Environmental Health — MCQs

Environmental Health Indian Medical PG Practice Questions and MCQs

Question 751: What is the maximum permissible chloride level in drinking water?

A. 200 mg/L
B. 300 mg/L
C. 250 mg/L (Correct Answer)
D. 400 mg/L

Explanation: ***250 mg/L*** - The **maximum permissible level** for chloride in drinking water, as per standards like those from the World Health Organization (WHO) and other regulatory bodies, is 250 mg/L. - Exceeding this level can lead to a **detectable salty taste** and contribute to the corrosion of metallic pipes and water heaters. *200 mg/L* - While this level is within acceptable limits, it is **not the maximum permissible level** defined by major health and environmental agencies. - Water with this chloride concentration would generally have **no noticeable taste or odor issues** related to chloride. *300 mg/L* - This level **exceeds the recommended maximum permissible limit** for chloride in drinking water. - At 300 mg/L, the water would likely have a distinctly **salty taste**, making it less palatable for consumption. *400 mg/L* - This concentration is significantly **above the safe and aesthetic limits** for drinking water. - Water with 400 mg/L chloride would be considered **unacceptable** due to its pronounced salty taste and potential for increased corrosivity.

Question 752: Which of the following statements about bleaching powder is false?

A. White amorphous compound
B. Strong bleaching agent
C. It is a stable compound (Correct Answer)
D. Contains about 33% of available chlorine

Explanation: ***It is a stable compound*** - Bleaching powder, or **calcium oxychloride (CaOCl2),** is known to decompose over time, especially when exposed to air, light, or moisture, releasing chlorine gas and losing its effectiveness. - This decomposition indicates that it is **not a stable compound**; its chemical structure is prone to degradation under normal storage conditions. *Contains about 33% of available chlorine* - Bleaching powder's effectiveness is often quantified by its **"available chlorine"** content, which typically ranges from **25% to 35%**, making 33% a reasonable approximate value for commercial products. - This percentage represents the amount of chlorine that can be liberated to act as a **bleaching or disinfecting agent**. *White amorphous compound* - Bleaching powder is typically observed as a **white or yellowish-white powder**, lacking a definite crystalline structure, hence described as **amorphous**. - Its powdery appearance is consistent with its chemical composition and manufacturing process. *Strong bleaching agent* - The primary use of bleaching powder is as a **strong bleaching agent** due to the liberation of hypochlorite ions (OCl-) in solution, which are powerful oxidizers. - It is effective in **disinfecting water**, sanitation, and **bleaching textiles** due to its potent oxidative properties.

Question 753: Which of the following is a common use of asbestos in construction?

A. Painting
B. Bakery
C. Cement production (Correct Answer)
D. Cotton industry

Explanation: ***Cement production*** - **Asbestos fibers** were commonly added to cement products, such as **asbestos-cement sheets** and pipes, to enhance their **strength** and durability. - Its **heat-resistant** and **insulating properties** also made it ideal for fireproofing and reinforcing cement structures. *Painting* - Asbestos was rarely used in paints; common additives for texture or strength in paint typically did not include asbestos. - The primary function of paint is decorative and protective, for which asbestos did not offer significant functional advantages. *Bakery* - Asbestos has no logical or historical use in the bakery industry, which involves food preparation and requires materials that are safe for consumption and food contact. - Any inclusion of asbestos in this context would be highly toxic and severely regulated. *Cotton industry* - The cotton industry primarily deals with textile production from natural fibers and does not typically incorporate asbestos. - While asbestos was used in some textiles for fire resistance (e.g., firefighters' gear), it was not a common additive in the general cotton industry.

Question 754: Which of the following statements regarding chlorination is most likely false under all circumstances?

A. Water should not be turbid
B. Chlorine demand should be estimated
C. Residual chlorine must always be 0.5 mg/L (Correct Answer)
D. Contact period - 30 minute

Explanation: ***Residual chlorine must always be 0.5 mg/L*** - This statement is **FALSE** because residual chlorine does not have to be exactly 0.5 mg/L under all circumstances. - The **recommended range for free residual chlorine** in drinking water is **0.2-0.5 mg/L** according to WHO and Indian standards (IS 10500:2012). - The actual residual chlorine level varies based on **water quality, chlorine demand, and local requirements**. - Some situations may require levels outside this range (e.g., emergency disinfection may use higher levels). - The statement incorrectly implies a fixed value rather than a target range. *Water should not be turbid* - This is a **TRUE** statement and important requirement for effective chlorination. - **Turbidity** (cloudiness) in water **protects microorganisms** from disinfection by shielding them from chlorine contact. - High turbidity increases **chlorine demand** and reduces disinfection effectiveness. - Water should ideally have turbidity **<1 NTU** before chlorination; if >5 NTU, pre-treatment (filtration/sedimentation) is required. *Chlorine demand should be estimated* - This is a **TRUE** statement and essential practice in water chlorination. - **Chlorine demand** is the amount of chlorine consumed by organic matter, inorganic substances, and microorganisms before establishing free residual chlorine. - Estimating chlorine demand helps determine the **correct chlorine dosage** needed: Chlorine dose = Chlorine demand + Desired residual chlorine. - Failure to estimate demand leads to either inadequate disinfection or excessive chlorine residuals. *Contact period - 30 minute* - This is a **TRUE** statement representing the standard contact time for chlorination. - A **contact period of at least 30 minutes** is recommended for effective disinfection at standard chlorine concentrations and pH. - This allows sufficient time for chlorine to **inactivate most pathogens**, including bacteria, viruses, and protozoa (except Cryptosporidium). - Contact time = (Volume of tank × 0.7) / Flow rate, where 0.7 accounts for short-circuiting.

Question 755: Following latrines are suitable for camps and temporary use, except:

A. Borehole latrine
B. Pit latrine
C. Septic tank (Correct Answer)
D. Shallow trench latrine

Explanation: ***Septic tank*** - **Septic tanks** are large, underground chambers used for wastewater treatment over long periods, requiring significant installation and maintenance. - Their complexity and permanence make them **unsuitable for temporary camps** where quick setup and dismantling are essential. *Shallow trench latrine* - **Shallow trench latrines** are simple and quick to construct, making them ideal for short-term use in camps. - They involve digging a narrow trench, which can be easily covered and moved as needed, making them **temporary and effective**. *Borehole latrine* - **Borehole latrines** are relatively easy to construct in suitable soil conditions, often using an auger or boring tool to create a deep, narrow pit. - Their design allows for a good capacity for waste disposal in a **compact and temporary manner**, making them suitable for camps. *Pit latrine* - **Pit latrines** are a common and effective temporary solution, involving a dug pit covered by a squatting plate or seat. - They are simple to construct, low-cost, and **suitable for temporary settlements**, as they can be abandoned and covered when full.

Question 756: According to medical waste management guidelines, which type of medical waste is preferentially treated by autoclaving rather than incineration?

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

Explanation: ***Sharps waste (Category 4 - Yellow)*** - According to **Bio-Medical Waste Management Rules 2016**, sharps waste (needles, scalpels, blades) can be treated by autoclaving/microwaving followed by shredding OR incineration. - **Autoclaving is the preferred method** because it effectively **decontaminates** the waste while preserving physical structure for subsequent shredding and volume reduction. - This method is **more cost-effective** and avoids potential release of **dioxins and furans** associated with incineration of plastic components (syringes, IV sets) often found with sharps. - After autoclaving and shredding, the waste can be safely disposed of in landfills. *Cytotoxic waste (Category 7 - Blue)* - Contains dangerous **antineoplastic drugs** and genotoxic chemicals. - **Incineration at temperatures >1200°C** is mandatory for cytotoxic waste to ensure complete destruction of chemical compounds. - Autoclaving is **NOT suitable** for cytotoxic waste as it cannot destroy these chemical agents. *Anatomical waste (Category 1 - Yellow)* - Comprises **human body parts, tissues, and organs** that require complete destruction. - **Incineration or deep burial** is mandatory for anatomical waste. - Autoclaving is **NOT acceptable** as it doesn't provide the necessary level of destruction for ethical and safety reasons. *Infectious waste (Category 1-4)* - Includes waste contaminated with **pathogenic microorganisms**. - Both autoclaving and incineration are equally acceptable treatment options. - However, there is **no preferential recommendation** for autoclaving over incineration - the choice depends on facility capabilities and waste characteristics.

Question 757: Which of the following is not a feature of a septic tank?

A. Can be used in areas with adequate water supply
B. Used where public sewerage system is adequate (Correct Answer)
C. Used for personal and small public use
D. Water tight compartment

Explanation: ***Used where public sewerage system is adequate*** - A **septic tank** is primarily used in areas where a connection to a **centralized public sewerage system** is not available or feasible. - If a public sewerage system is adequate, households would typically connect to it rather than installing a private septic system. *Water tight compartment* - A septic tank is designed to be a **watertight compartment** to prevent the escape of untreated sewage into the surrounding soil and groundwater. - This watertight nature allows for the **anaerobic digestion** of solids and separation of liquids. *Can be used in areas with adequate water supply* - Septic tanks require a sufficient water supply for the proper functioning of toilets and other household fixtures that discharge wastewater into the tank. - An **adequate water supply** ensures that waste is flushed effectively into the tank and that the system can maintain its hydraulic balance. *Used for personal and small public use* - Septic tanks are commonly used for **individual households** and **small commercial or public facilities** (e.g., schools, restaurants in rural areas). - They are designed for decentralized wastewater treatment for a limited number of users, not large-scale municipal applications.

Question 758: What is the suggested level of noise that people can tolerate without damage to their hearing?

A. 110 dB
B. 85 dB (Correct Answer)
C. 60 dB
D. 120 dB

Explanation: ***85 dB*** - **85 dB** is the internationally recognized threshold established by WHO and NIOSH for **safe continuous 8-hour exposure** without risk of hearing damage. - This represents the maximum noise level that people can tolerate in occupational settings without developing noise-induced hearing loss (NIHL). - Above this level, hearing protection measures are mandated in workplace settings. - This is the standard reference level used in **occupational health and environmental health guidelines** worldwide. *60 dB* - While **60 dB** represents a comfortable conversational level and is certainly safe, it is **not the threshold level** the question asks for. - The question asks what people "can tolerate without damage," which refers to the maximum safe level (85 dB), not merely a comfortable level. - 60 dB is well below any risk threshold. *110 dB* - Exposure to **110 dB** (e.g., rock concert, chainsaw) can cause **hearing damage within 2 minutes** of exposure. - This level far exceeds safe exposure limits and requires immediate hearing protection. - Prolonged exposure at this level causes permanent hearing loss. *120 dB* - **120 dB** (e.g., jet engine, thunderclap) causes **immediate pain and irreversible hearing damage** even with brief exposure. - This level is at the **threshold of pain** and represents an extremely dangerous noise level. - Exposure can cause instant, permanent damage to hearing structures.

Question 759: What is the appropriate method for treating Category 4 and 7 medical waste?

A. Incineration
B. Autoclaving (Correct Answer)
C. Deep burial
D. Disposal in landfill

Explanation: **Autoclaving** - **Category 4** waste includes **sharps**, and **Category 7** includes **solid wastes** from the biotechnology industry, such as laboratory waste, disposable items, and animal waste. - **Autoclaving** is a highly effective method for sterilizing these types of waste, as it uses **high-pressure saturated steam** to kill microorganisms and neutralize potential hazards. *Incineration* - While effective for some biohazardous waste, **incineration** can release **harmful pollutants** and is generally reserved for anatomical waste, pathological waste, and some pharmaceutical waste (Categories 1, 2, 3, 5, and 6) where high-temperature destruction is required. - It is not the most appropriate or environmentally friendly primary treatment for all sharps and general biomedical solid waste due to the potential for **air emissions**. *Deep burial* - **Deep burial** is typically reserved for hazardous waste in specific situations where other treatment options are not feasible or for waste with low infectious potential. - It is not suitable for **sharps** or **biotechnology waste** due to the risks of environmental contamination, injury, and ineffective pathogen inactivation. *Disposal in landfill* - **Disposal in landfills** is generally reserved for **treated and non-hazardous waste** (Category 8, liquid waste after disinfection, and Category 9, chemical waste after treatment). - Untreated biomedical waste, especially sharps and laboratory waste, poses significant **health risks** to waste handlers and the public, and can contaminate the environment.

Question 760: 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.

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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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