CHROMIUM CHEMISTRY AND IMPLICATIONS FOR ENVIRONMENTAL FATE AND TOXICITY

The same chemical properties that make chromium such an important comp onent of so many industrial and consumer products are the important fa ctors controlling ifs environmental fate and toxicity. Although only a bout 15% of the chromium mined is used in the manufacture of chromium chemicals, the chemistry of chromium is important in nearly all applic ations. For instance, the ''stainless'' nature of stainless steel is d ue to the chemical properties of the chromium oxides that form on the surface of the alloy. Similarly, the product protection afforded by ch rome plating of metals, CCA treatment of wood, and chrome tanning of l eather is directly dependent on chromium chemistry. In all of these ap plications the most important chemical property is that under typical environmental and biological conditions of pH and oxidation-reduction potential, the most stable form of chromium is the trivalent oxide. Th is form has very low solubility and low reactivity resulting in low mo bility in the environment and low toxicity in living organisms. The ch emical properties of the major commercial products of chromium are dis cussed in the context of the Eh-pH diagram. These same chemical proper ties control the environmental fate of chromium and are closely tied t o the toxicity of the various compounds.