How Toxic Is Coal Ash? A Laboratory Toxicity Case Study

Under a consent agreement among the Environmental Protection Agency (EPA) and proponents both for and against stricter regulation, EPA is to issue a new coal ash disposal rule by the end of 2014. Laboratory toxicity investigations often yield conservative estimates of toxicity because many standard test species are more sensitive than resident species, thus could provide information useful to the rule-making. However, few laboratory studies of coal ash toxicity are available; most studies reported in the literature are based solely on field investigations. This brief communication describes a broad range of toxicity studies conducted for the Tennessee Valley Authority (TVA) Kingston ash spill, results of which help provide additional perspective on the toxicity of coal ash. Integr Environ Assess Manag 2015;11:5–9. © 2014 SETAC


In 2010, the Environmental Protection Agency (EPA) proposed regulation of Coal Combustion Residuals (CCR) under the Resource Conservation and Recovery Act (RCRA), which may result in more stringent controls on the disposal of CCR, particularly fly ash, at coal-fired power plants (USEPA 2010). Clearly, there is a need for a comprehensive body of peer-reviewed scientific literature from which EPA can assess environmental impacts of CCR.

Rowe et al. (2002) provided a thorough review of research on the environmental effects of CCR disposal. A brief, independent review limited to studies that included aquatic and benthic organism exposures to ash or ash basin effluents identified only 13 published articles. Ten were field studies of benthic or fish biota in 1 lentic and 10 lotic habitats (Cherry et al. 1979; Reash et al. 1988; Lemly 1997; Lohner, Reash, Willet, Fletcher 2001; Lohner, Reash, Willet, Rose 2001; Lohner, Reash, Williams 2001; Smith 2003; Reash 2004, 2012; Otter et al. 2012); and 3 were laboratory studies (Stanley et al. 2013; Wang et al. 2013; Greeley et al. 2014a), all of which were investigations of the 2008 Tennessee Valley Authority (TVA) Kingston Fossil Plant ash spill. This imbalance between field- and laboratory-based studies is likely due to prevailing opinions that laboratory studies should predict toxic effects in the field (Lemly 1985). There is a widely held acceptance that laboratory studies are conservative (particularly in the use of test organisms that are usually more sensitive to toxicants than resident species) and provide for controlled exposure conditions that exclude the noise experienced in the natural environment (Chapman 2000; Wang et al. 2004).