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?

(a) Only one

(b) Only two

(c) All three

(d) None

12. Ans: b

Expalanation:

Mercury

Mercury is highly toxic to human health, posing a particular threat to the development of the child in utero and early in life. It occurs naturally and exists in various forms: elemental (or metallic); inorganic (for example, mercuric chloride); and organic (for example, methylmercury and ethylmercury). These forms all have different toxicities, with different implications for health and for measures to prevent exposure.

 Elemental mercury is a liquid that vaporizes readily. It can stay for up to a year in the atmosphere, where it can be transported and deposited globally. It ultimately settles in the sediment of lakes, rivers or bays, where it is transformed into methylmercury, absorbed by phytoplankton, ingested by zooplankton and fish, and accumulates especially in long-lived predatory species, such as sharks and swordfish .

Mercury releases 

• Natural: volcanic activity, weathering of rocks, water movements, biological processes.

 • Human activities: mercury-added products; manufacturing processes in which mercury or mercury compounds are used; artisanal and small-scale gold mining; coalfired power plants; coal-fired industrial boilers; smelting and roasting processes used in the production of non-ferrous metals; waste incineration facilities; cement clinker production facilities.

 • Remobilization of legacy sources: mercury in soil, sediment, water, landfill, waste 

Hence Statement 1& 2 are correct.

WHO guidance values: provisional tolerable weekly intake

Joint FAO/WHO Expert Committee on Food Additives (JECFA) established a tolerable intake of µg/kg body weight per week for dietary exposure to methylmercury & inorganic mercury.

Hence Statement 3 is incorrect.

The Minamata Convention on Mercury, which entered in to force in 2017, implemented guidelines, which includes banning new mercury mines and phasing-out existing ones; regulating the use of mercury in artisanal and small-scale gold mining, certain industrial processes and the production of everyday items such as certain Compact fluorescent lamps, batteries and teeth fillings; as well as controlling the emissions of mercury as a by-product from a range of industrial sectors including coal burning.

Read: Previous Year UPSC Environment Questions (PYQs) With Explanation 2023