The subject of mercury emissions from coal-fired power plants and cement plants has always been fraught with uncertainties (HCN, 1/18/10). Industry influence at the congressional level often got transferred down as pressure on the U.S. Environmental Protection Agency. Stephen Johnson, Bush's administrator of the EPA, and his deputy, Marcus Peacock, seemed intent on reducing EPA's effectiveness in this area. With Deputy Peacock leading the attack, the Bush administration moved to emasculate the Toxics Release Inventory Program, which annually collects industry releases of toxic chemicals like mercury from various types of manufacturing plants. (The Obama administration and a new administrator at the EPA are reversing this.)
Actually, the cement and power plants themselves are responsible for calculating their releases of mercury. The only way the EPA can determine the accuracy of their mercury release numbers is to make enforcement visits to review production data and the mercury release calculations. During the Bush years, the EPA's budgets for travel and enforcement were continually reduced, ultimately making enforcement visits impossible. So, mercury releases as reported by cement and power plants in the past can only be described as questionable.
Jack F. Salter