Hexavalent Chromium (Chromium-6) in Drinking Water
EPA limits, health effects, and what to do if your water is affected.
🩨 Health Effects
Hexavalent chromium (Cr-VI) is a probable human carcinogen. Long-term exposure through drinking water is associated with increased risk of stomach and other cancers. It can also cause allergic dermatitis, respiratory problems, and kidney damage. Made famous by the Erin Brockovich case in Hinkley, California, where contaminated groundwater from Pacific Gas & Electric caused health problems for residents.
📍 Sources in Water
Cr-VI is discharged from industrial operations including chrome plating, leather tanning, stainless steel production, and cooling towers. It also occurs naturally in some rock formations. Contamination is most common near industrial sites in California, New Jersey, Texas, and other industrial states.
✅ What To Do
The current EPA MCL covers total chromium (0.1 mg/L), not specifically Cr-VI. California has its own MCL of 10 ppb for Cr-VI specifically. Reverse osmosis is the most effective treatment for Cr-VI removal. Ion exchange also works. Standard carbon filters are generally not effective against hexavalent chromium.
📜 Regulation History
There is no separate federal MCL for hexavalent chromium; it is covered under the total chromium MCL of 0.1 mg/L set in 1991. California adopted a Cr-VI-specific MCL of 0.01 mg/L (10 ppb) in 2014, but it was withdrawn by courts in 2017 and is being re-established. The WHO guideline for total chromium is 0.05 mg/L. A 2010 NIH study found Cr-VI caused cancer in rodents via drinking water, intensifying calls for a federal Cr-VI standard.
🔬 How To Test Your Water
Standard water tests measure total chromium ($20-$40). Testing specifically for hexavalent chromium requires a separate lab analysis costing $40-$75 using EPA Method 218.7. Home test kits for Cr-VI are not available. If your total chromium is above 0.01 mg/L, speciation testing for Cr-VI is recommended.
💧 Which Filters Remove Hexavalent Chromium (Chromium-6)?
Reverse osmosis (NSF/ANSI 58 certified) is the most effective home treatment for hexavalent chromium, removing 90%+ of Cr-VI. Strong-base anion exchange resins also work. Standard activated carbon filters are generally not effective against Cr-VI. Some specialized media filters using iron-based adsorption have been developed for Cr-VI removal.
🔗 Related Contaminants
Check your tap water for Hexavalent Chromium (Chromium-6)
Search your ZIP code to see if your water system has had Hexavalent Chromium (Chromium-6) violations, plus lead testing results and an overall safety grade.
Search your ZIP code →Data from the EPA's Safe Drinking Water Information System (SDWIS). MCLs reflect minimum federal standards; some contaminants may pose health risks below these thresholds.