Chromium-6: Timeline for Drinking Water Regulations

Last Update: July 1, 2014

Here are significant events associated with development of a maximum contaminant level (MCL) for chromium-6 (hexavalent chromium) 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, which would become 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 Toxicology 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 2007NTP'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.
  • August 2013: CDPH proposes an MCL for chromium--6.
  • April 2014: CDPH submits the regulations package to the Office of Administrative Law (OAL) for review for compliance with the Administrative Procedure Act.
  • May 2014: OAL approves the regulations.
  • July 2014: The MCL for chromium-6 becomes effective.