Chromium-6 Drinking Water MCL

Announcements

November 2023

The State Water Board released documents for a 15-Day Comment Period

• Notice of Public Availability of Changes to Proposed Regulations
  • English | Spanish
• Text of Proposed Regulations
• Addendum to Initial Statement of Reasons (ISOR)

August 2023

The State Water Board held a hearing under the Administrative Procedure Act (APA) on August 2nd on the proposed maximum contaminant level (MCL) for hexavalent chromium in drinking water.

• Hearing recording (English | Spanish)
• Board staff presentation slides (English | Spanish)
• Written comments will be accepted until August 18 (noon)
  • Submit via email to commentletters@waterboards.ca.gov
  • For proposed MCL comments, use subject line "SWRCB-DDW-21-003: Hexavalent Chromium MCL"
  • For draft EIR comments, use subject line "Comment Letter - DEIR Hexavalent Chromium MCL"
  • Written comments on either document can also be mailed to Courtney Tyler, State Water Resources Control Board, PO Box 100, Sacramento, CA 95812
• Frequently asked questions (FAQ) - English
• Preguntas frequentes (FAQ) - Espanol
• Notice of Proposed Rulemaking
  • Notice of Proposed Rulemaking
  • Revised Notice of Proposed Rulemaking
  • Second Revised Notice of Proposed Rulemaking
  • Third Revised Notice of Proposed Rulemaking
• Aviso sobre regulaciones propuestas
  • Aviso sobre regulaciones propuestas
  • Aviso sobre regulaciones propuestas modificado
• Rulemaking page
  • ISOR Errata sheet (released July 31)

June 2023

The State Water Board released the Notice of Proposed Rulemaking for the Hexavalent Chromium MCL and associated Draft Environmental Impact Report.

Rulemaking and CEQA documents are available on the Hexavalent Chromium Rulemaking Page.

Additional questions may be answered by the Hexavalent Chromium MCL FAQ.

July 2022

Office of Environmental Health Hazard Assessment (OEHHA) Memorandum for Hexavalent Chromium Five-Year Review

March 2022

The State Water Board released a Notice of Public Workshop and Opportunity for Public Comment on Hexavalent Chromium MCL Administrative Draft.

• Notice of Public Workshop and Opportunity for Public Comment. Workshops will be held April 5, 2022 and April 7, 2022.
  • Notice | Aviso
• Draft Regulation Text
• Staff Report
• Attachment to Staff Report (Tables)

November 2021

CEQA Scoping Meeting

• Notice of Preparation of an environmental impact report
• Copies of comment letters received during the meeting available upon request at ddw-hexavalentchromium@waterboards.ca.gov

December 2020

Public Workshop on Cost Estimates

• Notice

Fall 2020

Occurrence Data Released
Preliminary Treatment Costs Released

• Cost Estimates Notice
• Methodology and Assumptions
• Treatment Costs Data
• Treatment Costs Equations
• Sources, Service Connections, and Population
• Community Water Systems Costs
• NTNC Water Systems Costs
• Health Effects
• Treatment Costs Figures

April 2020

White Paper Discussion on Economic Feasibility Analysis in Consideration of a Hexavalent Chromium Maximum Contaminant Level

• Revised Notice
• Notice

Background

In 1999, as part of the process of reviewing MCLs in response to public health goals (PHGs), The California Department of Public Health's (CDPH's) precursor, the California Department of Health Services (CDHS), identified the total chromium MCL (see below) as one for review (CDPH’s Drinking Water Program is now the State Water Board's Division of Drinking Water (DDW)).

In particular, DDW sought to determine whether or not an MCL that is specific for the hexavalent form of chromium—also known as chromium-6—would be appropriate. Subsequently, concerns about hexavalent chromium's potential carcinogenicity when ingested resulted in a state law that requires CDPH to adopt a hexavalent chromium-specific MCL (see hexavalent chromium timeline).

California's Health and Safety Code guides the development of an MCL for hexavalent chromium: §116365.5 requires the adoption of an MCL for hexavalent chromium by January 1, 2004. In addition, Health and Safety Code §116365(a) required CDPH to establish an MCL at a level as close as is technically and economically feasible to the contaminant's PHG, which is the concentration of a contaminant in drinking water that does not pose a significant risk to health. PHGs are developed by Cal/EPA's Office of Environmental Health Hazard Assessment (OEHHA).

In July 2011 OEHHA established a PHG for hexavalent chromium of 0.02 micrograms per liter (μg/L). The PHG represents a de minimis lifetime cancer risk from exposure to hexavalent chromium in drinking water, based on studies in laboratory animals. OEHHA also prepared a PHG fact sheet. The availability of the hexavalent chromium PHG enabled CDPH to proceed with setting a primary drinking water standard.

OEHHA reviews each PHG once every five years unless there has not been a detection of the corresponding contaminant in the preceding five years. In 2016, OEHHA initiated a PHG review for hexavalent chromium with a data call-in for information that could assist in updating the risk assessment. Based on the review of the information from the data call-in and authoritative groups, OEHHA concluded that there was not enough evidence to warrant a change in OEHHA’s approach for determining hexavalent chromium’s cancer potency and that an updated PHG would not vary significantly from the 2011 value.

As part of the rulemaking process, in August 2013 CDPH proposed an MCL for hexavalent chromium of 0.010 milligram per liter (equivalent to 10 μg/L) and announced the availability of the proposed MCL for public comment. The public comment period closed in October 2013. CDPH reviewed the comments submitted by interested parties and responded to them in the final statement of reasons, which is part of the final hexavalent MCL regulations package. Documents from the regulation package can be found here.

On April 15, 2014, CDPH submitted the hexavalent chromium MCL regulations package to the Office of Administrative Law (OAL) for its review for compliance with the Administrative Procedure Act. On May 28, OAL approved the regulations, which were effective on July 1, 2014.

On May 31, 2017, the Superior Court of Sacramento County issued a judgment invalidating the hexavalent chromium maximum contaminant level (MCL) for drinking water. The court ordered the State Water Resources Control Board (State Water Board or Board) to take the necessary actions to delete the hexavalent chromium MCL from the California Code of Regulations and to file with the court by August 15 proof that it has done so (California Manufacturers and Technology Association, et al. v. California Department of Public Health, et al. (Super. Ct. Sacramento County, 2017. No. 34-2014-80001850).

The change became effective with the Office of Administrative Law filing the change with the Secretary of State, on September 11, 2017. Thus, as of September 11, 2017, the maximum contaminant level for hexavalent chromium is no longer in effect.  However, the MCL for total chromium of 50 parts per billion will remain in place.

The court's primary reason for finding the MCL invalid is that the California Department of Public Health (which was responsible for the drinking water program before it was transferred to the State Water Board) failed to comply with one of the requirements in the Safe Drinking Water Act for adopting an MCL. In particular, the department "failed to properly consider the economic feasibility of complying with the MCL." The court did "not decide whether the MCL is economically feasible." The court did not make any finding about whether the MCL adequately protected public health, nor did it reach a conclusion about whether the MCL was too low or too high. The court merely found that the department did not adequately document why the MCL was economically feasible.

The court also ordered the State Water Board to adopt a new MCL for hexavalent chromium.

Historical Timeline

Below are significant historical events associated with the development of drinking water regulations for hexavalent chromium:

• 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.

MCL for Total Chromium

Hexavalent chromium has been regulated under the 50-µg/L primary drinking water standard (MCL) for total chromium. California's MCL for total chromium was established in 1977, when we adopted what was then a "National Interim Drinking Water Standard" for chromium. The total chromium MCL was established to address exposures to hexavalent chromium, the more toxic form of chromium. Chromium-3 (trivalent chromium) is a required nutrient.

The US Environmental Protection Agency (EPA) adopted the same 50-µg/L standard tor total chromium, but in 1991 raised the federal MCL to 100 µg/L. California did not follow US EPA's change and stayed with its 50-µg/L standard.