Quote (National Precast Concrete Association / The Future of Fly Ash Use in Concrete November 22, 2013)

It should be noted that environmentalists’ concerns about potentially toxic water pollution (particularly mercury) have no relevance to the use of fly ash in concrete production. The mercury level in most fly ash is the same as that found in most virgin soils. Further, if CCPs are high in mercury (mercury has an affinity for carbon), its carbon content would make it unsuitable for concrete. EPA’s main concern with fly ash has been certain unlined landfills and specific massive earth fills. Failures of fly ash settling ponds, like the 2008 TVA spill, are extremely rare events, and in any case, only dry fly ash is used in concrete – not wet material in settling ponds. And lastly, the EPA has not indicated any desire to restrict fly ash use in concrete.