Chromium-6: The Erin Brockovich Chemical Still in Your Water

218 million Americans exposed. Still no federal limit after 22 years.

The Problem

Chromium-6 (hexavalent chromium) is a known human carcinogen found in the drinking water of all 50 states. It is the same chemical that contaminated the water in Hinkley, California, the case made famous by Erin Brockovich in 2000. More than two decades later, there is still no federal limit specifically for chromium-6 in drinking water.

Chromium-6 enters water supplies both naturally, by leaching from rock and soil deposits, and through industrial contamination from steel mills, chrome plating facilities, and coal-burning power plants. Unlike many contaminants that cluster in specific regions, chromium-6 is widespread. A 2016 analysis found detectable levels in the tap water serving over 218 million Americans across more than 7,000 water systems.

The health concern is primarily cancer. The National Toxicology Program classified chromium-6 as a carcinogen after studies showed it causes stomach and intestinal cancers when ingested in drinking water. California set a public health goal (PHG) of 0.02 ppb, a level based on a one-in-a-million cancer risk over a lifetime. Most water systems in the US exceed that threshold by a wide margin.

Why No Limit

The EPA regulates total chromium at 100 ppb, but that limit covers all forms of chromium combined, including chromium-3, which is an essential nutrient. There has never been a separate federal MCL for the carcinogenic form, chromium-6. This is the regulatory gap that has persisted for over 20 years.

California came closest to fixing this. In 2014, the state set the first-ever chromium-6 MCL at 10 ppb. But the regulation was withdrawn in 2017 after a legal challenge by water utilities, who argued the compliance costs were too high relative to the health benefits. The California PHG of 0.02 ppb remains the best available health benchmark, but it carries no enforcement power.

At the federal level, the EPA has repeatedly delayed action. The agency added chromium-6 to its Contaminant Candidate List (a watchlist of chemicals being evaluated for potential regulation) but has not moved forward with a proposed rule. Meanwhile, water utilities are not required to test for chromium-6 specifically, only total chromium, meaning most consumers have no idea how much of the carcinogenic form is in their water.

The practical effect is that chromium-6 sits in a regulatory limbo. Science says it is dangerous at extremely low concentrations. Industry says compliance would cost billions. And the federal government has not resolved the standoff. For homeowners, the only reliable protection is point-of-use filtration.

Affected Cities

Chromium-6 is not limited to industrial areas. It has been detected in water systems across every region of the country, from Phoenix and Los Angeles to smaller cities throughout the Midwest and Southeast. The contamination comes from both natural geological sources and decades of industrial discharge that seeped into groundwater.

Cities that rely on groundwater tend to have higher chromium-6 levels than those using surface water, because the chemical leaches from underground rock formations. Parts of the Southwest and Southern California are particularly affected due to natural chromium-bearing geology. But industrial legacy sites in states like Michigan, North Carolina, and New Jersey also produce elevated levels.

The challenge for consumers is that standard water quality reports do not break out chromium-6 separately. Your utility's annual report will show total chromium, but that number includes the harmless chromium-3 form. To know your actual chromium-6 exposure, you either need a specialized lab test or can check your city's data on CheckMyTap, where we flag chromium-6 levels from available testing data.

Filtration

Standard carbon filters like Brita and PUR do not remove chromium-6. Granular activated carbon can reduce some chromium, but not reliably or consistently enough to protect against a carcinogen with a health goal of 0.02 ppb. You need a filter specifically tested and certified for chromium-6 removal.

Reverse osmosis (RO) is the most effective home treatment for chromium-6. RO membranes reject chromium-6 at rates above 95%, bringing even elevated levels well below the California PHG. Under-sink systems like the Waterdrop G3P800 handle the job and provide high flow rates for drinking and cooking water.

Among pitcher filters, the Clearly Filtered pitcher is one of the few that has been independently tested for chromium-6 removal, reducing it by over 97% in lab testing. Ion exchange filters can also be effective, particularly those designed for heavy metal reduction.

If you are on a budget, prioritize filtering the water you drink and cook with. Chromium-6 is an ingestion hazard, not a skin-contact or inhalation risk at typical tap water concentrations, so a point-of-use filter at the kitchen tap provides the critical protection. Take our quiz for a filter recommendation matched to your specific water profile.