Chromium-6 in Drinking Water: Regulation Update
Last Update: September 28, 2007
In 1999, as part of the process of reviewing maximum contaminant levels (MCLs) in response to public health goals (PHGs), CDPH's precursor, the California Department of Health Services (CDHS) identified the chromium MCL as one for review. In particular, CDHS sought to determine whether or not a MCL that is specific for chromium-6 would be appropriate.
Subsequently, events primarily between 1999-2001 (see chromium-6 timeline) and concerns about chromium-6's potential carcinogenicity when ingested resulted in a state law that requires CDPH to adopt a chromium-6-specific MCL.
Current Regulation of Chromium
Chromium-6 is currently regulated under the 50-micrograms per liter (µg/L) MCL for total chromium. The total chromium MCL is considered protective of public health for chromium-6, which is considered to be the more toxic form of chromium.
California's MCL was established in 1977, when we adopted what was then a "National Interim Drinking Water Standard" for chromium. The US Environmental Protection Agency (EPA) adopted the same standard, but in 1991 raised the federal MCL to 100 µg/L. California did not follow US EPA's lead and stayed with its 50-µg/L MCL for total chromium.
MCL and PHG Updates
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 and §116365(a) requires CDPH to establish an MCL at a level as close as is technically and economically feasible to the contaminant's PHG.
PHGs are contaminant concentrations that do not pose a significant risk to health; they are developed by the Office of Environmental Health Hazard Assessment (OEHHA). OEHHA's PHG for chromium-6 is anticipated soon. The comments of peer reviewers (PDF)
on the "pre-release" draft PHG for chromium-6 are on OEHHA's website.
Because the PHG for chromium-6 is not yet available, CDPH cannot proceed with the MCL process.
Monitoring Update
Results of monitoring chromium-6 as an unregulated contaminant for which monitoring is required showed it to be detectable in about one-third of more than 7,000 sources, using a 1-µg/L detection limit for purposes of reporting (DLR).
Though often found, it occurs at low levels: 86% of drinking water sources reporting chromium-6 detections had peak concentrations at or below 10 µg/L, which is the DLR for the regulated total chromium, and 65% had peak values at or below 5 µg/L.
Other Information
Readers interested in the levels of chromium in their drinking water should refer to their water systems' annual Consumer Confidence Reports (CCRs). Many CCRs for California water systems are available on the US EPA's CCR website.
More information is available from: