Coal contains trace quantities of many elements that can be toxic if present in high enough concentrations. Many of these elements are released after combustion into more available forms for human assimilation. Hence, burninq coal increases the potential for toxic trace element hazard. Assessment of the literature an measurements of trace elements during the combustion of coal has made it clear that these measurements are imprecise and contradictory. In this literature review, mass balance of measurements in coal-fired plants are evaluated and research in the enrichment of trace elements in coal ashes is reviewed. The problems in measuring trace elements in coal-fired facilities are presented with the intention that the knowledge of the difficulties outlined here will promote future study and active research in these areas