Chromium VI

Chromium exists in small quantities throughout the environment. Chromite ore (FeCr₂O₄) is the most important commercial ore and is usually associated with ultramafic and serpentine rocks. These are found in the western United States where commercial mining was formally conducted. Chromium is also associated with other ore bodies (e.g., uranium and phosphorites) and may be found in tailings and other beneficiation wastes from these mining operations. Acid mine drainage can make the chromium available to the environment. Chromium and its compounds are used in refractories, drilling muds, electroplating cleaning agents, catalytic manufacture, and in the production of chromic acid and specialty chemicals. Hexavalent chromium compounds are used in the manufacture of pigments, in metal finishing and chrome plating, in stainless steel production, in hide tanning, as corrosion inhibitors, and wood preservation.

A review of the 2005 Toxics Release Inventory showed that 51,419,716 pounds of chromium compounds and 9,939,677 pounds of chromium were released on and off site of facilities using them. This is down from the 2003 inventory where 61,441,233 pounds of chromium compounds and 10,383,384 pounds of chromium were released. It is difficult to classify these releases in terms of trivalent or hexavalent chromium. Combustion activities at utilities, fugitive emissions from road dust, and former (pre 1993) industrial cooling towers accounted for a large part of chromium in the atmosphere. Chromium found in utilities emissions and road dust tend to be chromium III. Cooling tower mists contained chromium VI. In general, most chromium in surface water bodies is found in the sediments in the +3 valence state. However, hexavalent chromium anions will be the predominant form of dissolved chromium. While hexavalent chromium contamination is generally associated with industrial activity, it can occur naturally. Chung, et al (see below), present an argument that the chromate found in groundwater at a site in California is most likely the result of the oxidation of trivalent chromium by native manganese oxides.

Information regarding levels of chromium in specific geographic locations or water bodies may be available in a monitoring or characterization report. The Library of the U.S. Geological Survey provides links to several databases in which such reports can be located.

For Further Information

Chemical Analyses of Soils and Other Surficial Materials of the Conterminous United States
Josephine G. Boerngen, and Hansford T. Shacklette, 1981, U.S. Geological Survey Open-File Report 81-197, U.S. Geological Survey, Denver, CO.
Contact: David Smith, dsmith@usgs.gov

Chromate Generation by Chromate Depleted Subsurface Materials
J. Chung, et al.
Water Air and Soil Pollution, 128: 407-417, 2001

Chromium in Soil - Perspectives in Chemistry, Health, and Environmental Regulation
Paul T Kostecki University of Massachusetts, Amherst
Cat. #: 1157
CRC Press, Boca Raton, FL. ISBN: 0849311578, 256 pp, 1998

Chromium Life Cycle Study
John F. Papp.
U. S. Department of Interior, Bureau of Mines Information Circular, IC-9411, 102 pp., 1994
Contact: John Papp, jpapp@usgs.gov

Chromium(VI) Handbook
Jacques Guertin; James A. Jacobs; Cynthia P. Avakian.
Lewis Publishers/CRC Press, Boca Raton, FL. ISBN: 1566706084, 800 pp., 2004.

This handbook consolidates literature on the topic of hexavalent chromium. The broad scope of this book is intended to improve the understanding of Cr(VI) behavior in the environment by providing a detailed explanation of the geochemistry that controls the distribution of chromium in its various forms in soil and ground water.

Conversion of Chromium Ore Processing Residue to Chrome Steel
Meegoda, J.N., Z. Hu, and W. Kamolpornwijit.
New Jersey Department of Environmental Protection, 49 pp, 2007

This report summarizes the characteristics of chromite ore processing residue (COPR) in terms of chemical composition, phases, and results from a melting study to convert to iron with chromium or steel. Chromate (hexavalent chromium, or Cr[VI]) was produced during the chromate extraction process when Cr(III) in chromite ore was oxidized to Cr(VI). The highly soluble Cr(VI) was then removed from the COPR, leaving un-oxidized Cr(III) and slow-dissolving Cr(VI) compounds. In the absence of information on the toxicity of Cr(VI), COPR subsequently was used for backfill on demolition sites, in building foundations, in construction of tank berms and roadways, for filling in wetlands, and for other construction and development-related purposes. Sites in the state of New Jersey provide examples.

Elements and Their Compounds in the Environment: Occurrence, Analysis and Biological Relevance, Second Edition
E. Merian, M. Anke, M. Ihnat, and M. Stoeppler (eds.).
John Wiley & Sons, New York. ISBN: 3-527-30459-2, 3 Vols, 2004.

Emissions of Metals, Chromium and Nickel Species, and Organics from Municipal Wastewater Sludge Incinerators
U.S. Environmental Protection Agency, Office of Research and Development.
EPA 600-SR-92-003, 8 pp., 1992
Contact: Robin Segall, segall.robin@epa.gov

Chromium-6 in Drinking Water Standard: Sampling Results (for public supply wells)
State of California, Department of Health Services

Genesis of hexavalent chromium from natural sources in soil and groundwater
Christopher Oze, Dennis K. Bird, and Scott Fendorf
Proceedings of the National Academy of Science, April 17, 2007, vol. 104, no. 16, 6544-6549.

Occurrence Survey of Boron and Hexavalent Chromium
M. Frey, C. Seidel, M. Edwards, and J. Parks.
IWA Pub., London. AwwaRF Report 91044F, 124 pp, ISBN: 1843399261, Jan 2006 [Originally published by AwwaRF for its subscribers in 2004]

Total Chromium and Hexavalent Chromium Occurrence Analysis
Seidel, C.J., C.J. Corwin, and R. Khera.
Water Research Foundation (WaterRF). Web Report #4414, 32 pp, 2012

This white paper is based on an analysis of total and hexavalent chromium occurrence data that compared datasets from WaterRF, U.S. EPA, and the California Department Public Health for spatial and temporal relationships.

Toxicological Profile for Chromium
Agency for Toxic Substances and Disease Registry (ATSDR), 2012