Hexavalent chromium (chromium-6)

WTR

500× California legal limit vs. health-based goal

The enforceable limit sits 500 times above the level California's own scientists call health-protective. No federal Cr-VI limit exists at all.

Settled science

Stasis Home Research Every claim on this page is graded against peer-reviewed health research and linked to its primary source.Updated July 2026

No level of chromium-6 in water is known to be free of risk. It is a confirmed human carcinogen, so any amount carries some cancer risk. The closest health-based marker is California's goal of 0.02 ppb, or parts per billion, one extra cancer per million over a lifetime. Its enforceable limit of 10 ppb is 500 times higher, a feasibility compromise, not a safety line. No federal chromium-6 limit exists, and carbon filters do not remove it.

Hexavalent chromium (chromium-6): what is it, and where does it come from?

Hexavalent chromium, also written Cr-VI or chromium-6, is one specific form of the metal chromium. The chromium in food is a different form (Cr-III), an essential trace nutrient your body needs. Cr-VI is the industrial form, and it dissolves in water as a small charged particle that ordinary treatment lets pass through. It reaches taps two ways. The first is natural rock: serpentine and ultramafic geology, widespread across the western states and present in pockets elsewhere, releases chromium that oxidizes into Cr-VI in groundwater. The second is old industry: chrome plating, metal finishing, leather tanning, cooling-tower additives, and aerospace work left Cr-VI plumes underground; the best known is the PG&E Hinkley case behind the Erin Brockovich story. Homes drawing groundwater are the most likely to show it.

Hexavalent chromium (chromium-6): why does it matter?

Cr-VI is a Group 1 carcinogen, the category the International Agency for Research on Cancer reserves for agents confirmed to cause cancer in humans. For drinking water the pivotal study fed Cr-VI to rats and mice for two years and found tumors of the mouth and small intestine. California's scientists used those small-intestine tumors to set a health-based goal at the level expected to cause one extra cancer per million people over a lifetime. That goal is 0.02 ppb. The enforceable California limit is 10 ppb, 500 times higher, and your utility can be fully compliant while your water sits roughly 35 times above the health-based goal. You take it in by drinking and cooking, not showering, so the fix belongs at the kitchen tap.

Cr-VI is a confirmed human carcinogen (IARC Group 1), based on lung cancer in workers who breathed it in chrome plating, chromate production, and pigment manufacturing.IARC, Chromium (VI) compounds, Group 1 carcinogen, 1990
Fed in drinking water to rats and mice for two years, Cr-VI caused tumors of the mouth in rats and the small intestine in mice, the basis for California's health-based goal.Stout et al., 2009 (Environ Health Perspect; NTP 2-year oral Cr-VI bioassay)
California's health-based goal is 0.02 ppb, set at one extra lifetime cancer per million; the enforceable limit of 10 ppb is 500 times higher and reflects what utilities can feasibly achieve, not where harm stops.CA OEHHA, Public Health Goal for Hexavalent Chromium in Drinking Water, 2011 (0.02 ppb)
The federal government sets no Cr-VI limit; its chromium standard covers total chromium at 100 ppb, treating Cr-VI the same as the nutritionally essential Cr-III.US EPA, National Primary Drinking Water Regulations (total chromium MCL 100 ppb; no Cr-VI limit)

Hexavalent chromium (chromium-6): what do we grade it against?

Hexavalent chromium (chromium-6) is held to two different numbers, and they do not agree. The health-based level for Chromium-6 (ppb) is 0.02 (one extra cancer per million, lifetime), from CA OEHHA PHG, 2011; CA SWRCB MCL, 2024. The enforceable legal limit is 10. The table below lists every level on this page next to the source that set it.

Where the health research draws the line, versus the legal limit.
Contaminant	Health-based level	Legal limit	Source (health-based)
Chromium-6 (ppb)	0.02 one extra cancer per million, lifetime	10 California MCL, effective Oct 2024; 500x the goal	CA OEHHA PHG, 2011; CA SWRCB MCL, 2024
Chromium-6, federal (ppb)	0.02 California goal; no federal Cr-VI value	none set no federal Cr-VI limit exists	US EPA NPDWR
Total chromium, federal (ppb)	100 federal goal lumps Cr-VI with the harmless Cr-III	100 federal total-chromium MCL	US EPA NPDWR

Health-based levels come from peer-reviewed research and government risk scientists working without cost constraints, while legal limits are enforceable compromises. Your report grades to the health column.

What helps against Hexavalent chromium (chromium-6)?

3 approaches below reduce Hexavalent chromium (chromium-6) in a home, ordered from the most direct fix to the smallest change in habit. The most direct is Under-sink reverse osmosis (RO) at the kitchen tap. Each entry also names what it cannot do, because no single fix covers every exposure route.

Direct fixes

Under-sink reverse osmosis (RO) at the kitchen tap
Rejects Cr-VI in the 90 to 97 percent range, and the same unit covers PFAS and most heavy metals at the tap you drink from.

Bigger retrofits

Strong base anion exchange (SBA)
Binds Cr-VI to a resin and removes it, and paired columns can bring treated water below 1 ppb. Utilities use it; at home, RO does the same job and consolidates the fix.

Free and behavioral

Carbon-block filter (NSF 53), pitcher or under-sink
Helps with chlorine taste and some other contaminants.
Carbon does not remove Cr-VI; the dissolved form is charged and slips straight through the block. A home with detected Cr-VI needs to step up to RO.

See how well each fix works

Method

Reverse osmosis

Cr-VI is the clearest case of the gap between what is legal and what is safe. The pattern matches leaded gasoline, asbestos, and DDT. Industry introduces an exposure. Regulators take a generation to respond, and the limit they eventually set lands well above the health-based level. California's own health goal sits 500 times below its enforceable limit, and the federal government still has no Cr-VI limit at all. A compliant report on this contaminant does not mean a safe one. Once you have the number for your own tap, an under-sink reverse osmosis unit brings it down.

Common questions about Hexavalent chromium (chromium-6)

Is chromium-6 the same as the chromium in my multivitamin?

No. Supplements and food contain trivalent chromium (Cr-III), an essential trace nutrient and the harmless cousin of chromium-6. Chromium-6 is the industrial form, a confirmed carcinogen, and it does not occur in food at meaningful levels.

What is a safe level of chromium-6 in water?

There is no level known to be free of risk, because chromium-6 is a confirmed human carcinogen. The closest thing to a safe target is California's health-based goal of 0.02 ppb, set at one extra cancer per million people over a lifetime. The enforceable California limit of 10 ppb is 500 times higher, a feasibility compromise rather than a safety line. Aim for 0.02 ppb or lower at the kitchen tap.

Is chromium-6 in drinking water dangerous?

Yes. Chromium-6 is a Group 1 carcinogen, the category the International Agency for Research on Cancer reserves for agents confirmed to cause cancer in humans. Fed to rats and mice in drinking water for two years, it caused tumors of the mouth and small intestine, the basis for California's health-based goal. The exposure that matters is drinking and cooking, so the fix belongs at the kitchen tap.

What is the drinking water limit for hexavalent chromium?

California sets an enforceable limit of 10 ppb for hexavalent chromium specifically, effective October 2024. There is no federal limit for chromium-6; the federal standard regulates total chromium at 100 ppb and treats it the same as the harmless Cr-III. Neither number is health-based. California's own health goal is 0.02 ppb, 500 times below the state's enforceable limit.

If my water utility says it is compliant, am I safe from chromium-6?

Compliant means below the California limit of 10 ppb; the federal standard covers only total chromium, with no Cr-VI-specific limit at all. California's health-based goal is 0.02 ppb, 500 times lower. Water can be fully compliant and still sit far above the health-protective level.

Will my pitcher or carbon filter remove chromium-6?

No. Chromium-6 dissolves as a small charged particle that passes through activated carbon. Removing it takes reverse osmosis or strong base anion exchange.

Do I need whole-house treatment for chromium-6?

No. The exposure that matters is drinking and cooking, not bathing, so point-of-use treatment at the kitchen tap is the right scope. Whole-house Cr-VI treatment belongs at utility scale.

Why is there no federal limit on chromium-6?

The federal government regulates total chromium at 100 ppb and has never set a Cr-VI-specific limit, lumping Cr-VI together with the harmless Cr-III. California adopted the first US Cr-VI limit in 2014; a court struck it down in 2017 on cost grounds, not health grounds, and it was re-adopted in 2024.

Is chromium-6 safe to drink in tap water?

No level of chromium-6 in tap water is known to be free of risk, because it is a confirmed human carcinogen. How much risk depends on how much is in your water, and that varies a lot between homes: the ones drawing groundwater are the most likely to show it, either from chromium-bearing rock or from old plating, metal finishing, and tanning sites. California's health-based goal is 0.02 ppb and its enforceable limit is 10 ppb, so a result anywhere in that range can be fully legal and still sit far above the health goal. The only way to know which situation you are in is to see the number for your own tap, from your utility's annual report or from a lab test.

How to get rid of chromium-6 in water?

Get rid of chromium-6 with an under-sink reverse osmosis unit at the kitchen tap, which rejects it in the 90 to 97 percent range. Carbon filters do not work on it, because chromium-6 dissolves as a small charged particle that passes straight through the block. Treat only the tap you drink and cook from, since the exposure that matters is swallowing it rather than showering in it, which makes whole-house treatment the wrong scope for a home. Confirm the number first, from a lab test or your utility's report, and then replace the membrane on schedule, because breakthrough has no taste, no smell, and no change in flow to warn you.

What type of filter can remove chromium-6 from water?

Reverse osmosis and strong base anion exchange are the two types that remove chromium-6. Reverse osmosis rejects it in the 90 to 97 percent range and is the practical choice for a house, because the same under-sink unit also covers PFAS and most heavy metals at the tap you drink from. Strong base anion exchange binds chromium-6 to a resin and removes 80 to 95 percent. With paired columns run one after another it can bring treated water below 1 ppb, which is why utilities use it. Activated carbon, the media in most pitchers and under-sink cartridges, does not remove it.

Do Brita filters remove chromium-6?

No. A carbon pitcher is built to strip the things that stick to carbon, and chromium-6 is not one of them: it dissolves as a small negatively charged particle that passes straight through. The ion-exchange resin some pitchers add works on positively charged metals, so it misses chromium-6 as well. A carbon pitcher is the wrong device here, though it handles chlorine taste, and models certified to NSF/ANSI 53 for lead do real work on lead. A home with detected chromium-6 needs to step up to under-sink reverse osmosis at the kitchen tap.

What neutralizes hexavalent chromium?

Chemically, hexavalent chromium is neutralized by reduction: a reductant such as ferrous iron converts it to trivalent chromium, the harmless form found in food, which is then coagulated and filtered out. That is a treatment train a utility installs to meet California's 10 ppb limit, not something that happens in a pitcher. At home the answer is removal rather than neutralization, and reverse osmosis or strong-base anion exchange takes the chromate anion out where carbon does not.