Environmental Health Practice Questions

Q: What type of wells are characterized by water rising above the level of the surrounding groundwater?

Artesian wells. **Explanation:** The correct answer is **Artesian wells**. This phenomenon occurs due to specific geological conditions where a water-bearing stratum (aquifer) is sandwiched between two impervious layers of rock or clay. This creates a "confined aquifer" under high hydraulic pressure. When a well is sunk into this layer, the internal pressure forces the water to rise above the level of the surrounding water table, and in some cases, it may even flow out onto the surface spontaneously. **Analysis of Options:** * **Shallow wells:** These tap into the first water-bearing stratum above the first impervious layer. The water level in these wells is simply the level of the surrounding groundwater (water table). They are highly prone to surface contamination. * **Deep wells:** These penetrate the first impervious layer to tap into a deeper aquifer. While they provide purer water than shallow wells, the water does not rise above the surrounding groundwater level unless specific artesian conditions exist. * **Dug wells:** This is a classification based on construction (manual excavation) rather than hydraulic properties. They are typically shallow and do not involve pressurized water. **High-Yield Facts for NEET-PG:** * **Step-well (Baoli):** A type of shallow well where people descend steps to fetch water. These are notorious for being the primary source of **Dracunculiasis (Guinea worm disease)** transmission. * **Sanitary Well:** To be considered "sanitary," a well must be located at least **15 meters (50 feet)** away from potential sources of contamination like latrines. * **Water Quality:** Deep wells are generally bacteriologically safer than shallow wells because the impervious layer acts as a natural filter against surface pollutants.

Q: One tablet of chlorine is effective to disinfect how much quantity of water?

20 L. ### Explanation **Correct Answer: B. 20 L** **Underlying Medical Concept:** Chlorine tablets (specifically **Halazone tablets** or calcium hypochlorite formulations) are a standard method for point-of-use water purification, especially during emergencies or travel. A standard chlorine tablet (usually weighing 0.5 grams) is designed to release approximately **2 mg of free chlorine per liter** of water. According to public health guidelines for small-scale disinfection, one such tablet is sufficient to disinfect **20 liters** of water. The contact time required for effective disinfection is at least **30/60 minutes** before the water is safe for consumption. **Analysis of Options:** * **A (5 L) & C (10 L):** These quantities are too small for a standard tablet. Using one tablet for 5 or 10 liters would result in an excessively high concentration of chlorine, leading to an unpleasant taste and odor (chlorinous taste) without providing additional safety benefits. * **D (30 L):** This quantity is too large. One tablet would be over-diluted, failing to achieve the required concentration of free residual chlorine (0.5 mg/L after 30 minutes) necessary to kill pathogenic bacteria and viruses. **High-Yield Clinical Pearls for NEET-PG:** * **Free Residual Chlorine:** The goal of water chlorination is to have a residual chlorine level of **0.5 mg/L** after a contact time of **30 minutes**. * **Horrocks' Apparatus:** Used to estimate the dose of bleaching powder required to disinfect 455 liters (100 gallons) of water. * **OT Test (Orthotolidine Test):** Used to determine both free and combined chlorine. The **OTA (Orthotolidine Arsenite) Test** is specifically used to distinguish between free and combined chlorine. * **Chlorine Demand:** The difference between the amount of chlorine added to the water and the amount of residual chlorine remaining after a specific period.

Q: Air pollution may cause which of the following conditions?

Carcinoma of the bronchus. ### Explanation **Correct Answer: B. Carcinoma of the bronchus** Air pollution is a complex mixture of particulate matter (PM), polycyclic aromatic hydrocarbons (PAHs), and toxic gases. The International Agency for Research on Cancer (IARC) classifies outdoor air pollution and particulate matter as **Group 1 carcinogens**. Chronic exposure to pollutants like benzopyrene and arsenic leads to DNA damage, oxidative stress, and chronic inflammation of the respiratory epithelium, significantly increasing the risk of **bronchogenic carcinoma**. **Analysis of Options:** * **Dermatitis (A):** While air pollution can exacerbate existing skin conditions (like eczema) due to oxidative stress, it is not considered a primary or definitive causative agent for dermatitis in the same direct epidemiological capacity as respiratory malignancies. * **Bronchiectasis (C):** This is a chronic condition characterized by permanent dilation of the bronchi, usually resulting from severe or recurrent childhood infections (e.g., measles, pertussis) or genetic factors (e.g., Cystic Fibrosis). Air pollution may aggravate symptoms but is not a primary cause. * **Pneumonia (D):** Pneumonia is an acute infectious process caused by bacteria, viruses, or fungi. While pollution can lower local immunity and predispose individuals to infections, it is not the direct cause of the disease itself. **High-Yield Clinical Pearls for NEET-PG:** * **Indicator of Air Pollution:** **Sulphur dioxide ($SO_2$)** is considered the best indicator of air pollution (specifically fossil fuel combustion). * **Smoke Index:** Calculated as $2 \times (SO_2 \text{ in } \mu g/m^3) + (\text{Suspended Matter in } \mu g/m^3)$. * **Health Effects:** Air pollution is most strongly associated with **COPD, Lung Cancer, and Cardiovascular diseases** (Ischemic Heart Disease). * **Lichens:** These are sensitive biological indicators used to monitor long-term air quality.

Q: Which of the following is NOT true about pyrethrum?

Stomach poison. **Explanation:** Pyrethrum is one of the most widely used natural insecticides in public health. Understanding its mechanism and properties is crucial for NEET-PG. **Why "Stomach Poison" is the correct answer (The False Statement):** Pyrethrum is primarily a **nerve poison** that acts through **direct contact**. It penetrates the insect's cuticle and affects the nervous system, leading to rapid paralysis (the "knock-down" effect). It is **not** a stomach poison; stomach poisons (like Paris Green or Sodium Fluoride) must be ingested by the insect to be effective, whereas pyrethrum works upon mere physical contact. **Analysis of Incorrect Options (True Statements):** * **Vegetable Origin:** Pyrethrum is a natural insecticide extracted from the dried flower heads of *Chrysanthemum cinerariaefolium*. * **Contact Poison:** As mentioned, it acts by penetrating the insect's body wall. It is highly effective against mosquitoes, flies, and bedbugs on contact. * **Used as Space Spray:** Because of its rapid "knock-down" effect and low mammalian toxicity, it is the agent of choice for space spraying (e.g., 0.1% pyrethrum extract) to kill adult mosquitoes indoors. **High-Yield Clinical Pearls for NEET-PG:** * **Knock-down Effect:** Pyrethrum is famous for its near-instantaneous paralysis of insects. * **Synergist:** It is often mixed with **Piperonyl Butoxide** to enhance its killing power and prevent insects from recovering from the initial paralysis. * **Safety:** It is relatively non-toxic to humans but can cause allergic reactions (dermatitis or asthma) in sensitive individuals. * **Stability:** It is unstable in light and air, which is why it has no residual action and is used only for immediate space clearance.

Q: What is the primary application of an electrostatic precipitator?

Control of air pollution emissions. **Explanation:** **Why Option B is Correct:** An **Electrostatic Precipitator (ESP)** is a highly efficient filtration device used to remove fine particulate matter (PM), such as dust and smoke, from flowing gases (like exhaust from power plants or industrial stacks). It works on the principle of **electrostatic attraction**: particles are given an electric charge as they pass through the unit and are subsequently attracted to and collected on oppositely charged plates. In Community Medicine, ESPs are considered the "gold standard" for industrial air pollution control because they can remove over 99% of particulate matter, significantly reducing the risk of respiratory diseases (like COPD and pneumoconiosis) in the surrounding population. **Analysis of Incorrect Options:** * **Option A:** Radiation risks are managed through shielding (lead aprons), distance, and time limitation, not air filtration. * **Option C:** Mosquito nuisance is managed via environmental modification (source reduction), chemical methods (larvicides/insecticides), or biological control (Gambusia fish). * **Option D:** Vibrations are mitigated through engineering controls like damping, isolation mounts, or administrative controls (limiting exposure time), not electrostatic devices. **High-Yield Clinical Pearls for NEET-PG:** * **Efficiency:** ESPs are preferred for very fine particles (<1 micron) where mechanical filters might fail. * **Air Quality Index (AQI):** Particulate matter (PM2.5 and PM10) is a major component of AQI; ESPs directly help in maintaining these levels. * **Other Air Cleaners:** * *Cyclonic Separators:* Use centrifugal force for large particles. * *Bag Filters:* Use fabric membranes. * *Scrubbers:* Use liquid spray to remove gases and particles.

Q: Which of the following types of waste is not typically disposed of by incineration?

Sharps waste and radioactive waste. **Explanation:** The disposal of biomedical waste is governed by specific guidelines to prevent environmental contamination and health hazards. **Incineration** is a high-temperature dry oxidation process used primarily to reduce the volume of waste and destroy pathogens and organic compounds. **Why Option B is Correct:** * **Sharps Waste:** Incineration of sharps (needles, scalpels) is generally avoided because the high temperatures can melt the metal, but they do not completely destroy it, and the resulting mass can damage incinerator linings. More importantly, sharps are ideally autoclaved/microwaved and then shredded or encapsulated to prevent injury. * **Radioactive Waste:** Incineration of radioactive materials is strictly prohibited as it can lead to the release of volatile radioactive isotopes into the atmosphere, causing widespread environmental radiation. These are managed through decay-in-storage or specialized lead-shielded disposal. **Analysis of Incorrect Options:** * **Anatomical Waste (Options C & D):** Human anatomical waste (tissues, organs, body parts) is the primary candidate for incineration (Yellow Bag) to ensure complete destruction and prevent aesthetic or biological hazards. * **Cytotoxic Drugs (Options A & D):** Outdated or discarded cytotoxic drugs must be incinerated at very high temperatures (usually >1200°C) to break down their complex chemical structures. **NEET-PG High-Yield Pearls:** * **Yellow Bag:** Anatomical waste, soiled waste, and cytotoxic drugs (Incineration). * **Red Bag:** Recyclable plastic waste (Autoclaving/Microwaving followed by recycling). * **White Container (Puncture-proof):** Sharps (Autoclaving/Dry Heat Sterilization followed by shredding). * **Blue Box:** Glassware and metallic body implants. * **Chlorinated plastics** should never be incinerated as they release toxic **dioxins and furans**.

Q: Biological oxygen demand is calculated to determine the amount of organic waste in water?

Organic. **Explanation:** **Biological Oxygen Demand (BOD)** is a critical indicator of water pollution. It is defined as the amount of dissolved oxygen required by aerobic microorganisms to decompose the **organic matter** present in a water sample over a specific period (usually 5 days) at a specific temperature (20°C). 1. **Why Organic is Correct:** BOD specifically measures the "biodegradable" organic load. When organic waste (like sewage) enters a water body, bacteria consume oxygen to break it down. Therefore, a high BOD indicates a high level of organic pollution and low dissolved oxygen, which can lead to the death of aquatic life. 2. **Why Inorganic is Incorrect:** Inorganic substances (like minerals, heavy metals, or ammonia) are not decomposed by aerobic bacteria in the same manner. Their oxygen requirement is measured via **Chemical Oxygen Demand (COD)**, which uses chemical oxidants to break down both organic and inorganic components. 3. **Why Total Solid is Incorrect:** Total solids include suspended and dissolved solids (both organic and inorganic). While they contribute to turbidity, they do not directly represent the biological oxygen requirement. **High-Yield NEET-PG Pearls:** * **BOD Values:** * **Clean Water:** < 1 mg/L * **Moderately Polluted:** 2–8 mg/L * **Municipal Sewage:** 100–400 mg/L * **COD vs. BOD:** COD is always greater than BOD because it measures both biodegradable and non-biodegradable substances. * **Indicator of Sewage Strength:** BOD is the most important test used by sanitary engineers to determine the "strength" of sewage and the efficiency of treatment plants.

Q: Paris green kills which of the following?

Anopheles larva only. **Explanation:** **Paris Green (Copper Acetoarsenite)** is a classic stomach poison used in public health for larval control. The correct answer is **Anopheles larva only** due to the specific feeding behavior of these larvae. 1. **Why Option A is correct:** Anopheles larvae are **surface feeders**. They lie horizontally at the water-air interface. Paris Green is an emerald-green micro-crystalline powder that is insoluble in water and floats on the surface. When dusted over water bodies, Anopheles larvae ingest these floating particles, leading to arsenic poisoning and death. 2. **Why Options B & D are incorrect:** **Culex larvae** are bottom feeders (or hang at an angle via a siphon). Since Paris Green floats on the surface, it does not reach the depth where Culex larvae feed. Therefore, it is ineffective against them. 3. **Why Options C & D are incorrect:** Paris Green is a **larvicide**, not an adulticide. It acts as a stomach poison that must be ingested; it does not have the contact toxicity or residual effect required to kill adult mosquitoes. **High-Yield Clinical Pearls for NEET-PG:** * **Composition:** It contains about 50% Arsenic. * **Application:** It is applied as a 2% dust (mixed with diluents like lime or soapstone). * **Safety:** It is safe for fish and domestic animals at recommended doses but can be toxic to humans if inhaled or ingested. * **Alternative Larvicides:** * **Abate (Temephos):** An organophosphorus compound used for both Anopheles and Culex (safe for drinking water). * **Mineral Oils (Malariol):** Kill larvae by suffocation (cutting off oxygen supply). * **Biological Control:** *Gambusia affinis* and *Poecilia reticulata* (Guppy) fish are used to eat larvae.

Q: What is the most important factor in sewage treatment?

Solids. **Explanation:** The primary objective of sewage treatment is the removal of organic and inorganic **solids** (suspended and dissolved). Sewage is approximately 99.9% water and only 0.1% solids. However, this tiny fraction of solids is the most critical factor because it contains the organic matter that exerts **Biochemical Oxygen Demand (BOD)**. If these solids are not removed, their decomposition consumes dissolved oxygen in receiving water bodies, leading to environmental degradation and public health hazards. Treatment processes like sedimentation (primary) and biological oxidation (secondary) are specifically designed to reduce the "Total Suspended Solids" (TSS) and organic load. **Analysis of Incorrect Options:** * **A. Bacterial count:** While sewage contains high pathogens, the treatment efficiency is measured by the reduction of organic load (BOD) rather than an absolute bacterial count. Disinfection is usually the final, not the primary, focus. * **C. Nitrite and phosphorus:** These are nutrients that contribute to eutrophication. While important in advanced (tertiary) treatment, they are secondary to the removal of bulk organic solids. * **D. Water content:** Since sewage is already 99.9% water, the water content itself is not the "factor" to be treated; rather, it is the medium from which pollutants must be extracted. **High-Yield NEET-PG Pearls:** * **Strength of Sewage:** Measured by BOD, Chemical Oxygen Demand (COD), and Suspended Solids. * **BOD (Biochemical Oxygen Demand):** The most important indicator of organic pollution. It is defined as the amount of oxygen consumed by aerobic bacteria to decompose organic matter in 5 days at 20°C. * **Efficiency:** A well-functioning sewage plant should remove 80-90% of BOD and suspended solids. * **Sludge:** The solid portion settled during treatment; its safe disposal is a major challenge in environmental sanitation.

Question 1

Which of the following is NOT a feature of hard water?

Accepted Answer

Decreased soap consumption

Answer

Increased fuel consumption

Answer

Erosion of lead pipe

Answer

Scaling of boiler

Question 2

What type of wells are characterized by water rising above the level of the surrounding groundwater?

Accepted Answer

Artesian wells

Answer

Shallow wells

Answer

Deep wells

Answer

Dug wells

Question 3

One tablet of chlorine is effective to disinfect how much quantity of water?

Accepted Answer

20 L

Answer

5 L

Answer

10 L

Answer

30 L

Question 4

Air pollution may cause which of the following conditions?

Accepted Answer

Carcinoma of the bronchus

Answer

Dermatitis

Answer

Bronchiectasis

Answer

Pneumonia

Question 5

Which of the following is NOT true about pyrethrum?

Accepted Answer

Stomach poison

Answer

Vegetable origin

Answer

Contact poison

Answer

Used as space spray

Question 6

What is the primary application of an electrostatic precipitator?

Accepted Answer

Control of air pollution emissions

Answer

Prevention of radiation risks

Answer

Management of mosquito nuisance

Answer

Mitigation of diffuse vibrations

Question 7

Which of the following types of waste is not typically disposed of by incineration?

Accepted Answer

Sharps waste and radioactive waste

Answer

Cytotoxic drugs

Answer

Anatomical waste and sharps waste

Answer

Anatomical waste and cytotoxic drugs

Question 8

Biological oxygen demand is calculated to determine the amount of organic waste in water?

Accepted Answer

Organic

Answer

Inorganic

Answer

Total solid

Answer

None

Question 9

Paris green kills which of the following?

Accepted Answer

Anopheles larva only

Answer

Culex larva only

Answer

Anopheles adult mosquito

Answer

Culex adult mosquito

Question 10

What is the most important factor in sewage treatment?

Accepted Answer

Solids

Answer

Bacterial count

Answer

Nitrite and phosphorus

Answer

Water content

Environmental Health — MCQs

Environmental Health — MCQs

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