The process of coal combustion leads to a concentration of trace elements in the resulting waste ash. While exposure to the traces of these elements in nature does not usually result in toxicity, their concentration in coal ash has the potential for dysfunction of multiple organ systems. 

There is copious evidence that suggests that exposure to coal ash is harmful to nearby residents (particularly children) and workers, so a precautionary approach must limit population exposure wherever possible. Research is urgently needed to clarify this risk in relation to the New South Wales populations under discussion. Appropriate epidemiologic assessment will help support health-related decision-making regarding ash dams at the individual and public health level. 
Read DEA’s full submission here