Managing cadmium in agricultural systems

Cadmium (Cd) is a naturally occurring element present in all soils from both geogenic and anthropogenic sources. The primary risk pathway to humans is exposure through dietary intake in foods and by inhalation through smoking, with the target affected organ being the kidney. In developed countries, Cd intakes by populations are below levels of concern as determined by the World Health Organization. However, in some developing countries Cd intakes are increasing, so management of Cd transfer through the food chain remains important to minimize human exposure. Significant advances have been made in understanding the behavior of Cd in agricultural systems and a range of management options are now available for farmers to minimize uptake into crops and forages. Our understanding of the genetics of root Cd uptake, translocation and accumulation in shoots, grains and tubers has advanced significantly and farmers now have the option to manage Cd through choice of crop and/or new low-Cd cultivars. High-risk soils can now be identified by soil testing and various agronomic options are available to minimize plant uptake on these high-risk soils. Combined, these management options can rapidly reduce Cd concentrations in foods, quicker than reductions in Cd inputs in fertilizers, manures or atmospheric sources. However, it is important that we limit Cd accumulation in soils and aim for zero-net accumulation. Calculating limits to Cd inputs necessary to achieve this are compromised by the lack of accurate information on measurement of rates of Cd leaching under field conditions.