Environmental Health Practice Questions

Q: Guineaworm disease was a common public health problem which was attributed to the use of which type of water source?

Step well. **Explanation:** **1. Why Step Wells are the Correct Answer:** Guineaworm disease (Dracunculiasis), caused by the nematode *Dracunculus medinensis*, is a water-borne parasitic infection. The transmission cycle depends on humans coming into direct physical contact with stagnant water sources. **Step wells (Baolis)** are the primary culprit because they require individuals to step into the water to collect it. When an infected person with a mature blister enters the water, the female worm releases thousands of larvae. these larvae are ingested by **Cyclops** (the intermediate host). When another person drinks this unfiltered water containing infected Cyclops, the cycle continues. **2. Analysis of Incorrect Options:** * **Dug Well:** While these are open wells, they typically involve drawing water with a bucket and rope. Unless people physically enter the water, the risk is significantly lower than step wells. * **Sanitary Well:** These are specifically designed to prevent contamination (covered top, hand pump, and parapet walls), making them the solution to, rather than the cause of, the disease. * **Arsenic Contaminated Water:** This leads to chronic arsenicosis (e.g., Blackfoot disease, hyperkeratosis), which is a chemical toxicity, not a parasitic infection. **3. High-Yield Clinical Pearls for NEET-PG:** * **Intermediate Host:** *Cyclops* (also known as water flea). * **Definitive Host:** Humans. * **Eradication Status:** India was declared **Guineaworm-free** by the WHO in **February 2000**. The last case in India was reported in July 1996 (Jodhpur, Rajasthan). * **Prevention:** The simplest method to prevent transmission is filtering water through a fine mesh cloth (to remove Cyclops) or converting step wells into sanitary wells. * **Treatment of choice for water:** Chemical treatment of water bodies using **Abate (Temephos)** to kill Cyclops.

Q: Aerobic digestion of sludge takes place in which of the following?

Trickling filter. ### Explanation The core concept here is the distinction between **aerobic** and **anaerobic** processes in sewage treatment. **1. Why Trickling Filter is correct:** A trickling filter (also known as a percolating filter) is a secondary treatment method where sewage is sprayed over a bed of crushed stones or slag. As the sewage trickles down, it comes into contact with a biological film (zoogleal layer) consisting of aerobic bacteria, algae, and fungi. Because the bed is ventilated, there is a constant supply of oxygen, ensuring that the **digestion of organic matter (sludge) occurs aerobically**. **2. Why the other options are incorrect:** * **Activated Sludge Process:** While this is an aerobic process, it involves the oxidation of *sewage* in an aeration tank. The resulting "activated sludge" is then sent to a separate **Sludge Digestion Tank**, where it typically undergoes **anaerobic digestion** to produce methane. * **Broad Irrigation:** This is a primary disposal method where raw or settled sewage is applied to land. It relies on surface filtration and natural soil bacteria, but it is not a specialized "digestion" process for sludge. * **Septic Tank:** This is a classic example of **anaerobic digestion**. The solids settle at the bottom and are decomposed by anaerobic bacteria over a period of months. ### High-Yield Pearls for NEET-PG: * **Trickling Filter:** Key features include the "Zoogleal layer" and the fact that it is a biological oxidation process. * **Activated Sludge Process:** The most efficient method for large-scale urban sewage treatment; it reduces BOD (Biochemical Oxygen Demand) by 90-95%. * **BOD (Biochemical Oxygen Demand):** The most important indicator of organic pollution. A high BOD indicates high pollution. * **Sludge Digestion:** In most modern plants, sludge is digested **anaerobically** in closed tanks to produce "sludge gas" (methane), which can be used for power.

Q: Which of the following is NOT true regarding malathion?

Most toxic of all members of the group. ### Explanation **Malathion** is a widely used organophosphorous insecticide in public health programs. The question asks for the statement that is **NOT** true. **1. Why Option C is the Correct Answer (The False Statement):** Malathion is actually considered one of the **least toxic** organophosphorous compounds for mammals. Its selective toxicity is due to the fact that mammals possess enzymes (carboxylesterases) that rapidly detoxify malathion, whereas insects convert it into the highly toxic metabolite **malaoxon**. In contrast, other members of the organophosphate group, such as Parathion or Nerve Gases (Sarin, VX), are significantly more lethal. **2. Analysis of Incorrect Options:** * **Option A (Used as a spray):** This is true. Malathion is used as a residual spray (at a dosage of 2g/m²) for indoor residual spraying (IRS) and as an ultra-low volume (ULV) fog for space spraying during epidemics. * **Option B (Alternative to DDT):** This is true. In areas where vectors (like *Anopheles* mosquitoes) have developed resistance to DDT and HCH, Malathion is the recommended alternative for malaria control. * **Option D (Belongs to organophosphorous insecticides):** This is true. It is a non-systemic organophosphate that acts by inhibiting acetylcholinesterase. **Clinical Pearls & High-Yield Facts for NEET-PG:** * **Antidote:** Atropine is the specific physiological antidote for malathion poisoning; Pralidoxime (2-PAM) is used as a cholinesterase reactivator. * **Dosage:** For IRS, it is applied at **2g/m²** every 3 months. * **Odor:** Malathion has a characteristic strong, pungent "garlic" or "rotten egg" odor due to its sulfur content. * **Safety:** Because of its low mammalian toxicity, it is the insecticide of choice for **delousing** (treating head and body lice).

Q: The mean radiant temperature is measured by:

Globe thermometer. ### Explanation **Correct Answer: D. Globe thermometer** The **Globe thermometer** (specifically the Vernon’s Globe Thermometer) is the standard instrument used to measure **Mean Radiant Temperature (MRT)**. It consists of a mercury-in-glass thermometer placed inside a 6-inch hollow copper sphere painted matte black. The black surface absorbs infrared radiation from surrounding objects, and the equilibrium temperature reached inside the globe reflects the combined effect of air temperature and radiant heat. **Analysis of Incorrect Options:** * **A. Dry bulb thermometer:** Measures the actual air temperature (ambient temperature). It is not influenced by radiation or humidity. * **B. Wet bulb thermometer:** Measures the lowest temperature reachable by evaporative cooling. It is used primarily to assess humidity and the cooling power of the air. * **C. Six’s maximum and minimum thermometer:** Used to record the highest and lowest temperatures reached during a specific period (usually 24 hours). It does not measure radiant heat. **High-Yield Clinical Pearls for NEET-PG:** * **Kata Thermometer:** Measures "cooling power" of air and air velocity (especially low velocities). * **Anemometer:** Measures high-velocity air/wind speed. * **Psychrometer (Sling Psychrometer):** Used to measure relative humidity (contains both dry and wet bulb thermometers). * **Corrected Effective Temperature (CET):** An index that adjusts the Effective Temperature to include the effect of radiant heat (measured by the Globe thermometer). * **Comfort Zone:** In India, the ideal indoor temperature is considered **25°C to 27°C**.

Q: How is human anatomical waste typically disposed of?

Incineration. **Explanation:** According to the **Biomedical Waste (BMW) Management Rules**, human anatomical waste (such as tissues, organs, and body parts) is categorized under **Yellow Category** waste. **Why Incineration is Correct:** The primary method for disposing of Yellow Category waste, particularly anatomical waste, is **Incineration** (high-temperature dry oxidation). This process reduces the waste to ash, ensuring complete destruction of pathogens and organic matter, while also preventing the illegal reuse of body parts. In areas where an incinerator is not available, **Deep Burial** (in cities with a population less than 5 lakhs) is the permitted alternative. **Why Other Options are Incorrect:** * **Autoclaving (Option B):** This is the preferred method for **Red Category** waste (contaminated recyclable waste like catheters, tubes, and gloves). While autoclaving sterilizes, it does not physically destroy anatomical structures, making it aesthetically and legally unsuitable for human body parts. * **Chemical Treatment (Option C):** This is typically used for liquid waste or as a pretreatment for certain types of laboratory waste (using 1-2% Sodium Hypochlorite). It is insufficient for the bulk disposal of solid anatomical tissues. **NEET-PG High-Yield Pearls:** * **Yellow Bag:** Used for anatomical waste, soiled waste (blood-soaked cotton), expired medicines, and chemical waste. * **Red Bag:** Used for plastic waste (Recyclable). **Mnemonic:** **R**ed for **R**ubber/Recycle. * **Blue Box:** Used for glass vials, ampoules, and metallic body implants. * **White Puncture-Proof Container:** Used for sharps (needles, scalpels). * **Cytotoxic drugs:** Must be incinerated at temperatures >1200°C.

Q: What is the appropriate method for disposing of a placenta in a Primary Health Centre (PHC)?

Incineration. ### Explanation **Correct Answer: D. Incineration** **1. Why Incineration is Correct:** According to the **Biomedical Waste Management (BMW) Rules 2016**, a placenta is classified as **Anatomical Waste (Category: Yellow)**. Yellow category waste consists of human tissues, organs, and body parts. The gold standard for disposing of anatomical waste is **Incineration** or **Deep Burial** (the latter is permitted only in rural/remote areas where an incinerator is not accessible). Incineration ensures complete combustion of organic matter, reducing it to ash and effectively destroying pathogens. **2. Why Other Options are Incorrect:** * **A. Microwaving & B. Autoclaving:** These methods are primarily used for **Red Category** waste (contaminated recyclable waste like catheters, IV tubes, and gloves). While they achieve sterilization, they do not physically "dispose of" anatomical tissue; the tissue remains intact, which is culturally and aesthetically unacceptable for anatomical waste. * **C. Chemical Treatment:** This is typically used for liquid waste or pre-treatment of laboratory waste. It is insufficient for solid anatomical structures like a placenta. **3. Clinical Pearls & High-Yield Facts for NEET-PG:** * **Yellow Bag Rule:** Remember that all human anatomical waste, soiled waste (blood-soaked cotton/dressings), and expired medicines go into the **Yellow Bag**. * **PHC Specifics:** In a PHC located in a "Deep Burial" zone (remote areas), deep burial in a lined pit is an acceptable alternative to incineration. * **Chlorinated Plastics:** Never incinerate chlorinated plastic bags (like Red bags) as they release toxic **dioxins and furans**. * **Cytotoxic Drugs:** These must be incinerated at high temperatures (>1200°C) and are also disposed of in Yellow bags (marked with a cytotoxic symbol).

Q: All of the following statements about Hardness of Water are true, except?

Bicarbonates cause permanent hardness.. ### Explanation **1. Why Option B is the Correct Answer (The Exception):** Hardness of water is classified into two types: **Temporary** and **Permanent**. Bicarbonates of calcium and magnesium cause **Temporary Hardness** (also known as carbonate hardness), not permanent hardness. Permanent hardness is caused by the presence of chlorides, sulfates, and nitrates of calcium and magnesium. Therefore, the statement "Bicarbonates cause permanent hardness" is factually incorrect. **2. Analysis of Other Options:** * **Option A:** Hardness is defined as the "soap-destroying power" of water. This occurs because calcium and magnesium ions react with soap to form an insoluble curd (scum), preventing the formation of lather until the hardness is neutralized. * **Option C:** Temporary (Carbonate) hardness is easily removed by **boiling**. Boiling decomposes the soluble bicarbonates into insoluble carbonates, which precipitate out (forming scale). * **Option D:** While other polyvalent metallic ions (like iron or aluminum) can contribute, hardness is **mainly** caused by the salts of Calcium and Magnesium. **3. High-Yield Clinical Pearls for NEET-PG:** * **Removal Methods:** Temporary hardness is removed by boiling or addition of lime (Clark’s process). Permanent hardness requires chemical methods like the **Permutit process** (ion exchange) or addition of sodium carbonate. * **Health Impact:** Hard water is associated with increased risk of **urolithiasis** (urinary stones) and may lead to higher soap consumption and scaling of boilers. * **Hardness Scale:** * Soft: 0–50 mg/L * Moderately hard: 50–150 mg/L * Hard: 150–300 mg/L * Very hard: >300 mg/L * **WHO Guideline:** There is no firm health-based guideline value, but water above 200 mg/L is generally considered poor for domestic use.

Q: All of the following are true about safe and wholesome water, except?

It is unusable for domestic purposes. ### Explanation **Concept of Safe and Wholesome Water** In Community Medicine, water is classified as "safe and wholesome" when it meets specific criteria that ensure it does not pose a health risk to the consumer and is aesthetically acceptable. By definition, safe and wholesome water must be **usable for domestic purposes** (such as drinking, cooking, and bathing). Therefore, Option C is the correct answer because it incorrectly states that such water is "unusable." **Analysis of Options:** * **Option A (Free from color and odor):** This is a true characteristic. Safe water must be aesthetically pleasing. It should be clear, colorless, and odorless to be acceptable for human consumption. * **Option B (Free from pathogenic agents):** This is a fundamental requirement. The water must not contain bacteria, viruses, protozoa, or helminths that cause water-borne diseases (e.g., Cholera, Typhoid, Hepatitis A). * **Option D (Free from harmful chemical contaminants):** This is also true. Safe water must not contain toxic substances like arsenic, fluorides, nitrates, or heavy metals in concentrations that exceed permissible limits. **High-Yield NEET-PG Pearls:** * **Definition:** Safe and wholesome water is defined as water that is: (1) Free from pathogenic agents, (2) Free from harmful chemical substances, (3) Pleasant to taste (free from color/odor), and (4) **Usable for domestic purposes.** * **Polluted vs. Contaminated Water:** *Polluted* water contains physical or chemical impurities (e.g., turbidity), while *Contaminated* water specifically contains infectious agents or poisonous substances. * **Standard:** The WHO Guidelines for Drinking-water Quality are the international benchmark used to define these parameters. * **Domestic Consumption:** In India, for an average urban community, the recommended supply is **150–200 liters per capita per day (lpcd)**.

Q: Auditory fatigue occurs most readily at which frequency range?

4000 Hz. **Explanation:** The correct answer is **4000 Hz**. This is a classic high-yield concept in Occupational Health and Environmental Medicine. **1. Why 4000 Hz is correct:** Auditory fatigue (Temporary Threshold Shift) and permanent noise-induced hearing loss (NIHL) occur most readily at **4000 Hz**. This phenomenon is known as the **"4000 Hz Notch"** or **Carhart's Notch** (though the latter is more specific to otosclerosis, the term "notch" is universally used for noise damage). The anatomical reason is the resonance of the external auditory canal, which peaks between 2000–5000 Hz. This amplifies sound pressure levels reaching the cochlea in this range. Specifically, the basal turn of the cochlea, which is responsible for sensing high-frequency sounds, is most susceptible to mechanical and metabolic exhaustion from loud noise. **2. Why other options are incorrect:** * **2000 Hz & 3000 Hz:** While these frequencies are within the range of human speech and can be affected by prolonged noise exposure, they are not the *initial* or *most sensitive* points of fatigue. * **8000 Hz:** This is at the higher end of the clinical audiogram. While noise can affect this frequency, the maximum dip typically occurs at 4000 Hz and then shows a slight recovery at 8000 Hz (the "V-shaped" notch). **3. NEET-PG High-Yield Pearls:** * **Definition of Noise:** Sound that is unwanted. * **Safe Limit:** 85 dB is generally considered the limit for an 8-hour workday. * **Audiometry:** The first sign of noise-induced hearing loss is a notch at 4000 Hz. * **Presbycusis:** Age-related hearing loss, which typically affects high frequencies but lacks the specific 4000 Hz notch seen in noise trauma. * **Unit of Sound:** Frequency is measured in **Hertz (Hz)**, while intensity is measured in **Decibels (dB)**.

Q: What is a drawback of using ozone as a water disinfectant?

No residual action. **Explanation:** Ozone ($O_3$) is a powerful oxidizing agent used in water purification. While highly effective, its primary drawback is its instability in water. **1. Why "No residual action" is correct:** Unlike chlorine, which leaves a "residual" concentration in the water to protect against re-contamination during distribution through pipes, ozone decomposes rapidly back into oxygen. Once the ozone treatment is complete, the water has no ongoing antimicrobial protection. If the distribution system has leaks or biofilms, the water can become re-contaminated before reaching the consumer. **2. Analysis of Incorrect Options:** * **A. No virucidal effect:** This is incorrect. Ozone is actually a more potent virucide and bactericide than chlorine. It effectively inactivates viruses, bacteria, and even chlorine-resistant cysts like *Giardia* and *Cryptosporidium*. * **B. Long time period for action:** This is incorrect. Ozone has a very high oxidation potential and works much faster than chlorine (shorter contact time required). * **C. Teratogenicity:** There is no evidence that ozonated water is teratogenic. In fact, ozone is often preferred because it does not produce halogenated disinfection by-products (like Trihalomethanes) which are linked to carcinogenicity. **High-Yield NEET-PG Pearls:** * **Ozone vs. Chlorine:** Ozone is more effective at killing spores and cysts but is more expensive and lacks residual protection. * **Residual Chlorine:** The recommended free residual chlorine in drinking water is **0.5 mg/L** for a contact time of 1 hour. * **Horrocks' Apparatus:** Used to estimate the dose of bleaching powder required to disinfect a well. * **OT Test (Orthotolidine):** Used to detect both free and combined chlorine; however, the **OTA (Orthotolidine Arsenite)** test is preferred to specifically distinguish between the two.

Question 1

Guineaworm disease was a common public health problem which was attributed to the use of which type of water source?

Accepted Answer

Step well

Answer

Dug well

Answer

Sanitary well

Answer

Arsenic contaminated water source

Question 2

Aerobic digestion of sludge takes place in which of the following?

Accepted Answer

Trickling filter

Answer

Broad irrigation

Answer

Activated sludge

Answer

Septic tank

Question 3

Which of the following is NOT true regarding malathion?

Accepted Answer

Most toxic of all members of the group

Answer

Used as a spray

Answer

Can be used as an alternative to DDT

Answer

Belongs to organophosphorous insecticides

Question 4

The mean radiant temperature is measured by:

Accepted Answer

Globe thermometer

Answer

Dry bulb thermometer

Answer

Wet bulb thermometer

Answer

Six's maximum and minimum thermometer

Question 5

How is human anatomical waste typically disposed of?

Accepted Answer

Incineration

Answer

Autoclaving

Answer

Chemical treatment

Answer

None of the above

Question 6

What is the appropriate method for disposing of a placenta in a Primary Health Centre (PHC)?

Accepted Answer

Incineration

Answer

Microwaving

Answer

Autoclaving

Answer

Chemical treatment

Question 7

All of the following statements about Hardness of Water are true, except?

Accepted Answer

Bicarbonates cause permanent hardness.

Answer

Hardness is the soap-destroying power of water.

Answer

Carbonate hardness can be removed by boiling.

Answer

Hardness is mainly caused by calcium and magnesium salts.

Question 8

All of the following are true about safe and wholesome water, except?

Accepted Answer

It is unusable for domestic purposes

Answer

It is free from color and odor

Answer

It is free from pathogenic agents

Answer

It is free from harmful chemical contaminants

Question 9

Auditory fatigue occurs most readily at which frequency range?

Accepted Answer

4000 Hz

Answer

2000 Hz

Answer

3000 Hz

Answer

8000 Hz

Question 10

What is a drawback of using ozone as a water disinfectant?

Accepted Answer

No residual action

Answer

No virucidal effect

Answer

Long time period for action

Answer

Teratogenicity

Environmental Health — MCQs

Environmental Health — MCQs

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