Why trace elements are important

The widespread presence of trace elements is shown by reviewing their roles during the mining, beneficiation and combustion of coal and during metal mining and treatments. Special attention is given to Hg, to the environmentally important mineral, pyrite, to radioactivity, to waste disposal, to reclamation after mining and to health aspects. The 26 trace elements that are considered to be of environmental interest are listed. Important topics for future research are discussed. Although many trace element problems are under control, constant vigilance is a sine qua non and ongoing research is important.