Chromium-6:  Timeline for Drinking Water Regulations

Last Update: January 9, 2013

Here are significant events associated with development of a maximum contaminant level (MCL) for chromium-6 in drinking water:

• February 1999: As part of its activities associated with the development of Public Health Goals (PHGs), OEHHA evaluated total chromium and established a  2.5-µg/L PHG for total chromium (PDF), reflecting a view that chromium-6, a component of total chromium, poses a cancer risk when ingested. 
• March 1999: Following OEHHA's PHG for total chromium, the California Department of Health Services (CDHS, now the California Department of Public Health, CDPH) identified chromium as a contaminant for possible MCL review.  CDHS also announced it would include chromium-6 among the unregulated chemicals requiring monitoring.
• March 2000: The film Erin Brockovich was released.  Subsequent press and political attention raised public awareness and concern about chromium-6.

• September 2000: The Governor signed SB 2127 (Schiff) into law.  It requires CDHS to determine the levels of chromium-6 in drinking water supplied by public water systems in the San Fernando Basin aquifer, and, in consultation with OEHHA, assess the associated exposures and risks to the public.

• January 2001: With adoption of a regulation identifying chromium-6 as an unregulated chemical requiring monitoring, CDHS began receiving sampling results.

• March 2001:  Cal/EPA asked the University of California to convene an expert panel to address the carcinogenicity of ingested chromium-6, and CDHS requested OEHHA to prepare a PHG for chromium-6.  A PHG is needed for the development of a chromium-6-specific MCL.

• May 2001: The National Toxicity Program (NTP) announced it would conduct long-term rodent bioassays to evaluate the potential carcinogenicity of ingested chromium-6.  Results are expected in 2005.  Updates of protocols and results of preliminary studies are available at the NTP website.

• July 2001:  UC expert panel meets regarding carcinogenicity of ingested chromium-6.

• August 2001: The expert panel's report (PDF)is released. Among its findings, the panel considered the mouse study providing the basis for the PHG's 0.2-µg/L de minimis cancer risk for ingested chromium-6 to be unsuitable for such use. The panel also concluded that the current total chromium MCL (50 µg/L) provides adequate public health protection, pending the completion of the NTP studies.

• October 2001:  The Governor signed SB 351 (Ortiz) (Health and Safety Code Section 116365.5, Chapter 602, Statutes of 2001) into law. It requires CDHS to adopt a chromium-6 MCL by January 1, 2004.

• November 2001: OEHHA announced its withdrawal of the total chromium PHG.  A chromium-6-specific PHG will be developed by OEHHA.

• April 2003:  At a legislative hearing in Sacramento on April 2, Cal/EPA announced it would not use the expert panel's report in the chromium-6 PHG—citing concerns about panelists' possible conflicts of interest—and OEHHA indicated the draft PHG would not be available until later that year.

• August 2005:  OEHHA released comments of peer reviewers (PDF) of a "pre-release" draft PHG for chromium-6. 

• May 2007:  NTP's reports on studies on the carcinogenesis of chromium-6 (dichromate dihydrate) in drinking water—which found there to be sufficient evidence of carcinogenicity in rodents—are reviewed and approved by the Board of Scientific Counselors Technical Reports Review Subcommittee. 

• August 2009:  OEHHA releases a draft PHG for chromium-6.

• September 2010:  OEHHA releases comments of peer reviewers of the August 2009 draft PHG.

• September 2010:  US EPA's IRIS releases its Toxicological Review of Hexavalent Chromium (External Review Draft) - now archived.

• December 2010:  OEHHA releases a revised draft PHG for chromium-6.

• January 2011:  US EPA releases its recommendations for enhanced chromium-6 monitoring for public water systems. 

• July 2011:  OEHHA releases the final PHG for chromium-6.

• Current status:  See status of the MCL for chromium-6.