Environmental Health Practice Questions

Q: Which of the following is used for recording very low air velocity?

Kata thermometer. **Explanation:** The **Kata thermometer** is the instrument of choice for measuring **very low air velocities** (cooling power of air), particularly in indoor environments or workplaces. It is an alcohol thermometer with a large bulb that is heated in hot water until the alcohol rises into the top reservoir. The time taken for the alcohol to fall from 100°F to 95°F (or 38°C to 35°C) is recorded. This "cooling time" is then used to calculate air velocity using a specific formula. It is sensitive enough to detect air movements as low as 10 feet per minute, which other instruments might miss. **Analysis of Incorrect Options:** * **A. Globe thermometer:** Used to measure **mean radiant heat** (infrared radiation). It consists of a thermometer encased in a hollow copper sphere painted matte black. * **C. Anemometer:** Used to measure **high air velocities**, typically for outdoor meteorological purposes (wind speed). It is generally not sensitive enough for the very low air currents found indoors. * **D. Sling psychrometer:** Used to measure **humidity** (relative humidity). It consists of two thermometers (dry bulb and wet bulb) that are whirled in the air. **High-Yield Pearls for NEET-PG:** * **Kata Thermometer:** Primarily measures the "cooling power" of air; used for assessing ventilation. * **Silvered Kata Thermometer:** Specifically used to eliminate the effect of radiation, focusing purely on air velocity. * **Psychrometer:** Measures humidity; the difference between the dry and wet bulb readings is the "wet-bulb depression." * **Corrective Effective Temperature (CET):** An index that combines air temperature, humidity, and air velocity, while also accounting for **radiant heat** (unlike the standard Effective Temperature).

Q: What is the safe limit of Fluorine in drinking water?

0.5-0.8 mg/L. **Explanation:** The concentration of fluoride in drinking water is a classic "double-edged sword" in public health. The correct answer is **0.5–0.8 mg/L** because this range is considered the "optimal" or safe level that provides maximum protection against dental caries while minimizing the risk of dental fluorosis. * **Why 0.5–0.8 mg/L is correct:** At this concentration, fluoride promotes remineralization of tooth enamel and inhibits bacterial enzymes. According to the WHO and Indian standards (CPHEEO), the recommended level for dental health is approximately 0.5–0.8 mg/L (often rounded to 1 mg/L as the upper ideal limit). * **Why A (0.2–0.5 mg/L) is wrong:** This level is too low to provide significant protection against dental caries (tooth decay). * **Why C & D (0.8–2.0 mg/L) are wrong:** When fluoride levels exceed **1.5 mg/L**, the risk of **Dental Fluorosis** (mottling of enamel) increases significantly. Levels above **3–10 mg/L** lead to **Skeletal Fluorosis**, characterized by bone deformities and "Knock-knee" syndrome (Genu valgum). **High-Yield NEET-PG Pearls:** 1. **Dental Fluorosis:** Occurs when intake is >1.5 mg/L. It is a cosmetic index of fluoride toxicity. 2. **Skeletal Fluorosis:** Occurs with prolonged intake of >3.0–6.0 mg/L. 3. **Nalgonda Technique:** The method of choice for **defluoridation** at the domestic/community level, using alum, lime, and bleaching powder. 4. **Biomarkers:** Urinary fluoride is the best indicator of recent fluoride exposure. 5. **Safe Limit (BIS):** The Bureau of Indian Standards (BIS) accepts 1.0 mg/L as the permissible limit, extendable to 1.5 mg/L if no alternative source is available.

Q: Which of the following organophosphorus compounds is considered the least toxic?

Malathion. **Explanation:** The correct answer is **Malathion**. The toxicity of organophosphorus (OP) compounds is generally determined by their rate of metabolism and detoxification within the body. **Why Malathion is the correct answer:** Malathion is considered the least toxic OP compound for mammals because of a specific biochemical mechanism involving **carboxylesterase enzymes**. In humans and mammals, these enzymes rapidly hydrolyze malathion into non-toxic metabolites. In contrast, insects lack high levels of these enzymes, making malathion highly toxic to them but relatively safe for humans. This "selective toxicity" makes it a preferred agent for public health measures, such as space spraying for mosquito control. **Analysis of Incorrect Options:** * **DDT (Dichlorodiphenyltrichloroethane):** This is an **organochlorine**, not an organophosphorus compound. While it has low acute toxicity, it is notorious for environmental persistence and bioaccumulation. * **Paris Green (Copper acetoarsenite):** This is an **inorganic arsenical** compound used historically as a larvicide. It is highly toxic to humans if ingested. * **Parathion:** This is one of the **most toxic** organophosphorus compounds. Unlike malathion, it is rapidly absorbed through the skin and lungs and is highly potent, leading to severe cholinergic crises. It is generally banned or strictly restricted for agricultural use. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism of Action:** OP compounds inhibit **Acetylcholinesterase (AChE)**, leading to an accumulation of acetylcholine and a "cholinergic crisis" (SLUDGE syndrome). * **Antidote of Choice:** **Atropine** (to reverse muscarinic effects) and **Pralidoxime/2-PAM** (to reactivate the enzyme, if given before "aging" occurs). * **Public Health Use:** Malathion is the insecticide of choice for **Ultra Low Volume (ULV)** fogging/space spraying to control adult mosquitoes during epidemics (e.g., Dengue).

Q: Exposure to noise above which level causes permanent hearing loss?

160 dB. **Explanation:** The correct answer is **160 dB**. This question tests the distinction between chronic noise-induced hearing loss and acute acoustic trauma. **1. Why 160 dB is correct:** In environmental health, noise levels are categorized by their physiological impact. Exposure to noise at or above **160 dB** is considered the threshold for **instantaneous, permanent hearing loss**. At this intensity, the mechanical energy is so great that it causes immediate physical rupture of the tympanic membrane and permanent destruction of the delicate hair cells in the Organ of Corti (acoustic trauma). **2. Analysis of Incorrect Options:** * **90 dB (Option A):** This is the maximum permissible noise level for an 8-hour work shift (as per WHO and Indian Factory Act). Chronic exposure above this level leads to gradual, progressive hearing loss, but not immediate permanent damage. * **100 dB (Option B):** This level causes significant discomfort and, with prolonged exposure, can lead to a "temporary threshold shift." * **125 dB (Option C):** This is the threshold of **pain**. While extremely loud, it may not cause immediate permanent deafness in all individuals compared to the 160 dB threshold. **3. High-Yield Clinical Pearls for NEET-PG:** * **Threshold of Hearing:** 0 dB. * **Normal Conversation:** 60 dB. * **Occupational Exposure Limit:** 85–90 dB for 8 hours. * **Audiometric Finding:** Noise-induced hearing loss typically shows a characteristic "dip" or notch at **4000 Hz** (Boiler-maker's notch). * **Rule of thumb:** For every 5 dB increase in noise level, the permissible exposure time is halved.

Q: Indoor smoke contains a range of health-damaging pollutants, which include all of the following except?

Lead oxide. **Explanation:** The question focuses on the composition of **Indoor Air Pollution (IAP)**, primarily caused by the combustion of solid fuels (biomass like wood, dung, and crop residues) and tobacco smoke. **Why Lead Oxide is the correct answer:** Lead oxide is not a typical byproduct of biomass combustion or indoor tobacco smoke. Lead contamination in the environment is usually associated with **outdoor sources** such as industrial emissions, leaded gasoline (historically), or specific indoor sources like **lead-based paints** and battery recycling. It is not a gaseous or particulate pollutant naturally released during the burning of organic indoor fuels. **Analysis of incorrect options:** * **Carbon Monoxide (CO):** A major product of incomplete combustion of carbon-based fuels. It is a significant indoor hazard, leading to carboxyhemoglobin formation and tissue hypoxia. * **Sulfur Oxides (SOx):** Produced during the burning of coal and certain biomass fuels. They are potent respiratory irritants that contribute to chronic obstructive pulmonary disease (COPD). * **Benzopyrenes:** These are Polycyclic Aromatic Hydrocarbons (PAHs) found in wood smoke and tobacco smoke. They are highly **carcinogenic** and are linked to an increased risk of lung cancer. **High-Yield Clinical Pearls for NEET-PG:** * **Major Indoor Pollutants:** Include Respirable Particulate Matter (RPM), CO, Nitrogen dioxide (NO2), SO2, Formaldehyde, and PAHs. * **Health Impact:** Indoor smoke is a leading risk factor for **Acute Respiratory Infections (ARI)** in children and **COPD/Cor Pulmonale** in women in developing countries. * **Indicator:** The most common indicator used to measure indoor air pollution is **Particulate Matter (PM2.5 and PM10)**. * **Radon:** Another critical indoor pollutant (from soil/building materials), which is the second leading cause of lung cancer after smoking.

Q: What is the optimal temperature for plasma pyrolysis?

1200°C. **Explanation:** **Plasma Pyrolysis** is an advanced, eco-friendly waste disposal technology that uses a plasma torch to convert organic matter into syngas and inorganic matter into inert slag. It is particularly effective for treating hazardous and biomedical waste. 1. **Why 1200°C is Correct:** In plasma pyrolysis, the core of the plasma arc can reach temperatures up to 10,000°C. However, the **optimal operating temperature** for the effective thermal disintegration of complex medical waste into elemental components (carbon, hydrogen, oxygen) is generally cited as **1200°C**. At this temperature, the process ensures the complete destruction of pathogens and toxic compounds like dioxins and furans, which are common byproducts of lower-temperature incineration. 2. **Analysis of Incorrect Options:** * **700°C (Option A):** This is too low for plasma technology. It is closer to the temperature range used in conventional low-temperature incineration or basic pyrolysis, which may not fully decompose hazardous chemicals. * **1000°C (Option B):** While high, this is the standard requirement for the secondary chamber of a regular incinerator. Plasma pyrolysis aims for higher thermal efficiency to ensure zero toxic emissions. * **1500°C (Option D):** While plasma torches can exceed this temperature, 1200°C is the recognized "optimal" threshold for standard waste treatment protocols in medical literature. **High-Yield NEET-PG Pearls:** * **Plasma Pyrolysis vs. Incineration:** Unlike incineration, plasma pyrolysis occurs in an **oxygen-starved environment**, preventing the formation of dioxins and furans. * **End Products:** The process produces **Syngas** (CO + H₂), which can be used for energy, and **Vitrified Slag**, which is non-leachable and safe for landfills. * **BMW Management:** It is considered the "Gold Standard" for disposing of anatomical waste and cytotoxic drugs where land availability is limited.

Q: What is the recommended level of fluorides in drinking water?

0.5 mg/L. **Explanation:** The correct answer is **0.5 mg/L**. Fluoride is often called a "double-edged sword" in public health because the margin between its beneficial and toxic effects is very narrow. 1. **Why 0.5 mg/L is correct:** According to the World Health Organization (WHO) and standard public health guidelines, the **optimal level** of fluoride in drinking water to prevent dental caries while minimizing the risk of dental fluorosis is approximately **0.5 to 0.8 mg/L**. In India, the recommended level is generally cited as 0.5–0.8 mg/L, making 0.5 mg/L the most appropriate choice among the options. At this concentration, fluoride promotes remineralization of enamel. 2. **Why other options are incorrect:** * **1.5 mg/L:** This is the **permissible upper limit** (WHO). Concentrations above this level significantly increase the risk of **Dental Fluorosis** (mottling of teeth). * **2.5 mg/L and 3.5 mg/L:** These levels are dangerously high. Chronic exposure to fluoride levels above 3.0–10.0 mg/L leads to **Skeletal Fluorosis**, characterized by bone deformities, ligament calcification, and "Genu Valgum" (knock-knees). **High-Yield NEET-PG Pearls:** * **Dental Fluorosis:** Occurs when fluoride >1.5 mg/L; affects teeth during the period of formation (calcification). * **Skeletal Fluorosis:** Occurs with long-term exposure to >3.0 mg/L. * **Defluoridation:** The **Nalgonda Technique** (using alum and lime) is the most common method used in India to remove excess fluoride. * **Biomarkers:** Urinary fluoride is the best indicator of recent fluoride exposure.

Q: What is considered strong sewage?

Biological oxygen demand >300 mg/L. ### Explanation **1. Understanding the Correct Answer (A):** Sewage strength is primarily determined by its **Biochemical Oxygen Demand (BOD)**, which measures the amount of dissolved oxygen needed by aerobic biological organisms to break down organic material in a water sample. In public health engineering, sewage is classified based on its BOD concentration: * **Strong Sewage:** BOD >300 mg/L * **Average Sewage:** BOD ~200 mg/L * **Weak Sewage:** BOD 200 mg/L):** This value represents "Average" or medium-strength sewage. While it is more concentrated than weak sewage, it does not meet the threshold for the "Strong" classification. * **Option C ( 150 mg/L):** This is a non-specific threshold that falls between the weak and average categories and is not a standard benchmark for classifying strong sewage. **3. High-Yield Facts for NEET-PG:** * **BOD Definition:** It is the amount of oxygen consumed by bacteria in **5 days at 20°C**. * **Chemical Oxygen Demand (COD):** Always higher than BOD; it measures both biodegradable and non-biodegradable organic matter. * **Suspended Solids:** Strong sewage typically contains suspended solids **>500 mg/L**. * **Efficiency:** A well-functioning sewage treatment plant should reduce the BOD of the effluent by at least **90%**. * **River Health:** If the BOD of a water body is high, the Dissolved Oxygen (DO) drops, leading to the death of aquatic life (Eutrophication).

Question 1

Which of the following is used for recording very low air velocity?

Accepted Answer

Kata thermometer

Answer

Globe thermometer

Answer

Anemometer

Answer

Sling psychrometer

Question 2

What is the safe limit of Fluorine in drinking water?

Accepted Answer

0.5-0.8 mg/L

Answer

0.2-0.5 mg/L

Answer

0.8-1.2 mg/L

Answer

1.2-2.0 mg/L

Question 3

Which of the following organophosphorus compounds is considered the least toxic?

Accepted Answer

Malathion

Answer

DDT

Answer

Paris green

Answer

Parathion

Question 4

Exposure to noise above which level causes permanent hearing loss?

Accepted Answer

160 dB

Answer

90 dB

Answer

100 dB

Answer

125 dB

Question 5

Indoor smoke contains a range of health-damaging pollutants, which include all of the following except?

Accepted Answer

Lead oxide

Answer

Carbon monoxide

Answer

Sulfur oxides

Answer

Benzopyrenes

Question 6

What is the optimal temperature for plasma pyrolysis?

Accepted Answer

1200°C

Answer

700°C

Answer

1000°C

Answer

1500°C

Question 7

What is the recommended level of fluorides in drinking water?

Accepted Answer

0.5 mg/L

Answer

1.5 mg/L

Answer

2.5 mg/L

Answer

3.5 mg/L

Question 8

When orthotoludine reagent is added to water containing free chlorine, what color will be produced?

Accepted Answer

Yellow

Answer

Pink

Answer

Green

Answer

Red

Question 9

What is considered strong sewage?

Accepted Answer

Biological oxygen demand >300 mg/L

Answer

Biological oxygen demand >200 mg/L

Answer

Biological oxygen demand <250 mg/L

Answer

Biological oxygen demand >150 mg/L

Question 10

All of the following statements regarding disposal of biomedical waste are true, except?

Accepted Answer

Blue bags' contents are disposed of in a secured landfill.

Answer

Human Anatomical Waste is disposed of in a yellow bag.

Answer

Contents from a red bag may be a source of contamination.

Answer

Black bags are used for disposal of ash from incineration.

Environmental Health — MCQs

Environmental Health — MCQs

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