Is Your Tap Water Safe? What We Know and What We Don’t Know About Chromium-6

A new report from the Environmental Working Group (EWG) says the dangerous levels of chromium-6 in tap water could affect more than 200 million Americans.

Chromium-6 is often called the “Erin Brockovich chemical”, named after the fiery female lawyer and environmental activist who battled utilities giant Pacific Gas and Electric in a highly publicized court case over chromium-6 levels in PG&E’s tap water.

An email from the EWG sent out to its subscribers included this summary:

“EWG just released a groundbreaking new analysis showing the notorious ‘Erin Brockovich’ carcinogen, otherwise known as chromium-6, contaminates the tap water of two-thirds of Americans at levels above those scientists deem safe.”

The report created a big stir among major news outlets across the country:

We saw these headlines and wanted to know what was going on with chromium-6. What went into the EWG’s analysis? What is chromium-6? What do we know in the wake of the EWG’s analysis? What don’t we know? Are Americans really at risk?

We’re going to tackle each of these questions, using expert sources and the EWG’s analysis to answer them.

How Did the EWG Do Their Analysis?

One of the first things we noticed was that the EWG didn’t actually conduct tests on the water, but used data gathered by the Environmental Protection Agency from 1,370 counties between 2013 and 2015.

The raw data from the EPA’s study is called “Unregulated Contaminant Monitoring Rule #3 Data”, which is a really complex name that basically means: “We tested water for 28 chemicals and two viruses.”

Once the EWG reviewed this data, they produced statistics about the levels of chromium-6 in some of the country’s biggest city water systems:

EWG study data

As you can see, there are some pretty big metropolitan areas included in this table: New York City, Chicago, Houston, Philadelphia, and Phoenix, just to name a few.

A significant amount of people could be at risk here, but before we figure out how dangerous the water is, we need to review what chromium-6 is and why the EWG says it’s a risk.

What is Chromium-6 ?

Chromium is a metallic element that has no taste or odor. According to the EPA, it is found in nature in “rocks, plants, soil and volcanic dust, and animals.”

Chromium also shows up in water in two different forms: chromium-3 (trivalent) and chromium-6 (hexavalent).

Chromium-3 isn’t a big deal. Aside from water, it also appears in fruits, vegetables, meats, grain, and yeast. Chromium-6 also shows up in the natural world when natural chromium deposits erode, but it also enters the environment through manufacturing facilities.

Chromium-6 has a variety of industrial uses, according to the Occupational Safety and Health Administration (OSHA): 

  • Mixed with steel to harden it and help combat corrosion
  • Used in pigments, dyes, inks and plastics
  • Added to metal to give it a protective coating (chrome)

It is this form of chromium that has been known to cause cancer and target “the respiratory system, kidneys, liver, skin, and eyes,” OSHA says. For this reason, chromium-6 is called a “carcinogen”.

Pretty scary stuff, right? But it’s important to remember that workers exposed to chromium-6 may be at risk because the chemical is present in the air – it’s breathable and contacts the skin.

OSHA says most exposures to chromium-6 occur when workers are welding, spraying colorants or giving materials a chrome bath.

To combat chromium-6’s airborne toxicity, plants are required to treat it so that it returns to its more stable chromium-3 form before it heads out into the environment.

While all of this can cause some worry, it’s important to remember that exposure to chromium-6 in the workplace is far different than exposure to chromium-6 in drinking water.

That’s not to say that chromium-6 in drinking water isn’t dangerous, but the effects could be different since it’s not behind inhaled or touched in high-temperature, industrial settings.

This reminds me of a scenario I encountered a few years ago when a study came out that said a certain chemical in microwave popcorn may have caused cancer in factory workers.

When I emailed the scientist who conducted the study, he responded by saying media attention had gotten out of hand and the widespread panic about cancer wasn’t his intention.

In that situation, there was a big difference between a guy working 40 hours a week in a factory producing microwave popcorn and a guy who downs a bag of Orville Redenbacher once a month while bingeing on Netflix.

This brings up our next question: What do we really know about chromium-6 and tap water at this point?

What Do We Know About Chromium-6 for Sure? 

When studies like this come out, it’s important to take an objective stance by looking at the data, understanding what is dangerous and knowing what science says about all of it. Like most environmental issues, there are two sides to the story: the EPA and the watchdog.

What the EPA is Saying

Let’s start with what the EPA says are safe levels of chromium-6 in drinking water: 100 parts per billion, a standard which was set in 1991.

The EPA went back to revisit that standard in 2010, launching a human health assessment of the effects of hexavalent chromium.

The study has yet to be completed, but the EPA notes, “When this human health assessment is finalized EPA will carefully review the conclusions and consider all relevant information to determine if the current chromium standard should be revised.”

So, if the EPA doesn’t seem as freaked out about EWG’s analysis as the EWG is, it’s understandable. As far as they’re concerned, there’s yet to be any evidence that chromium-6’s presence in drinking water is unsafe, or that it will cause cancer via tap water.

What the EWG is Saying

The EWG, on the other hand, is really concerned about the data they uncovered. They want the EPA to speed up their health assessment because they believe millions of lives are at risk.

Here’s what they said in their study summary: “Federal regulations are stalled by a chemical industry challenge that could mean no national regulation of a chemical that state scientists in California and elsewhere say causes cancer when ingested at even extraordinarily low levels.”

In fact, the EWG’s summary of their study said that the EPA has acknowledged that chromium-6 most likely causes cancer in humans.

However, when we clicked on the source for that claim, we were directed to the EPA watchdog site, and needed a password and username to access the source that allegedly included the EPA’s acknowledgment.

What the Studies Say About Chromium-6 and Cancer

While the 2008 study on rats was interesting, we think a study that came 10 years before was more interesting.

In the study, the EPA acknowledged that chromium-6 was more dangerous to humans than chromium-3. That report also acknowledged that “epidemiological studies of chromate production plants in Japan, Great Britain, West Germany, and the United States have revealed a correlation between occupational exposure to chromium and lung cancer.”

The 1951 Cancer Study

In that same section of the report, the authors referred to a 1951 study in which 18.2% of workers in a chromate plant had respiratory cancer compared to just 1.2% of people in the town where the plant was located.

Even more sobering was the fact that, two decades after the initial study, researchers went back to the original group of workers and found that more than half of those who participated in the study were dead. Of those who died from cancer, more than 58% of them had lung cancer.

These numbers are pretty startling, but it’s important to remember the principle of dosage.

The men working in these plants were subject to really high levels of chromium-6 floating around in the air as the result of industrial processes. They were around the element 40 hours a week (probably more) for years and years. Their exposure levels were much more intense than what we face in our drinking water.

What We Don’t Know About Chromium-6

As we just mentioned, a dosage is probably the most important part of this discussion. Yes, chromium-6 most likely causes and increased chance of respiratory cancer in people who work in chromate factories.

However, the EPA pointed out that researchers don’t know what form of chromium-6 was responsible for those cancers, and nobody has released data on how low levels of chromium-6 in tap water effect humans (more on that in a second).

We Don’t Know If Tap Water Chromium-6 Causes Cancer

We know that the EPA has said that 10 parts per billion is a safe level of chromium-6 in drinking water, but we don’t know at what point chromium-6 levels in water actually cause cancer, as there have been no studies provided by the EPA or the EWG that show clear evidence that specific levels of chromium-6 ingested through drinking water cause cancer in humans.

The EWG did say that scientists in California, North Carolina, and New Jersey said that low levels of tap-water chromium-6 consumption over a lifetime can cause cancer, but their conclusions were based on the 2010 study on rats “and other animal studies,” not in a human study.

We Don’t Know of Any Studies Suggesting Legal Parts-Per-Billion Limits

We know that the EWG says safe levels of chromium are 0.02 parts per billion (a drop of chromium-6 in an Olympic-sized pool) based on the opinion of the scientists we just mentioned, but, again, we don’t know which studies support that number because those studies don’t exist.

We do know that the state of California’s legal standards for chromium-6 are 10 parts per billion and that none of the major cities listed in EWG’s report have average levels above that.

As you can see, while the initial reports from the EWG are pretty scary and have stirred up a lot of worries, there are a lot of things we don’t know about chromium-6; particularly, how dangerous it is to humans when present in drinking water in low levels.

Our Conclusions About the Dangers of Chromium-6

Let’s wrap this up with a quick review and our conclusions.

Chromium is an element that occurs in the natural world and is produced in industrial settings. Chromium-3 appears in fruits and vegetables and is beneficial to our bodies, while chromium-6 has proven to be dangerous in high levels in industrial settings, and in lab tests performed on rats.

The EWG’s recent report states that chromium-6 is present in tap water across the country and has the potential to put more than 200 million people at risk.

Those conclusions, however, are based on studies conducted in industrial settings where chromate-factory workers were exposed to very high levels of airborne chromium-6.

While it’s true that many of those workers died of cancer and, specifically, lung cancer, we think it’s an awfully big leap of logic to conclude the presence of low levels of chromium-6 are just as dangerous, as the EWG seems to be implying.

In our opinion, the principle at stake here is dosage. High doses of dangerous chemicals can most certainly cause cancer in humans. But that doesn’t mean that the simple presence of the chemical will cause cancer.

In fact, the 1998 EPA report to which we referred earlier in this article pointed out one case study that failed to appear in the EWG’s news release about chromium-6.

In the study, researchers observed a small village of people who lived near a chromium alloy plant. The village’s well water contained 20 parts per billion of chromium-6. The results? A lot of vomiting, diarrhea, indigestion, mouth sores and increased white blood cell counts (common with infections), but no cancer.

Our conclusion on all of this, which is based on our review of existing studies, EPA statements, and the EWG’s recent news release, is most of us shouldn’t be too worried about the reports at this point.

The EPA says they’re releasing next year the results of the health assessment we mentioned earlier. When those results come out, we’ll know a lot more about the specific effects of tap-water chromium-6 on humans.

For now, we think it’s important to stick to the facts and avoid conjecture. Chromium-6 is dangerous in high levels in industrial settings, but scientists have yet to prove tap water is a source of cancer caused by chromium-6.

If you’re still worried about contaminated drinking water, it’s okay. We think that worry is a natural part of understanding contaminants and pollutants.

Water filters are a good way to ease your concerns. This article from PBS recommends purchasing a reverse-osmosis filter. The EWG suggests using the Zero Technologies ZP-001, a pitcher-style filtration system that filters out chromium-6.

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J.R. Duren

J.R. is an award winning journalist who uncovers the hard truths about personal finance, health and fitness through in-depth research and interviews with experts.


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