Hexavalent Chromium (Chromium-6)
What is Hexavalent Chromium (Chromium-6)?
Hexavalent chromium, or chromium-6, is a metal that enters water both naturally, by dissolving out of rocks and soil, and from industrial pollution such as metal plating, manufacturing, and corrosion control. It's the same contaminant made famous by the Erin Brockovich case in Hinkley, California.
Health effects
Chromium-6 is a recognized carcinogen when inhaled, and a growing body of research links ingesting it in drinking water to increased cancer risk, along with possible liver and kidney effects. There is no separate federal limit for chromium-6: the EPA regulates only total chromium at 100 ppb, while EWG and California's public-health goal put the health-based guideline near 0.02 ppb, thousands of times lower.
In DC-metro tap water
Chromium-6 shows up across DC-metro systems that draw from the Potomac, and it is one of the most commonly detected unregulated contaminants in EWG's national testing. Because there's no federal limit for it specifically, a utility can be fully compliant while chromium-6 sits well above the health guideline.
How to remove it at the tap
Reverse osmosis is one of the most effective point-of-use methods for reducing chromium-6, because the membrane rejects the dissolved metal. Standard carbon filtration alone does not reliably remove it, so a multi-stage RO system like the Sanavia Hydra is the dependable fix at the tap.
Where Hexavalent Chromium (Chromium-6) shows up locally
Local water reports where this contaminant class is documented in the utility's data or watershed. Open your area to see the specifics and look up your exact zip code.
Frequently asked
Is chromium-6 regulated in drinking water?
Not on its own. The EPA sets a limit for total chromium (100 ppb) but has no separate standard for chromium-6, so it is effectively unregulated at the health-relevant level. California is the only state to have moved toward a specific chromium-6 limit.
Does reverse osmosis remove chromium-6?
Yes. Reverse osmosis reduces dissolved hexavalent chromium at the point of use, which is why it is the recommended treatment for affected homes.
Is chromium-6 the Erin Brockovich chemical?
Yes. Chromium-6 is the contaminant at the center of the Hinkley, California case dramatized in the film Erin Brockovich.
Related guides
The gap between what's legal and what's healthy
A utility can pass every federal test and still deliver water far above the levels health scientists consider safe. Federal legal limits were largely set decades ago; the health-based guidelines below reflect current cancer- and development-risk research.
Not federally regulated, no legal limit at all
Sources: EPA National Primary Drinking Water Regulations (legal limits) and the EWG Tap Water Database / state public-health goals (health-based guidelines). A reverse osmosis system reduces every contaminant above at the point of use.