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Make it concise as per wbuhs mbbs exam oriented answers

Here are all the questions from Chapter 3 (Environmental Health Problems) rewritten as concise, WBUHS MBBS exam-oriented answers:

CHAPTER 3: ENVIRONMENTAL HEALTH PROBLEMS

Competency-Based Q&A (WBUHS Exam Format)

GROUP A — LONG ANSWER QUESTIONS

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

Safe and Wholesome Water is water that is:

Free from pathogenic agents
Free from harmful chemicals
Pleasant to taste, free from colour and odour
Usable for domestic purposes

Tests for Bacteriological Surveillance:

1. Presumptive Coliform Test (two methods):

(i) Multiple Tube Method (MPN Method):

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 hours
Tubes showing acid + gas = positive
MPN estimated from statistical table = "Presumptive Coliform Count"

Confirmatory Test:

Gas production from lactose in Brilliant Green Bile Broth at 44°C
Indole production at 44°C

(ii) Membrane Filtration Technique:

Water filtered through cellulose ester membrane
Bacteria retained on surface, inoculated on media
Results in 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, inoculated into DRC medium, incubated 37°C for 2 days; presence of spores suggests remote faecal contamination

3. Colony (Plate) Count:

Estimates general purity of water
Sudden rise = earliest sign of contamination

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

Q.2. Name chemicals of health significance in West Bengal groundwater. Describe health effects and control of one. (WBUHS 2017)

Chemicals: Arsenic (commonest), Fluoride, Lead, Cadmium, Chromium

ARSENIC

Health Effects:

Acute: Vomiting, abdominal pain, diarrhoea, numbness/tingling of extremities, muscle cramps, death

Chronic (long-term):

Skin: pigmentation changes, hyperkeratosis (palms and soles) after min. 5 years - precursor to skin cancer
Cancers: bladder, lung
Other: neurotoxicity, diabetes, cardiovascular disease, portal hypertension with hepatosplenomegaly
Adverse pregnancy outcomes, infant mortality, impaired cognitive development

Prevention and Control:

Substitute high-arsenic groundwater with low-arsenic/rain/surface water
Test wells and mark high/low arsenic sources (colour-code pumps)
Blend high-arsenic with low-arsenic water
Install arsenic removal systems (centralized or domestic)
- Technologies: oxidation, coagulation-precipitation, absorption, ion exchange, membrane techniques
Reduce occupational/industrial exposure
Monitor high-risk populations
Treatment of arsenicosis: symptomatic only

Q.3. Enumerate water-borne diseases. Discuss household water purification. Define Problem Village. (WBUHS 2010, 2023)

Water-Borne Diseases:

(1) Caused by infective organisms:

Viral: Hepatitis A, Hepatitis E, Polio, Rotavirus diarrhoea
Bacterial: Typhoid, Paratyphoid, Bacillary dysentery, E. coli diarrhoea, Cholera
Protozoal: Amoebiasis, Giardiasis
Helminthic: Ascariasis, Enterobiasis, Hydatid disease
Leptospiral: Weil's disease

(2) Caused by aquatic hosts:

Snail: Schistosomiasis
Cyclops: Dracunculosis, Fish tapeworm

Household Water Purification:

(1) Physical:

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

(2) Chemical:

Bleaching powder (33% available Cl): ensures 0.5 mg/L free residual Cl after 1 hour
Chlorine solution: 5% solution from bleaching powder (4 kg + 20 L water)
HTH (High Test Hypochlorite): 60-70% Cl, more stable than bleaching powder
Halazone tablets: 0.5 mg tablet disinfects 20 L water
Iodine: 2 drops of 2% ethanol solution per 1 L (emergency use)
Potassium permanganate: kills cholera vibrios; limited spectrum

(3) Mechanical: Ceramic candle filters (Pasteur-Chamberland, Berkefeld, Katadyn); need regular cleaning

(4) UV Irradiation (Acquaguard): Germicidal against bacteria, viruses, fungi, algae, protozoa

(5) Multistage Reverse Osmosis: Removes dissolved solids, hardness, heavy metals, bacteria, viruses, cysts

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

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

Classification (Bradley, 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 lives in water	Guinea worm, Schistosomiasis
Water-related	Vectors breed in water	Malaria, Filaria, Dengue, Chikungunya

Surveillance of Drinking Water Quality (WHO 1976 - "continuous vigilant public health assessment of safety and acceptability"):

Sanitary Survey: First step; detects faults in entire water supply system
Collection of water sample:
- Tap/pump: clean outlet, flame-sterilize, allow water to flow 1 min, collect in sterile bottle
- Well/tank: lower sterile bottle on string, allow to fill, raise and stopper
Transport: Begin analysis ASAP; keep in ice if delayed; analyze within 48 hours
Bacteriological Surveillance: As in Q.1

Q.5. Describe water conservation and rainwater harvesting in urban areas. (RGUHS 2010, 2012)

Water Conservation has two components:

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

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

Components of Rainwater Harvesting System:

Catchment: Collects and stores captured rainwater
Conveyance system: Transports harvested water to recharge zone
Flush: Flushes out first spell of rain (contaminated)
Filter: Removes pollutants from collected water
Tanks and recharge structures: Store filtered water ready for use

Catchment areas include rooftops, compounds, rock surfaces, hill slopes, artificially repaired impervious/semi-pervious land surfaces.

Q.6. What is air pollution? Mention its sources and hazards. (SSUHSA 2010; DU 2013; WBUHS 2019)

Air Pollution: Presence of toxic chemicals/compounds (including biological origin) in air at levels that pose a health risk, or compounds not normally present that lower air quality or cause detrimental changes (e.g., ozone depletion, global warming).

Sources:

Domestic: Combustion of coal, wood, oil (London 1952 disaster - domestic coal burning)
Automobiles: Emit hydrocarbons, CO, lead, nitrogen oxides, particulate matter
Industries: Iron/steel, paper, cement, fertilizers, thermal power plants, petroleum refineries
Miscellaneous: Tobacco smoking, burning refuse, incinerators, nuclear explosions, forest fires

Hazards:

Immediate/Acute (due to photochemical oxidants):

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

Delayed/Chronic:

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

Q.7. Indicators of air pollution. Prevention and control. (BNMU 2013; WBUHS 2019)

Indicators:

SO₂ index: Concentration of SO₂ estimated in all surveys
Smoke (Soiling) index: Air filtered through white filter paper; stain measured by photoelectric meter; expressed as CoH units/1000 linear feet
Suspended particles: Dust measured by 'Midget impinger'; expressed in mg/m³
Coefficient of haze: Amount of smoke/aerosol per m³ of air
Air pollution index: Arbitrary index; in USA = 10×[SO₂] + 2×[CO] + 2×[coefficient of haze]; alarm when >50

Prevention and Control:

Engineering measures:
- Locate industries away from habitation
- Containment: wet methods for dust, enclosures, exhaust pipes, arresters
- Replacement: electricity/natural gas instead of coal; unleaded petrol
Legislation:
- Indian Factories Act, 1948
- Air (Prevention and Control of Pollution) Act, 1981
- Smoke Nuisance Act
General measures:
- Traffic control (bypass roads)
- Dilution (green belts between industrial and residential areas)
- Health education
- Population stabilisation
International action: WHO - network of 20 labs worldwide (London, Washington centres); issue warnings when necessary

Q.8. Impact of climate change on human health. (WBUHS)

Change	Effect on Environment	Health Hazard
More extreme weather	Air pollution; vector ecology changes	Asthma, CVD; Malaria, Dengue, Encephalitis, Rift Valley fever, Chikungunya, West Nile virus
Rising sea levels	Increasing allergens; water quality impacts	Respiratory allergies, asthma; Cholera, Cryptosporidiosis, Leptospirosis, algal blooms
Increasing CO₂	Water/food supply impacts; environmental degradation	Malnutrition, diarrhoeal disease; Forced migration, civil conflict, mental health impacts
Rising temperature	Extreme heat; severe weather	Heat illness, death, cardiovascular failure; Injuries, fatalities, mental health impacts

Q.9. Enumerate soil-borne diseases. Criteria for sanitary latrine. Importance of water-seal latrine. (WBUHS 2023)

Soil-Borne Diseases (common in India):

Intestinal roundworms (Ascariasis)
Hookworms (Necator americanus / Ancylostoma duodenale)
Whipworm (Trichuris trichiura)

Criteria of a Sanitary Latrine:

Excreta must not contaminate ground or surface water
Excreta must not pollute the soil
Excreta must not be accessible to flies, rodents, animals
Excreta must not create nuisance due to odour or unsightly appearance

Importance of Water-Seal Type Latrine:

(a) Prevents fly access - night soil sealed by water in the trap (bent pipe)
(b) Prevents escape of odours and foul gases
(c) Night soil not visible once flushed

Q.10. Criteria and health effects of poor ventilation. (WBUHS)

Ventilation Standards:

Floor space: 50-100 ft² per person
Cubic space: 1000-1200 ft³ fresh air/person/hour
Air changes: 2-3 per hour (living room); 4-6 per hour (workrooms/assemblies)
Windows:
- At least 2 per living room; one opening to open space
- Height: not more than 3 ft from ground
- Window area = 1/5 of floor area
- Doors + windows = 2/5 of floor area

Health Effects of Poor Ventilation:

Spread of airborne diseases
Poor indoor air quality → fatigue, hypersensitivity, headache, sinus congestion
Sick Building Syndrome: Eye/nose irritation, headache, fatigue, susceptibility to colds/flu
Dampness → rat and insect infestations
High CO₂ / low O₂ → fatigue, loss of concentration
Workplace odours → discomfort, poor concentration

Q.11. What is smog? What is AQI? If AQI of your city is 200-300 for last 7 days in March, what are the health effects and measures? (WBUHS 2024)

Smog: Air pollution that reduces visibility; a mix of smoke and fog. Most modern smog is photochemical smog.

AQI (Air Quality Index): Tool for communicating air quality to people. Transforms data of 8 pollutants (PM10, PM₂.₅, NO₂, SO₂, CO, O₃, NH₃, Pb) into a single index value with colour coding.

AQI	Air Quality	Health Impact
0-50	Good	Minimal
51-100	Satisfactory	Minor breathing discomfort to sensitive
101-200	Moderate	Breathing discomfort to lung/heart disease patients, elderly, children
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 everyone on prolonged exposure

Measures: As in Q.7 (engineering, legislation, general, international measures)

Q.12. Different methods of solid waste management. Composting and biogas in detail. (WBUHS 2024)

Methods of Solid Waste Disposal:

Recycling: Recovery and reuse of materials
Dumping: Refuse dumped in low-lying areas; method of land reclamation
Controlled tipping/Sanitary Landfill: Material placed in trench, compacted, covered with earth daily - most satisfactory method
Composting: Biodegradable organic matter subjected to aerobic digestion
Incineration: Combustion of waste; reduces volume
Manure pits: Rural areas; garbage, dung, straw, leaves covered daily
Sewage treatment: Raw sewage treated to produce non-toxic effluent and semisolid sludge

Composting:

Combined disposal of refuse + nightsoil/sludge; organic matter breaks down by bacterial action into stable humus-like compost with manurial value
Advantages: Reduces landfill waste; recovers useful organic matter as soil amendment
Disadvantages: Bioaerosols (bacteria/fungal spores), volatile organic compounds, contaminants may enter food chain

Biogas Generation:

Renewable fuel produced by anaerobic digestion of organic matter (food waste, animal waste) by microorganisms in absence of oxygen
Biogas Plant components:
1. Reception area: Raw materials received and prepared (crop residues, sewage, livestock manure, seaweed)
2. Digester: Air-tight, water-proof container; biomass transformed into energy; agitators prevent layer formation
3. Gas holder: Air-proof steel container; collects gas during fermentation; gas outlet produces energy and heat
Produces sustainable energy + fertilisers; carbon neutral process

GROUP B — SHORT NOTES

Q.1. Biological Filter (WBUHS 2019)

Also called slow sand filter or biological filtration
Water percolates through sand bed; impurities removed by straining, sedimentation, biochemical and biological processes
Key feature: "Zoogleal" / "Vital" layer (Schmutzdecke) - slimy layer on sand bed composed of algae, diatoms, plankton, minute plants and protozoa
This layer:
- Feeds on organic matter
- Converts it into small harmless substances
- Oxidizes ammoniacal nitrogen into nitrates
- Holds back bacteria
- Yields bacteria-free water

Exam Tip: For WBUHS, always write definitions first, use numbered/bulleted points, include tables where relevant (especially Bradley's classification and AQI table), and conclude SAQs with a one-line summary. Bold key terms.

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