Consider the following statements about mercury pollution:

1. Artisanal and small-scale gold mining, where mercury is used to extract gold from ore, is one of the largest sources of mercury pollution globally.

2. Coal-based thermal power plants are a significant source of atmospheric mercury emissions.

3. According to the World Health Organization, there exists a well-established safe threshold of mercury exposure below which no adverse health effects occur.

How many of the statements given above are correct?