In its natural state, chromium mainly occurs in its trivalent chromium (Cr(III)) and hexavalent chromium (Cr(VI)) forms. Trivalent chromium is an essential microelement for humans, and is nontoxic in normal doses in the food supply; at higher doses, however, trivalent chromium can exhibit cytotoxicity. Due to its highly oxidizing properties and its high skin permeability, hexavalent chromium is extremely toxic and has been confirmed to have a carcinogenic effect.