Chromium-6, also called hexavalent chromium or Cr(VI), is a form of chromium that can occur naturally in groundwater and can also enter water supplies through industrial activities. Because chromium-6 is odorless and tasteless, you cannot determine whether it is present in drinking water by looking at, smelling, or tasting the water.
For homeowners concerned about chromium-6, understanding where it comes from, how it is regulated, how to test for it, and which filtration technologies can reduce it is an important part of making informed drinking-water decisions.
This article is part of the RevOsmo Drinking Water Contaminants Explained series. See our complete guide to Drinking Water Contaminants Explained for information about PFAS, lead, fluoride, arsenic, nitrates, chlorine, chloramines, and other common drinking-water contaminants.
What Is Chromium-6?
Chromium is a naturally occurring metallic element that exists in several chemical forms. The two forms most relevant to drinking water are trivalent chromium (chromium-3) and hexavalent chromium (chromium-6).
Chromium-3 is an essential nutrient in very small amounts, while chromium-6 is the form that has generated significant concern because of its toxicity and potential cancer risks. Chromium-6 can occur naturally when chromium-containing deposits erode, but it can also enter groundwater and surface water from industrial activities, including improper handling or disposal of chromium-containing materials.
One important distinction is that a test for total chromium does not necessarily tell you the concentration of chromium-6 specifically. Total chromium includes both chromium-3 and chromium-6.
Where Can Chromium-6 Come From?
Potential sources include:
- Naturally occurring chromium deposits
- Industrial manufacturing and waste
- Metal plating and finishing operations
- Improper disposal of chromium-containing materials
- Contaminated groundwater
- Industrial sites where chromium compounds were historically used
Chromium-6 can be particularly important for households using private wells because private wells generally do not have the same monitoring and treatment requirements as regulated public water systems.
What Are the Health Risks of Chromium-6?
The primary concern surrounding chromium-6 is long-term exposure through ingestion.
California’s State Water Resources Control Board identifies hexavalent chromium as a carcinogenic contaminant and states that studies have linked long-term ingestion to an increased risk of cancer. The agency also identifies chromium-6 as toxic to the liver.
The federal regulatory picture is somewhat different. The U.S. Environmental Protection Agency (EPA) currently regulates total chromium, rather than chromium-6 as a separate federal drinking-water contaminant. EPA states that it is conducting a comprehensive evaluation of the health effects of chromium-6 and has considered evidence from toxicological research and peer-reviewed studies.
This distinction is important: the absence of a separate federal chromium-6 limit does not mean chromium-6 is considered harmless. It means that the current federal drinking-water regulation is written around total chromium.
EPA Guidelines for Chromium-6
As of 2026, the EPA’s federal drinking-water standard is:
100 parts per billion (ppb), or 0.1 mg/L, for total chromium.
That federal standard includes both chromium-3 and chromium-6. EPA requires public water systems to test for total chromium. The current federal standard was established in 1991 and is based on potential adverse effects associated with long-term exposure. EPA continues to evaluate the science surrounding chromium-6.
What About California?
California has adopted a considerably more specific standard.
California’s hexavalent chromium MCL is:
10 ppb (0.010 mg/L) for chromium-6.
The regulation became effective October 1, 2024. California also maintains a separate 50 ppb total chromium MCL.
California’s approach is therefore substantially more stringent for chromium-6 than the current federal total-chromium standard.
If you live in California, it is especially useful to check your local water-quality information and Consumer Confidence Report (CCR) for chromium-6 results.
How to Test for Chromium-6 in Drinking Water
Because chromium-6 is invisible and has no distinctive taste or smell, laboratory testing is the best way to determine whether it is present in your water.
1. Check Your Public Water Report
If you receive water from a municipal utility, start by checking your annual Consumer Confidence Report.
Your water provider may report chromium or chromium-6 measurements, depending on the applicable regulations and monitoring requirements. California’s State Water Board specifically directs consumers to their water system’s annual CCR for information about chromium-6 levels.
2. Test Your Private Well
Private well owners should consider laboratory testing if chromium-6 is a concern in their area.
Look for a laboratory capable of testing specifically for hexavalent chromium, rather than relying exclusively on a total-chromium test.
California identifies EPA Methods 218.6 and 218.7 as methods used by accredited laboratories for measuring dissolved hexavalent chromium in drinking water.
3. Don’t Rely on a Generic Water Test
A basic home water-quality test kit may test for common parameters such as hardness, chlorine, pH, or nitrates but may not measure chromium-6.
If chromium-6 is the contaminant you’re investigating, look for a laboratory test specifically designed to measure hexavalent chromium.
How to Remove Chromium-6 From Drinking Water
If testing confirms chromium-6 in your water, the appropriate treatment depends on the concentration, water chemistry, and whether you need treatment for a single drinking-water tap or the entire home.
Several treatment technologies can reduce chromium-6.
Reverse Osmosis
Reverse osmosis (RO) is one of the most useful point-of-use options for reducing dissolved contaminants in drinking water.
RO systems push water through a semipermeable membrane that can remove many dissolved inorganic contaminants. EPA identifies reverse osmosis and nanofiltration as membrane technologies capable of removing a broad range of contaminants.
For chromium-6 specifically, the California State Water Board identifies reverse osmosis as one of its best available treatment technologies for hexavalent chromium, alongside ion exchange and reduction-coagulation-filtration.
However, don’t assume every RO system removes chromium-6 simply because it uses reverse osmosis.
Look for a Specific Chromium-6 Reduction Claim
When choosing an RO system, look for third-party certification and a specific hexavalent chromium reduction claim.
NSF/ANSI 58, the standard covering reverse osmosis drinking-water treatment systems, includes optional testing for hexavalent and trivalent chromium reduction.
This is an important distinction when shopping for an RO system:
“RO system” does not automatically mean “certified for chromium-6 reduction.”
Check the manufacturer’s performance data and certification listing before purchasing.
Ion Exchange
Ion exchange is another treatment technology that can be used for chromium-6. California lists ion exchange among the best available treatment technologies for hexavalent chromium in drinking water.
Ion-exchange systems can be highly effective, but their suitability depends on water chemistry and system design. They may also require periodic media replacement or regeneration.
Reduction-Coagulation-Filtration
Reduction-coagulation-filtration is primarily a treatment approach used by water utilities and larger treatment systems rather than the typical homeowner’s under-sink solution.
California identifies it as another best available technology for treating hexavalent chromium.
For most homeowners looking for drinking-water treatment at a single faucet, a properly selected point-of-use RO system is generally a more practical option.
Recommended Water Filtration Products
If chromium-6 is a known concern, don’t choose a filter solely because it is marketed as an RO system. Look for a product with independently verified performance for hexavalent chromium.
NSF’s contaminant-reduction guidance specifically identifies reverse osmosis systems as a category in which consumers can find products certified to reduce hexavalent chromium.
One example in the current NSF listings is the A.O. Smith AORO-50, which is listed under NSF/ANSI 58 with claims including both hexavalent and trivalent chromium reduction.
Another example is the HALO H-RO-PLUS, which the current NSF listing identifies with claims for hexavalent and trivalent chromium reduction, among other contaminants.
For RevOsmo readers, the key buying criteria should be:
- Specific chromium-6 reduction claim
- NSF/ANSI 58 certification or equivalent independent verification
- Appropriate capacity for your household
- Replacement-filter availability
- Verified performance at the contaminant concentration found in your water
- Proper installation and maintenance
Certification should be verified against the current manufacturer’s documentation and certification listing before purchasing because product models, certifications, and claims can change.
Is Reverse Osmosis Effective for Chromium-6?
Yes, reverse osmosis can be an effective technology for chromium-6 reduction, but the specific system matters.
The California State Water Board lists RO as a best available treatment technology for hexavalent chromium, while NSF/ANSI 58 provides a framework for verifying chromium-reduction claims for RO systems.
For homeowners, this makes an appropriately certified under-sink RO system an attractive option when the goal is to treat water used for:
- Drinking
- Cooking
- Coffee and tea
- Ice
- Baby formula preparation
A point-of-use system also allows you to focus treatment on the water you actually consume instead of treating every gallon used throughout the home.
Frequently Asked Questions About Chromium-6
Is chromium-6 the same as chromium?
No. Chromium is the broader element, while chromium-6 is one specific chemical form. Drinking-water regulations may refer to total chromium, which includes both chromium-3 and chromium-6.
Can you see or taste chromium-6 in water?
No. Chromium is described by EPA as an odorless and tasteless metallic element, so appearance, taste, or smell cannot reliably tell you whether chromium-6 is present.
Does a Brita filter remove chromium-6?
Don’t assume that a conventional pitcher filter reduces chromium-6 unless the specific product has a verified chromium-6 reduction claim. NSF identifies reverse osmosis systems among the filter categories with certified hexavalent-chromium reduction claims.
Does reverse osmosis remove chromium-6?
Reverse osmosis can reduce chromium-6, and California identifies RO as a best available treatment technology for hexavalent chromium. However, consumers should select a system with a specific verified chromium-6 reduction claim rather than assuming all RO systems perform identically.
What is the EPA limit for chromium-6?
The current federal EPA standard is 100 ppb for total chromium, which includes chromium-6. EPA is continuing its evaluation of the health effects of chromium-6.
California has a separate 10 ppb MCL specifically for hexavalent chromium, effective October 1, 2024.
Final Thoughts
Chromium-6 deserves attention because it is a distinct and potentially harmful form of chromium that can occur naturally or result from industrial contamination. While the federal EPA standard currently regulates total chromium at 100 ppb, EPA continues to evaluate the health effects and potential regulation of chromium-6 specifically.
California has taken a more stringent approach by establishing a 10 ppb drinking-water standard for chromium-6.
If you’re concerned about chromium-6, start by checking your local water-quality report or having your water tested by an appropriate laboratory. If treatment is necessary, consider a reverse osmosis system with a verified hexavalent-chromium reduction claim, rather than selecting a filter based solely on its general marketing claims.
For more information about other contaminants and filtration technologies, visit RevOsmo’s Drinking Water Contaminants Explained pillar page.
Disclaimer: This article is for general educational purposes and is not a substitute for advice from a qualified water-treatment professional, laboratory, physician, or public-health agency. Drinking-water regulations and product certifications can change, so verify current requirements and product claims before making treatment decisions.
