Environmental Health — MCQs
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Which of the following does not cause hardness of water?
Which among the following is an active form of chlorination?
In water testing from a well using Horrock's apparatus, blue color appears from the 4th cup onwards. What is the amount of bleaching powder required to disinfect 75000 litres of water?
Which indicator is used in Horroch's apparatus?
Waste Sharps should be disposed in ?
At what fluoride concentration in drinking water does skeletal fluorosis typically occur?
Swajaldhara programme is associated with:
Which of the following statements about Culex larvae is correct?
Which of the following is not typically incinerated?
Anemometer measures?
Environmental Health Indian Medical PG Practice Questions and MCQs
Question 711: Which of the following does not cause hardness of water?
- A. Calcium bicarbonate
- B. Magnesium bicarbonate
- C. Calcium carbonate (Correct Answer)
- D. Calcium sulphate
Explanation: ***Calcium carbonate*** - Calcium carbonate (CaCO₃) in its **pure solid form has very low solubility** in water (~15 mg/L), making it the least likely of these compounds to directly contribute to water hardness. - While CaCO₃ can react with dissolved CO₂ to form soluble calcium bicarbonate, **pure calcium carbonate itself tends to precipitate out** as scale or sediment rather than remaining dissolved as ions that cause hardness. - This makes it the correct answer as the compound that **does not directly cause hardness** among the options listed. *Calcium bicarbonate* - **Calcium bicarbonate [Ca(HCO₃)₂] is highly soluble** in water and readily dissociates into Ca²⁺ and HCO₃⁻ ions. - This dissolved compound is a **primary cause of temporary hardness** in water, which can be removed by boiling. *Magnesium bicarbonate* - Similar to calcium bicarbonate, **magnesium bicarbonate [Mg(HCO₃)₂] is soluble** in water. - Its presence as dissolved Mg²⁺ ions contributes significantly to **temporary hardness**. *Calcium sulphate* - **Calcium sulphate (CaSO₄) is moderately soluble** in water. - It is a common cause of **permanent hardness** in water, as it cannot be removed by boiling and remains dissolved.
Question 712: Which among the following is an active form of chlorination?
- A. Hypochlorite ion
- B. Hydrogen chloride
- C. Hypochlorous acid (Correct Answer)
- D. Chloride ion
Explanation: ***Hypochlorous acid*** - **Hypochlorous acid (HOCl)** is the most potent and effective disinfectant form of chlorine in water due to its uncharged nature, allowing it to penetrate cell membranes easily. - Its high oxidizing potential enables it to rapidly destroy enzymes and structural components of microorganisms, making it the primary active agent in chlorination for water purification. *Hypochlorite ion* - The **hypochlorite ion (OCl-)** is also an active chlorine disinfectant, but it is less effective than hypochlorous acid. - Being negatively charged, it has greater difficulty penetrating the negatively charged cell walls of microorganisms, especially at lower pH levels where the non-ionized HOCl predominates. *Hydrogen chloride* - **Hydrogen chloride (HCl)** is a strong acid and does not possess direct disinfectant properties in the same way as hypochlorous acid or hypochlorite ions. - While it can lower the pH of water, which might influence the HOCl/OCl- equilibrium, it is not an active chlorinating agent itself. *Chloride ion* - The **chloride ion (Cl-)** is a stable, non-oxidizing ion that results from the dissociation of chlorine compounds or salts like NaCl [1]. - It has no disinfectant properties and is not involved in the active killing of microorganisms during chlorination [1].
Question 713: In water testing from a well using Horrock's apparatus, blue color appears from the 4th cup onwards. What is the amount of bleaching powder required to disinfect 75000 litres of water?
- A. 1600 gm
- B. 2000 gm
- C. 1300 gm
- D. 100 gm (Correct Answer)
Explanation: ***100 gm*** - In **Horrock's apparatus** test, blue color appearing from the 4th cup indicates a **chlorine demand of 0.4 ppm (0.4 mg/L)** for the water sample. - **Total chlorine required** = 0.4 mg/L × 75,000 L = **30,000 mg = 30 gm** of pure chlorine. - Standard bleaching powder contains **30% available chlorine**, so: **Bleaching powder needed = 30 gm ÷ 0.30 = 100 gm**. - This is the scientifically accurate amount for disinfecting 75,000 liters of water with 0.4 ppm chlorine demand. *1000 gm* - This represents a **10-fold excess** over the actual requirement of 100 gm based on the measured chlorine demand. - Using 1000 gm would result in severe **over-chlorination** (4 ppm instead of 0.4 ppm), causing strong unpleasant taste, odor, and potential health concerns. *1600 gm* - This amount represents **16 times the required dose**, leading to dangerously high chlorine levels in the water. - Such excessive chlorination would make the water unpalatable and potentially toxic to consumers. *2000 gm* - This represents a **20-fold excess**, providing extreme and harmful over-disinfection. - Such excessive amounts could lead to **chlorine toxicity** and would be wasteful and harmful to consumers. *1300 gm* - This amount exceeds the calculated requirement by **13 times**, providing unnecessary and harmful over-disinfection. - The precise calculation based on **0.4 ppm chlorine demand** and **75,000 L volume** yields exactly **100 gm**, not 1300 gm.
Question 714: Which indicator is used in Horroch's apparatus?
- A. Potassium permanganate
- B. Bleaching powder
- C. Soda-lime
- D. Starch iodine (Correct Answer)
Explanation: ***Starch iodine*** - Horroch's apparatus is specifically designed for testing the **sterilizing efficiency of hypochlorite solutions** in dairies. - **Starch iodine** (starch-iodide paper) is used as an indicator because it reacts with residual free chlorine to produce a **blue-black color**, which confirms that adequate free chlorine is present for effective sterilization. - The principle: Free chlorine oxidizes iodide to iodine, which then reacts with starch to give the characteristic blue color. *Bleaching powder* - **Bleaching powder** (calcium hypochlorite) is the active ingredient in hypochlorite sterilizing solutions being tested, not an indicator itself. - It's the substance whose sterilizing efficacy is being evaluated using the apparatus. *Soda-lime* - **Soda-lime** is primarily used as an absorbent for **carbon dioxide (CO2)** and other acidic gases in various laboratory and anesthetic applications. - It has no role as an indicator in Horroch's apparatus for testing hypochlorite solutions. *Potassium permanganate* - **Potassium permanganate** is a strong oxidizing agent often used as an indicator in redox titrations, as its deep purple color disappears when reduced. - It is not suitable for indicating residual chlorine in Horroch's test, which specifically relies on the starch-iodine reaction.
Question 715: Waste Sharps should be disposed in ?
- A. Black bag
- B. Yellow bag (Correct Answer)
- C. None of the options
- D. Blue bag
Explanation: ***Yellow bag (Historical answer per BMW Rules 1998)*** - Under the **Biomedical Waste Management Rules 1998** (applicable at the time of NEET-PG 2015), **sharps waste** including needles, syringes, and scalpels were disposed in **yellow puncture-proof containers**. - This was the correct answer when this question was asked in the 2015 examination. - **Current Guidelines (BMW Rules 2016):** Sharps are now disposed in **white/translucent puncture-proof containers**, NOT yellow bags. Yellow bags are currently used for soiled infectious waste like dressings and body fluid-contaminated materials. *Black bag* - **Black bags** are used for **general non-hazardous waste** that poses no biological risk. - Disposing of sharps in black bags creates serious **risk of needlestick injuries** and potential transmission of bloodborne pathogens. *None of the options* - This is incorrect because there is a specific, regulated method for disposing of sharps in healthcare settings. - Proper waste segregation is **mandatory** for safety and regulatory compliance. *Blue bag* - **Blue bags** (per BMW Rules 2016) are used for disposal of **glassware** (broken or discarded) and **metallic body implants**. - Under older guidelines, blue bags were for certain pharmaceutical waste. - They are not designated for sharps disposal.
Question 716: At what fluoride concentration in drinking water does skeletal fluorosis typically occur?
- A. < 1.5 mg/L
- B. 1.5-3 mg/L
- C. 3-6 mg/L (Correct Answer)
- D. > 10 mg/L
Explanation: ***3-6 mg/L*** - Chronic exposure to drinking water with **fluoride concentrations of 3-6 mg/L** represents the **threshold range** where **early skeletal fluorosis** begins to manifest. - At concentrations **≥4 mg/L**, fluoride accumulation in bones exceeds the body's excretory capacity, leading to **increased bone density, osteosclerosis**, and early symptoms like **joint stiffness and bone pain**. - This range captures the **onset of skeletal manifestations**, though more severe changes occur at higher concentrations. *< 1.5 mg/L* - This range is **optimal for preventing dental caries** without causing adverse effects. - Fluoride concentrations below 1.5 mg/L are **safe** and do not cause skeletal or dental fluorosis. - Many water fluoridation programs target **0.5-1.0 mg/L** for dental health benefits. *1.5-3 mg/L* - This range primarily causes **dental fluorosis** (enamel mottling and discoloration) with chronic exposure, especially during tooth development. - **Skeletal fluorosis does not typically occur** at these concentrations, as the threshold for bone involvement is higher. - This is considered the range for cosmetic concerns rather than systemic skeletal disease. *> 10 mg/L* - Concentrations exceeding 10 mg/L lead to **severe, crippling skeletal fluorosis** with marked bone deformities, ligament calcification, and potential neurological complications. - This represents **advanced disease** rather than the typical onset of skeletal fluorosis. - Such high concentrations are found in endemic fluorosis regions with contaminated groundwater.
Question 717: Swajaldhara programme is associated with:
- A. Provision of safe drinking water (Correct Answer)
- B. Provision of food supplements for destitute women
- C. Provision of relief for victim of sexual abuse
- D. Provision of health care for sick tribals
Explanation: ***Provision of safe drinking water*** - The **Swajaldhara programme** was launched by the Government of India in 2002 to accelerate coverage of **drinking water supply** in rural areas - Its primary objective was to ensure access to **safe and sustainable drinking water sources** through community participation and decentralized management - The program emphasized local ownership with communities contributing 10% of project costs *Provision of food supplements for destitute women* - Food security programs for women fall under separate social welfare schemes like ICDS and PDS - The **Swajaldhara programme** was specifically focused on **water supply infrastructure**, not nutrition *Provision of relief for victim of sexual abuse* - Relief for victims of sexual abuse is addressed through **justice and women's safety initiatives** (e.g., One Stop Centres, Nirbhaya Fund) - This is unrelated to the water supply mandate of Swajaldhara *Provision of health care for sick tribals* - Health care for tribal populations is managed through dedicated programs under the Ministry of Health and Family Welfare - Swajaldhara's scope was limited to **rural drinking water infrastructure**, not healthcare delivery
Question 718: Which of the following statements about Culex larvae is correct?
- A. Rest parallel to surface water
- B. Long Palmate hair
- C. Siphon tube present (Correct Answer)
- D. All are false
Explanation: ***Siphon tube present*** - **Culex larvae** possess a prominent **siphon tube** at their posterior end, which is used for breathing by extending to the water surface. - This **siphon tube** is a key morphological feature that helps distinguish them from *Anopheles* larvae. *Rest parallel to surface water* - **Anopheles larvae** typically rest parallel to the water surface because they lack a long siphon and obtain oxygen directly through spiracles on their dorsal surface. - **Culex larvae**, due to their siphon tube, hang head-down at an angle from the water surface. *Long Palmate hair* - **Palmate hairs** are characteristic structures found on the abdomen of **Anopheles larvae** that help them float horizontally at the water surface. - **Culex larvae** do not possess well-developed palmate hairs. *All are false* - This statement is incorrect because the presence of a **siphon tube** is a defining characteristic of **Culex larvae**.
Question 719: Which of the following is not typically incinerated?
- A. Animal waste
- B. Broken thermometers (Correct Answer)
- C. Infected solid waste
- D. Human anatomical waste
Explanation: ***Broken thermometers*** - **Broken thermometers** often contain **mercury**, which, when incinerated, releases **toxic mercury vapor** into the atmosphere. - This poses a severe environmental and health hazard, requiring them to be handled as **hazardous waste** and recycled or disposed of in specialized facilities to prevent mercury release. *Human anatomical waste* - **Human anatomical waste**, including body parts, tissues, and recognizable organs, is highly infectious and poses significant biohazard risks. - **Incineration** is the preferred method for its disposal to ensure complete destruction of pathogens and reduce environmental contamination. *Animal waste* - **Animal waste** from research or healthcare settings (e.g., infected animal carcasses, bedding with animal excreta) is considered **biohazardous**. - **Incineration** effectively neutralizes pathogens and reduces the volume of such waste, preventing disease transmission. *Infected solid waste* - **Infected solid waste**, such as bandages, swabs, and disposable medical devices contaminated with blood or bodily fluids, carries a high risk of spreading infectious diseases. - **Incineration** at high temperatures ensures sterilization and safe disposal of these materials, destroying pathogenic microorganisms.
Question 720: Anemometer measures?
- A. Humidity
- B. Air velocity (Correct Answer)
- C. Room temperature
- D. Radiant temperature
Explanation: ***Air velocity*** - An **anemometer** is a device specifically designed to measure **wind speed** or the **velocity of air currents**. - It is commonly used in **meteorology**, HVAC (Heating, Ventilation, and Air Conditioning) systems, and aerodynamic research. *Humidity* - **Humidity** is measured by a **hygrometer**, which quantifies the amount of water vapor in the air. - An anemometer does not have the capability to measure atmospheric moisture content. *Room temperature* - **Room temperature** is measured by a **thermometer**, which detects the thermal energy of the air. - While air velocity can influence perceived temperature, the anemometer directly measures movement, not heat. *Radiant temperature* - **Radiant temperature** is measured by a **radiometer** or an **infrared thermometer**, which assesses the heat emitted by surfaces. - This is distinct from air movement and requires different sensor technology.
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