Ashes (residues), coal

Endpoint summary

Additional information

Ashes are inorganic complex compounds consisting of multitude of unknown and variable constituents (UVCB), and it is therefore technically not possible to determine an overall bioaccumulation for this substance. However, most of metals contained in ashes, which are of concern have been reviewed in literature. 

End of 2008 4.1 million m^3 coal ash were released into the Emory, Tennessee and Clinch rivers due to an accident in the Tennessee Valley Authority (TVA) Kingston Fossil Plant. This unfortunate accidence provided an opportunity to directly study the impact of coal fly ash in a large lotic system since more than one rivers were affected. A variety of studies were initiated by multiple actors to assess ecological risks to different organisms. More than 24 metals (e.g. As, Cr, Hg, Se, Ag, Al, Ba, Be, Ca, Cd, Co, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, Pb, Sb, Tl, V, Zn) were investigated. Among multiple toxicological and ecotoxicological studies, bioaccumulation potential of metals associated to fly ash was investigated either as an endpoint solely or in combination with toxicological effects.

Bioavailability and consequently bioaccumulation of ash-related metals is complex and dependent on multiple factors like pH, redox potential, geochemical interactions etc. The site monitoring and lab investigations of the presented publications and monitoring data for aquatic, sediment and terrestric compartments showed in a weight of evidence approach that bioaccumulation of ash associated metals is generally very low and not of concern for any compartment. In only very few cases (e.g. for As and Se) concentrations in organisms exceeded proposed thresholds (e.g. from US EPA, FDA) for the protection of the environment and humans but was observed for only very high ash concentration in the river and under the extreme conditions caused by the spill.