Environmental Health Practice Questions

Q: Recommended reflection factors include each of the following, except?

Roofs 40%. ### Explanation In environmental health and housing standards, **Reflection Factor** (or reflectance) refers to the percentage of light that is reflected by a surface. Proper reflectance is essential to ensure adequate indoor illumination, reduce glare, and minimize the need for artificial lighting. **Why "Roofs 40%" is the correct answer (the exception):** Standard guidelines for indoor lighting and housing (often cited in Park’s Textbook of Preventive and Social Medicine) focus on **internal surfaces** to optimize the distribution of light. **Roofs** are external structures and are not typically included in the standard "Reflection Factor" recommendations for indoor illumination. Furthermore, if the question refers to floors (a common distractor), the recommended reflection factor for **floors is 15–20%**, not 40%. **Analysis of Incorrect Options:** * **A. Ceilings (80%):** This is a standard recommendation. Ceilings should have the highest reflectance (white or off-white) to reflect light downward and provide uniform illumination. * **C. Walls (50–60%):** Walls require a moderate reflection factor. This range ensures the room stays bright without causing excessive glare for the occupants. * **D. Furniture (30–40%):** Furniture and office equipment should have a lower reflectance to provide visual comfort and contrast against walls and ceilings. **NEET-PG High-Yield Pearls:** * **Daylight Factor:** The ratio of indoor light at a specific point to the outdoor light available simultaneously. For dwellings, a daylight factor of **1%** is recommended; for kitchens, it is **2%**. * **Luminance/Illumination:** Measured in **Lux**. * **Standard for Housing:** The window area should be at least **1/10th to 1/5th** of the floor area to ensure adequate light and ventilation. * **Color Impact:** Light colors increase the reflection factor, while dark colors absorb light, necessitating higher wattage for artificial lighting.

Q: What is the average lifespan of a housefly?

1 month. **Explanation:** The housefly (*Musca domestica*) is a significant mechanical vector in community medicine. The correct answer is **1 month**, as the average lifespan of an adult housefly under optimal environmental conditions (warmth and food availability) typically ranges from **15 to 30 days**. **Why Option C is Correct:** In tropical climates like India, the life cycle from egg to adult is rapid (8–12 days). Once the adult emerges, its survival depends on temperature and humidity. While some may die sooner, the biological average cited in standard public health textbooks (like Park’s PSM) for the adult stage is approximately 30 days. **Why Other Options are Incorrect:** * **A & B (5–10 days):** These durations are too short for the average lifespan. While high predatory pressure or extreme heat may kill flies early, they are biologically capable of living much longer. * **D (1 year):** This is far beyond the physiological limit of a housefly. Only certain insects with diapause or hibernation stages live this long; houseflies have high metabolic rates and short reproductive cycles. **High-Yield Clinical Pearls for NEET-PG:** * **Transmission:** Houseflies act as **mechanical vectors** (carrying pathogens on their feet, body hairs, or through vomitus/faeces). They do not support the biological development of the pathogen. * **Diseases Spread:** Typhoid, paratyphoid, cholera, bacillary dysentery, amoebiasis, and helminthic infestations. * **Breeding Sites:** They prefer decaying organic matter, especially horse manure and human excreta. * **Control Measure of Choice:** Environmental sanitation (proper disposal of refuse and excreta) is more effective than chemical insecticides due to rapidly developing resistance.

Q: At what level of fluoride in drinking water does crippling fluorosis occur?

> 10 mg/litre. **Explanation:** The correct answer is **D (> 10 mg/litre)**. Fluoride is often called a "two-edged sword" because while it prevents dental caries at low concentrations, excessive intake leads to progressive toxic effects known as fluorosis. The severity of fluorosis is strictly dose-dependent: * **Dental Fluorosis:** Occurs at levels of **1.5–3 mg/L**. It manifests as "mottling" of enamel (chalky white patches or brownish discoloration). * **Skeletal Fluorosis:** Occurs with prolonged exposure to **3–10 mg/L**. It involves increased bone density (osteosclerosis) and calcification of ligaments. * **Crippling Fluorosis:** Occurs when levels exceed **10 mg/L**. This is the most severe form, characterized by permanent deformities, "poker back" (rigid spine), and severe neurological complications due to spinal cord compression. **Analysis of Incorrect Options:** * **A (0.5–0.8 mg/L):** This is the **optimal level** recommended for drinking water to prevent dental caries. * **B (1.5 mg/L):** This is the WHO upper limit for fluoride in drinking water. Beyond this, dental fluorosis begins. * **C (3–6 mg/L):** This range is associated with skeletal fluorosis but is not yet considered "crippling." **High-Yield Clinical Pearls for NEET-PG:** * **Safe Limit:** 0.5–0.8 mg/L (India) or up to 1.0 mg/L (WHO). * **Genu Valgum (Knock-knees):** A manifestation of endemic fluorosis seen in the "Nalgonda technique" context (though the technique itself is for defluoridation). * **Defluoridation:** The **Nalgonda Technique** uses alum and lime to remove fluoride. * **Biomarker:** Urinary fluoride levels are the most reliable indicator of recent fluoride exposure.

Q: The Coliform test is used to detect which type of contamination?

Water contamination. **Explanation:** The **Coliform test** is the standard microbiological procedure used to detect **water contamination**, specifically fecal pollution. Coliform bacteria (such as *E. coli*, *Klebsiella*, and *Enterobacter*) are normal inhabitants of the intestinal tract of humans and warm-blooded animals. Their presence in a water sample serves as a "surrogate marker" or **indicator organism**, signaling that the water has been contaminated with fecal matter and may contain dangerous enteric pathogens like *Salmonella typhi*, *Vibrio cholerae*, or Hepatitis A. **Why other options are incorrect:** * **Air pollution:** Monitored using parameters like PM2.5, PM10, Sulfur dioxide, and Nitrogen dioxide levels. Biological indicators for air are rarely used in standard testing. * **Sound pollution:** Measured in Decibels (dB) using a Sound Level Meter. It is a physical hazard, not a biological one. **High-Yield Clinical Pearls for NEET-PG:** * **Indicator Organisms:** *E. coli* is the best indicator of **recent** fecal contamination because it does not survive long outside the gut. *Streptococcus faecalis* and *Clostridium perfringens* indicate remote/past contamination. * **Presumptive Coliform Count:** Usually performed using the Multiple Tube Fermentation method to derive the **Most Probable Number (MPN)**. * **WHO Standard:** For drinking water, coliforms must be **zero per 100 ml** of water. * **OT Test (Orthotolidine):** Do not confuse this with the Coliform test; OT is used to detect **free and combined chlorine** in water.

Q: In a slow sand filter, what element is responsible for yielding bacteria-free water?

Vital layer. ### Explanation The **Slow Sand Filter** (or biological filter) is a cornerstone of large-scale water purification. The correct answer is the **Vital Layer**, also known as the **Schmutzdecke**, biological layer, or zoogleal layer. **Why the Vital Layer is Correct:** The vital layer is a slimy, gelatinous membrane that forms on the surface of the sand bed over a period of a few days. It consists of algae, plankton, diatoms, and bacteria. This layer is the "heart" of the filter because it performs the actual purification through: 1. **Biological Action:** Organic matter is oxidized by the bacteria in the layer. 2. **Mechanical Strainer:** It traps very fine particles. 3. **Bacteriological Action:** It is responsible for removing **98% to 99% of bacteria** and reducing the organic content of the water. **Why Other Options are Incorrect:** * **Valve:** These are mechanical components used to regulate the flow of water and maintain a constant rate of filtration; they have no biological purification properties. * **Supernatant Water:** This is the 1–1.5 meter column of raw water above the sand. Its primary role is to provide a constant head of pressure and allow time (3–12 hours) for sedimentation; it does not filter bacteria. * **Under-drainage System:** Located at the bottom of the filter, this consists of porous pipes that collect the filtered water and provide support for the filter medium. It does not contribute to the removal of pathogens. **High-Yield Facts for NEET-PG:** * **Rate of Filtration:** 0.1 to 0.4 $m^3/m^2/hour$ (Slow sand filters are roughly 20–50 times slower than Rapid Sand Filters). * **Effective Size of Sand:** 0.2 to 0.35 mm. * **Cleaning:** Done by **scraping** the top layer of sand (unlike Rapid Sand Filters, which use backwashing). * **Efficiency:** Highly efficient at removing bacteria but less effective at removing high turbidity compared to rapid sand filters.

Q: The soiling index is a measure for what type of pollution?

Air pollution. **Explanation:** The **Soiling Index**, also known as the **Coefficient of Haze (COH)**, is a traditional method used to measure **Air Pollution**, specifically the concentration of suspended particulate matter (smoke) in the atmosphere. 1. **Why Air Pollution is Correct:** The index is determined by drawing a known volume of air through a filter paper (usually for 24 hours). The resulting dark spot or "soiling" on the paper is measured using a reflectometer or densitometer. The degree of darkness (optical density) correlates directly with the amount of smoke and particulate matter present in the air. It is a key indicator of the aesthetic and physical "dirtiness" of urban air. 2. **Why Other Options are Incorrect:** * **Water Pollution:** Measured using parameters like BOD (Biochemical Oxygen Demand), COD, and dissolved oxygen, not by filter paper staining. * **Faecal Contamination:** Assessed via bacteriological indicators, primarily the **Coliform count** (E. coli) or the Multiple Tube Method (MPN). * **Milk Contamination:** Evaluated using the **Methylene Blue Reduction Test (MBRT)** for bacterial load or Phosphatase tests for pasteurization efficiency. **High-Yield Clinical Pearls for NEET-PG:** * **Indicator of Air Pollution:** While the Soiling Index measures smoke, **Sulphur Dioxide ($SO_2$)** is considered the best single indicator for air pollution levels in general. * **Air Quality Index (AQI):** Modern monitoring uses AQI, which tracks five major pollutants: Ground-level ozone, particulate matter (PM2.5/PM10), CO, $SO_2$, and $NO_2$. * **Lichens:** These are biological indicators of air pollution (sensitive to $SO_2$).

Q: When was the International Drinking Water Supply and Sanitation Decade Programme launched?

1981. **Explanation:** The **International Drinking Water Supply and Sanitation Decade (IDWSSD)** was a global initiative launched by the United Nations to provide universal access to safe drinking water and adequate sanitation. **1. Why 1981 is Correct:** The decade was officially launched in **1981** and spanned from **1981 to 1990**. It was a direct outcome of the 1977 UN Water Conference in Mar del Plata, Argentina. The primary goal was to reduce the burden of water-borne diseases (like cholera and typhoid) and improve hygiene in developing nations. In India, this led to the accelerated implementation of the National Water Supply and Sanitation Programme. **2. Why Other Options are Incorrect:** * **1975:** This year is associated with the launch of the **Integrated Child Development Services (ICDS)** scheme in India, not water sanitation. * **1978:** This is a landmark year in public health for the **Alma-Ata Declaration**, which established the concept of "Primary Health Care" (PHC). While PHC includes "safe water and basic sanitation" as one of its eight essential components, the specific Decade Programme was not launched until 1981. * **1984:** This year is significant in environmental health for the **Bhopal Gas Tragedy**, but it does not mark the start of any major international water decade. **3. High-Yield Clinical Pearls for NEET-PG:** * **Target:** The decade aimed for 100% coverage of safe water and 50-80% coverage of sanitation. * **Current Context:** The IDWSSD was a precursor to the **Millennium Development Goals (MDGs)** and the current **Sustainable Development Goal (SDG) 6**, which aims for "Clean Water and Sanitation for all" by 2030. * **India Specific:** The **Jal Jeevan Mission (2019)** is the current flagship program in India aiming to provide Functional Household Tap Connections (FHTC) to every rural household by 2024.

Question 1

Which of the following is resistant to DDT, except?

Accepted Answer

Phlebotomus

Answer

Culex fatigans

Answer

Anopheles stephensi

Answer

Musca domestica

Question 2

Recommended reflection factors include each of the following, except?

Accepted Answer

Roofs 40%

Answer

Ceilings 80%

Answer

Walls 50 to 60%

Answer

Furniture 30 to 40%

Question 3

What is the average lifespan of a housefly?

Accepted Answer

1 month

Answer

5 days

Answer

10 days

Answer

1 year

Question 4

At what level of fluoride in drinking water does crippling fluorosis occur?

Accepted Answer

> 10 mg/litre

Answer

0.5-0.8 mg/litre

Answer

1.5 mg/litre

Answer

3-6 mg/litre

Question 5

The Coliform test is used to detect which type of contamination?

Accepted Answer

Water contamination

Answer

Air pollution

Answer

Sound pollution

Answer

None of the above

Question 6

In a slow sand filter, what element is responsible for yielding bacteria-free water?

Accepted Answer

Vital layer

Answer

Valve

Answer

Supernatant water

Answer

Under-drainage system

Question 7

The soiling index is a measure for what type of pollution?

Accepted Answer

Air pollution

Answer

Water pollution

Answer

Faecal contamination

Answer

Milk contamination

Question 8

When was the International Drinking Water Supply and Sanitation Decade Programme launched?

Accepted Answer

1981

Answer

1975

Answer

1978

Answer

1984

Question 9

What is the number of holes per square inch of a standard mosquito net?

Accepted Answer

150

Answer

100

Answer

250

Answer

175

Question 10

All of the following are indicators of air pollution except?

Accepted Answer

Smoking index

Answer

CO

Answer

SO2

Answer

Soiling index

Environmental Health — MCQs

Environmental Health — MCQs

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