Chromium-6 Drinking Water MCL
In February 2020, the State Water Board staff published the White Paper Discussion on Economic Feasibility Analysis in Consideration of a Hexavalent Chromium Maximum Contaminant Level. On April 27, 2020, State Water Board staff held a public workshop on the White Paper. The public comment period ended on May 15, 2020. Download the White Paper.
Preliminary occurrence data and treatment cost estimates were released in October and November 2020, with public workshops on the cost estimates held on December 8 and 9, 2020.
- Occurrence Data
- Treatment Costs
State Water Board is evaluating comments received regarding treatment technologies and cost estimating methodology. Publication of a Notice of Proposed Rulemaking is projected for late spring or early summer 2021.
Background (The section below includes historical information related to the MCL adopted in 2014 prior to the judgment invalidating the hexavalent chromium MCL described above)
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 chromium-6 would be appropriate. Subsequently, concerns about chromium-6's potential carcinogenicity when ingested resulted in a state law that requires CDPH to adopt a chromium-6-specific MCL (see chromium-6 timeline).
California's Health and Safety Code guides the development of an MCL for chromium-6: §116365.5 requires the adoption of an MCL for chromium-6 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 chromium-6 of 0.02 μg/L. The PHG represents a de minimis lifetime cancer risk from exposure to chromium-6 in drinking water, based on studies in laboratory animals. OEHHA also prepared a PHG fact sheet. The availability of the chromium-6 PHG enabled CDPH to proceed with setting a primary drinking water standard.
As part of the rulemaking process, in August 2013 CDPH proposed an MCL for chromium-6 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 September 4, 2015, Senate Bill 385 (SB385) was signed by the Governor and chaptered on that date. The primary purpose of this bill was to provide public water systems, with sources that produce water with hexavalent chromium concentration above the State’s adopted maximum contaminant level (MCL), time to come into compliance without being deemed in violation of the MCL. SB 385 Hexavalent Chromium MCL Compliance Period Criteria (PDF)
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.
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.
While the Board staff disagrees with the court's conclusion, the Board staff's recommendation is to not appeal the trial court's decision. It will likely be more expedient to begin the process of adopting a new MCL, rather than expending time and resources appealing the court's order. The State Water Board hopes that the wealth of data obtained during the nearly three years the MCL has been in place will enable the Board to adopt the new regulation more quickly. While the Board staff disagrees with the court's conclusion, the Board staff's recommendation is to not appeal the trial court's decision. It will likely be more expedient to begin the process of adopting a new MCL, rather than expending time and resources appealing the court's order. The State Water Board hopes that the wealth of data obtained during the nearly three years the MCL has been in place will enable the Board to adopt the new regulation more quickly.
The Board recognizes that many public water systems and their customers have questions about next steps. The State Water Board will not be enforcing any compliance plans that public water systems entered into for hexavalent chromium, as the MCL will no longer be in effect. However, the MCL for total chromium of 50 parts per billion will remain in place.
Hexavalent chromium remains present in the water supply of many public water systems, and continues to pose a threat to public health. Furthermore, the Board will establish a new MCL for hexavalent chromium, which could be at the same level as the invalidated MCL. The State Water Board commends the many public water systems that diligently tested and monitored for hexavalent chromium, planned and, in some case, completed construction projects to install treatment, and worked with the State Water Board on compliance plans. Those public water systems will be able to use that information and experience in any work necessary to comply with the new MCL when it is adopted.
Public water systems that have already installed and are operating treatment systems for hexavalent chromium are encouraged to continue to operate these treatment facilities; however they are not required to do so and may request a change in their operating permit by submitting a permit application to allow such after the regulations are formally withdrawn by the Office of Administrative Law.
The Board has developed a frequently asked questions (FAQ) document which will be kept up to date as additional question come up. You can access the FAQ here: September, 2017 FAQs
Readers interested in the levels of hexavalent chromium in their drinking water should refer to the water systems' annual Consumer Confidence Reports (CCRs). Many CCRs are available from DDW's Drinking Water Watch website, which also includes other information about drinking water quality.
MCL for Total Chromium
Chromium-6 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 chromium-6, 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.
Additional Information on Chromium-6Letter to Public Water Systems describing new regulations (June 20, 2014)
Fact Sheet (September 25,2015 Update)
September, 2017 FAQs on the previous MCL for Chromium-6
Monitoring Results and Timeline of Chromium-6-Related ActivitiesChromium-6 Sampling Results (includes monitoring and analytical information, along with US EPA recommendations)
Information from the Division of Water Quality
Information on Chromium-6 from Federal Agencies
US EPA's Method 218.7 for Hexavalent Chromium (November 2011) (PDF, New Window)
US EPA's Recommendations for Enhanced Monitoring for Hexavalent Chromium (January 2011)
US EPA's IRIS - Toxicological Review of Hexavalent Chromium (2010 External Review Draft) - Archived
US EPA's Basic Information on Chromium in Drinking Water
US EPA's Technology Innovation Office
National Toxicology Program
Agency for Toxic Substances Disease Registry
General InformationInformation for Public Water Systems
Division of Drinking Water