Geochemistry and human selenium imbalances in China

Se is a naturally occurring non-metallic trace element which is essential to human and other animal health in small doses (0.04 μg/g) but is harmful in excess (> 4 μg/g). China possesses one of the best epidemiological databases in the world on Se related diseases which has been used in conjunction with geochemical data to demonstrate a significant geological control on human Se exposure. Se deficiency in soils and crops has been linked to an endemic cardiomyopathy (Keshan Disease (KD)), osteoarthropathic disorders (Kashin-Beck Disease) and oesophageal cancer whereas selenium toxicity causes hair loss and nail deformation. However, the precise geographic areas at risk, the geochemical factors controlling environmental Se levels and human Se status are poorly defined and appropriate remediation strategies have yet to be established.