Approximately 1, 100 such units at more than 450 existing power plants emit 48 tons of mercury into the air each year, with 11 tons of that deposited on to U.S. soil and waters, says EPA. Those plants also release arsenic, lead and other heavy metals, all of which are considered hazardous and are therefore subject to clean air laws that require those facilities to use modern pollution controls.

FORBES: Coal Plants Belching Out Less Mercury