Hexavalent chromium (chromium-6)

WTR

500xCalifornia 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 ResearchEvery claim on this page is graded against peer-reviewed health research and linked to its primary source.Updated 2026-06

Hexavalent chromium (chromium-6) is a confirmed human carcinogen that enters tap water from natural rock and old industrial sites. California's health-based goal is 0.02 ppb. Its enforceable limit is 10 ppb, 500 times higher, a feasibility compromise rather than a safety line. The federal government sets no Cr-VI limit. A standard carbon filter does not remove it.

What it is, and where it comes 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.

Why it matters

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)

What we grade it against

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

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

What helps

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; in lead-lag column setups it can bring treated water below 1 ppb. It is the standard at utility scale; 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.

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. The point of measuring is that a known number is a fixable one, and the fix at the kitchen tap is simple.

Common questions

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.

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.