Two faces of chromium - pollutant and bioelement

Life and growth of plants and animals depends on some metals as micronutrients. However, certain forms of some metals can also be toxic, even in relatively small amounts, and therefore determine risk to the health of animals and people. Chromium is a heavy metal whose concentration in the environment is increasing. Chromium in inorganic systems occurs in several chemical forms. Only Cr(III) and Cr(VI) are significant in biological systems. Trivalent chromium is an essential nutrient component while excess chromium(VI) in biological systems has been implicated in specific forms of cancer.