Environmental Health Practice Questions

Q: Which statement is true about the sand flea?

Not found in India. **Explanation:** The **Sand Flea** (*Tunga penetrans*), also known as the Jigger flea or Chigoe, is a parasitic insect primarily found in tropical and subtropical regions of **Central and South America** and **Sub-Saharan Africa**. 1. **Why Option A is correct:** The sand flea is **not indigenous to India**. While other fleas (like the Rat Flea) are common, *Tunga penetrans* has not established a presence in the Indian subcontinent, making this a high-yield geographical fact for preventive medicine. 2. **Why Option B is incorrect:** While the sand flea causes **Tungiasis** (an inflammatory skin disease where the female flea burrows into the skin, usually the feet), the question asks for the "true" statement in a comparative context. In many medical exams, its absence in India is considered the definitive epidemiological characteristic. 3. **Why Options C and D are incorrect:** These refer to the **Rat Flea** (*Xenopsylla cheopis*). The Rat Flea is the vector for *Yersinia pestis*, which causes **Plague**. Bubonic plague is characterized by "bubos" (painful, swollen lymph nodes). The Sand Flea does not transmit plague. **High-Yield NEET-PG Pearls:** * **Tungiasis:** Caused by the gravid female *Tunga penetrans*. It burrows into the periungual region of the toes, causing intense irritation and secondary infections. * **Vector Distinction:** * **Sand Flea:** *Tunga penetrans* (Not in India). * **Sand Fly:** *Phlebotomus argentipes* (Vector for Kala-azar; found in India). * **Rat Flea:** *Xenopsylla cheopis* (Vector for Plague and Endemic Typhus; found in India). * **Key Index:** The **Rat Flea Index** is used to monitor plague potential (an index >1 is considered a danger signal).

Q: Which among the following is used in defluoridation of water?

Alum and lime. **Explanation:** The correct answer is **Alum and lime**, which are the primary chemicals used in the **Nalgonda Technique**, a method developed by the National Environmental Engineering Research Institute (NEERI) for defluoridation of water at the domestic or community level. **Why Alum and Lime?** In the Nalgonda Technique, **Alum** (Aluminium sulphate) acts as a coagulant that helps in the precipitation of fluoride ions. **Lime** (Calcium oxide) or Sodium carbonate is added to maintain the alkalinity of the water, which ensures optimal flocculation and neutralizes the acidity produced by the alum. This process involves rapid mixing, flocculation, sedimentation, and filtration to reduce fluoride levels to permissible limits (<1.0 mg/L). **Analysis of Incorrect Options:** * **B. Potassium permanganate:** Used primarily as an oxidizing agent to remove iron, manganese, and to disinfect water (e.g., in wells), but it has no effect on fluoride. * **C. Ozonisation:** A powerful disinfection and oxidation process used to kill pathogens and remove organic micro-pollutants; it does not remove dissolved fluoride. * **D. Bromides:** These are not used for water treatment; in fact, bromides in source water can lead to the formation of harmful disinfection by-products (bromates) during ozonation. **High-Yield Facts for NEET-PG:** * **Ideal Fluoride level:** 0.5–0.8 mg/L. * **Dental Fluorosis:** Occurs when levels exceed **1.5 mg/L** (mottling of enamel). * **Skeletal Fluorosis:** Occurs with chronic intake of **3–6 mg/L**. * **Genu Valgum:** A characteristic clinical sign of endemic fluorosis (also known as "Knock-knee" syndrome). * **Other Defluoridation methods:** Activated Alumina (Prashanti technology) and Ion exchange resins.

Q: Which of the following is a naturally occurring radioactive substance found in small quantities in the human body?

Potassium 40. ### Explanation **Correct Answer: D. Potassium 40** **Why it is correct:** Potassium is an essential mineral required for cellular function, and it occurs naturally in the human body. Natural potassium contains a very small fraction (0.0117%) of the radioactive isotope **Potassium-40 ($^{40}K$)**. Because the body strictly regulates potassium levels through homeostasis, $^{40}K$ is maintained at a constant concentration, making it the **primary source of natural internal radiation** in humans. An average adult contains approximately 140g of potassium, of which a tiny portion is radioactive $^{40}K$, emitting both beta and gamma radiation. **Analysis of Incorrect Options:** * **A. Radium 226:** While found in the environment (soil/water) and potentially ingested, it is not a fundamental constituent of the human body like potassium. It is a "bone-seeker" that can cause toxicity but is not considered a standard internal radioactive source in healthy physiology. * **B. Bismuth 60:** This is a distractor. Bismuth has several isotopes, but "Bismuth 60" does not exist as a stable or clinically relevant isotope. (Note: Cobalt-60 is a common medical isotope, but it is synthetic, not naturally occurring in the body). * **C. Iodine 131:** This is a **synthetic** fission product. While it is used in the treatment of thyroid disorders (Graves' disease, Thyroid cancer), it is not naturally present in the human body. **High-Yield Clinical Pearls for NEET-PG:** * **Internal Emitters:** The two most significant natural internal radionuclides are **Potassium-40** and **Carbon-14**. * **Radon Gas:** The largest source of **external** natural background radiation is Radon-222 (a decay product of Uranium). * **Cosmic Radiation:** Increases with altitude; frequent flyers and aircrews are at higher risk. * **Sievert (Sv):** The SI unit used to measure the biological effect of ionizing radiation (Effective Dose).

Q: Which instrument is used to measure humidity?

Hygrometer. **Explanation:** **Correct Answer: C. Hygrometer** A **Hygrometer** is the standard instrument used to measure the moisture content or humidity in the atmosphere. In Community Medicine and Environmental Health, monitoring humidity is crucial because it affects human thermal comfort and the transmission of certain pathogens. The most common type used in field studies is the **Psychrometer** (Sling Psychrometer), which consists of a dry-bulb and a wet-bulb thermometer to calculate relative humidity. **Analysis of Incorrect Options:** * **A. Pressure gauge:** Used to measure the pressure of gases or liquids (e.g., measuring blood pressure via a sphygmomanometer or cylinder pressure). Atmospheric pressure specifically is measured by a **Barometer**. * **B. Anemometer:** Used to measure **wind speed** or velocity. This is a high-yield point for environmental health assessments regarding ventilation. * **D. Thermometer:** Used to measure **temperature**. While related to thermal comfort, it does not directly measure moisture content. **High-Yield Clinical Pearls for NEET-PG:** * **Kata Thermometer:** Measures "cooling power" of air and low air velocities. * **Globe Thermometer:** Measures **radiant heat** (mean radiant temperature). * **Relative Humidity:** For optimal human comfort, the relative humidity should ideally range between **30% and 60%**. * **Dry Bulb vs. Wet Bulb:** If both readings are the same, the relative humidity is 100% (the air is fully saturated).

Q: Which of the following is the most reliable bacteriological indicator of water pollution?

Escherichia coli. **Explanation:** The primary goal of bacteriological water analysis is to detect fecal contamination. **Escherichia coli (E. coli)** is considered the most reliable indicator of recent fecal pollution for several reasons: 1. **Habitat:** It is a normal inhabitant of the human intestine and is found in enormous numbers in feces. 2. **Specificity:** Its presence in water specifically indicates fecal contamination; it cannot grow in pure water. 3. **Detection:** It can be easily detected and differentiated from other coliforms (e.g., *Klebsiella*) by the production of indole at 44°C (Eijkman test). **Analysis of Incorrect Options:** * **Fecal streptococci (A):** While these also indicate fecal pollution, they are less numerous than E. coli and die off more rapidly in water. They are primarily used as supplementary indicators to confirm fecal origin when results are ambiguous. * **Salmonella typhi (B):** This is a pathogen, not an indicator. Pathogens are often present in low numbers, occur intermittently, and are difficult to isolate directly from water samples. * **Clostridium tetani (D):** This is a soil-dwelling anaerobe and is not used as a water quality indicator. *Clostridium perfringens*, however, is sometimes used to detect remote (past) pollution because its spores survive longer than E. coli. **High-Yield Clinical Pearls for NEET-PG:** * **Coliform Count:** The standard measure of water safety. E. coli is the "Gold Standard" indicator. * **Viability:** E. coli survives about as long as most enteric pathogens (like *Salmonella* or *Shigella*), making it an ideal surrogate. * **Presumptive Coliform Count:** Usually performed using the Multiple Tube Method (MPN - Most Probable Number). * **Ideal Indicator Criteria:** It should be present when pathogens are present, absent when they are absent, and should not multiply in water.

Q: What is the amount of bleaching powder necessary to disinfect choleraic stools?

50 gm/lit. ### Explanation **1. Why 50 gm/lit is the Correct Answer:** Disinfection of excreta (stools and urine) in cases of enteric infections like Cholera requires a high concentration of disinfectant due to the heavy organic load. Bleaching powder (calcium hypochlorite) is the agent of choice. The standard recommendation for disinfecting choleraic stools is **50 grams of bleaching powder per liter of excreta**. This concentration ensures a sufficient "contact period" (usually 1–2 hours) to neutralize the *Vibrio cholerae* bacteria despite the presence of organic matter which typically inhibits the action of chlorine. **2. Analysis of Incorrect Options:** * **75 gm/lit & 90 gm/lit (Options B and C):** These concentrations are unnecessarily high. While they would certainly disinfect the stool, they are not the standard public health recommendation and would lead to excessive wastage of resources and pungent chlorine fumes. * **100 gm/lit (Option D):** This is double the required dose. Such high concentrations are generally not used for routine stool disinfection unless specified for highly resistant spores in specific laboratory settings, which does not apply to Cholera. **3. NEET-PG High-Yield Pearls:** * **Bleaching Powder Composition:** Fresh bleaching powder contains approximately **33% available chlorine**. * **Contact Time:** For effective disinfection of stools using bleaching powder, a contact time of **1 to 2 hours** is essential before final disposal. * **Other Disinfectants for Stools:** 5% Cresol (Lysol) is another common alternative, requiring a 1-hour contact period. * **Water Disinfection:** Do not confuse stool disinfection with water disinfection. For drinking water, the dose is usually **0.5 mg/liter** (residual chlorine) after a 30-minute contact period. * **Storage:** Bleaching powder is unstable; it should be stored in a cool, dark, and dry place in airtight containers to prevent loss of chlorine content.

Q: What is the most important prerequisite in a sanitary latrine?

Water seal. **Explanation:** In Community Medicine, a **sanitary latrine** (specifically the RCA type or pour-flush latrine) is defined by its ability to break the chain of infection. The **Water Seal** is considered the most vital component because it serves as a physical and biological barrier. 1. **Why Water Seal is the Correct Answer:** The water seal is a column of water (typically **2 cm or 0.75 inches** deep) retained in the 'P' or 'S' trap. Its primary functions are: * **Exclusion of odors:** It prevents foul gases from the pit from entering the latrine. * **Fly-proofing:** It prevents flies from accessing the excreta, thereby stopping the mechanical transmission of enteric pathogens (fecal-oral route). This is the "prerequisite" that transforms a simple pit into a sanitary one. 2. **Analysis of Incorrect Options:** * **Squatting plate/slab:** While necessary for user stability and hygiene, it does not prevent the breeding of flies or the escape of odors on its own. * **Smooth slope of pan:** A slope (usually 25-30 degrees) is important for easy flushing with minimal water, but it is a design feature for convenience rather than the primary sanitary barrier. * **Adequate drainage:** This refers to the disposal of effluent. While important for environmental sanitation, it is secondary to the immediate containment provided by the water seal. **High-Yield Pearls for NEET-PG:** * **Ideal Water Seal Depth:** 2 cm (0.75 inches). If it is too deep, more water is required for flushing; if too shallow, the seal may break. * **RCA Latrine:** Developed by the Research Cum Action projects, it is the gold standard for rural sanitation in India. * **Distance Rule:** A sanitary latrine should be located at least **15 meters (50 feet)** away from a source of drinking water to prevent groundwater contamination.

Q: Which of the following is NOT true for Rapid sand filters?

Frequent washing is not required.. **Explanation:** The core principle of **Rapid Sand Filters (RSF)**, also known as Mechanical Filters, is their high rate of filtration (5–15 m³/m²/hr), which is about 40–50 times faster than Slow Sand Filters. Because of this high velocity, the filter bed becomes clogged with impurities much faster. **1. Why Option C is the correct answer (The False Statement):** In RSF, the sand bed gets "choked" quickly due to the rapid accumulation of suspended matter. Therefore, **frequent washing is mandatory**—usually every 24 to 48 hours. This is done via **backwashing** (reversing the flow of water and compressed air), which cleans the sand grains. Stating that frequent washing is *not* required is incorrect. **2. Analysis of Incorrect Options:** * **Option A:** Unlike Slow Sand Filters, which require long periods of storage for sedimentation, RSF uses **chemical coagulation and flocculation** (using Alum) as pretreatment. This allows the process to bypass lengthy storage. * **Option B:** RSF involves complex mechanical parts, chemical dosing, and the backwashing process, all of which necessitate **highly skilled personnel** for operation and maintenance. * **Option D:** RSF can be designed as **Gravity type** (e.g., Paterson’s Filter) or **Pressure type** (e.g., Candy’s Filter), depending on whether the water flows by its own weight or is forced through under pressure. **High-Yield Facts for NEET-PG:** * **Vital Layer:** RSF does *not* have a "Schmutzdecke" (Vital Layer) initially; it forms during the process but is less critical than in Slow Sand Filters. * **Efficiency:** RSF is highly effective at removing **turbidity** but less effective than Slow Sand Filters at removing bacteria (98-99% vs 99.9%). * **Pre-treatment:** Coagulation (Alum) is the most crucial step before filtration in RSF. * **Space:** RSF occupies very little land area compared to Slow Sand Filters.

Q: Paris green is a type of:

Stomach poison. **Explanation:** **Paris Green (Copper acetoarsenite)** is a highly toxic inorganic compound historically used as a pigment and insecticide. In public health and community medicine, it is classified as a **stomach poison**. 1. **Why it is a Stomach Poison:** Paris green acts through ingestion. When used in anti-larval operations, it is applied as a 2% dust over stagnant water bodies. The surface-feeding larvae of *Anopheles* mosquitoes ingest the floating particles. Once inside the digestive tract, the arsenic component acts as a potent metabolic toxin, leading to the death of the larvae. It does not penetrate the cuticle, hence it is not a contact poison. 2. **Analysis of Incorrect Options:** * **Contact Poison:** These (e.g., DDT, Malathion) kill insects upon physical contact by penetrating the exoskeleton and targeting the nervous system. Paris green is ineffective unless swallowed. * **Repellent:** These (e.g., DEET, Dimethyl phthalate) merely deter insects from biting or landing; they do not aim to kill the larvae or adults. * **Rodenticide:** While arsenic compounds are toxic to mammals, Paris green is specifically categorized under "Larvicides" in environmental sanitation for malaria control. Common rodenticides include Zinc phosphide or Warfarin. **High-Yield Facts for NEET-PG:** * **Target Organism:** Specifically used for **Anopheline larvae** (surface feeders). It is ineffective against *Culex* larvae as they are bottom feeders. * **Composition:** It is chemically **Copper acetoarsenite**. * **Application:** It is used as a **2% dust** (mixed with diluents like lime or soapstone). * **Limitation:** It does not kill mosquito eggs or pupae (as pupae do not feed).

Question 1

What is the color of the bag used to dispose of sharps waste?

Accepted Answer

Blue white translucent

Answer

Red

Answer

Yellow

Answer

Black

Question 2

Which statement is true about the sand flea?

Accepted Answer

Not found in India

Answer

Causes ulcer in the foot

Answer

Causes bubo

Answer

Causes plague

Question 3

Which among the following is used in defluoridation of water?

Accepted Answer

Alum and lime

Answer

Potassium permanganate

Answer

Ozonisation

Answer

Bromides

Question 4

Which of the following is a naturally occurring radioactive substance found in small quantities in the human body?

Accepted Answer

Potassium 40

Answer

Radium 226

Answer

Bismuth 60

Answer

Iodine 131

Question 5

Which instrument is used to measure humidity?

Accepted Answer

Hygrometer

Answer

Pressure gauge

Answer

Anemometer

Answer

Thermometer

Question 6

Which of the following is the most reliable bacteriological indicator of water pollution?

Accepted Answer

Escherichia coli

Answer

Fecal streptococci

Answer

Salmonella typhi

Answer

Clostridium tetani

Question 7

What is the amount of bleaching powder necessary to disinfect choleraic stools?

Accepted Answer

50 gm/lit

Answer

75 gm/lit

Answer

90 gm/lit

Answer

100 gm/lit

Question 8

What is the most important prerequisite in a sanitary latrine?

Accepted Answer

Water seal

Answer

Squatting plate or slab

Answer

Smooth slope of pan

Answer

Adequate drainage

Question 9

Which of the following is NOT true for Rapid sand filters?

Accepted Answer

Frequent washing is not required.

Answer

No preliminary storage of raw water is required.

Answer

Operation requires highly skilled persons.

Answer

Can be gravity type or pressure type.

Question 10

Paris green is a type of:

Accepted Answer

Stomach poison

Answer

Contact poison

Answer

Repellent

Answer

Rodenticide

Environmental Health — MCQs

Environmental Health — MCQs

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