Environmental Health Practice Questions

Q: Which of the following represents a non-deliberate cultural practice leading to an anti-mosquito effect?

Use of alkaline detergent. In Community Medicine, environmental control of vectors is categorized into deliberate and non-deliberate (unintentional) practices. **Explanation of the Correct Answer:** **Option A (Use of alkaline detergent)** is the correct answer because it represents a **non-deliberate cultural practice**. In many rural or traditional settings, people wash clothes or utensils in or near small water bodies using alkaline soaps and detergents. This practice unintentionally alters the **pH of the water**, making it unfavorable for mosquito breeding (specifically *Anopheles* and *Culex*). The primary intent of the individual is hygiene/cleaning, but the secondary, unintentional result is an anti-mosquito effect. **Analysis of Incorrect Options:** * **Option B (Larvicidal agents):** These are chemical control measures (e.g., Temephos, Abate) specifically applied to water bodies with the **sole intention** of killing mosquito larvae. * **Option C (Bed nets):** These are physical barriers (Personal Protective Measures) used with the **deliberate intent** of preventing mosquito bites during sleep. * **Option D (Repellents):** Whether chemical (DEET) or natural (Citronella), these are used with the **specific purpose** of deterring mosquitoes from landing on the skin. **High-Yield NEET-PG Pearls:** * **Cultural Control:** Refers to traditional habits that influence disease transmission. Another example is the storage of water in narrow-necked containers, which prevents *Aedes* mosquitoes from laying eggs. * **Environmental Modification:** A permanent change to land/water (e.g., drainage, filling) to prevent breeding. * **Environmental Manipulation:** A recurrent activity (e.g., changing water in coolers, cleaning overhead tanks) to create temporary unfavorable conditions for vectors.

Q: Which of the following is an indoor air pollutant?

Carbon dioxide. **Explanation:** **Carbon dioxide (CO₂)** is considered a primary indicator of indoor air quality. While it is a natural component of the atmosphere, it accumulates indoors primarily due to human respiration in poorly ventilated spaces. In the context of environmental health, CO₂ levels are used to monitor the adequacy of ventilation; levels exceeding 1000 ppm typically indicate "stuffy" air and poor air exchange, leading to symptoms like headache, fatigue, and loss of concentration. **Analysis of Incorrect Options:** * **Hydrogen cyanide (HCN):** While it can be found in tobacco smoke, it is primarily classified as a systemic chemical asphyxiant and a byproduct of industrial combustion or fires, rather than a standard indoor air pollutant. * **Methane (CH₄):** This is a potent greenhouse gas associated with agricultural activities, landfills, and natural gas leaks. It is categorized as an outdoor/global warming pollutant rather than a routine indoor air quality parameter. * **Perfluorocarbons (PFCs):** These are synthetic compounds used in industrial applications (like electronics manufacturing). They are potent greenhouse gases but are not common indoor pollutants in residential or office settings. **High-Yield Clinical Pearls for NEET-PG:** * **Indicator of Ventilation:** CO₂ is the most common surrogate marker for indoor air freshness. * **Sick Building Syndrome (SBS):** Poor indoor air quality (high CO₂, VOCs, and molds) leads to SBS, where occupants experience acute health effects linked to time spent in a building. * **Other Key Indoor Pollutants:** Radon (leading cause of lung cancer in non-smokers), Formaldehyde (from furniture/carpets), and Particulate Matter (from indoor cooking/chulhas). * **WHO Guideline:** The most dangerous indoor pollutant globally is **Particulate Matter (PM2.5)** from solid fuel combustion.

Q: Eutrophication of water bodies is mainly caused by which of the following?

Phosphates and nitrates. ### Explanation **Correct Answer: D. Phosphates and nitrates** **Concept Overview:** Eutrophication is the process of **nutrient enrichment** of water bodies, leading to an overgrowth of algae (algal blooms). The primary limiting nutrients for plant growth in aquatic ecosystems are **phosphates and nitrates**. When these enter water bodies—primarily through agricultural runoff (fertilizers) and domestic sewage—they trigger rapid multiplication of algae. As these algae die and decompose, aerobic bacteria consume the dissolved oxygen (DO) in the water, leading to hypoxia, the death of aquatic life (fish kills), and the eventual "aging" or filling up of the lake. **Analysis of Options:** * **A & C (Carbonates, Oxides, and Sulphates):** While these ions contribute to water hardness and total dissolved solids (TDS), they are not primary limiting nutrients for plant growth. They do not trigger the rapid biomass production characteristic of eutrophication. * **B (Hydrocarbons and metals):** These are classified as chemical pollutants or toxins. Metals (like mercury or lead) lead to **biomagnification** and toxicity rather than nutrient enrichment. **NEET-PG High-Yield Pearls:** * **Steps of Eutrophication:** Nutrient enrichment → Algal bloom → Increased BOD (Biochemical Oxygen Demand) → Decreased Dissolved Oxygen (DO) → Death of aquatic ecosystem. * **Indicator:** A high **BOD** is a direct indicator of water pollution by organic matter. * **Health Impact:** High nitrates in drinking water (often from the same sources causing eutrophication) can lead to **Infantile Methemoglobinemia** (Blue Baby Syndrome). * **Water Bloom:** This is the visible manifestation of eutrophication, often giving water a green, pea-soup appearance.

Q: The 'NALGONDA technique' is used in which condition?

Endemic fluorosis. **Explanation:** The **Nalgonda technique** is a method for the **defluoridation** of water, specifically designed for use at both the community and household levels in areas where **Endemic Fluorosis** is prevalent. Developed by the National Environmental Engineering Research Institute (NEERI) in Nagpur, it involves the sequential addition of **Alum (Aluminium sulphate)**, **Lime (Calcium oxide)**, and **Bleaching powder** to water, followed by rapid mixing, flocculation, sedimentation, and filtration. Alum acts as the coagulant to remove fluoride ions, while lime ensures the correct pH and bleaching powder provides disinfection. **Analysis of Incorrect Options:** * **B. Epidemic dropsy:** Caused by the ingestion of mustard oil adulterated with **Argemone mexicana** (Sanguinarine toxin). Management focuses on removing the adulterated oil and symptomatic treatment, not water purification. * **C. Endemic ascites:** Associated with the consumption of **Pyrrolizidine alkaloids** (found in *Crotalaria* seeds) contaminating staple grains like millet. * **D. Neurolathyrism:** A neurological condition caused by the excessive consumption of *Lathyrus sativus* (Khesari dal) containing the neurotoxin **BOAA**. Prevention involves parboiling or steeping the pulse, not the Nalgonda technique. **High-Yield Clinical Pearls for NEET-PG:** * **Fluoride levels:** Ideal in water is **0.5–0.8 mg/L**. Dental fluorosis occurs at >1.5 mg/L; Skeletal fluorosis at >3–6 mg/L. * **Other Defluoridation methods:** Activated Alumina (Prashanti technique), Ion exchange resins, and Reverse Osmosis. * **Nalgonda Technique sequence:** Alum (Removal) → Lime (pH adjustment) → Bleaching powder (Disinfection). * **Target:** It reduces fluoride to the permissible limit of <1.0 mg/L.

Q: Which of the following is NOT a feature of a septic tank?

Ideal retention period is 48 hours. ### Explanation A septic tank is a watertight masonry tank used for the primary treatment of domestic sewage. It operates on the principle of anaerobic digestion and sedimentation. **Why Option A is the Correct Answer (The False Statement):** The ideal retention period for a septic tank is **24 hours**, not 48 hours. While the retention period can range from 12 to 36 hours depending on the design and population load, 24 hours is the standard benchmark used in public health engineering. A period of 48 hours is unnecessarily long and would require a much larger tank capacity without significant added benefit. **Analysis of Other Options:** * **Option B (Minimum capacity is 500 gallons):** This is a standard technical requirement. A septic tank must be large enough to allow for the settling of solids and the formation of scum; 500 gallons is the recommended minimum capacity for a small household. * **Option C (Aerobic oxidation takes place outside):** This is a true statement. Inside the septic tank, only **anaerobic** digestion occurs. The effluent (liquid) that leaves the tank is still highly contaminated and must undergo **aerobic oxidation** in a subsoil dispersion trench or soak pit. * **Option D (Sludge is solids settling down):** This is the definition of sludge. In the tank, organic solids settle to the bottom (sludge) where they are decomposed by anaerobic bacteria, while lighter materials like fat and grease float to the top (scum). **High-Yield NEET-PG Pearls:** * **Biological Action:** The primary process inside the tank is **Anaerobic Digestion**. * **Cleaning Frequency:** Sludge should be removed at least once a year (or every 2–3 years depending on usage). * **Inlet/Outlet:** The outlet is usually 5 cm lower than the inlet to prevent backflow. * **Efficiency:** A septic tank removes about 60% of Suspended Solids and 30% of BOD (Biochemical Oxygen Demand).

Q: In a slow sand filter, what element is responsible for yielding bacteria-free water?

Vital layer. ### Explanation The **Slow Sand Filter** (or biological filter) is a cornerstone of large-scale water purification. The correct answer is the **Vital Layer**, also known as the **Schmutzdecke**, biological layer, or zoogleal layer. **Why the Vital Layer is Correct:** The vital layer is a slimy, gelatinous membrane that forms on the surface of the sand bed over a period of a few days. It consists of algae, plankton, diatoms, and bacteria. This layer is the "heart" of the filter because it performs the actual purification through: 1. **Biological Action:** Organic matter is oxidized by the bacteria in the layer. 2. **Mechanical Strainer:** It traps very fine particles. 3. **Bacteriological Action:** It is responsible for removing **98% to 99% of bacteria** and reducing the organic content of the water. **Why Other Options are Incorrect:** * **Valve:** These are mechanical components used to regulate the flow of water and maintain a constant rate of filtration; they have no biological purification properties. * **Supernatant Water:** This is the 1–1.5 meter column of raw water above the sand. Its primary role is to provide a constant head of pressure and allow time (3–12 hours) for sedimentation; it does not filter bacteria. * **Under-drainage System:** Located at the bottom of the filter, this consists of porous pipes that collect the filtered water and provide support for the filter medium. It does not contribute to the removal of pathogens. **High-Yield Facts for NEET-PG:** * **Rate of Filtration:** 0.1 to 0.4 $m^3/m^2/hour$ (Slow sand filters are roughly 20–50 times slower than Rapid Sand Filters). * **Effective Size of Sand:** 0.2 to 0.35 mm. * **Cleaning:** Done by **scraping** the top layer of sand (unlike Rapid Sand Filters, which use backwashing). * **Efficiency:** Highly efficient at removing bacteria but less effective at removing high turbidity compared to rapid sand filters.

Q: Which of the following chemicals is not included in the WHO's list of 10 chemicals of major public health concern?

Radium. The World Health Organization (WHO) has identified **10 chemicals or groups of chemicals** that constitute a major public health concern due to their widespread use, environmental persistence, and significant toxicity. **Explanation of the Correct Answer:** **D. Radium** is the correct answer because it is **not** included in the WHO’s top 10 list. While radium is a known radioactive hazard (linked to bone cancers and osteosarcoma), it is not considered a global "major public health concern" in the same category as the others, which have more pervasive environmental and industrial exposure routes affecting larger populations. **Explanation of Incorrect Options:** * **A. Arsenic:** Included. It is a major contaminant of groundwater in regions like West Bengal and Bangladesh, leading to chronic arsenicosis and skin/lung cancers. * **B. Asbestos:** Included. All forms of asbestos are carcinogenic, causing mesothelioma, lung cancer, and asbestosis. * **C. Dioxins:** Included. These are persistent organic pollutants (POPs) produced as by-products of industrial processes and waste incineration, known for their immunotoxic and reproductive effects. **High-Yield NEET-PG Facts:** To master this topic, memorize the complete **WHO List of 10 Chemicals of Major Public Health Concern**: 1. **Arsenic** 2. **Asbestos** 3. **Benzene** 4. **Cadmium** 5. **Dioxins and dioxin-like substances** 6. **Inadequate or excess Fluoride** 7. **Lead** (Most common cause of chronic metal poisoning) 8. **Mercury** (Associated with Minamata disease) 9. **Highly hazardous pesticides** 10. **Air pollution** (Specifically particulate matter and gases) **Clinical Pearl:** Note that **Lead** is often cited as the most important environmental toxin for children (neurotoxicity), while **Fluoride** is unique on this list because it is a concern in both deficiency (dental caries) and excess (fluorosis).

Question 1

Which of the following represents a non-deliberate cultural practice leading to an anti-mosquito effect?

Accepted Answer

Use of alkaline detergent

Answer

Use of larvicidal agents

Answer

Use of bed nets

Answer

Use of repellents

Question 2

Which of the following is an indoor air pollutant?

Accepted Answer

Carbon dioxide

Answer

Hydrogen cyanide

Answer

Methane

Answer

Perfluorocarbons

Question 3

Eutrophication of water bodies is mainly caused by which of the following?

Accepted Answer

Phosphates and nitrates

Answer

Carbonates and oxides

Answer

Hydrocarbons and metals

Answer

Carbonates and sulphates

Question 4

The 'NALGONDA technique' is used in which condition?

Accepted Answer

Endemic fluorosis

Answer

Epidemic dropsy

Answer

Endemic ascites

Answer

Neurolathyrism

Question 5

An epidemiologic study evaluates the rate of dental caries and tooth abscesses among children living in communities within a metropolitan area. Investigators discover that the rate is high among children living in an upper-middle-class community but low in children living in a community below the poverty level. The levels of trace elements in the water supplies for those communities are measured. A higher level of which of the following minerals in the water is most likely to be associated with a lower rate of dental decay among the children living in the poor community?

Accepted Answer

Fluoride

Answer

Copper

Answer

Iodine

Answer

Selenium

Question 6

A known HIV-positive patient admitted in an isolation ward after abdominal surgery following an accident. The resident doctor who changed his dressing the next day found it to be soaked in blood. Which of the following would be the right method of choice for discarding the dressing?

Accepted Answer

Put the dressing material directly in an appropriate bag and send for incineration.

Answer

Pour 1% hypochlorite on the dressing material and send it for incineration in an appropriate bag.

Answer

Pour 5% hypochlorite on the dressing material and send it for incineration in an appropriate bag.

Answer

Pour 2% Lysol on the dressing material and send it for incineration in an appropriate bag.

Question 7

Which of the following is NOT a feature of a septic tank?

Accepted Answer

Ideal retention period is 48 hours

Answer

Minimum capacity is 500 gallons

Answer

Aerobic oxidation takes place outside

Answer

Sludge is solids settling down

Question 8

In a slow sand filter, what element is responsible for yielding bacteria-free water?

Accepted Answer

Vital layer

Answer

Valve

Answer

Supernatant water

Answer

Under-drainage system

Question 9

All of the following are indicators of air pollution except?

Accepted Answer

Smoking index

Answer

CO

Answer

SO2

Answer

Soiling index

Question 10

Which of the following chemicals is not included in the WHO's list of 10 chemicals of major public health concern?

Accepted Answer

Radium

Answer

Arsenic

Answer

Asbestos

Answer

Dioxin

Environmental Health — MCQs

Environmental Health — MCQs

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