Environmental Health — MCQs

Environmental Health Indian Medical PG Practice Questions and MCQs

Question 761: Biological oxygen demand (BOD) measures the total organic content of water based on the consumption of oxygen in a sample at 20°C over five days. A consumption of 10 to 20 mg of O2 per liter most likely represents a sample from what?

A. Treated freshwater
B. Untreated freshwater
C. Treated sewage (Correct Answer)
D. Industrial wastewater

Explanation: ***Treated sewage*** - A **BOD** range of 10 to 20 mg O2/L indicates a moderate level of organic pollution, characteristic of successfully **treated sewage**. - Treatment processes remove the bulk of organic matter, but some residual content remains, hence it's not as low as pristine freshwater. *Treated freshwater* - **Treated freshwater** (e.g., drinking water) typically has a very low **BOD**, usually less than 1-2 mg O2/L, indicating minimal organic contamination. - The goal of treating freshwater for consumption is to remove almost all organic matter and pathogens. *Untreated freshwater* - **Untreated freshwater** can vary widely based on its source (e.g., river, lake), but if it shows signs of pollution, its **BOD** would likely be higher than 20 mg O2/L, especially if it receives runoff. - Pristine, unpolluted freshwater typically has a **BOD** below 5 mg O2/L. *Industrial wastewater* - **Industrial wastewater** can have an extremely high **BOD**, often hundreds or even thousands of mg O2/L, depending on the industry and the nature of its waste products. - This high BOD reflects a significant concentration of biodegradable organic substances.

Question 762: Which of the following waste disposal methods provides the greatest benefit for soil enrichment?

A. Incineration
B. Controlled tipping
C. Composting (Correct Answer)
D. Dumping

Explanation: ***Composting*** - **Composting** breaks down organic waste into **humus**, a nutrient-rich material that significantly improves soil structure, water retention, and fertility. - It enriches soil by adding essential **macronutrients** (e.g., nitrogen, phosphorus, potassium) and micronutrients, fostering healthy plant growth and microbial activity. *Incineration* - **Incineration** involves burning waste at high temperatures, reducing its volume and generating energy, but it destroys all organic matter. - While it can reduce landfill burden, it offers no direct benefit to **soil enrichment** and may release air pollutants. *Controlled tipping* - **Controlled tipping**, or sanitary landfilling, involves burying waste in an engineered site to minimize environmental impact. - Although some organic decomposition occurs, it is often anaerobic and produces **methane**, with limited direct benefit for **soil enrichment** in the immediate vicinity or for agricultural use. *Dumping* - **Dumping** refers to the uncontrolled disposal of waste in open areas, which is environmentally harmful and poses significant public health risks. - This method pollutes soil and water, attracts pests, and offers no benefits for **soil enrichment**; instead, it degrades soil quality.

Question 763: Incineration is not appropriate for which of the following types of waste?

A. Anatomical waste
B. Radioactive waste (Correct Answer)
C. Cytotoxic drugs
D. Sharps waste

Explanation: ***Radioactive waste*** - Incineration does not neutralize **radioactive materials**; instead, it can disperse them into the atmosphere as radioactive particles or concentrate them in the incinerator ash, posing significant environmental and health risks. - Due to the hazards associated with radioactivity, **specialized decay facilities** or secure long-term storage solutions are required for its safe disposal, not combustion. *Cytotoxic drugs* - **High-temperature incineration** is an effective method for destroying the active components of cytotoxic drugs, preventing environmental contamination. - This process breaks down complex chemical structures into non-hazardous substances, making it a preferred disposal route for these **hazardous pharmaceutical wastes**. *Anatomical waste* - **Incineration** is a widely accepted and effective method for the disposal of anatomical waste, such as body parts and tissues. - The high temperatures ensure complete destruction, **sterilization**, and reduction of volume, minimizing public health risks and ethical concerns. *Sharps waste* - **Sharps waste**, including needles, scalpels, and lancets, is safely disposed of through high-temperature incineration. - This process effectively **sterilizes** the sharps and melts down the metal, preventing needlestick injuries and the spread of infectious agents.

Question 764: Which of the following statements about DDT is false?

A. It is contact poison
B. Residual effect lasts for 18 months (Correct Answer)
C. Is lipophilic in nature
D. Belongs to organochlorine group

Explanation: ***Residual effect lasts for 18 months*** - **DDT's residual insecticidal effect** typically lasts only **3-12 months** when applied as an indoor residual spray, making 18 months definitively **FALSE**. - While DDT persists in the environment for years due to bioaccumulation, its **active insecticidal residual effect** on treated surfaces is much shorter than 18 months. - This is the **FALSE statement** among the options. *It is contact poison* - **TRUE**: DDT acts as a **contact poison**, being absorbed through the insect's **cuticle** upon direct contact. - It disrupts **sodium channels** in the nervous system, causing neurological overstimulation, tremors, and paralysis. *Is lipophilic in nature* - **TRUE**: DDT is highly **lipophilic** (fat-soluble), which explains its bioaccumulation in fatty tissues. - This lipophilicity leads to **biomagnification** through the food chain, causing environmental and health concerns. *Belongs to organochlorine group* - **TRUE**: DDT (Dichlorodiphenyltrichloroethane) is a classic example of an **organochlorine insecticide**. - Other organochlorines include lindane, aldrin, and dieldrin.

Question 765: In doubtful cases, the presence of which organism confirms the fecal contamination of water?

A. Protozoa
B. Yeast
C. Fungi
D. Clostridium perfringens (Correct Answer)

Explanation: ***Clostridium perfringens*** - **Clostridium perfringens** is a reliable indicator of **fecal contamination** in doubtful cases, especially when coliform tests are inconclusive. - It is a **spore-forming anaerobe** that is highly resistant to environmental stresses, including **chlorination** and adverse conditions. - The spores persist longer than vegetative bacteria, making it an excellent indicator of **remote or intermittent fecal contamination**. - Its presence suggests a persistent source of contamination and is particularly useful in assessing the efficiency of water treatment processes. *Protozoa* - While some pathogenic protozoa can be transmitted through fecally contaminated water (e.g., *Giardia*, *Cryptosporidium*), they are not used as general indicators of fecal contamination. - Monitoring for specific protozoa primarily indicates a **health risk** rather than serving as a routine contamination indicator. - Protozoa are tested as **specific pathogens** rather than indicator organisms. *Yeast* - **Yeasts** are ubiquitous in the environment and can be found in various sources including soil, air, and water. - Their presence is not specifically associated with fecal contamination. - They are not considered reliable indicators for **water quality assessment**. *Fungi* - **Fungi** are common in natural environments and can originate from many non-fecal sources. - They are not used as indicators of **fecal pollution** in water quality testing. - Their presence has no correlation with fecal contamination levels.

Question 766: Which of the following light sources is mercury-free and most environmentally responsible?

A. Fluorescent tube light
B. Incandescent bulb
C. LED bulb (Correct Answer)
D. Compact fluorescent lamp (CFL)

Explanation: ***LED bulb*** - **LEDs** (Light Emitting Diodes) are inherently **mercury-free**, making them the most environmentally responsible option. - They also offer high **energy efficiency** and long lifespan, reducing energy consumption and waste. *Incandescent bulb* - **Incandescent bulbs** do not contain mercury but are highly energy-inefficient, converting most energy into heat instead of light. - Their short lifespan leads to frequent replacement and increased waste. *Fluorescent tube light* - **Fluorescent tube lights** contain **mercury**, which is a hazardous substance requiring special disposal to prevent environmental contamination. - While more efficient than incandescents, their mercury content poses an environmental risk. *Compact fluorescent lamp (CFL)* - **CFLs** also contain **mercury**, similar to fluorescent tube lights, and thus require specific handling for disposal. - Although more energy-efficient than incandescent bulbs, their mercury content makes them less environmentally friendly than LEDs.

Question 767: What are the specific causes of endemic ascites and epidemic dropsy due to adulterated substances?

A. Crotalaria seeds (endemic ascites) and Argemone mexicana oil (epidemic dropsy) (Correct Answer)
B. Crotalaria seeds (endemic ascites) and Khesari Dal (epidemic dropsy)
C. Argemone mexicana oil (epidemic dropsy) and Claviceps fusiformis (not related to ascites)
D. Claviceps fusiformis (ergotism) and Lathyrus sativus (epidemic dropsy)

Explanation: ***Crotalaria seeds (endemic ascites) and Argemone mexicana oil (epidemic dropsy)*** - **Crotalaria seeds** contain pyrrolizidine alkaloids causing **veno-occlusive disease of the liver**, leading to **endemic ascites** (Senecio poisoning) - **Argemone mexicana oil** (Mexican prickly poppy) contains sanguinarine and causes **epidemic dropsy** when mustard oil is adulterated with it, characterized by bilateral leg edema, erythema, respiratory distress, and glaucoma - This is the classic and most specific pairing for these two food adulteration diseases *Crotalaria seeds (endemic ascites) and Khesari Dal (epidemic dropsy)* - While **Crotalaria seeds** correctly cause endemic ascites, **Khesari Dal (Lathyrus sativus)** causes **lathyrism** (neurolathyrism), NOT epidemic dropsy - Lathyrism presents with spastic paraplegia due to ODAP (β-N-oxalyl amino-L-alanine) toxin affecting motor neurons, not generalized edema *Argemone mexicana oil (epidemic dropsy) and Claviceps fusiformis (not related to ascites)* - **Argemone mexicana oil** correctly causes epidemic dropsy - However, **Claviceps fusiformis** causes ergotism with vasoconstriction and gangrene, not endemic ascites - This option has the phrasing issue with "not related to ascites" in the option itself *Claviceps fusiformis (ergotism) and Lathyrus sativus (epidemic dropsy)* - **Claviceps fusiformis** causes ergotism (gangrenous and convulsive forms), not endemic ascites - **Lathyrus sativus** causes lathyrism (spastic paraplegia), not epidemic dropsy - Both parts of this option are incorrect for the conditions asked

Question 768: What is the primary purpose of pasteurization in milk processing?

A. To reduce pathogens in milk (Correct Answer)
B. To completely sterilize milk
C. To increase shelf life
D. To enhance flavor

Explanation: ***To reduce pathogens in milk*** - Pasteurization is a heat treatment process specifically designed to **kill harmful bacteria and other pathogens** that may be present in milk. - This process significantly reduces the risk of **foodborne illnesses** transmitted through milk, such as tuberculosis, brucellosis, and salmonellosis. *To completely sterilize milk* - **Sterilization** involves much higher temperatures and longer holding times than pasteurization, aiming to destroy all microorganisms, including spores. - Pasteurization does not achieve complete sterility; it only reduces the microbial load to safe levels, allowing for refrigeration to prevent spoilage. *To increase shelf life* - While pasteurization does contribute to increasing the **shelf life** of milk by reducing spoilage organisms, this is a secondary benefit. - The primary goal is to ensure the **safety** of the product for consumption by eliminating health risks from pathogens. *To enhance flavor* - Pasteurization primarily focuses on **microbial safety** and has minimal, if any, positive impact on the flavor of milk. - In some cases, very high-temperature pasteurization methods might even subtly alter the flavor, though modern techniques minimize this effect.

Question 769: What is the name of the defluoridation process of drinking water developed by the NEERI?

A. Activated sludge process
B. Recarbonation process
C. Nalgonda process (Correct Answer)
D. Double pot method

Explanation: ***Nalgonda process*** - The **Nalgonda technique** is a defluoridation method developed by the **National Environmental Engineering Research Institute (NEERI)** in India. - It utilizes **aluminum salts**, **lime**, and **bleaching powder** for fluoride removal through precipitation and adsorption. *Activated sludge process* - This is a **wastewater treatment method** that uses microorganisms to consume organic pollutants, primarily for sewage treatment, not defluoridation. - It involves aeration of wastewater with a flocculated biological growth of bacteria and other microorganisms. *Recarbonation process* - **Recarbonation** is a step in **water softening**, specifically after lime-soda ash treatment, to lower the pH and stabilize the water by converting excess calcium hydroxide to calcium carbonate. - It is used to prevent scale formation and is not a defluoridation method. *Double pot method* - The **double pot method** is a technique for **household water purification**, often used in rural areas, that typically involves filtration and disinfection, but not specific defluoridation. - It usually consists of two pots, one placed inside the other, with a filter medium or coagulant treatment.

Question 770: Which of the following biomedical wastes can be incinerated?

A. Radiographic wastes
B. PVC
C. Pressurized gas containers
D. Human anatomical wastes (Correct Answer)

Explanation: ***Human anatomical wastes*** - **Human anatomical wastes**, such as **tissues**, **organs**, and **body parts** obtained from surgical procedures or autopsies, are typically incinerated. - **Incineration** is an effective method for sterilizing and safely disposing of such bio-hazardous materials, reducing them to ash and destroying pathogens. *Pressurized gas containers* - **Pressurized gas containers**, like oxygen tanks or aerosol cans, contain **flammable** or **explosive gases** and can rupture under extreme heat. - Incineration poses a significant **safety risk** due to potential explosions and the release of harmful gases. *Radiographic wastes* - **Radiographic wastes** include items such as **used X-ray films** and **spent fixer/developer solutions**, which contain heavy metals like silver. - Incineration can release **toxic fumes** and **pollutants** into the atmosphere and is not the recommended disposal method for these materials. *PVC* - **Polyvinyl chloride (PVC)**, when incinerated, releases **toxic fumes** including **dioxins** and **furans**, which are harmful to human health and the environment. - **Non-chlorinated plastics** are preferred for incineration to minimize the release of these highly toxic compounds.

Practice by Chapter

Water Quality and Health

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Air Pollution and Health Effects

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Solid Waste Management

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Hazardous Waste Management

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Housing and Health

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Noise Pollution

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Radiation Health Effects

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Climate Change and Health

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Environmental Impact Assessment

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Disaster Management and Preparedness

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Vector Control

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Environmental Legislation

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