ester membrane; bacteria retained on surface; incubated on suitable media; results within 20 hours.

2. Tests for Faecal Streptococci and Cl. Perfringens:

Faecal streptococci = evidence of recent faecal pollution
Cl. Perfringens (anaerobic spore-bearer): water heated at 75°C for 10 min, then inoculated into DRC medium, incubated 37°C for 2 days. Presence = faecal contamination at remote time.

3. Colony (Plate) Count:

Estimates general purity; sudden increase = earliest sign of contamination

Water	Plate count (2 days/37°C)	Plate count (3 days/22°C)
Disinfected	0	20
Not disinfected	10	100

Q.2. Chemicals of health significance in West Bengal groundwater - Arsenic. (WBUHS 2017)

Common chemicals: Arsenic (commonest), fluoride, lead, cadmium, chromium.

Arsenic - Health Effects:

(a) Acute: Vomiting, abdominal pain, diarrhoea, numbness, tingling of extremities, muscle cramping, death.

(b) Long-term:

Skin: Pigmentation changes, hyperkeratosis (palms/soles) after min. 5 years - precursor to skin cancer
Cancers of bladder and lungs
Neurotoxicity, diabetes, cardiovascular disease, portal hypertension with hepato-splenomegaly
Adverse pregnancy outcomes, infant mortality

Prevention and Control:

Substitute high-arsenic groundwater with rain water/treated surface water
Test wells and mark high/low arsenic sources with different coloured paint
Blend low and high arsenic water to achieve acceptable levels
Install arsenic removal systems (oxidation, coagulation-precipitation, ion exchange, membrane techniques)
Monitor high-risk populations
Reduce occupational/industrial exposure
Treatment of arsenicosis is mostly symptomatic

Q.3. Water-borne diseases + household water purification + Problem Village. (WBUHS 2010, 2023)

Water-borne Diseases:

(1) Due to infective organisms:

Viral: Hepatitis A, E; poliomyelitis; rotavirus diarrhoea
Bacterial: Typhoid, paratyphoid, dysentery, E. coli diarrhoea, cholera
Protozoal: Amoebiasis, giardiasis
Helminthic: Ascariasis, enterobiasis, hydatid disease
Leptospiral: Weil's disease

(2) Due to aquatic hosts:

Snail: Schistosomiasis
Cyclops: Dracanculosis (guinea worm), fish tapeworm

Household Water Purification:

(1) Physical:

Boiling: Rolling boil for 10-20 min; kills bacteria, spores, cysts, ova, viruses. Disadvantages: alters taste, no residual protection.

(2) Chemical:

Bleaching powder: 33% available chlorine; free residual chlorine 0.5 mg/L at 1 hr contact
Chlorine solution: 5% solution from 4 kg bleaching powder (25% available chlorine) + 20 L water
HTH (High Test Hypochlorite): 60-70% available chlorine; more stable
Halazone tablets: 0.5 mg tablet disinfects 20 L; also reduces turbidity
Iodine: 2 drops of 2% ethanol solution for 1 L clear water; emergency use
KMnO₄: Kills cholera vibrios; little use against other organisms

(3) Mechanical: Ceramic filters (Pasteur-Chamberland, Berkefeld, Katadyn) - arrests all microorganisms except viruses

(4) UV Irradiation (Acquaguard): Kills bacteria, yeast, viruses, fungi, algae, protozoa

(5) Multistage RO: Makes water chemically and microbiologically potable; removes TDS, hardness, heavy metals

Problem Village: Where no safe water source is within 1.6 km / 15 m deep, OR water is exposed to toxic elements, OR excess salinity, iron, fluorides - or risk of cholera.

Q.4. Classification of water-related diseases + surveillance of drinking water quality. (WBUHS 2013, 2023)

Bradley's Classification (1977):

Type	Cause	Examples
Water-borne	Consumption of contaminated water	Diarrhoea, hepatitis A, cholera, typhoid, guinea worm
Water-washed	Poor hygiene due to inadequate water	Diarrhoea, typhoid, trachoma, skin/eye infections
Water-based	Intermediate host dwells in water	Guinea worm, schistosomiasis
Water-related	Vectors breed in water	Malaria, filaria, dengue, chikungunya

Surveillance of Drinking Water Quality (WHO 1976): Continuous and vigilant public health assessment of safety and acceptability of drinking water supplies.

Elements:

Sanitary Survey: Detect/correct faults in entire water supply system; essential for interpreting lab results
Collection of Water Sample:
- Tap/pump: Remove attachments, clean outlet with flame, let water flow 1 min, collect in sterile bottle
- Well/tank: Lower sterile bottle on string, allow to fill, raise and stopper
Transport: Analysis ASAP; if not feasible, keep in ice, analyze within 48 hours
Bacteriological Surveillance: As in Q.1

Q.5. Water Conservation and Rainwater Harvesting in Urban Areas. (RGUHS 2010, SAMU 2011)

Water Conservation has two components:

(a) Prevention of wastage: Awareness about economical water use
(b) Water harvesting: Preserve and build underground water reserves

Rainwater Harvesting: Process of collecting, storing, conveying and purifying rainwater from rooftops, parks, roads, open grounds for later use.

Components:

Catchment: Collects and stores captured rainwater
Conveyance system: Transports water from catchment to recharge zone
Flush: Flushes out first spell of rain
Filter: Filters collected rainwater and removes pollutants
Tanks/Recharge structures: Stores filtered water ready for use

Q.6. Air Pollution - Sources and Hazards. (WBUHS 2019, MU 2019)

Definition: Presence of toxic chemicals/compounds in air at levels posing health risk.

Sources:

Domestic: Combustion of coal, wood, oil (e.g., London disaster 1952)
Automobiles: Hydrocarbons, CO, lead, nitrogen oxides, particulate matter
Industries: Iron/steel, paper, cement, fertilisers, thermal plants, petroleum refineries
Miscellaneous: Tobacco smoking, burning refuse, incinerators, nuclear explosions, forest fires

Hazards:

(1) Immediate/Acute (due to photochemical oxidants):

Conjunctivitis, allergic rhinitis, acute pharyngitis, acute bronchitis, bronchial asthma attacks
May cause suffocation and death
Examples: London disaster (1952), Bhopal gas tragedy (1984)

(2) Delayed/Chronic:

Chronic bronchitis, bronchiectasis, emphysema, COPD, bronchial asthma, lung cancer

Q.7. Indicators of Air Pollution + Prevention and Control. (WBUHS 2019, BNMU 2013)

Indicators:

Sulphur dioxide index: Estimated in all air pollution surveys
Smoke (Soiling) index: Air filtered through white filter paper; stain measured by photoelectric meter; expressed as Coh units/1000 linear ft of air
Suspended particles: Measured by 'Midget impinger'; expressed in mgm/m³ of air
Coefficient of haze: Amount of smoke/aerosol per m³ of air
Air pollution index: Arbitrary index - US formula: 10×SO₂ + 2×CO + 2×coefficient of haze; alarm if >50

Prevention and Control:

1. Engineering Measures:

Location of industries away from habitation
Containment: wet dust control, enclosures, exhaust pipes, arresters
Replacement: electricity/natural gas instead of coal; unleaded petrol

2. Legislation:

Indian Factories Act 1948
Air (Prevention and Control of Pollution) Act 1981
Smoke Nuisance Act

3. General Measures:

Traffic control (bypass roads)
Dilution: green belts between industrial and residential areas
Health education
Population stabilisation

4. International Action: WHO established global network; 20 laboratories worldwide; 2 international centres (London and Washington)

Q.8. Impact of Climate Change on Human Health. (WBUHS)

Climate Change	Effect on Environment	Health Hazards
More extreme weather	Air pollution; changed vector ecology	Asthma, CVD; Malaria, dengue, encephalitis, Rift valley fever, Lyme disease, West Nile virus
Rising sea levels	Increasing allergens; water quality impacts	Respiratory allergies, asthma; cholera, cryptosporidiosis, leptospirosis
Increasing CO₂	Water/food supply impacts; environmental degradation	Malnutrition, diarrhoeal disease; forced migration, mental health impacts
Rising temperature	Extreme heat; severe weather	Heat-related illness/death, cardiovascular failure; injuries, fatalities, mental health impacts

Q.9. Soil-borne diseases, Sanitary Latrine criteria, Water Seal Latrine, Sanitation Barrier. (WBUHS 2023)

Common Soil-borne Diseases in India:

Intestinal roundworm (Ascariasis)
Hookworm (Necator americanus, Ancylostoma duodenale)
Whipworm (Trichuris trichiura)

Criteria for Sanitary Latrine:

Excreta should NOT contaminate ground/surface water
Excreta should NOT pollute soil
Excreta should NOT be accessible to flies, rodents, animals
Excreta should NOT create nuisance (odour/unsightly appearance)

Importance of Water Seal Latrine: Water seal performs 3 functions:

(a) Prevents fly access (night soil sealed by water in trap)
(b) Prevents escape of odours and foul gases
(c) Night soil not visible after flushing

(Sanitation barrier - covered in Group B)

Q.10. Criteria and Health Effects of Poor Ventilation. (WBUHS)

Ventilation Standards (criteria):

Floor space: 50-100 ft² per person
Cubic space: 1000-1200 ft³ fresh air/person/hour
Air change: 2-3 per hour in living rooms; 4-6 per hour in workrooms/assemblies
Windows:
- Minimum 2 windows per living room; at least one opening to open space
- Height ≤ 3 ft from ground
- Window area = 1/5th of floor area
- Doors + windows combined = 2/5th of floor area

Health Effects of Poor Ventilation:

Increased spread of airborne diseases
Poor indoor air quality: fatigue, hypersensitivity, headache, sinus congestion
Sick Building Syndrome: Eye/nose irritation, headache, fatigue, susceptibility to colds and flu
Dampness leading to rats and insect infestations
High CO₂ and low O₂ levels causing fatigue and poor concentration

Q.11. Smog, AQI (200-300 range) - Health Effects and Measures. (WBUHS 2024)

Smog: Air pollution that reduces visibility. Mix of smoke and fog. Most modern smog = photochemical smog.

AQI (Air Quality Index): Tool to communicate air quality status. Converts pollutant data into single index value with color codes. 8 pollutants measured: PM10, PM2.5, NO₂, SO₂, CO, O₃, NH₃, Pb.

AQI	Air Quality	Health Impacts
0-50	Good	Minimal impact
51-100	Satisfactory	Minor breathing discomfort to sensitive people
101-200	Moderate	Breathing discomfort with lung/heart disease, children, elderly
201-300	Poor	Breathing discomfort on prolonged exposure
301-400	Very Poor	Respiratory illness on prolonged exposure
>400	Severe	Respiratory effects even in healthy people

AQI 200-300 (Poor) - Health Effects: Breathing discomfort to people on prolonged exposure, especially those with pre-existing respiratory/cardiac disease.

Measures: Same as Q.7 (Engineering + Legislation + General + International)

Q.12. Solid Waste Management - Methods, Composting, Biogas Generation. (WBUHS 2024)

Methods of Solid Waste Disposal:

Recycling: Materials recovered and reused
Dumping: Refuse dumped in low-lying areas for land reclamation
Controlled tipping/Sanitary landfill: Most satisfactory method; material placed in trench, compacted, covered with earth daily
Composting: Biodegradable organic matter subjected to aerobic digestion
Incineration: Combustion of waste to reduce volume
Manure pits: Rural areas; garbage, cattle dung, straw covered with earth daily
Sewage treatment: Produces non-toxic effluent + semisolid sludge; effluent discharged to water bodies, sludge incinerated/landfilled

Composting:

Combined disposal of refuse + nightsoil/sludge; organic matter breaks down under bacterial action forming humus-like compost
Advantages: Reduces landfill waste; recovers organic matter as soil amendment
Disadvantages: Bioaerosols (bacteria/fungal spores); volatile organic compounds; contaminants can enter food chain

Biogas Generation:

Organic matter broken down by microorganisms anaerobically (anaerobic digestion) to produce biogas (renewable fuel)
Biogas Plant Components:
1. Reception area: Raw materials arrive (crop residues, municipal/industrial sewage, livestock manures, food wastes)
2. Digester: Air-tight, waterproof container; agitators shift biomass to free gases
3. Gas holder: Airproof container (steel); collects gas; gas outlet produces energy and heat

Group B - Short Notes

Q.1. Biological Filter. (WBUHS 2019)

Also called slow sand filtration.

Water percolates through sand bed; impurities removed by straining, sedimentation, biochemical and biological processes
A slimy "Zoogleal" layer (Schmutzdecke/vital layer) forms on sand bed = consists of algae, diatoms, plankton, minute plants, protozoa
This vital layer:
- Feeds on organic matter
- Converts it into small harmless substances
- Holds back bacteria
- Oxidizes ammoniacal nitrogen into nitrates
- Yields bacteria-free water

Exam Tips for WBUHS 2026:

Tables and classifications (Bradley's, AQI) are high yield

Know MPN method and membrane filtration for bacteriology questions

Arsenic health effects (acute vs chronic) frequently asked

Composting + biogas asked in WBUHS 2024 - expect repeat

Water seal latrine functions = 3 points to remember

AQI question (Q.11) is a new pattern from WBUHS 2024 - master it

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