Chromium-6 (Hexavalent Chromium)
Contaminant Profile
Chromium-6, also known as hexavalent chromium, is a toxic form of chromium that enters drinking water through industrial discharge and natural erosion. Environmental Working Group (EWG) detected chromium-6 in tap water serving over 200 million Americans, present in roughly 75% of US tap water samples tested.
Despite its known carcinogenicity, no federal MCL exists specifically for chromium-6. The EPA regulates only total chromium at 100 ppb -- a standard that fails to distinguish between harmless chromium-3 and carcinogenic chromium-6.
Health Effects
- Cancer -- stomach and intestinal cancers. Classified as a Group 1 carcinogen by IARC for inhalation exposure; probable carcinogen via ingestion.
- Liver damage -- chronic exposure linked to hepatotoxicity.
- Kidney damage -- nephrotoxicity observed in animal and occupational studies.
- Reproductive toxicity -- evidence of adverse reproductive outcomes in animal models.
Regulatory Thresholds
Federal EPA MCL
Chromium-6 specific
Federal EPA MCL (total chromium)
Does not distinguish Cr-3 from Cr-6
California Public Health Goal
Set 2011, withdrawn 2017 under industry pressure
California MCL (total chromium)
EWG Health Guideline
WHO (total chromium)
The EPA MCL of 100 ppb for total chromium does not distinguish between harmless chromium-3 and carcinogenic chromium-6.
Exposure Sources
- Industrial discharge -- chrome plating, leather tanning, steel manufacturing
- Naturally occurring -- present in certain rocks and soil formations
- Coal combustion -- released through coal-fired power generation
- Drinking water -- EWG found chromium-6 in water serving 200+ million Americans
- Erin Brockovich case -- Hinkley, CA: PG&E contaminated groundwater with chromium-6 from cooling towers
Where Tested on AH
Some bottled water COA panels test total chromium as part of heavy metals analysis. Individual chromium-6 testing is less common in commercial COAs.
The tap water lookup on Alternative Health surfaces total chromium data from utility reports, which may include chromium-6 where utilities voluntarily test for it.
Frequently Asked Questions
Why is there no federal limit for chromium-6?
The EPA's total chromium MCL (100 ppb) doesn't distinguish between chromium-3 (nutritionally essential) and chromium-6 (carcinogenic). California attempted to set a specific chromium-6 standard but it was withdrawn after industry legal challenges.
Is chromium-6 in my tap water?
EWG found chromium-6 in tap water serving over 200 million Americans. Use the AH tap water lookup to check your utility's data.
Do water filters remove chromium-6?
RO systems remove 90-97%. Ion exchange filters are effective. Standard carbon filters have limited chromium-6 removal.
What is the Erin Brockovich connection?
The 1993 case in Hinkley, CA involved PG&E contaminating groundwater with chromium-6 from cooling towers. It became the most famous environmental contamination case in US history and established public awareness of chromium-6 in drinking water.