Page 2: Guidelines for Canadian Drinking Water Quality: Guideline Technical Document – Chromium
General
Chromium can exist in valences from -2 to 6 but is present in the environment mainly in the trivalent or hexavalent state. Trivalent chromium (Cr[III]) is the most common naturally occurring state; most soils and rocks contain small amounts of chromic oxide (Cr2O3). Hexavalent chromium (Cr[VI]) occurs infrequently in nature, and chromates (CrO42-) and dichromates (Cr2O72-) present in the environment are generally the result of industrial and domestic emissions. Chromium is present in Canadian soils at concentrations ranging from 20 to 125 mg/kgFootnote 1 and is found in trace quantities in most plant and animal tissues.
Chromium is widely used in industry. The hexavalent chromium compounds are used in the metallurgical industry for chrome alloy and chromium metal production and chrome plating, and in the chemical industry as oxidizing agents and in the production of other chromium compounds. Trivalent chromium salts are used less widely, being employed in textile dyeing, in the ceramic and glass industry, and in photography.
The only commercially important chromium mineral is chromite (FeOCr2O3). Canadian deposits of this mineral are usually low-grade, and consequently all Canadian requirements for chromium are filled by importation. Canadian consumption of chromite in 1981 was 24 771 tonnes.Footnote 2