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?
Explanation
* Statement 1 is Correct: Gold mining is poisoning Amazon forests with mercury. To separate the gold, miners mix liquid mercury into the sediment, which forms a coating around the gold.
* Statement 2 is Correct: Fly ash generated by TPPs is one of the ways mercury is released into the environment. Fly ash is usually disposed of in ash ponds in the form of ash slurry, forming an aquatic ecosystem of its own. Coal-based TPPs are the major source of mercury – the ninth most toxic element found on earth — emissions into the environment. Mercury contributed over 80 percent of emissions released by the TPPs, according to 2016 estimates by the Delhi-based think-tank Centre for Science and Environment.
* Statement 3 is Incorrect: While mercury is unquestionably toxic, toxicology works on the principle of dose: "The dose makes the poison." Hence, scientific bodies define reference doses (RfD) or tolerable intake levels, not zero exposure. WHO's Provisional Tolerable Weekly Intake (PTWI) for methylmercury (from fish) → 1.6 µg/kg body weight/week and 1 µg/litre for total mercury in drinking water. If no safe level truly existed: Mercury would be completely banned, not regulated.
NOTE: UPSC usually considers extreme statement to be wrong.