Chromium 6 in California tap water
The 2024 limit, who must comply when, and how to read a hexavalent chromium result.
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What chromium 6 is
Chromium shows up in water in two main forms. Trivalent chromium (chromium 3) is a nutrient in small amounts. Hexavalent chromium (chromium 6) is the more toxic form and is the one regulators focus on. In California, chromium 6 occurs naturally in some groundwater because of the geology of certain aquifers, and it can also come from industrial sources such as plating, wood treatment and cooling-tower operations.
California's most famous chromium 6 case is Hinkley in San Bernardino County, where industrial contamination of groundwater became the subject of a long legal and cleanup history. Most chromium 6 detections in California public water, however, are linked to natural sources in groundwater, not a single polluter.
California's chromium 6 limit
According to the State Water Board's hexavalent chromium page and the adopted regulation:
- The MCL is 10 µg/L (0.010 mg/L, or 10 parts per billion), effective October 1, 2024.
- California's Public Health Goal is 0.02 µg/L, set by OEHHA in 2011. The MCL is far above the PHG because the board must set MCLs as close to the PHG as is technologically and economically feasible.
- The separate total chromium MCL of 50 µg/L remains in effect. (The federal total chromium limit is 100 µg/L; there is no separate federal chromium 6 MCL.)
Compliance dates depend on system size, measured by service connections on October 1, 2024:
| System size | Compliance date |
|---|---|
| 10,000 connections or more | October 1, 2026 |
| 1,000 to 9,999 | October 1, 2027 |
| Fewer than 1,000 | October 1, 2028 |
Systems had to complete initial sampling by April 1, 2025. If a source exceeded the MCL before the system's compliance date, the system had to submit a compliance plan within 90 days. After the compliance date, an exceedance is a violation. The board's compliance plan guidance explains that a single sample over 10 µg/L triggers quarterly sampling, and the MCL is exceeded when the running annual average of those quarterly samples is over 10 µg/L.
California had an earlier chromium 6 MCL of 10 µg/L adopted in 2014, which a court invalidated in 2017 because the economic feasibility analysis was inadequate. The 2024 rule is the state's second attempt, and it is the one in force now.
Check your own water by ZIP
Enter a California ZIP to see your matched public water system, its recent detections, and the legal limit next to California's health goal.
How to read a chromium 6 result
- Check the units. Results are in µg/L (ppb). 10 µg/L is the MCL; 0.02 µg/L is the PHG.
- Check which form is listed. "Chromium, hexavalent" and "chromium, total" are different tests with different limits.
- Look at the range, not just the average. CCRs list an average and a range across sources. If your utility blends wells, the water at your tap reflects that blend.
- Check the date. Large systems' compliance began October 1, 2026, so treatment and source changes may be recent. Your utility's latest CCR and the State Water Board's Drinking Water Watch show the most current results.
Filters that reduce chromium 6
Reverse osmosis is the most common home option for reducing hexavalent chromium in drinking water. Look for systems certified under NSF/ANSI 58 with a specific chromium (hexavalent) reduction claim in the NSF certified products listings. Some specialty ion-exchange and media cartridges also carry certified claims. Standard carbon pitchers that are only certified for chlorine taste and odor (NSF/ANSI 42) should not be assumed to remove chromium 6.
Utilities typically use larger-scale methods such as ion exchange or reduction/coagulation/filtration. If your utility is adding treatment to comply with the MCL, the water you receive should come down over time; a home system is a choice for people who want levels closer to the PHG. Compare system types on our filter basics page.
Where chromium 6 tends to show up
Detections are mostly a groundwater issue, so utilities that pump local wells are more likely to report it than those relying mainly on imported surface water. Parts of the Inland Empire, the Central Valley and other groundwater-dependent areas have reported detections. Do not assume; check your utility. Start with the Inland Empire region, or city pages such as Riverside, San Bernardino, Fresno and Bakersfield.
Related guides
- Hard water in California
- PFAS in California drinking water
- How to check tap water by ZIP
- City water guides
- Regional water guides
FAQ
What is the chromium 6 limit in California?
10 µg/L (10 ppb), effective October 1, 2024. Large systems (10,000+ connections) had to comply by October 1, 2026; smaller systems by 2027 or 2028.
What is California's public health goal for chromium 6?
0.02 µg/L, set by OEHHA in 2011. It is a non-enforceable health goal, far below the legal limit.
Is there a federal chromium 6 limit?
No. EPA regulates total chromium at 100 µg/L. California's total chromium MCL is 50 µg/L, and California also has the separate 10 µg/L hexavalent chromium MCL.
Does reverse osmosis remove chromium 6?
Reverse osmosis is the most common home option. Choose a system certified under NSF/ANSI 58 with a hexavalent chromium reduction claim.
How do I know if my water has chromium 6?
Check your ZIP report, your utility's Consumer Confidence Report, or the system's results in the State Water Board's Drinking Water Watch.