Environmental Health — MCQs

An epidemiologic study of a community shows an increased incidence of basal cell and squamous cell carcinomas in adults. These lesions are distributed predominantly on palms and soles. Analysis of groundwater pumped from wells for drinking shows increased levels of heavy metal used in pressure-treated lumber (with a greenish hue), insecticides, and herbicides. Which of the following metals is most likely implicated by this study?

Environmental Health Indian Medical PG Practice Questions and MCQs

Question 231: Which of the following insecticides is a natural product?

A. Dieldrin
B. Pyrethrum (Correct Answer)
C. Parathion
D. Carbaryl

Explanation: **Explanation:** The correct answer is **Pyrethrum (Option B)**. **Why Pyrethrum is the correct answer:** Pyrethrum is a potent, rapid-acting natural insecticide derived from the dried flower heads of ***Chrysanthemum cinerariaefolium***. The active principles, known as **pyrethrins**, act as nerve poisons that cause immediate paralysis (the "knock-down" effect) in insects. Because it is a natural botanical product, it is relatively non-toxic to mammals and is biodegradable, making it a preferred choice for indoor sprays and space sprays (e.g., against mosquitoes and houseflies). **Why the other options are incorrect:** * **A. Dieldrin:** This is a synthetic **Organochlorine** compound. It is highly persistent in the environment and has been largely banned globally due to its toxicity and bioaccumulation. * **C. Parathion:** This is a synthetic **Organophosphorus** compound. It is a potent acetylcholinesterase inhibitor and is highly toxic to humans, often associated with acute poisoning cases. * **D. Carbaryl:** This is a synthetic **Carbamate** insecticide. Like organophosphates, it inhibits cholinesterase but the binding is reversible. **High-Yield Facts for NEET-PG:** * **Knock-down effect:** Characteristic of Pyrethrum; it paralyzes insects almost instantly. * **Synergist:** Pyrethrum is often mixed with **Piperonyl Butoxide** to enhance its efficacy by inhibiting the insect's detoxifying enzymes. * **Synthetic Pyrethroids:** These are man-made versions (e.g., **Permethrin, Deltamethrin**) used in Long-Lasting Insecticidal Nets (LLINs). They are more stable in sunlight than natural pyrethrum. * **Paris Green:** Another high-yield "natural" related term; it is an inorganic copper-acetoarsenite compound used historically as a larvicide.

Question 232: What is the daily water supply considered adequate to meet the need for all urban domestic purposes?

A. 10 litres per capita
B. 20 litres per capita
C. 40-60 litres per capita
D. 150-200 litres per capita (Correct Answer)

Explanation: ### Explanation **Correct Answer: D. 150-200 litres per capita** In Community Medicine, water requirements are categorized based on the setting and the level of service provided. For **urban domestic purposes**, a supply of **150-200 litres per capita per day (lpcd)** is considered adequate. This volume accounts for all physiological and domestic needs, including drinking, cooking, bathing, flushing toilets, washing clothes/utensils, and house cleaning. This standard ensures not only basic survival but also the maintenance of personal hygiene and environmental sanitation, which are critical in preventing water-washed and water-borne diseases in densely populated urban areas. **Analysis of Incorrect Options:** * **A & B (10–20 litres):** These amounts represent the **minimum survival allocation** during emergencies or disasters to prevent dehydration and basic cooking. They are insufficient for long-term hygiene or sanitation. * **C (40–60 litres):** This is the standard recommended for **rural areas** (under the Jal Jeevan Mission, the target is 55 lpcd). Rural requirements are lower due to the absence of elaborate water-carriage sewerage systems (flushing) and different lifestyle patterns compared to urban centers. **High-Yield NEET-PG Pearls:** * **Safe and Wholesome Water:** Must be free from pathogenic agents, harmful chemicals, pleasant to taste, and usable for domestic purposes. * **Basic Physiological Need:** A minimum of **2 litres** of water per capita per day is required for drinking in moderate conditions. * **Water Consumption Trend:** As the economic status and level of urbanization increase, the per capita water consumption typically rises. * **Environmental Health Standard:** In India, the *Bureau of Indian Standards (BIS)* and the *Manual on Water Supply and Treatment* recommend 135 lpcd for urban areas with full flushing systems, though 150-200 lpcd is the broader academic benchmark for comprehensive urban needs.

Question 233: What is waste water from a kitchen classified as?

A. Sullage (Correct Answer)
B. Compost
C. Sewage
D. Hog feeding

Explanation: **Explanation:** In Environmental Health and Sanitation, wastewater is classified based on its source and the presence of human excreta. **1. Why Sullage is Correct:** **Sullage** refers to wastewater derived from household activities such as **kitchens, bathrooms, and laundries**. The defining characteristic of sullage is that it **does not contain human excreta** (feces or urine). It typically contains organic matter, soap, grease, and food particles. Because it lacks high concentrations of pathogens found in human waste, it is easier to treat and manage than sewage. **2. Why the Other Options are Incorrect:** * **Sewage:** This is wastewater that **contains human excreta**. It is a mixture of sullage and discharge from water closets (toilets) and urinals. It is highly infectious and requires rigorous treatment. * **Compost:** This is not wastewater; it is the end product of the decomposition of organic solid waste (like food scraps and leaves) used as a soil conditioner. * **Hog feeding:** This refers to the practice of using food waste (garbage) as animal feed. While kitchen waste can be used for hog feeding, the liquid wastewater itself is not classified this way. **NEET-PG High-Yield Pearls:** * **Sewerage:** The infrastructure (pipes and pumps) used to transport sewage. * **Refuse:** A general term for solid waste (excluding excreta). * **BOD (Biochemical Oxygen Demand):** The most important measure of the strength of sewage. Higher BOD indicates more organic pollution. * **Self-Purification:** A natural process where running water (rivers) purifies itself through dilution, sedimentation, and oxidation.

Question 234: Dental fluorosis is best seen in which of the following teeth?

A. Central & Lateral Incisors
B. Central Incisors & 1st Molars (Correct Answer)
C. 1st & 2nd Molars
D. Canines

Explanation: ### Explanation **Concept:** Dental fluorosis occurs due to excessive fluoride intake (usually >1.5 mg/L in drinking water) during the period of **enamel formation (amelogenesis)**. The severity and distribution of fluorosis depend on the timing, duration, and dose of fluoride exposure. The teeth most commonly and severely affected are those that undergo calcification during the first few years of life. **Why Option B is Correct:** The **Central Incisors and 1st Molars** are the most frequently affected teeth because their permanent buds undergo significant mineralization during the **first 2–3 years of life**, which is the peak period of susceptibility to fluoride toxicity. These teeth are often the first to show the characteristic "mottling" (chalky white patches or brownish discolorations). **Analysis of Incorrect Options:** * **Option A (Central & Lateral Incisors):** While incisors are commonly involved, the 1st molar is equally susceptible due to its early calcification timeline. * **Option C (1st & 2nd Molars):** The 2nd molars calcify much later (usually after age 3). Fluorosis is less common in teeth that mineralize later unless high fluoride exposure is chronic. * **Option D (Canines):** Canines mineralize later than central incisors and 1st molars, making them less primary indicators of early childhood fluoride exposure. **High-Yield Clinical Pearls for NEET-PG:** * **Safe Limit:** The optimum fluoride level in drinking water is **0.5–0.8 mg/L**. * **Dental Fluorosis:** Occurs at levels **>1.5 mg/L**. It is a cosmetic index of fluoride toxicity. * **Skeletal Fluorosis:** Occurs with prolonged exposure at levels **>3–10 mg/L**. * **Genu Valgum:** Also known as "Knock-knees," this is a characteristic manifestation of the **"Symptom of endemic fluorosis"** (often seen in the Nalgonda district). * **Defluoridation:** The **Nalgonda Technique** (using alum and lime) is the most common method used in India for water treatment.

Question 235: What is the optimum floor space recommended per adult person in a house?

A. 101–150 sq.ft.
B. 70–90 sq. ft. (Correct Answer)
C. 151–200 sq.ft.
D. 201–250 sq. ft.

Explanation: ### Explanation **Concept Overview:** In Community Medicine, housing standards are defined to prevent overcrowding, which is a significant risk factor for the transmission of respiratory infections (like Tuberculosis and Influenza) and skin infestations. The **optimum floor space** is a key metric used to determine the "degree of overcrowding" in a dwelling. **Why Option B is Correct:** According to standard public health guidelines (Park’s Textbook of Preventive and Social Medicine), the recommended floor space for an adult is **70–90 sq. ft.** This space is considered sufficient to ensure adequate ventilation and maintain physical distance to minimize the spread of droplet-borne diseases. **Analysis of Incorrect Options:** * **Option A (101–150 sq. ft.):** This exceeds the minimum public health requirement. While more space is better for comfort, it is not the "optimum" standard used for assessing overcrowding in public health statistics. * **Options C & D (151–250 sq. ft.):** These values are significantly higher than the recommended threshold. In the context of national housing policies and social medicine, standards are set at the minimum functional level required to maintain health. **High-Yield Facts for NEET-PG:** * **Overcrowding Criteria:** A house is considered overcrowded if two persons over 9 years of age (of opposite sexes, not being husband and wife) must sleep in the same room. * **Space per Person (Standard Table):** * 110 sq. ft. or more: 2 persons * 90–110 sq. ft.: 1.5 persons * 70–90 sq. ft.: 1 person * 50–70 sq. ft.: 0.5 person (infant) * Under 50 sq. ft.: Nil * **Age Adjustments:** For calculation, a baby under 12 months is not counted; a child between 1–10 years counts as **half a unit** (0.5); and anyone over 10 years counts as **one unit**.

Question 236: What is the percentage of available chlorine in bleaching powder?

A. 10%
B. 33% (Correct Answer)
C. 66%
D. 95%

Explanation: **Explanation:** **Bleaching powder (Chlorinated lime)** is a chemical compound (Calcium hypochlorite) used extensively in public health for the disinfection of drinking water and sanitary disposal of waste. 1. **Why 33% is Correct:** Freshly manufactured bleaching powder contains approximately **33% available chlorine**. This "available chlorine" is the active oxidizing agent responsible for killing pathogens. Over time, bleaching powder is unstable; it loses its chlorine content when exposed to air, light, or moisture. For effective water disinfection, the powder used must have a chlorine content of at least 20% to 33%. 2. **Analysis of Incorrect Options:** * **10%:** This is too low for fresh bleaching powder. If the chlorine content falls below 20%, the powder is considered "weak" or "spent" and is generally discarded for large-scale water treatment. * **66%:** This value is associated with **High-Test Hypochlorite (HTH)** or Perchloron. HTH is a more stable, concentrated form of calcium hypochlorite containing 60–70% available chlorine. * **95%:** This concentration is not found in bleaching powder. Pure elemental chlorine gas or liquid chlorine approaches this level of purity but is not used in powder form. **High-Yield Clinical Pearls for NEET-PG:** * **Horrocks' Apparatus:** Used to estimate the dose of bleaching powder required to disinfect a specific volume of water. * **Contact Time:** For effective chlorination, the water must be in contact with chlorine for at least **30 to 60 minutes**. * **Orthotolidine (OT) Test:** Used to detect **Free Residual Chlorine** (ideal level: 0.5 mg/L after 1 hour). * **Storage:** Bleaching powder should be stored in a **cool, dark, and dry place** in airtight containers to prevent the loss of chlorine.

Question 237: What is the color-coding of bags used in hospitals for the disposal of discarded medicines?

A. Blue
B. Black (Correct Answer)
C. Yellow
D. Red

Explanation: The disposal of biomedical waste is governed by the **Biomedical Waste Management Rules (2016)** and its subsequent amendments. Understanding the color-coding is crucial for hospital safety and environmental protection. ### **Explanation of the Correct Answer** **B. Black:** Historically, **Black bags/bins** were designated for general waste and specific chemical waste, including **discarded medicines and cytotoxic drugs**. * *Note for NEET-PG:* Under the 2016 rules, discarded medicines (other than cytotoxic) are technically disposed of in **Yellow bags** for incineration. However, in many clinical settings and older question patterns still tested, **Black** remains the standard answer for "discarded medicines/general waste." If "Yellow" and "Black" are both present, prioritize Yellow for medicines unless "Cytotoxic" is specified (which requires Yellow with a Cytotoxic label). ### **Explanation of Incorrect Options** * **A. Blue:** Used for **glassware** (broken or discarded) and **metallic body implants**. These are treated by autoclaving or chemical disinfection. * **C. Yellow:** Used for **anatomical waste** (human/animal), soiled waste (blood-stained cotton/dressings), and expired/discarded medicines (as per 2016 rules). * **D. Red:** Used for **recyclable plastic waste** such as IV sets, catheters, tubing, and gloves (without blood). These undergo autoclaving/microwaving followed by shredding. ### **High-Yield Clinical Pearls for NEET-PG** 1. **Cytotoxic Drugs:** Must be disposed of in **Yellow bags** marked with a "Cytotoxic" symbol. 2. **White (Translucent) Container:** Specifically for **sharps** (needles, scalpels, blades) to prevent needle-stick injuries. 3. **Chlorinated Plastic Bags:** These are strictly prohibited in BMW management to prevent the release of dioxins during incineration. 4. **Incineration:** This is the preferred method for Yellow bag waste, while Red bag waste is never incinerated.

Question 238: What is considered the purest form of water found in nature?

A. Rainwater (Correct Answer)
B. River water
C. Deep well water
D. Impounding reservoir water

Explanation: **Explanation:** **Rainwater** is considered the purest form of water in nature because it is essentially a product of natural distillation. As solar energy evaporates water from the earth's surface, it leaves behind salts and impurities. When this vapor condenses in the atmosphere, it forms clouds and eventually falls as rain. In its pure state, it is very soft, containing only trace amounts of dissolved gases (like CO2) and negligible dissolved solids. **Analysis of Incorrect Options:** * **River Water:** This is a type of surface water and is generally considered the most impure. It collects sewage, industrial waste, and surface runoff containing organic matter and pathogens as it flows. * **Deep Well Water:** While often bacteriologically safer than surface water because of soil filtration, it contains high amounts of dissolved mineral salts (calcium, magnesium, fluorides) picked up from underground strata, making it "hard" water. * **Impounding Reservoir Water:** These are artificial lakes used for water storage. While they undergo some natural purification through sedimentation and oxidation, they remain prone to algae growth and surface contamination. **High-Yield Facts for NEET-PG:** * **Softness:** Rainwater is the softest water in nature; it contains no hardness-producing salts, which makes it ideal for laundry but corrosive to metal pipes. * **Impurities:** Rainwater becomes impure only as it passes through the lower atmosphere, picking up dust, soot, and gases (SO2, NO2), or when it touches the ground. * **Groundwater Characteristics:** Deep wells are safer than shallow wells because they draw water from below the first impervious layer of the earth, providing better natural filtration.

Question 239: Man is the intermediate host for which of the following parasitic infections?

A. Kala azar
B. Filariasis
C. Hydatid cyst (Correct Answer)
D. All of the above

Explanation: **Explanation** In parasitology, the **Definitive Host** is where the parasite reaches maturity and undergoes sexual reproduction, while the **Intermediate Host** harbors the larval or asexual stages. **Why Hydatid Cyst is correct:** Hydatid disease is caused by the tapeworm *Echinococcus granulosus*. * **Definitive Host:** Dogs (and other canines), which harbor the adult worm in their intestines. * **Intermediate Host:** Normally sheep or cattle. **Humans act as accidental intermediate hosts** by ingesting eggs (via contaminated food/water or contact with dogs). In humans, the eggs hatch into oncospheres that migrate to organs (liver, lungs) to form **larval cysts** (Hydatid cysts). Because the cycle usually ends with the human, we are also considered "dead-end hosts." **Why other options are incorrect:** * **Kala-azar (Visceral Leishmaniasis):** Humans are the **definitive host** (harboring the amastigote stage), while the Sandfly (*Phlebotomus*) is the intermediate host/vector. * **Filariasis (*W. bancrofti*):** Humans are the **definitive host** (harboring adult worms in lymphatics), while the Mosquito (*Culex*) is the intermediate host/vector. **High-Yield Clinical Pearls for NEET-PG:** 1. **Man as Intermediate Host:** Remember the mnemonic **"THE"** — **T**aenia solium (Cysticercosis), **H**ydatid disease, **E**chinococcus, and Malaria (*Plasmodium*). 2. **Malaria Exception:** In Malaria, humans are the **intermediate host** (asexual cycle), and the Female Anopheles mosquito is the **definitive host** (sexual cycle). 3. **Hydatid Cyst Diagnosis:** Look for "Eggshell calcification" on X-ray or "Water lily sign" on USG/CT. Casoni’s test is a historical skin test for this.

Question 240: An epidemiologic study of a community shows an increased incidence of basal cell and squamous cell carcinomas in adults. These lesions are distributed predominantly on palms and soles. Analysis of groundwater pumped from wells for drinking shows increased levels of heavy metal used in pressure-treated lumber (with a greenish hue), insecticides, and herbicides. Which of the following metals is most likely implicated by this study?

A. Arsenic (Correct Answer)
B. Beryllium
C. Cadmium
D. Lead

Explanation: **Explanation** The correct answer is **Arsenic (Option A)**. This question tests the recognition of chronic arsenic poisoning (Arsenicosis) through its classic environmental sources and clinical presentation. **Why Arsenic is correct:** 1. **Environmental Sources:** Arsenic is historically used in **pressure-treated lumber** (Chromated Copper Arsenate or CCA, which gives wood a greenish hue), as well as in pesticides and herbicides. Contamination of groundwater (well water) is a major global source of chronic exposure. 2. **Clinical Presentation:** Chronic arsenic exposure is unique because it causes skin lesions on the **palms and soles**, specifically **hyperkeratosis** and "raindrop" pigmentation. 3. **Carcinogenicity:** It is strongly associated with **Basal Cell Carcinoma (BCC)** and **Squamous Cell Carcinoma (SCC)**. Unlike UV-induced skin cancers, arsenic-induced lesions often appear in non-sun-exposed areas like the palms and soles. **Why other options are incorrect:** * **Beryllium (B):** Primarily causes **Berylliosis** (a granulomatous lung disease) in aerospace or electronics workers. It is not associated with palmoplantar skin cancers. * **Cadmium (C):** Associated with **Itai-Itai disease** (osteomalacia and osteoporosis) and renal tubular damage. Sources include batteries and fertilizers, not wood preservatives. * **Lead (D):** Causes anemia (basophilic stippling), peripheral neuropathy (wrist drop/foot drop), and "Burtonian lines" on gums, but does not cause skin carcinomas. **NEET-PG High-Yield Pearls:** * **Blackfoot Disease:** A severe form of peripheral vascular disease (gangrene) caused by chronic arsenic poisoning. * **Internal Malignancies:** Arsenic is also linked to cancers of the **lung, bladder, and liver (Angiosarcoma)**. * **Diagnosis:** Hair and nail samples (Mees' lines) are used for detecting chronic exposure; urine is best for acute exposure. * **Safe Limit:** The WHO/BIS limit for arsenic in drinking water is **0.01 mg/L (10 ppb)**.

Practice by Chapter

Water Quality and Health

Practice Questions

Air Pollution and Health Effects

Practice Questions

Solid Waste Management

Practice Questions

Hazardous Waste Management

Practice Questions

Housing and Health

Practice Questions

Noise Pollution

Practice Questions

Radiation Health Effects

Practice Questions

Climate Change and Health

Practice Questions

Environmental Impact Assessment

Practice Questions

Disaster Management and Preparedness

Practice Questions

Vector Control

Practice Questions

Environmental Legislation

Practice Questions

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free