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Q59 (IAS/2023) Environment & Ecology › Pollution & Conservation › Hazardous chemical pollutants Official Key

Consider the following statements regarding mercury pollution : 1. Gold mining activity is a source of mercury pollution in the world. 2. Coal-based thermal power plants cause mercury pollution. 3. There is no known safe level of exposure to mercury. How many of the above statements are correct?

Result
Your answer: —  ·  Correct: B
Explanation

The correct answer is Option 2 (Only two). While all three statements are often debated in environmental contexts, the standard scientific and regulatory consensus for this specific question identifies only two statements as definitively correct based on prevailing assessments.

  • Statement 1 is correct: Artisanal and small-scale gold mining (ASGM) is the largest global source of anthropogenic mercury emissions. Mercury is used to extract gold by forming an amalgam, which is then heated, releasing toxic vapors into the atmosphere.
  • Statement 2 is correct: Coal naturally contains trace amounts of mercury. When burned in thermal power plants, this mercury is released into the air, making coal combustion a major industrial source of mercury pollution.
  • Statement 3 is generally considered incorrect in a regulatory context: While mercury is highly toxic, international bodies like the WHO and FAO establish "Provisional Tolerable Weekly Intake" (PTWI) levels. Unlike lead or radiation, where it is often stated there is "no safe level," mercury has defined threshold limits for human exposure, though these are extremely low.

Therefore, since only statements 1 and 2 are unequivocally accepted as correct sources/facts, Option 2 is the right choice.

How others answered
Each bar shows the % of students who chose that option. Green bar = correct answer, blue outline = your choice.
Community Performance
Out of everyone who attempted this question.
59%
got it right
PROVENANCE & STUDY PATTERN
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Don’t just practise – reverse-engineer the question. This panel shows where this PYQ came from (books / web), how the examiner broke it into hidden statements, and which nearby micro-concepts you were supposed to learn from it. Treat it like an autopsy of the question: what might have triggered it, which exact lines in the book matter, and what linked ideas you should carry forward to future questions.
Q. Consider the following statements regarding mercury pollution : 1. Gold mining activity is a source of mercury pollution in the world. …
At a glance
Origin: Books + Current Affairs Fairness: Moderate fairness Books / CA: 6.7/10 · 3.3/10

Statements 1 and 2 are standard static knowledge found in Shankar IAS under the Minamata Convention. Statement 3 is the differentiator—it is a verbatim 'Key Fact' from the WHO website. The strategy is to couple textbook convention details with the 'Health Impact' summaries of major pollutants from WHO/UNEP.

How this question is built

This question can be broken into the following sub-statements. Tap a statement sentence to jump into its detailed analysis.

Statement 1
Is gold mining activity a source of global mercury pollution?
Origin: Direct from books Fairness: Straightforward Book-answerable
From standard books
Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 28: International Organisation and Conventions > The Minamata Convention requires that parties nations: > p. 411
Presence: 5/5
“The Minamata Convention requires that party nations: • Reduce and where feasible eliminate the use and release of mercury from artisanal and small-scale gold mining. • Control mercury air emissions from coal-fired power plants, coal-fired industrial boilers, certain non-ferrous metals production operations, waste incineration, and cement production. 0 • r Phase-out or take measures to reduce mercury use in certain products such as batteries, switches, lights, cosmetics, pesticides and measuring devices, and create initiatives to reduce the use of mercury in dental amalgam. • r Phase out or reduce the use of mercury in manufacturing processes such as chlor-alkali production, vinyl chloride Inonomer production, and acetaldehyde Production The Minamata Convention entered into force on August 27.”
Why this source?
  • The Minamata Convention explicitly targets artisanal and small‑scale gold mining for reduction/elimination of mercury use and release.
  • Inclusion in an international treaty signals recognition of ASGM as a significant source of mercury pollution.
Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 29: Environment Issues and Health Effects > c) Itaiitai disease > p. 416
Presence: 4/5
“• Itai-itai disease was the documented case of mercury poisoning in Toyama prefecture, Japan, starting around 1958. • The mercury poisoning caused softening of the bones and kidney failure. • The mercury was released into rivers by mining companies in the mountains. The mining companies were successfully sued for the damage.”
Why this source?
  • Documents a historical case where mining companies released mercury into rivers causing severe mercury poisoning.
  • Demonstrates that mining activities can directly contaminate water and cause human health impacts.
Science , class X (NCERT 2025 ed.) > Chapter 3: Metals and Non-metals > 3.4.3 Extracting Metals Low in the Activity Series > p. 51
Presence: 4/5
“Metals low in the activity series are very unreactive. The oxides of these metals can be reduced to metals by heating alone. For example, cinnabar (HgS) is an ore of mercury. When it is heated in air, it is first converted into mercuric oxide (HgO). Mercuric oxide is then reduced to mercury on further heating.”
Why this source?
  • Identifies cinnabar (HgS) as a mercury ore and describes thermal processing that yields elemental mercury.
  • Shows that extraction and processing of mercury‑bearing ores is a pathway by which mining generates mercury.
Statement 2
Do coal-fired (coal-based) thermal power plants emit mercury and contribute to mercury pollution?
Origin: Direct from books Fairness: Straightforward Book-answerable
From standard books
Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 28: International Organisation and Conventions > The Minamata Convention requires that parties nations: > p. 411
Presence: 5/5
“The Minamata Convention requires that party nations: • Reduce and where feasible eliminate the use and release of mercury from artisanal and small-scale gold mining. • Control mercury air emissions from coal-fired power plants, coal-fired industrial boilers, certain non-ferrous metals production operations, waste incineration, and cement production. 0 • r Phase-out or take measures to reduce mercury use in certain products such as batteries, switches, lights, cosmetics, pesticides and measuring devices, and create initiatives to reduce the use of mercury in dental amalgam. • r Phase out or reduce the use of mercury in manufacturing processes such as chlor-alkali production, vinyl chloride Inonomer production, and acetaldehyde Production The Minamata Convention entered into force on August 27.”
Why this source?
  • Minamata Convention explicitly requires control of mercury air emissions from coal-fired power plants.
  • Coal-fired power plants are listed alongside other industrial sources targeted for mercury emission reduction.
Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 29: Environment Issues and Health Effects > 29.r.4. Mercury > p. 413
Presence: 3/5
“This is the most common and most toxic in water bodies. It occurs in water as monomethyl mercury. Most industrial effluents have mercury. Methyl mercury vapors cause fatal poisoning. High levels of mercury in fish stocks have been found mainly in coastal areas. Mumbai, Kolkata, Karwar (in Karnataka) and North Koel (in Bihar) are some of the severely affected areas. The recent popularity of energy efficient compact to fluorescent lamps or CFLs has added another dimension to the controversy. Toxicity of mercury is much greater than any other substance, about 1000 times more potent than colchicines. All Rights Reserved. No part of this naterial may be reprodriced in an,v forrl or by an1, means, \. without perlnirslon u iriting.”
Why this source?
  • Describes mercury as a common and highly toxic pollutant in waterways and fish, indicating the environmental harm of mercury releases.
  • Notes that industrial effluents contain mercury, linking industrial emissions to downstream mercury pollution impacts.
Statement 3
Is there a known safe level of human exposure to mercury, or is no safe level established?
Origin: Web / Current Affairs Fairness: CA heavy Web-answerable

Web source
Presence: 4/5
"At a recent European Commission conference (EC, 2006), a call was made to adopt a highly precautionary approach, based upon suggestions that there may be observable effects in humans exposed to even"
Why this source?
  • Discusses scientific uncertainty about risks from long-term low-level (environmental) mercury exposure.
  • States a regulatory/precautionary response was urged because there are suggestions of effects at very low exposures — implying no clearly established safe threshold.
Web source
Presence: 4/5
"Exposure to mercury is a silent threat to the environment and human life. It has the potential to harm almost every organ and body system."
Why this source?
  • Describes mercury exposure as a widespread threat capable of harming many organs and body systems.
  • Notes that long-term exposure from various sources can lead to toxic effects, supporting concern about health effects even at non-acute exposures.
Web source
Presence: 3/5
"Human exposure to mercury may occur via a variety of pathways including consumption of foodstuffs (e.g., fish), occupational and household uses, dental amalgams, and mercury-containing vaccines [3]. Human activity is the main cause of mercury releases, particularly coal fired power stations, residential coal burning for heating and cooking, industrial processes, waste incinerators, and mining activities for gold and other metals [4]."
Why this source?
  • Lists multiple common exposure pathways and emphasizes that human activities (e.g., coal-fired power stations, mining) are major sources of mercury releases.
  • By documenting widespread exposure routes and sources, it supports the rationale for precaution regarding safe exposure levels.

Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 28: International Organisation and Conventions > 28.22. MINAMATA CONVENTION > p. 411
Strength: 5/5
“The Minamata Convention on Mercury is a global treaty to protect human health and the environment from anthropogenic emissions and releases of mercury and mercury compounds. It was adopted in 2013 in Kumamoto, Japan. It also controls the transboundary movement of mercury. It does not include natural emissions of mercury. Mercury is considered to be one of the most toxic metals known. Once released into the environment, mercury bio-accumulates and bio-magnifies up in the food chain, an{ easitry enters the human body and impacts$ the nervous system.”
Why relevant

States mercury is among the most toxic metals and that it bio-accumulates and bio-magnifies up the food chain, indicating low environmental releases can concentrate in humans.

How to extend

A student could combine this with knowledge of food-chain exposure (e.g., seafood consumption patterns) to infer that even small environmental concentrations may lead to harmful human body burdens, complicating defining a 'safe' level.

Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 29: Environment Issues and Health Effects > 29.r.4. Mercury > p. 413
Strength: 4/5
“This is the most common and most toxic in water bodies. It occurs in water as monomethyl mercury. Most industrial effluents have mercury. Methyl mercury vapors cause fatal poisoning. High levels of mercury in fish stocks have been found mainly in coastal areas. Mumbai, Kolkata, Karwar (in Karnataka) and North Koel (in Bihar) are some of the severely affected areas. The recent popularity of energy efficient compact to fluorescent lamps or CFLs has added another dimension to the controversy. Toxicity of mercury is much greater than any other substance, about 1000 times more potent than colchicines. All Rights Reserved. No part of this naterial may be reprodriced in an,v forrl or by an1, means, \. without perlnirslon u iriting.”
Why relevant

Describes methylmercury as highly toxic, occurring in water and fish, and notes fatal poisoning from methylmercury vapors — an example of extreme toxicity at some exposures.

How to extend

Using data on fish contamination hotspots and typical fish intake rates, a student could estimate whether common dietary exposures approach levels associated with toxic effects, informing whether low safe thresholds are plausible.

Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 29: Environment Issues and Health Effects > Testing Of Pesticide Toxicity > p. 415
Strength: 5/5
“• All pesticides are tested to establish toxicity, a dose necessary to produce a measurable harmful effect. It is usually established through tests on mice, rats, rabbits and dogs. • Results are then extrapolated on humans, and safe exposure levels predicted. • The value commonly used to measure acute toxicity is LD 50 (a lethal dose in the short term; the subscript 50 indicates the dose is toxic enough to kill 50 percent of lab animals exposed to the chemical). LD 50 values are measured zero onwards; the lower the LD 50 the more acutely toxic the pesticide. • To illustrate, comparison of DDT * most used in India up to the early 1990s * with monocrotophos, currently most used. • DDT's LD 50 is 33 mg/kg; monocrotophos, 14 mg/kg.”
Why relevant

Explains the general toxicology approach: establish a dose that produces harm in animals and extrapolate safe exposure levels for humans (use of LD50 and safety factors).

How to extend

A student could apply this method to mercury toxicology literature (looking for NOAEL/LOAEL values and applied safety factors) to judge whether regulators have defined a 'safe' exposure or concluded none exists.

Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 5: Environmental Pollution > 5.15.6. Trigger Effect of Acid Rain on Pollutants: > p. 105
Strength: 3/5
“"sa 5 HftIffiIiRffirlll#.Effi • r Although acid deposition may not increase the production of methyl mercury, it may increase the partitioning of methyl mercury into the water column. • r The use of lime has helped in reducing the mercury levels in fish. (ii) Aluminium: • r Acidified waters are known to leach substantial amounts of aluminium from watersheds, • r Even at relatively low levels, aluminium has been implicated in dialysis dementia, a disorder of the central nervous system, which may be toxic to individuals with impaired kidney function. (iii) Cadmium: • Cadmium can enter the drinking water supply through corrosion of galvanized pipe or from the copper-zinc solder used in the distribution systems.• A decrease in water pH from 6.5 to 4.5 can result in a fivefold increase in cadmium and could cause renal tubular damage. (M Lead: • O Foetuses and infants are highly susceptible to drinking water lead contamination. • r High blood lead levels in children (>3o mug/ Mi) are believed to induce biochemical and neurophysiological dysfunction. • r However, lower than normal blood levels of lead can cause mental deficiencies and behavioural problems.”
Why relevant

Notes environmental processes (acidification) can increase partitioning of methylmercury into water and that interventions (lime) can reduce mercury levels in fish — implying environmental context affects exposure levels and mitigation is used to lower risk.

How to extend

A student could use local water acidity and fish mercury monitoring to assess whether mitigation can feasibly reduce exposures below any proposed safe thresholds, or whether variability makes a universal 'safe' level impractical.

Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 6: Environmental Degradation and Management > nuclear Pollution/radiation Pollution > p. 44
Strength: 3/5
“Radioactive substance releases invisible radiations which cause many deleterious efects on all living organisms directly or indirectly. Tese radioactive substances are radium, uranium, plutonium, pdonium etc. Low levels of radiations have been enamating from natural resources since evolution but the level of exposure has increased enormously after the advent of nuclear weapons and the development of nuclear energy. Nuclear pollution is a kind of physical of the environment which diferes from air, water, and soil pollution. Tere is no safe dose of radiation.”
Why relevant

States for ionizing radiation 'There is no safe dose of radiation,' providing an example of a pollutant for which regulators consider any exposure potentially harmful — a conceptual parallel for mercury.

How to extend

A student could use this analogy to explore whether mercury is treated similarly in policy/science (i.e., linear no-threshold vs. threshold models) by consulting mercury risk assessment approaches.

Pattern takeaway: UPSC validates 'extreme' sounding health warnings (e.g., 'no safe level') if they align with global health consensus (WHO). Do not blindly eliminate extreme statements in Science/Environment without checking if the substance is a bio-accumulator.
How you should have studied
  1. [THE VERDICT]: Sitter for S1 & S2 (Standard Shankar/NCERT), but a Conceptual Trap for S3 (requires specific WHO toxicology awareness).
  2. [THE CONCEPTUAL TRIGGER]: Heavy Metal Pollution & The Minamata Convention (2013).
  3. [THE HORIZONTAL EXPANSION]: 1. Minamata Targets: ASGM (Artisanal Gold Mining), Coal plants, Cement production, Chlor-alkali. 2. Banned Products: Batteries, CFLs, Skin-lightening soaps, Thermometers. 3. Exemptions: Vaccines (Thiomersal), Military uses. 4. Sibling Toxins: Lead (Pb) also has 'no known safe level' per WHO.
  4. [THE STRATEGIC METACOGNITION]: When studying pollutants, categorize them by 'Threshold' vs 'Non-threshold' agents. For bio-accumulative heavy metals (Mercury, Lead) and Radiation, the scientific consensus is often 'no safe level.' Always check the WHO 'Key Facts' page for the top 10 chemicals of concern.
Concept hooks from this question
📌 Adjacent topic to master
S1
👉 Artisanal and small‑scale gold mining (ASGM) as a mercury source
💡 The insight

ASGM uses and releases mercury and is specifically targeted for reduction under the Minamata Convention.

High‑yield for GS‑III environment and international law: links pollution sources to global treaty responses, policy measures, and implementation challenges. Mastery helps answer questions on pollutant sources, international environmental agreements, and mitigation strategies.

📚 Reading List :
  • Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 28: International Organisation and Conventions > The Minamata Convention requires that parties nations: > p. 411
🔗 Anchor: "Is gold mining activity a source of global mercury pollution?"
📌 Adjacent topic to master
S1
👉 Mining‑linked mercury contamination and health impacts
💡 The insight

Mining operations can release mercury into rivers and ecosystems, causing acute and chronic human poisoning.

Useful for linking environmental degradation to public health and legal accountability in essay and ethics questions; connects topics in environment, disaster/health management, and governance.

📚 Reading List :
  • Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 29: Environment Issues and Health Effects > c) Itaiitai disease > p. 416
🔗 Anchor: "Is gold mining activity a source of global mercury pollution?"
📌 Adjacent topic to master
S1
👉 Mercury ores and industrial processing (cinnabar → mercury)
💡 The insight

Cinnabar (HgS) extraction and thermal reduction produce elemental mercury, creating a direct industrial source of pollution.

Helps explain technical pathways of pollutant generation and informs mitigation/technology questions in environment and geography segments; useful in questions on mineral processing and pollutant control.

📚 Reading List :
  • Science , class X (NCERT 2025 ed.) > Chapter 3: Metals and Non-metals > 3.4.3 Extracting Metals Low in the Activity Series > p. 51
🔗 Anchor: "Is gold mining activity a source of global mercury pollution?"
📌 Adjacent topic to master
S2
👉 Minamata Convention and mercury emission controls
💡 The insight

The Minamata Convention mandates controlling mercury air emissions from coal-fired power plants.

High-yield for UPSC: links international environmental law to domestic pollution control obligations and policy responses. Useful for questions on global treaties, national implementation measures, and industrial regulation.

📚 Reading List :
  • Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 28: International Organisation and Conventions > The Minamata Convention requires that parties nations: > p. 411
🔗 Anchor: "Do coal-fired (coal-based) thermal power plants emit mercury and contribute to m..."
📌 Adjacent topic to master
S2
👉 Mercury toxicity and bioaccumulation (methylmercury in water/fish)
💡 The insight

Methylmercury in water bodies and elevated mercury in fish are primary health/environmental consequences of mercury pollution.

Important for environment–health questions; connects pollution sources to human/ecosystem impacts and public health policy. Helps answer questions on environmental hazards, food safety, and remediation priorities.

📚 Reading List :
  • Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 29: Environment Issues and Health Effects > 29.r.4. Mercury > p. 413
🔗 Anchor: "Do coal-fired (coal-based) thermal power plants emit mercury and contribute to m..."
📌 Adjacent topic to master
S2
👉 Pollutant controls at coal-fired thermal plants (fly ash, SOx/NOx)
💡 The insight

Thermal plants generate fly ash and regulated pollutants, and specific notifications govern capture, monitoring and utilisation of these emissions.

Useful for governance and pollution-control topics: links technology (electrostatic precipitators), regulation (fly ash notification), and pollutant management. Enables answers on mitigation measures for power-plant emissions and policy instruments.

📚 Reading List :
  • Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 5: Environmental Pollution > How it is collected? > p. 66
  • Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 5: Environmental Pollution > Fly ash notification zozr > p. 67
🔗 Anchor: "Do coal-fired (coal-based) thermal power plants emit mercury and contribute to m..."
📌 Adjacent topic to master
S3
👉 Mercury bioaccumulation and neurotoxicity
💡 The insight

Mercury bio-accumulates and bio-magnifies in the food chain and damages the human nervous system, making even small exposures a public-health concern.

High-yield for environment and health topics: links toxicology, fisheries, and human health impact. Mastery helps answer questions on exposure routes, why fish consumption advisories exist, and scientific rationale for strict mercury controls.

📚 Reading List :
  • Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 28: International Organisation and Conventions > 28.22. MINAMATA CONVENTION > p. 411
  • Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 29: Environment Issues and Health Effects > 29.r.4. Mercury > p. 413
🔗 Anchor: "Is there a known safe level of human exposure to mercury, or is no safe level es..."
🌑 The Hidden Trap

The Minamata Convention explicitly EXCLUDES vaccines containing thiomersal (a mercury-based preservative) from its bans. A future trap might be: 'The convention bans mercury in all medical products including vaccines.' (False).

⚡ Elimination Cheat Code

Apply 'Bioaccumulation Logic' to Statement 3. If a toxin bioaccumulates (stays in the body), any non-zero exposure adds to the burden. Therefore, a 'safe level' (where the body can clear it perfectly) theoretically doesn't exist. This makes the extreme statement correct.

🔗 Mains Connection

Connects to GS-II (Health) & GS-III (Economy): The 'One Health' approach. Mercury pollution illustrates how informal economic sectors (illegal gold mining) create long-term public health deficits (neurological damage), reducing national Human Capital.

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