In 1993, a small desert town in California became the center of one of the most dramatic environmental lawsuits in American history. Hinkley, California, a community of about 1,500 people, discovered that their drinking water was contaminated with an industrial chemical called hexavalent chromium, or chromium-6 (Cr-VI). The contamination came from a nearby natural gas compressor station run by Pacific Gas and Electric Company (PG&E). The resulting lawsuit, immortalized in the 2000 film "Erin Brockovich," brought national attention to this toxic contaminant and raised a critical question: is chromium-6 in YOUR tap water?
Today, more than 30 years later, chromium-6 remains a serious public health concern. It has been found in the drinking water of millions of Americans across multiple states, yet most people have never heard of it. If you have never checked what is actually in your tap water, chromium-6 should be on your radar. In this article, we explain what chromium-6 is, why it became famous, what current regulations say about safe levels, and what you can do to protect your family.
What Is Chromium-6 and Why Should You Care?
Chromium is a naturally occurring metal found in rocks, soil, and sometimes groundwater. It exists in several chemical forms, but the two most important ones are chromium-3 (Cr-III) and chromium-6 (Cr-VI). Not all forms of chromium are equally dangerous.
Chromium-3 (Cr-III) is considered essential to human health. Your body needs small amounts of it to regulate blood sugar and support metabolism. Cr-III is found naturally in many foods and is generally recognized as safe by the U.S. Food and Drug Administration.
Chromium-6 (Cr-VI), also called hexavalent chromium, is a different story. This form is highly toxic and has been classified as a known human carcinogen. Unlike Cr-III, your body has no beneficial use for Cr-VI. When you drink water contaminated with chromium-6, it enters your bloodstream and can accumulate in your organs over time.
The key difference comes down to chemistry. Chromium-6 is much more readily absorbed by the body than chromium-3, and it is capable of damaging DNA in your cells. This is why public health officials are far more concerned about Cr-VI in drinking water than they are about total chromium levels.
The Erin Brockovich Case: Why One Town Changed Everything
The Hinkley case is the reason most Americans have ever heard the name "chromium-6." Here is what happened.
In the 1950s, Pacific Gas and Electric (PG&E) opened a natural gas compressor station in Hinkley, California. The facility used chromium-6 as a corrosion inhibitor in its cooling towers. For decades, contaminated water from these towers seeped into the groundwater that supplied the town's drinking water.
By the 1980s and early 1990s, residents of Hinkley began reporting an unusual cluster of serious health problems: cancer, reproductive issues, and other illnesses. A legal assistant named Erin Brockovich began investigating and discovered the chromium-6 contamination. Her team tested the water and found chromium-6 levels far exceeding what scientists considered safe.
In 1996, PG&E settled a class action lawsuit for $333 million (one of the largest environmental settlements at that time) without admitting liability. The case brought international attention to chromium-6 as a drinking water contaminant and prompted regulators to take a much harder look at how common this problem actually was.
Today, the Hinkley case serves as a cautionary tale. It shows how industrial pollution can quietly contaminate a town's water supply for years before anyone realizes the danger. It also demonstrates that large corporations knew about chromium-6's toxicity but did not always prioritize protecting the public water supply from it.
Is Chromium-6 a Carcinogen? What the Science Says
Yes. Chromium-6 is classified as a known human carcinogen by the International Agency for Research on Cancer (IARC) and the U.S. Environmental Protection Agency (EPA).
The evidence is clear: studies in animals have shown that chromium-6 causes cancer when ingested in water. In 2008, the National Toxicology Program (NTP), a federal research program, completed a landmark study feeding rats chromium-6 in their drinking water. The study found a clear dose-dependent increase in tumors, particularly in the mouth, stomach, and small intestine.
While long-term studies in humans are limited (because we cannot ethically expose people to known carcinogens in experiments), the animal evidence is strong enough that regulatory agencies worldwide treat chromium-6 as a serious cancer risk.
The International Agency for Research on Cancer classifies chromium-6 in the highest risk category (Group 1), meaning there is sufficient evidence that it causes cancer in humans, based on both animal and limited human evidence.
In addition to cancer risk, chromium-6 has been linked to other health problems including kidney damage, reproductive harm, and immune system effects at high exposure levels.
Current EPA Standards and Regulations for Chromium
Here is where the situation becomes confusing for many Americans: the EPA currently has a drinking water standard, but it may not protect you as much as you think.
The Federal MCL for Total Chromium
The EPA's Maximum Contaminant Level (MCL) for total chromium in drinking water is 100 parts per billion (ppb). This means water suppliers are required to keep the combined level of all forms of chromium below 100 ppb.
However, this standard applies to total chromium, which includes both the relatively harmless chromium-3 and the toxic chromium-6. A water sample could have 90 ppb of chromium-6 (highly toxic) and still comply with the federal standard if the remaining 10 ppb is chromium-3.
Why There Is No Separate Federal Standard for Chromium-6
For years, environmental advocates and health experts have pushed the EPA to create a specific drinking water standard for chromium-6 alone. The EPA has not yet done so, despite the chemical's classification as a known carcinogen. This is a subject of ongoing debate among public health officials.
The EPA began the process of evaluating chromium-6 as early as the 2000s, but the process has been slow. Some critics argue that political pressure from industries that use chromium-6 has delayed the creation of a stricter standard. Others say the EPA is still gathering data to determine the safest possible level.
Until a federal standard for chromium-6 specifically is established, the 100 ppb total chromium standard remains the federal requirement.
California's Stricter Standard
California took matters into its own hands. In 2014, after years of study, California established the nation's first and (currently) only state-specific drinking water standard for chromium-6: 10 ppb.
This is 10 times stricter than the federal standard for total chromium, reflecting what California's regulators determined to be a safer level based on the carcinogenic potential of chromium-6. California water utilities were required to begin meeting this standard in 2018.
For California residents, this means water suppliers must actively test for chromium-6 and maintain levels below 10 ppb. If you live in California, you can check whether your local water system is meeting this standard by using ClearWater's free ZIP code lookup tool to see your water quality report.
Where Is Chromium-6 Found in U.S. Tap Water?
After the Hinkley case became public, researchers began testing water supplies across the United States. What they found was sobering: chromium-6 is not rare.
States and Regions with the Highest Contamination
A 2010 Environmental Working Group (EWG) study tested water from 35 cities and found chromium-6 in 31 of them. Some of the highest levels were found in:
- California, particularly in agricultural and industrial areas where chromium-6 has been used for decades
- Texas, where industrial sites have historically used chromium-6 in cooling systems
- Illinois, the Chicago area in particular
- New Jersey, in parts of northern New Jersey
- North Carolina, in areas near industrial facilities
However, chromium-6 has been detected in at least 218 million Americans' tap water, according to an EWG analysis. This includes people in rural areas, small towns, and major cities.
Why Chromium-6 Gets Into Drinking Water
Chromium-6 enters groundwater and surface water from several sources:
- Industrial discharge: Metal plating facilities, cooling towers, and other manufacturing plants use chromium-6 and can release it into the environment
- Legacy contamination: Old industrial sites, even those that have closed, can continue to leach chromium-6 into groundwater for decades
- Soil and geology: In some areas, chromium-6 occurs naturally in certain rock formations, though human industrial use is the primary source of elevated levels
- Military sites: Some military bases have chromium-6 contamination from historical weapons manufacturing and maintenance
Water treatment plants can remove chromium-6, but many utilities do not have the equipment to do so. Even when they do, the cost is substantial, and not all municipalities prioritize removing chromium-6 when the federal law only requires them to monitor total chromium.
How to Find Out If Chromium-6 Is in Your Water
The first step in protecting your family is knowing what is in your tap water. Here is how to find out.
Check Your Water Quality Report
Every public water utility in the United States is required by the EPA to provide an annual water quality report, called a Consumer Confidence Report (CCR). This report lists all contaminants that have been detected in your water supply.
You can usually find this report on your local water utility's website or by calling them directly. The report should include chromium levels (though it may list total chromium rather than chromium-6 specifically).
If your report shows chromium levels above 50 ppb (half the federal limit), or if you live in California and levels are above 10 ppb, that is a cause for concern.
Use ClearWater to Identify Your Water Quality
ClearWater's free ZIP code lookup tool allows you to see what contaminants have been detected in your tap water based on EPA data from your local water utility. Simply enter your ZIP code on checkclearwater.com to find your water quality report and see if chromium has been detected in your area.
This is a quick, free way to get a snapshot of your water quality without having to call your utility or dig through government websites.
Test Your Water Yourself
If you want to be absolutely certain about chromium-6 levels in your specific home, you can have your water tested by a certified laboratory. Many state health departments maintain lists of certified labs. The test will cost anywhere from $100 to $300 depending on the lab and how comprehensive the analysis is.
Self-testing is particularly important if you use a private well, which is not regulated by the EPA and does not have mandatory testing requirements like public water systems do.
What Can You Do to Reduce Chromium-6 in Your Drinking Water?
If you find that chromium-6 is present in your water, you have several options.
Home Filtration and Treatment Options
Certain types of home water filters can reduce chromium-6, though not all filters are equally effective.
Reverse osmosis systems are among the most effective at removing chromium-6. These systems use pressure to force water through a semi-permeable membrane that blocks many contaminants, including chromium. Reverse osmosis can be installed as a whole-house system or as a point-of-use system under your sink.
Ion exchange systems and distillation systems can also remove chromium-6, though they work somewhat differently than reverse osmosis. Ion exchange replaces chromium ions with other ions, while distillation boils water and condenses the steam, leaving contaminants behind.
Activated carbon filters, which are common in pitcher filters and faucet-mounted filters, are generally not effective at removing chromium-6. If your filter package does not specifically state that it removes chromium or heavy metals, it probably will not help with chromium-6.
When choosing a filter, look for certification from NSF International or the Water Quality Association (WQA) specifically stating that the filter removes chromium.
Contact Your Water Utility
If you discover chromium-6 in your drinking water, contact your local water utility and ask what they are doing to address it. Ask whether they test specifically for chromium-6 (not just total chromium) and what their plans are to reduce it.
Public pressure is one of the most effective tools for improving water quality. When customers ask questions and express concern, utilities are more likely to prioritize testing and treatment upgrades.
Support Stronger Regulations
Advocate for a federal drinking water standard specifically for chromium-6. You can contact your representatives in Congress and your state legislature expressing support for stricter chromium-6 regulations. Several states are considering their own standards following California's example.
Consider Drinking Water Alternatives
If your water tests high for chromium-6 and you cannot install a home treatment system, bottled water is an alternative, though it is more expensive over time and has environmental impacts from plastic waste. If you choose bottled water, look for brands that test for chromium-6.
Should You Be Worried About Your Water?
Chromium-6 is a real public health concern, but it is not a reason to panic. Most Americans do not have unsafe levels of chromium-6 in their tap water. However, millions do, and the only way to know which group you are in is to check.
What we know for certain: chromium-6 is a known carcinogen, it is found in drinking water across the country, and the federal government has not set a protective standard for it specifically. Until that changes, it is up to you to learn what is in your water and decide whether you want to take steps to reduce your exposure.
The good news is that information and solutions are available. Start with ClearWater or your local water utility's report to see if chromium has been detected where you live. If it has, explore filtration options. If it has not, stay informed about your water quality and check your report again in a year or two.
The Erin Brockovich case taught us that environmental contamination can hide in plain sight. The best defense against chromium-6 in your drinking water is knowledge. Know what is in your water. Make informed decisions about treatment. And hold your water utility accountable for providing clean drinking water to your family.