UPSC Prelims 2023 Q59: Environment & Ecology – Pollution & Waste Management
- (a) Only one
- (b) Only two
- (c) All three
- (d) None
Answer: (b) Only two
Explanation
Mercury Pollution — Sources and Safety
| Statement | Claim | Verdict | Detail |
|---|---|---|---|
| 1 | Gold mining is a source of mercury pollution | TRUE | Artisanal Small-scale Gold Mining (ASGM) is the largest source of mercury pollution globally. Miners use mercury to form amalgam with gold, then burn it off, releasing mercury vapour. ASGM accounts for ~37% of global mercury emissions. |
| 2 | Coal-based thermal power plants cause mercury pollution | TRUE | Coal contains trace amounts of mercury. When burned, mercury is released as gas. Coal combustion is the second largest source of mercury pollution, contributing ~21% of global emissions. |
| 3 | There is no known safe level of exposure to mercury | FALSE | While mercury is highly toxic, regulatory bodies (WHO, EPA) have established reference doses and tolerable intake levels — maximum safe exposure thresholds. The statement is too absolute. |
Statements 1 and 2 correct → Only two.
Answer: (b) Only two.
Why each option is right or wrong
- (a) Incorrect. 'Only one' — both gold mining and coal power plants are well-documented mercury pollution sources.
- (b) CORRECT. Gold mining and coal thermal plants are both mercury sources. Statement 3 is false — safe exposure thresholds exist (e.g., WHO provisional tolerable weekly intake for methylmercury).
- (c) Incorrect. 'All three' — Statement 3 overstates mercury toxicity; regulatory agencies have defined safe exposure levels.
- (d) Incorrect. 'None' — ASGM as a mercury pollution source is one of the most documented environmental facts in the Minamata Convention context.
Key point
Gold mining + coal power plants = mercury pollution sources (TRUE). 'No known safe level' = FALSE (WHO/EPA have established reference doses). Two of three correct. Minamata Convention specifically targets mercury from these sources.
Remember
Gold mining and coal-based thermal power plants are genuine sources of mercury pollution. However, it is incorrect that there is no known safe level of exposure — WHO and EPA have established reference doses and tolerable intake levels for mercury.
Common mistakes
- Accepting 'no known safe level' as true for all forms of mercury — while methylmercury is extremely dangerous, regulatory agencies DO establish maximum tolerable limits.
- Not knowing ASGM is the largest mercury pollution source — artisanal gold mining surpasses coal plants in mercury emissions globally.
- Confusing absolute toxicity with absence of safety thresholds — mercury is dangerous but not without defined safe exposure levels.
Exam tip
Minamata Convention = global mercury treaty. Top mercury sources: ASGM (37%) + coal combustion (21%). Statement 3 trap: WHO/EPA DO have mercury safety thresholds — 'no safe level' is an overstatement. Same reasoning applies to lead ('no safe level for children' is a specific statement, not universal).
Sources
- UNEP Minamata Convention — Mercury Sources and Emissions
- WHO — Mercury and Health: Exposure Limits