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?

1. Gold mining activity is a source of mercury pollution — Correct. Artisanal and small-scale gold mining widely uses mercury to extract gold and is a major global source of mercury emissions.
2. Coal-based thermal power plants cause mercury pollution — Correct. Coal contains trace mercury, which is released during combustion in thermal power plants.
3. There is no known safe level of exposure to mercury — Correct. WHO and public health guidance treat mercury as highly toxic, especially to the nervous system, and no exposure level is considered completely risk-free.
Hence, all three statements are correct.