Environmental Health Practice Questions

Q: What is the percentage of available chlorine in bleaching powder?

33%. **Explanation:** **Bleaching powder (Chlorinated lime)** is a chemical compound (Calcium hypochlorite) used extensively in public health for the disinfection of drinking water and sanitary disposal of waste. 1. **Why 33% is Correct:** Freshly manufactured bleaching powder contains approximately **33% available chlorine**. This "available chlorine" is the active oxidizing agent responsible for killing pathogens. Over time, bleaching powder is unstable; it loses its chlorine content when exposed to air, light, or moisture. For effective water disinfection, the powder used must have a chlorine content of at least 20% to 33%. 2. **Analysis of Incorrect Options:** * **10%:** This is too low for fresh bleaching powder. If the chlorine content falls below 20%, the powder is considered "weak" or "spent" and is generally discarded for large-scale water treatment. * **66%:** This value is associated with **High-Test Hypochlorite (HTH)** or Perchloron. HTH is a more stable, concentrated form of calcium hypochlorite containing 60–70% available chlorine. * **95%:** This concentration is not found in bleaching powder. Pure elemental chlorine gas or liquid chlorine approaches this level of purity but is not used in powder form. **High-Yield Clinical Pearls for NEET-PG:** * **Horrocks' Apparatus:** Used to estimate the dose of bleaching powder required to disinfect a specific volume of water. * **Contact Time:** For effective chlorination, the water must be in contact with chlorine for at least **30 to 60 minutes**. * **Orthotolidine (OT) Test:** Used to detect **Free Residual Chlorine** (ideal level: 0.5 mg/L after 1 hour). * **Storage:** Bleaching powder should be stored in a **cool, dark, and dry place** in airtight containers to prevent the loss of chlorine.

Q: What is the confirmatory test for coliform count?

Eijkman test. ### Explanation **1. Why the Correct Answer is Right:** The **Eijkman test** (also known as the Differential Coliform Test) is the confirmatory test used to identify fecal coliforms, specifically *Escherichia coli*, in water samples. While the presumptive coliform count (Multiple Tube Fermentation) suggests the presence of the coliform group, the Eijkman test confirms fecal origin. It involves incubating the sample in MacConkey broth at a specific temperature of **44°C**. The production of **gas** at this temperature is diagnostic for *E. coli*, distinguishing it from non-fecal coliforms which cannot produce gas at such high temperatures. **2. Why the Other Options are Incorrect:** * **Casoni’s test:** This is an immediate hypersensitivity skin test used for the diagnosis of **Hydatid disease** (*Echinococcus granulosus*). It has largely been replaced by serological tests and imaging. * **Nitrate test:** This test detects the ability of bacteria to reduce nitrate to nitrite. It is commonly used to identify members of the *Enterobacteriaceae* family and is a component of the **Urinalysis** dipstick to screen for UTIs. * **Urease test:** This biochemical test identifies organisms that produce the enzyme urease (e.g., *Proteus*, *Klebsiella*, and *H. pylori*), which hydrolyzes urea into ammonia and CO₂. **3. High-Yield Clinical Pearls for NEET-PG:** * **Indicator Organism:** *E. coli* is the best indicator of **recent** fecal contamination of water. * **Presumptive Coliform Count:** Performed using the Multiple Tube Method; results are expressed as the **Most Probable Number (MPN)** per 100 ml. * **WHO Standards:** For drinking water, *E. coli* or thermotolerant coliform bacteria must **not be detectable in any 100 ml sample**. * **Coliform Characteristics:** Gram-negative, non-spore-forming bacilli that ferment lactose with the production of acid and gas within 48 hours at 35°C.

Q: Anatomical waste is discarded in which color bag?

Yellow. **Explanation:** The management of Biomedical Waste (BMW) is governed by the **BMW Management Rules (2016)** and its subsequent amendments. According to these guidelines, **Yellow Bags** are designated for highly infectious, non-plastic waste that is primarily disposed of via incineration or deep burial. **Why Yellow is Correct:** Anatomical waste (human tissues, organs, body parts, and fetuses) along with soiled waste (blood-soaked cotton, dressings), expired medicines, and chemical waste are categorized under the Yellow category. These materials require high-temperature incineration to ensure complete destruction of pathogens and organic matter. **Analysis of Incorrect Options:** * **Red Bag:** Used for **Recyclable** plastic waste (e.g., IV sets, catheters, gloves, syringes without needles). These undergo autoclaving/microwaving followed by shredding. * **Black Bag/Bin:** Previously used for general municipal waste; however, under current rules, general non-infectious waste is discarded in **Green** (biodegradable) and **Blue** (non-biodegradable) bins. * **Blue Box/Pouch:** Specifically reserved for **Glassware** (broken or intact vials, ampoules) and metallic body implants. **High-Yield Clinical Pearls for NEET-PG:** * **Cytotoxic drugs:** Must be discarded in **Yellow** bags/containers labeled with the "Cytotoxic" symbol. * **Sharps (Needles/Scalpels):** Always go into a **White** translucent, puncture-proof container. * **Chlorinated plastic bags:** These are strictly prohibited for incineration; hence, BMW bags must be non-chlorinated. * **Pre-treatment:** Laboratory waste, blood bags, and microbiology waste must be pre-treated (autoclaved) before being placed in the Yellow bag.

Q: What is the basic minimum illumination required for satisfactory vision?

15-20 foot candles. ### Explanation **1. Understanding the Correct Answer (Option B: 15-20 foot candles)** In Community Medicine and Environmental Health, illumination is measured to ensure visual comfort and prevent eye strain. According to standard public health guidelines (often cited from Park’s Textbook of Preventive and Social Medicine), the **basic minimum illumination** required for satisfactory vision—allowing for comfortable reading and general work without fatigue—is **15 to 20 foot candles**. This level ensures adequate contrast and detail recognition for the human eye under standard conditions. **2. Analysis of Incorrect Options** * **Option A (10-15 foot candles):** This level is considered insufficient for tasks requiring sustained mental concentration or detailed visual work. It may be adequate for corridors or storage areas but falls below the "satisfactory" threshold for general functional vision. * **Options C & D (20-30 foot candles):** While these levels provide excellent visibility, they exceed the *basic minimum* requirement. These higher intensities are typically recommended for specialized tasks involving fine detail, such as precision engineering, sewing, or surgical procedures, rather than general satisfactory vision. **3. High-Yield Clinical Pearls for NEET-PG** * **Units of Measurement:** * **Luminous Intensity:** Measured in **Candela**. * **Luminous Flux:** Measured in **Lumens**. * **Illumination (Illuminance):** Measured in **Lux** (metric) or **Foot-candles** (imperial). * *Conversion:* **1 Foot-candle ≈ 10.76 Lux.** * **Standards for Schools:** The recommended illumination for classrooms is generally higher, around **15-30 foot candles** (or 150-300 Lux) to prevent myopia and asthenopia (eye strain) in children. * **Factors Affecting Lighting:** Satisfactory lighting depends on five factors: Intensity, Distribution, Absence of Glare, Absence of Sharp Shadows, and Color of light.

Q: Which of the following diseases is NOT caused by exposure to cold?

Trench fever. **Explanation:** The correct answer is **Trench fever** because it is an infectious disease, not a physical injury caused by cold exposure. 1. **Trench Fever (Correct Option):** This is a bacterial infection caused by ***Bartonella quintana*** and is transmitted by the **human body louse** (*Pediculus humanus corporis*). It gained prominence during World War I. While the name is similar to "Trench foot," its etiology is biological (vector-borne) rather than environmental/thermal. 2. **Why other options are incorrect (Cold Injuries):** * **Trench Foot:** A non-freezing cold injury caused by prolonged exposure to damp, unsanitary, and cold conditions (just above freezing). It leads to nerve and blood vessel damage. * **Chilblains (Pernio):** Characterized by localized inflammatory lesions (itching, redness, swelling) resulting from an abnormal vascular response to repeated exposure to cold, non-freezing damp air. * **Frostbite:** A freezing cold injury where the skin and underlying tissues actually freeze (ice crystal formation), typically occurring at temperatures below 0°C. **High-Yield NEET-PG Pearls:** * **Classification of Cold Stress:** * **Non-freezing:** Chilblains, Trench foot, Erythrocyanosis. * **Freezing:** Frostbite. * **General:** Hypothermia (Core temp <35°C). * **Rule of Thumb:** If the condition name includes "Fever," look for a pathogen (e.g., *B. quintana*). If it includes "Bite" or "Blain," it is usually a physical environmental injury. * **Bartonella quintana** is also associated with Bacillary Angiomatosis in HIV patients.

Question 1

What is the percentage of available chlorine in bleaching powder?

Accepted Answer

33%

Answer

10%

Answer

66%

Answer

95%

Question 2

An epidemiologic study of a community shows an increased incidence of basal cell and squamous cell carcinomas in adults. These lesions are distributed predominantly on palms and soles. Analysis of groundwater pumped from wells for drinking shows increased levels of heavy metal used in pressure-treated lumber (with a greenish hue), insecticides, and herbicides. Which of the following metals is most likely implicated by this study?

Accepted Answer

Arsenic

Answer

Beryllium

Answer

Cadmium

Answer

Lead

Question 3

Disinfection of water is not required if the source is from which of the following?

Accepted Answer

Tube well

Answer

Step well

Answer

Draw well

Answer

River

Question 4

What is a feature of a slow sand filter compared to a rapid sand filter?

Accepted Answer

Requires more time for purification

Answer

Occupies less space

Answer

Requires highly skilled operation

Answer

Results in poor bacterial quality of water

Question 5

What is the confirmatory test for coliform count?

Accepted Answer

Eijkman test

Answer

Casoni's test

Answer

Nitrate test

Answer

Urease test

Question 6

If the second cup of Horrock's apparatus shows a blue color after 3 drops of starch-iodine indicator, what dose of bleaching powder is required to disinfect 910 L?

Accepted Answer

8 gm

Answer

30 gm

Answer

4 gm

Answer

15 gm

Question 7

Anatomical waste is discarded in which color bag?

Accepted Answer

Yellow

Answer

Red

Answer

Black

Answer

Blue

Question 8

What is the basic minimum illumination required for satisfactory vision?

Accepted Answer

15-20 foot candles

Answer

10-15 foot candles

Answer

20-25 foot candles

Answer

25-30 foot candles

Question 9

Which of the following health hazards are associated with environmental lead exposure?

Accepted Answer

Lowering of IQ in children, reduced RBC survival and reduced heme biosynthesis, and higher rates of miscarriages, stillbirths, and preterm deliveries

Answer

Lowering of IQ in children, lowering of systolic blood pressure, reduced RBC survival and reduced heme biosynthesis, and higher rates of miscarriages, stillbirths, and preterm deliveries

Answer

Lowering of IQ in children and lowering of systolic blood pressure

Answer

Lowering of IQ in children, lowering of systolic blood pressure, and reduced RBC survival and reduced heme biosynthesis

Question 10

Which of the following diseases is NOT caused by exposure to cold?

Accepted Answer

Trench fever

Answer

Trench feet

Answer

Chilblains

Answer

Frost bite

Environmental Health — MCQs

Environmental Health — MCQs

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