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2316211 
Technical Report 
State of the science of Hexavalent Chromium in drinking water 
Mcneill, L; Mclean, J; Edwards, M; Parks, J 
2012 
Water Research Foundation 
Denver, CO 
36 
English 
INTRODUCTION
Chromium typically occurs in two oxidation states in the natural environment, water treatment processes and water distribution systems: trivalent chromium (chromium-3, Cr(III), Cr+3), and hexavalent chromium (chromium-6, Cr(VI), Cr+6). Trivalent chromium has been considered an essential human nutrient. Recent studies, however, have shown no deleterious effects from low Cr(III) in the diet and there is no known biological mechanistic function for Cr(III) in cells calling into questions whether Cr(III) is truly an essential nutrient (Di Bona et al. 2011). Hexavalent chromium has been demonstrated to be a human carcinogen when inhaled. The health effects of hexavalent chromium through ingestion—the dominant exposure route for drinking water—are currently under review at the federal level by the U.S. Environmental Protection Agency (USEPA).

Hexavalent chromium in drinking water was first brought to the public’s attention in 1993 when Erin Brockovich highlighted contamination in groundwater near Hinkley, CA. In 2010, the Environmental Working Group (EWG) reported trace levels of hexavalent chromium in 31 of 35 US tap waters tested (Environmental Working Group, 2010); although this was not a peer-reviewed scientific study, it did renew public interest in hexavalent chromium. USEPA is currently considering whether or not to establish an MCL specifically for hexavalent chromium (USEPA, 2011a). A February 2011 U.S. congressional hearing largely focused on the EWG study (U.S. Senate Committee on Environment and Public Works 2011) further highlighted the hexavalent chromium issue. The goal of this review is to better inform potential regulatory action on this issue by summarizing what is known about hexavalent chromium, as well as pointing out gaps in current knowledge. 
IRIS
• Chromium VI
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