California’s Office of Environmental Health Hazard Assessment (OEHHA) Proposes New, More Stringent, Drinking Water Standard for Hexavalent Chromium

August 21, 2009

On August 20, 2009, California’s Office of Environmental Health Hazard Assessment (OEHHA) announced a new, and significantly more stringent, proposed Public Health Goal (PHG) for the compound hexavalent chromium, or chromium(VI).  Concluding that “there is now sufficient concern” that hexavalent chromium is carcinogenic by the “oral route of exposure,” the Office proposed a new limit of 0.06 parts per billion (ppb) or micrograms per liter (μg/L) in drinking water.  This proposal reflects a dramatically lower number from California’s current drinking water standard of 50 ppb total chromium, which is already half the national standard for total chromium.  A PHG is not a legally enforceable standard but it can lead to a need for warnings and notifications for drinking water, and some public agencies use PHGs as a target for clean up.  The adoption of a PHG generally leads to consideration by the state of a Maximum Contaminant Level (“MCL”) for that same compound in drinking water, which is a legally enforceable standard.  However, MCLs are adopted by following a different procedure and using different criteria.

While long-anticipated, OEHHA’s new proposed PHG promises to be controversial.  Not only is it almost 900 times more stringent than California’s current standard, it is based in large part on a recent two-year study conducted by the National Institute of Environmental Health Studies’ National Toxicology Program (NTP) regarding the effect of oral exposure to hexavalent chromium on different species of laboratory mice and rats.  The NTP study, published in 2007, found increased incidences of malignant tumors in the mouths and small intestines of mice and rats exposed to hexavalent chromium through their drinking water, but it did little to quell the decades-long scientific debate over whether oral ingestion of hexavalent chromium causes cancer in humans.  Because gastric acids in the stomach are known to reduce hexavalent chromium to chromium III (a non-toxic form of chromium and an essential mineral), the difference between a human stomach’s and a rodent stomach’s capacity to reduce the compound makes extrapolating the results of the rodent studies to humans problematic and, as a result, OEHHA’s prominent reliance on the NTP’s data in formulating its draft PHG may be criticised.

OEHHA’s markedly low 0.06 ppb draft PHG is not entirely without precedent in California, where hexavalent chromium has been detected in approximately 30% of drinking water sources.  In 1999 the State adopted a 2.5 ppb PHG for hexavalent chromium in drinking water, only to rescind that standard in 2001 after a government-appointed peer review panel concluded that the key study relied upon by California’s scientists was inadequate to assess the risk posed by hexavalent chromium in drinking water.

OEHHA’s draft technical support document for its proposed PHG is available at  An initial 45-day public comment period expires on October 19, 2009.  The Office will also hold a public workshop with OEHHA scientists on October 19, 2009 in Oakland to discuss the scientific basis of the proposed PHG, and to receive additional comments.  Following the workshop, OEHHA will evaluate all the comments received, revise the document as appropriate, and make it available for another 30-day comment period.

Gibson, Dunn & Crutcher’s Environment and Natural Resources Practice Group has particular expertise in toxic tort and cost recovery actions related to hexavalent chromium. We also handle a range of other environmental litigation and counseling matters nationwide. 

To learn more about the firm’s environmental litigation, please contact the Gibson Dunn attorney with whom you work or practice group co-chairs Patrick W. Dennis (213-229-7567, [email protected]) or Jeffrey D. Dintzer (213-229-7860, [email protected]) in Los Angeles, Alan N. Bick (949-451-4211, [email protected]) in Orange County, or Peter E. Seley (202-887-3689, [email protected]) in Washington, D.C.

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