Mercury is a naturally occurring metal in the Earth’s crust. As a chemical element, it cannot be created or destroyed. The same amount of mercury has existed since the Earth was formed.
Most human intake of mercury comes from eating certain types of fish or seafood containing a form of mercury called "methylmercury." But there is disagreement among experts over the level of mercury considered safe for public health.
The electric power industry will reduce mercury emissions about 90 percent through implementation of the Utility MACT rule beginning in 2015.