Update. Below is an extract sent to me by CFACT.
Professor Willie Soon and CFACT senior policy advisor Paul Driessen co-authored an article regarding the EPA’s mercury rule that provides valuable perspective. In it they note:
"The latest government, university and independent studies reveal that those power plants emit an estimated 41-48 tons of mercury per year. However, U.S. forest fires emit at least 44 tons per year; cremation of human remains discharges 26 tpy; Chinese power plants eject 400 tpy; and volcanoes, subsea vents, geysers and other sources spew out 9,000-10,000 additional tons per year!”
All these emissions enter the global atmospheric system and become part of the U.S. air mass.
Thus, U.S. power plants account for less than 0.5% of all the mercury in the air Americans breathe. Even eliminating every milligram of this mercury will do nothing about the other 99.5% in America’s atmosphere."