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Hexavalent chromium (chromium-6) is a known carcinogen found in the drinking water of over 200 million Americans. Learn about the health risks, regulatory gaps, and how to protect your family.
Chromium-6, also known as hexavalent chromium or Cr(VI), is a toxic form of the element chromium. Unlike chromium-3 (trivalent chromium), which is an essential nutrient found in foods, chromium-6 is a known human carcinogen that poses serious health risks when ingested or inhaled.
Chromium-6 gained national attention through the Erin Brockovich case, where Pacific Gas & Electric contaminated groundwater in Hinkley, California. However, this contaminant is far more widespread than most people realize, detected in drinking water supplies serving over 200 million Americans across all 50 states.
Critical: The EPA has no specific limit for chromium-6. The 100 ppb limit covers total chromium, allowing potentially dangerous levels of the carcinogenic form to remain in drinking water.
Key Issue: The EPA's 100 ppb limit is for "total chromium" (both forms combined). This means water with 99 ppb of carcinogenic chromium-6 would still be considered "safe" under federal regulations, even though health research suggests harmful effects at much lower levels.
A 2008 National Toxicology Program study found that chromium-6 in drinking water caused cancer in laboratory animals, confirming what occupational studies had long suggested about inhalation exposure.
California's Office of Environmental Health Hazard Assessment determined that chromium-6 can cause cancer even at very low levels, establishing a public health goal of 0.02 ppb - 5,000 times lower than the federal limit.
The federal limit applies to all forms of chromium combined. This standard was set in 1991 and has not been updated despite significant new research on chromium-6 cancer risks from ingestion.
Key limitation: The EPA has not established a separate standard for chromium-6, despite classifying it as a known human carcinogen.
Based on California's public health goal, this level represents one-in-a-million cancer risk over a lifetime of exposure. The Environmental Working Group recommends this as the benchmark for safe drinking water.
Reality check: Most water systems serving over 200 million Americans exceed this health guideline.
California established the first state-specific chromium-6 limit in 2014, though it was later withdrawn due to a legal challenge over cost analysis. California continues to monitor chromium-6 and report levels to residents.
| Standard | Level | Applies To | Note |
|---|---|---|---|
| EPA MCL | 100 ppb | Total chromium | Set in 1991, no chromium-6 specific limit |
| EWG Guideline | 0.02 ppb | Chromium-6 | One-in-million cancer risk level |
| California PHG | 0.02 ppb | Chromium-6 | Public health goal (non-enforceable) |
Steel mills, chrome plating facilities, leather tanning operations, and textile manufacturing release chromium-6 into wastewater and groundwater. Historical contamination persists for decades.
Coal combustion produces ash containing chromium-6. Improperly stored coal ash can leach into groundwater, affecting nearby communities and water supplies.
Chromium occurs naturally in certain rock formations. When groundwater contacts these rocks, chromium can dissolve and convert to the hexavalent form under certain conditions.
Ironically, some water treatment processes using chlorine or ozone can convert harmless chromium-3 to carcinogenic chromium-6, potentially increasing levels in treated water.
Chromium-6 was widely used in aircraft and military equipment coating. Former military bases and aerospace facilities often have chromium-6 contamination in soil and groundwater.
Chromium-6 is present in drinking water across all 50 states. According to EWG analysis, over 200 million Americans are served by water systems with detectable chromium-6 levels exceeding the California public health goal.
High levels detected, natural and industrial sources
Elevated chromium-6 in public water
Industrial contamination legacy
Steel and manufacturing legacy
Coal ash contamination risk
Aerospace coating contamination
Check Your Water: Search for your city on our site to see chromium levels reported in your area. Even if below federal limits, levels may exceed health guidelines.
Contact your water utility and ask specifically about chromium-6 testing. While federal law only requires total chromium reporting, some utilities voluntarily test for chromium-6.
The most accurate method. Labs use EPA Method 218.6 or 218.7 to detect chromium-6 at very low levels (sub-ppb detection limits). Important: Specify chromium-6 testing, not just total chromium.
Contact your state health department for certified lab lists, or call the EPA Safe Drinking Water Hotline: 800-426-4791.
The Environmental Working Group maintains a database of chromium-6 test results from water systems nationwide. Search by ZIP code at ewg.org/tapwater.
Testing Notes:
Removes 90-97% of chromium-6. Point-of-use under-sink systems are the most practical and cost-effective solution for drinking water.
Cost: $200-500 for under-sink system + $50-100/year maintenance
Effective for chromium-6 removal. Requires periodic regeneration or replacement. Works best when water chemistry is optimized.
Cost: $1,000-3,000 for whole-house systems
Converting chromium-6 to chromium-3 (using reducing agents like ferrous sulfate), then removing through coagulation. Primarily used in municipal treatment.
Effective for removing chromium. Energy-intensive and produces limited quantities. Good for drinking water only.
Cost: $300-800 for countertop units
Does NOT Effectively Remove Chromium-6:
Request chromium-6 test results from your water utility or get your water tested independently. Compare to the 0.02 ppb health guideline.
A reverse osmosis system under your kitchen sink is the most practical solution for drinking and cooking water.
Contact your representatives to support EPA action on chromium-6 and ask your local utility to voluntarily reduce levels.
Replace RO membranes and filters on schedule. Effectiveness decreases as filters age.
The EPA acknowledged chromium-6 as a carcinogen when ingested in 2010 but has not completed the rulemaking process to set a specific limit. The agency faces pressure from industry groups concerned about treatment costs.
The primary concern is ingestion, not skin contact. Chromium-6 is not well absorbed through skin. However, reducing all exposure is prudent, especially for households with young children.
No. Boiling concentrates chromium-6 by evaporating water while leaving the contaminant behind. Use reverse osmosis or distillation instead.
Standard pitcher filters using activated carbon are not effective at removing chromium-6. Only reverse osmosis, distillation, or specialized ion exchange systems provide meaningful reduction.
Bottled water is subject to the same 100 ppb total chromium limit. Some spring water sources may contain chromium-6. Choose brands that publish test results showing levels below health guidelines.
See your city's water quality report and check for chromium-6 detections in your area.
This information is provided for educational purposes only and is not intended as medical advice. If you are concerned about chromium-6 exposure, consult with a healthcare provider. Water quality data is sourced from EPA databases and the Environmental Working Group. Always verify with your local water utility for the most current information.