Zinc, copper, cadmium and chromium in polished and unpolished rice.

One hundred samples of polished and 27 of unpolished rice were collected from 22 countries and areas and analyzed for Zn and Cu by flame atomic absorption, for Cd by carbon furnace atomic absorption, and for Cr by neutron activation. Unpolished rice contains on average 16.4 mug/g Zn, 4 mug/g Cu, 0.029 mug/g Cd and 0.011 mug/g Cr. Polished rice contains 13.7 mug/g Zn, 3 mug/g Cu, 0.029 mu/g Cd and 0.012 mug/g Cr. Thus, polishing brings about a loss of the essential elements Zn and Cu, but not of Cd, a toxic pollutant. Japanese rece has high Cd content. In countries where rice is a major staple food, high Cd content in rice may cause excessive absorption of this toxic metal.