Environmental Health Practice Questions

Q: Which method is used for the disposal of chemical waste under Biomedical waste management guidelines?

Incineration. **Explanation:** Under the **Biomedical Waste Management (BMWM) Rules**, chemical waste is categorized under **Yellow Bag** waste. The preferred method for its disposal is **Incineration** (specifically high-temperature incineration >1200°C for hazardous chemicals) or disposal in a **Secured Landfill**. **Why Incineration is Correct:** Chemical waste often contains toxic organic compounds or hazardous substances that require thermal decomposition to be neutralized. Incineration ensures the complete combustion of these chemicals, reducing them to non-toxic ash and gases, thereby preventing environmental contamination and chemical hazards. **Analysis of Incorrect Options:** * **Autoclaving (Option B):** This is a method of sterilization using pressurized steam. It is used for **Red Bag** waste (infected plastics) and **Yellow Bag** waste like soiled cotton/dressings, but it is ineffective for chemicals as it does not neutralize chemical toxicity. * **Microwaving (Option C):** Similar to autoclaving, this uses radiant energy to disinfect waste. It is used for infectious waste but is not suitable for chemical or pharmaceutical waste. * **Recycling (Option D):** While some metals or glass may be recycled after disinfection, raw chemical waste is hazardous and cannot be recycled due to the risk of toxicity and environmental persistence. **High-Yield NEET-PG Pearls:** * **Yellow Bag:** Includes human anatomical waste, animal waste, soiled waste, expired/discarded medicines, and **chemical waste**. * **Cytotoxic Drugs:** Must be incinerated at temperatures **>1200°C** (Yellow bag with "Cytotoxic" label). * **Chemical Liquid Waste:** Requires pre-treatment (neutralization) before being discharged into the drain/effluent treatment plant (ETP). * **Chlorinated Plastic Bags:** Should **never** be incinerated as they release toxic dioxins and furans.

Q: Sullage consists of:

Wastewater from kitchen. ### Explanation **Sullage** is a specific term used in environmental sanitation to describe wastewater that does **not** contain human excreta. It originates from domestic activities such as kitchens, bathrooms, and laundries. **1. Why Option D is Correct:** Sullage refers to "greywater." It includes wastewater from kitchen sinks, washbasins, and showers. While it contains organic matter (food particles) and detergents, it is significantly less pathogenic than sewage because it lacks fecal contamination. **2. Analysis of Incorrect Options:** * **Option A (Solid vegetable waste matter):** This is categorized as **Refuse** or "Garbage." Refuse refers to solid waste, whereas sullage is strictly liquid waste. * **Option B (Inorganic waste):** This refers to non-biodegradable dry refuse (e.g., glass, plastic, metals). Sullage is liquid and primarily organic in nature. * **Option C (Waste containing human excreta):** This is defined as **Sewage**. Sewage is a mixture of sullage and "night soil" (human excreta). It is highly hazardous and requires more complex treatment than sullage. **3. High-Yield Facts for NEET-PG:** * **Sewage vs. Sullage:** Sewage = Sullage + Night Soil (Human excreta). * **Sewer:** The underground pipe/conduit that carries sewage. * **Sewerage:** The entire infrastructure (pipes, pumps, treatment plants) designed to remove and treat sewage. * **BOD (Biochemical Oxygen Demand):** A key indicator of water pollution. Sewage has a much higher BOD compared to sullage. * **Health Impact:** Improper disposal of sullage leads to stagnant pools, which act as breeding grounds for *Culex* mosquitoes (vector for Filariasis).

Q: What is the percentage of the para-para isomer in DDT?

70-80%. **Explanation:** DDT (Dichloro-diphenyl-trichloroethane) is a crystalline organochlorine insecticide used primarily for vector control in public health programs. Technical-grade DDT is not a pure substance but a mixture of several closely related compounds. **Why Option D is Correct:** The most potent and active insecticidal component of technical DDT is the **p,p'-DDT (para-para isomer)**. In the standard manufacturing process, this isomer constitutes approximately **70-80%** of the final product. This high concentration is essential for its efficacy as a residual insecticide against mosquitoes (Anopheles) and lice. **Analysis of Incorrect Options:** * **Option A (20-30%):** This range typically represents the **o,p'-DDT (ortho-para isomer)**, which is the second most common component (roughly 15-21%) but possesses significantly less insecticidal activity. * **Options B & C (40-70%):** These percentages are too low for the para-para isomer content in technical-grade DDT and do not correspond to standard chemical specifications used in public health. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism of Action:** DDT acts as a neurotoxin by keeping sodium channels open in neuronal membranes, leading to repetitive discharges. * **Residual Spraying:** For malaria control, DDT is applied as a "Residual Spray" on indoor walls. The standard dosage is **1-2 g/m²**, effective for 6 months. * **Environmental Impact:** It is highly lipophilic and undergoes **biomagnification** (concentrating up the food chain). * **Storage:** It is stored in the body's adipose tissue. * **Current Status:** Under the Stockholm Convention, its use is restricted globally but permitted for disease vector control (Malaria/Kala-azar) in specific regions like India.

Q: Softening of water is recommended when the hardness exceeds which of the following levels?

150 mg/litre. **Explanation:** The correct answer is **150 mg/litre**. Water hardness is primarily caused by the presence of calcium and magnesium bicarbonates, sulfates, and chlorides. While hardness is not a direct health hazard, it has significant economic and aesthetic implications, such as excessive soap consumption and scaling in pipes. According to standard public health guidelines (Park’s Preventive and Social Medicine), the recommendation for water softening is based on the following thresholds: * **Hardness 150 mg/L:** Softening is recommended to prevent scale formation and ensure effective lathering of soap. **Analysis of Options:** * **A (50 mg/L):** This is the threshold below which water is classified as "soft." No softening is required at this level. * **B (75 mg/L) & C (100 mg/L):** While water in this range is considered "moderately hard," it is still acceptable for most municipal supplies. Softening is not strictly recommended until the level exceeds 150 mg/L. **High-Yield NEET-PG Pearls:** 1. **Hardness Classification:** 0-50 (Soft), 50-150 (Moderately Hard), 150-300 (Hard), >300 (Very Hard). 2. **Temporary Hardness:** Caused by carbonates/bicarbonates of Calcium and Magnesium; removed by **boiling** or adding **lime**. 3. **Permanent Hardness:** Caused by sulfates, chlorides, and nitrates; removed by **base exchange process (Permutit)** or soda ash. 4. **Health Link:** Some epidemiological studies suggest a weak inverse correlation between water hardness and cardiovascular disease (hard water may be protective), though this remains a topic of debate.

Q: "Nuisance mosquito" refers to which of the following?

Culex. **Explanation:** The term **"Nuisance Mosquito"** is specifically attributed to **Culex fatigans** (also known as *Culex quinquefasciatus*). This designation arises from its pervasive behavior; it is a ubiquitous, domestic mosquito that breeds prolifically in polluted stagnant water, such as open drains and septic tanks. Unlike other species, Culex is a persistent biter, particularly active at night, causing significant irritation and sleep disturbance to humans, even in the absence of disease transmission. **Analysis of Options:** * **Culex (Correct):** Beyond being a "nuisance," it is the primary vector for **Bancroftian Filariasis** and **Japanese Encephalitis**. It is characterized by its "sit-down" posture (body parallel to the surface) and its preference for dirty water. * **Anopheles (Incorrect):** Known as the vector for **Malaria**. It is often referred to as the "clean water breeder." While it bites humans, it is not colloquially termed the nuisance mosquito in public health literature. * **Tsetse fly (Incorrect):** This is not a mosquito; it is a large biting fly found in Africa, responsible for transmitting **African Trypanosomiasis** (Sleeping Sickness). **High-Yield Clinical Pearls for NEET-PG:** * **Breeding Habitats:** Culex = Dirty/stagnant water; Anopheles = Clean/fresh water; Aedes = Artificial containers (man-made collections). * **Resting Posture:** Anopheles rests at an angle (45°); Culex and Aedes rest parallel to the surface. * **Flight Range:** Culex is a strong flier (up to 11 km), whereas Aedes has a very short range (<100 meters). * **Control:** The most effective way to control "nuisance" mosquitoes is through environmental sanitation and improving drainage systems.

Q: What is the location of the vital layer in a slow sand filter?

On the sand bed. The **Vital Layer** (also known as the **Schmutzdecke**, zoogleal layer, or biological layer) is the most critical component of a slow sand filter. ### **Explanation of the Correct Answer** The vital layer forms **on the surface of the sand bed** after the filter has been in operation for a few days. It consists of a slimy, gelatinous film made of algae, bacteria, protozoa, and plankton. This layer is the "heart" of the filter because it performs the primary purification functions: 1. **Biological Action:** It oxidizes organic matter and metabolizes ammoniacal nitrogen into nitrates. 2. **Mechanical Action:** It acts as an extremely fine sieve, trapping bacteria and suspended particles. 3. **Bactericidal Action:** It is responsible for removing 98–99% of the bacterial load from the water. ### **Analysis of Incorrect Options** * **Option B (On top of the water):** The water column above the sand (supernatant water) provides constant pressure and time for sedimentation, but it does not contain the biological film. * **Option C (Near the filter valves):** Valves regulate the rate of flow (filter control) but have no role in the biological purification process. ### **High-Yield NEET-PG Pearls** * **Ripening of Filter:** The process of the Schmutzdecke forming (taking 2–3 days) is called "ripening." Water filtered during this period is not fit for consumption. * **Cleaning:** When the "loss of head" exceeds a certain limit (usually 1.3 meters), the filter is cleaned by **scraping** the top 1–2 cm of the sand layer. * **Effective Size of Sand:** In slow sand filters, the sand has an effective size of **0.2 to 0.35 mm**. * **Rate of Filtration:** 0.1 to 0.4 $m^3/h/m^2$ (much slower than rapid sand filters).

Q: What is an anaerobic method of solid waste disposal?

Bangalore method. ### Explanation The core concept in solid waste disposal is the biological decomposition of organic matter, which can occur either in the presence of oxygen (**Aerobic**) or in its absence (**Anaerobic**). **Why the Bangalore Method is Correct:** The **Bangalore Method** (also known as the Anaerobic Trench Method) was developed by Dr. Gilbert Fowler and C.N. Acharya. In this method, layers of refuse and night soil are placed in trenches and covered with a final layer of earth. This seals the pile from the atmosphere. Over the next 4–6 months, anaerobic bacteria decompose the waste, generating heat to destroy pathogens and producing nutrient-rich manure. **Analysis of Incorrect Options:** * **Mechanical Composting:** This is a primarily **aerobic** process. It involves the use of machinery to rotate and aerate the waste, ensuring a constant oxygen supply to speed up decomposition (completed in 4–6 weeks). * **Controlled Tipping (Sanitary Landfill):** While the deep layers may eventually become anaerobic, it is fundamentally described as a method of "modified" disposal where waste is compacted and covered daily. In the context of NEET-PG, it is categorized separately from the specific biological "composting" methods. * **Incineration:** This is a **high-temperature dry oxidation** process. It is a chemical/thermal method of waste disposal, not a biological one, and is the method of choice for hospital (biomedical) waste. **High-Yield Facts for NEET-PG:** * **Indore Method:** The aerobic counterpart to the Bangalore method. It requires frequent turning of the heap to maintain oxygen levels. * **Health Aspect:** The Bangalore method is considered more "environmentally friendly" as it does not require manual turning, reducing the exposure of workers to pathogens. * **Temperature:** In composting, temperatures rise to **60°C (140°F)** or higher, which is essential for killing weed seeds and pathogenic organisms (e.g., Ascaris eggs).

Question 1

The amount of good quality bleaching powder required for chlorinating a round well measuring 4 meters in diameter and with a water column depth of 6 meters, to achieve a residual chlorine level indicated by the Horrocks' test giving a definite blue color in the 3rd cup onwards, is?

Accepted Answer

993.8 grams

Answer

99.38 grams

Answer

9.938 grams

Answer

0.9938 grams

Question 2

Which method is used for the disposal of chemical waste under Biomedical waste management guidelines?

Accepted Answer

Incineration

Answer

Autoclaving

Answer

Microwaving

Answer

Recycling

Question 3

Sullage consists of:

Accepted Answer

Wastewater from kitchen

Answer

Solid vegetable waste matter

Answer

Inorganic waste

Answer

Waste containing human excreta

Question 4

All are TRUE regarding bacteriological surveillance of drinking water quality EXCEPT:

Accepted Answer

Clostridium perfringens is routinely used for bacteriological surveillance of drinking water.

Answer

Fecal streptococci are the indicator of recent contamination of water.

Answer

Clostridium perfringens indicate remote contamination.

Answer

Screening test for coliform in drinking water is the presumptive coliform test.

Question 5

What is the percentage of the para-para isomer in DDT?

Accepted Answer

70-80%

Answer

20-30%

Answer

40-50%

Answer

60-70%

Question 6

What is true about incineration?

Accepted Answer

65% pharmaceutical waste, 15% lime, 15% cement, and 5% water

Answer

85% pharmaceutical waste and 15% cement

Answer

75% pharmaceutical waste, 15% cement, and 10% water

Answer

70% pharmaceutical waste, 20% cement, and 10% lime

Question 7

Softening of water is recommended when the hardness exceeds which of the following levels?

Accepted Answer

150 mg/litre

Answer

50 mg/litre

Answer

75 mg/litre

Answer

100 mg/litre

Question 8

"Nuisance mosquito" refers to which of the following?

Accepted Answer

Culex

Answer

Anopheles

Answer

Tsetse fly

Answer

None of the above

Question 9

What is the location of the vital layer in a slow sand filter?

Accepted Answer

On the sand bed

Answer

On top of the water

Answer

Near the filter valves

Answer

None of the above

Question 10

What is an anaerobic method of solid waste disposal?

Accepted Answer

Bangalore method

Answer

Mechanical composting

Answer

Controlled tipping

Answer

Incineration

Environmental Health — MCQs

Environmental Health — MCQs

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