Hexavalent Chromium: Timeline for Drinking Water Regulations

Last Update: March 9, 2022

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 hexavalent chromium, 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 hexavalent chromium 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 hexavalent chromium.
• September 2000: The Governor signed SB 2127 (Schiff) into law. It requires CDHS to determine the levels of hexavalent chromium 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 hexavalent chromium 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 hexavalent chromium, and CDHS requested OEHHA to prepare a PHG for hexavalent chromium. A PHG is needed for the development of a hexavalent chromium-specific MCL.
• May 2001: The National Toxicology Program (NTP) announced it would conduct long-term rodent bioassays to evaluate the potential carcinogenicity of ingested hexavalent chromium. 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 hexavalent chromium.
• 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 hexavalent chromium 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 hexavalent chromium MCL by January 1, 2004.
• November 2001: OEHHA announced its withdrawal of the total chromium PHG. A hexavalent chromium-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 hexavalent chromium 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 hexavalent chromium.
• May 2007:  NTP's reports on studies on the carcinogenesis of hexavalent chromium (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 hexavalent chromium.
• 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 hexavalent chromium.
• January 2011: US EPA releases its recommendations for enhanced hexavalent chromium monitoring for public water systems.
• July 2011: OEHHA releases the final PHG for hexavalent chromium.
• August 2013: CDPH proposes an MCL for hexavalent chromium.
• 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 hexavalent chromium becomes effective.
• July 2017: Superior Court of Sacramento County invalidates the hexavalent chromium MCL and orders the State Water Board to adopt a new MCL.
• February 2020: State Water Board publishes the White Paper Discussion on Economic Feasibility Analysis in Consideration of a Hexavalent Chromium Maximum Level. 
• November 2020: State Water Board publishes preliminary occurrence data and treatment cost estimates and holds public workshops on the cost estimates.
• November 2021: State Water Board publishes Notice of Preparation of a Draft Environmental Impact Report for the hexavalent chromium MCL.
• March 2022: State Water Board publishes Notice of Public Workshop and Opportunity for Public Comment on Administrative Draft.