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Posted on Wed, Dec 22, 2010 : 6:02 a.m.

Impact of hexavalent chromium detected in Ann Arbor drinking water unclear

By Juliana Keeping

An environmental watchdog organization announced earlier this week it detected a potentially harmful industrial pollutant called chromium-6 in Ann Arbor’s tap water.

That was among the findings of the Environmental Working Group’s national report that asserts millions of Americans might be drinking tap water that contains some level of the probable human carcinogen.

But what does that mean?

Clear-cut answers may not exist yet. But the report, released Monday, has raised all sorts of questions, a University of Michigan expert said Tuesday.

“This is the kind of investigation that raises eyebrows, and that will hopefully generate additional testing so we have a fuller picture of what the exposure profiles are like in any given community and what the incremental risk of cancer might be,” said Howard Hu, a professor and chair of environmental health at the U-M School of Public Health.

Officials from the EWG, a Washington D.C.-based non-profit, detected chromium-6 at .21 parts per billion in a single sample of Ann Arbor tap water taken from one residence in the spring. 

Chromium-6 is also called hexavalent chromium. While it can occur in nature, it is also an industrial pollutant discharged from metal-plating and leather-tanning facilities, as well as steel and pulp mills. The human body, depending on the acidity in the stomach, can convert chromium-6 to less toxic forms — and to some extent, the conversion also occurs in nature, Hu said.

“This is a snapshot of contamination, and indicates the contaminant is present in the water of Ann Arbor,” Rebecca Sutton, a senior scientist for the Environmental Working Group, wrote in an e-mail to

A lab test showed the Ann Arbor sample was three-and-a-half times the .06 ppb limit proposed by California officials in 2009. Much higher levels were detected in other cities. Of 35, 31 had chromium-6 in the drinking water. The highest level detected was 12.9 ppb in Norman, Okla.

So what does .21 ppb of chromium-6 mean for Ann Arbor residents?

“No one really knows,” Hu said.

California is the only state that requires municipalities to test for chromium-6, according to the EWG. Officials there took the first step to establish a statewide-enforceable limit of chromium-6 in response to recent research that links the chemical in drinking water to an increased risk of rare gastrointestinal tumors in lab animals.

“There’s no expectation that if you’re over .06, you’re automatically going to get cancer,” Hu said. “But I think that what’s less clear is what is the incremental risk that one could anticipate once you go over the proposed safe limit. Let’s say you go double — .12 — in a community of 100,000 people. How many people will get cancer who would not have gotten cancer otherwise after drinking the water for 20 years?”

“I haven’t seen a good risk analysis of that yet,” Hu said.

According to the EWG, the EPA doesn’t require municipalities to test specifically for chromium-6 and hasn’t established any legal threshold for how much of it can be in drinking water. It is, however, classified as a probable human carcinogen by the federal government.

Molly Wade, water treatment services manager for the city, said Ann Arbor tests its water supply once a year for all types of chromium, though the EPA requires testing only every nine years. The detection limit for the test they use is 2 parts per billion. The levels of all chromium read “non-detect,” which means they are under 2 ppb, she said. The EPA standard for total chromium is 100 ppb.

That means the water is safe under the current EPA standards.

The EWG argues in its report that the federal standard for total chromium is too vague and too high. The standard includes an essential mineral called trivalent chromium, which regulates glucose metabolism, as well as chromium-6, the probable human carcinogen, and other types.

“The 100 ppb limit is designed to protect against skin irritation, and doesn’t consider cancer at all,” Sutton said in an e-mail to

According to the EWG, the majority of chromium it detected in the drinking water in 31 of 35 cities it tested for its report was the hexavalent form.

Hu said hexavalent chromium is a carcinogen that carries a risk of respiratory cancers. But things are less clear when the water-soluble pollutant shows up in drinking water — as well as more controversial, Hu said.

“There’s been quite a bit of recent research…the EWG goes over some of the controversy surrounding industry-funded studies,” Hu said.

Sutton said she hopes the report prompts the EPA to recognize hexavalent chromium contamination is widespread.

“We need a drinking water safety standard to protect public health,” she added.


A high-pressure pump is shown at Ann Arbor’s water treatment plant on Sunset Road.

File photo

In 1996, California resident Erin Brockovich helped cancer-stricken residents and their families in Hinkley file a lawsuit against Pacific Gas & Electric Company for contaminating their drinking water with hexavalent chromium. The suit resulted in a $333 million settlement from the company; the saga inspired the 2000 film starring Julia Roberts. Levels of hexavalent chromium in Hinkley's groundwater supply were as high as 580 ppb.

“We now know that this is not an issue confined to Hinkley, California, it’s something that impacts the nation,” Sutton said via e-mail.

Hu agreed.

“I think the rest of the country is behind in trying to both appreciate the importance of distinguishing hexavelant chromium from other forms and in doing the kind of testing with sensitive instruments that would be able to test for chromium-6 levels as low as .06 ppb,” Hu said.

But Hu added there are levels of uncertainty involving the findings.

There are sub-groups of the population who are more susceptible to chromium-induced toxicity and cancer, Hu and the EWG said. It’s not clear whether California’s proposed .06 ppb limit would protect that group. Hu wondered what the distribution of chromium-6 at any one time in a range of households might be. That’s not clear either, since the EWG only tested a sample of tap water from one Ann Arbor household.

Hu said he is familiar with the EWG, which in the past has criticized the Food and Drug Administration for its standards involving the toxicity of bisphenol-A, a common chemical used in re-usable water bottles, the protective lining of metal food and beverage cans and many other common products. The FDA commissioned him to provide outside expert review of the EWG’s report on BPA.

In 2008, the FDA withdrew its draft statement on BPA and is still working on a review, Hu said.

“They were among the first (non-governmental organizations) pushing the scientific community and the public to have a broader appreciation for the recent science and its implications,” rather than accepting federal standards, he said.

BPA has since captured global attention as an environmental contaminant with endocrine-disrupting properties. Scientists have recently linked the chemical that makes plastic hard and clear to everything from fertility problems to early puberty in American girls.

Juliana Keeping is a health and environment reporter for Reach her at or 734-623-2528. Follow Juliana Keeping on Twitter


Roger Rayle

Thu, Dec 23, 2010 : 10:01 a.m.

I've got to correct a couple of my earlier points... they should have read... - the population of the communities affected by the Pall-Gelman plumes is about *130* times bigger than that at the Hickley site (~130,000 vs ~1000), - the maximum *recent* concentration at the Pall-Gelman plume was 53,872 ppb vs 2350 ppb at Hinkley. Note to self-- don't make comments at 3am.

Kai Petainen

Thu, Dec 23, 2010 : 9:34 a.m.

Roger, fascinating... I never knew about that.

Roger Rayle

Thu, Dec 23, 2010 : 3:28 a.m.

For those curious as to how the Hinkley hexavalent chromium groundwater contamination compares to the Pall-Gelman 1,4-dioxane groundwater contamination site, I placed an approximately scaled image of the Hickley plume adapted from the PDF map in the article along side the Pall-Gelman plume and created this annotated screen shot of it: While the area of the Hinkley plume at 50 ppb is about the same as the area of the Pall-Gelman plume at 85 ppb, and while the current cleanup limits are somewhat comparable at 100 ppp and 85 ppb, there are key differences: - the current Hinkley plume maps are drawn lower than the current cleanup standard of 100 ppb (4, 10, & 50 ppb) while Pall-Gelman is allowed to draw its plume maps at the Michigan cleanup standard of 85 ppb instead of where the dioxane can be detected (at 1 ppb), - the population of the communities affected by the Pall-Gelman plumes is about 1300 times bigger than that at the Hickley site (~130,000 vs ~1000), - the maximum concentration at the Pall-Gelman plume was 53,872 ppb vs 2350 ppb at Hinkley, - the areas of higher concentrations are larger for the Pall-Gelman plumes - the Pall-Gelman plumes are moving in at least 5 directions in various layers while the Hinkley plume appears to be following a meandering path in one layer, - the DNRE has negotiated (in secret) an expanded prohibition zone plan for the Pall-Gelman plumes (after first rejecting the plan in 2009) which means most of the dioxane can spread unremediated at up to 2800 ppb.


Wed, Dec 22, 2010 : 9:27 p.m.

@say it plain, thanks. So if EWG detected.21 ppb that converts to 210 ppt (parts per trillion), correct? That leads me to agree with @Plubius.


Wed, Dec 22, 2010 : 9:23 p.m.

It's good that we as a species have become self aware enough to recognize that some things have been a threat to us so we have eliminated them, e.g. saber-tooth tigers, polio, etc. We have enough natural threats that will eventually kill us -- we don't need a whole lot of man-made chemicals to hasten the process. Consider that 18 grams of water contain Avogadro's number (6.02 * 10^23) of H2O molecules. 1 gram of water (= 1 cc) is (6.02 * 10^23) / 18 = about 3.3 * 10^22 water molecules 1 Kg of water = 1000 g/Kg * 3.3 * 10^22 water molecules/g = 3.3 10^25 water molecules/Kg According to, the average weight for an adult male in the United States is 191 pounds = ~86 Kg The average adult male is ~60% water so the average adult male is 60% of 86 Kg = 51 Kg water. 51 Kg water/adult male * 3.34 * 10^25 water molecules/Kg = 1.7 10^27 water molecules/adult male or about 1,700,000,000,000,000,000,000,000,000 water molecules in the average adult male. At.21 parts hexavalent chromium per billion there would be (1.7 * 10^27) * (210/1,000,000,000,000,000) = 3.57 * 10^14 = 357,000,000,000,000 molecules of hexavalent chromium in an average adult male body. At 100 ppb, there would be 100/.21 times more or about 1.7 * 10^17 (170,000,000,000,000,000) molecules of hexavalent chromium in an average adult male body. An average human body may have 100 trillion cells (100,000,000,000,000 or 1.0 * 10^14). How many of those cells do you want affected by man-made compounds like hexavalent chromium or 1,4-dioxane or bromate?... every day over a lifetime? And don't forget that babies and children have a higher percentage of water in their bodies than do adults.


Wed, Dec 22, 2010 : 9:07 p.m.

"@AlphaAlpha If you read the headline it says that the "impact...[is] unclear". I don't think the purpose was to elaborate on the side effects, but rather report the information that has been discovered." Thank you, amyreneeh. The reference to side effects was with respect to BPA. It is disappointing to see various over reactions by some commenters. There is seemingly no evidence that the single 'test' was conducted appropriately, and no context in which to place the results of the single test. Too many variables appear to be completely unaccounted for. These issues, and others, lead to the inescapable conclusion that the single test result is worthless. Perhaps the majority know this; perhaps they chose not to comment. Meanwhile, BPA is a substantial and growing problem, already affecting many. When they say 'endocrine disrupting', you should run; avoid it at all costs. Many people already suffer from this under publicized and growing threat; the list of side effects is long; potentially, most of us are affected. The negligible, questionable read of hexavalent chromium is comparatively meaningless.


Wed, Dec 22, 2010 : 6:17 p.m.

I gained superpowers to detect BS due to the chromium-6 in the water supply. Reading all the hullaballoo about this issue causes my new found spidey senses to tingle.


Wed, Dec 22, 2010 : 5:09 p.m.

OK, so I'm just an average citizen who wantsto kinow whose responsibility it is to evaluate this and fix it, if needed. Anybody know? and let's all talk to those people.


Wed, Dec 22, 2010 : 2:56 p.m.

The logic that 'oh, we need Chromium' its in our vitamins and foods, so let's not worry about chromium-6 is ridiculous and dangerous. We also need carbon and we need oxygen, so why don't we just turn on our cars in our garages and take in some deep breaths of some good ole CO (carbon monoxide). Same logic that @DonBee is using. I'm not arguing that we demand this to be fixed, the concentrations are low. But it is worth monitoring.

Juliana Keeping

Wed, Dec 22, 2010 : 12:25 p.m.

In Hinkley, levels of chromium-6 in the groundwater were much higher than the levels detected in one Ann Arbor home, according to the EWG spokesperson, Lee Ann Brown. Today, the contamination in a plume of contaminated groundwater measures differently in different areas. Some wells show hundreds of ppb of hexavalent chromium, while others are 5 to 10. I've linked pdf of the Hinkley's plume in the story where I talk about the town.


Wed, Dec 22, 2010 : 12:11 p.m.

If this group is making claim of detection capability in part per trillion someone needs to examine their lab and records of how they test as well as the equipment used and if that lab is accredited by anyone. I think they are making a false claim for publicity.

say it plain

Wed, Dec 22, 2010 : 11:26 a.m.

Totally logical @DonBee, and good point about looking into the various ways treatment processes may be adding to the levels of chromium-6 in the water. Perhaps this is behind the too-high levels in many of the tested communities! Now, would it be okay to say hmm, yes, I like my broccoli and my wine just fine, and will do my best to avoid somehow creating 'oxidized' versions of these lol, but just as there is arsenic in my apple seeds, can I nonetheless prefer that there be no unsafe levels of the stuff in my water?

say it plain

Wed, Dec 22, 2010 : 11:14 a.m.

@kbk and others, the level the EWG test found would *not* have been picked up by the Ann Arbor Water Authorities, because it falls *under* their detection-thresholds. AA officials found no presence of at least 2.0 ppb, while the EWG found.21 ppb. So, if the EPA standards are good enough for everyone, then we don't have a problem in AA. *But* CA officials test with a lower threshold, believing that we should aim for 0.06 ppb to be safe. The EPA now seems ready to consider that hexavalent chromium is dangerous--and not just due to carcinogenic activity but also effects on kidney and liver functioning for instance--at levels lower than what had previously been considered toxic. Looks like the standard stuff is happening: the government (here, AA officials) are trying to cover their butts, and the watchdog group (here the EWG, and in the case of the Erin Brokovitch suit, the lawyers) are trying to sound an alarm. Is it unreasonable to sound alarms? Not if you believe that as humans we err, both due to greed for profit and due to ignorance. I love the comments about how this desire to avoid *manufactured* toxins is somehow an attempt to cheat the Reaper lol. As if steel plants, industrial waste, factory-farming, etc., are somehow "nature's own" endogenous features lol, coming to get us along with Father Time. I think that's ultimately a rather dim sort of fatalism.


Wed, Dec 22, 2010 : 11:06 a.m.

@GRANDPABOB - According to court records the level of Chromium-6 in the water in Hinkley was 580 parts per billion or 0.58 parts per million. The suggested "Health Goal" not standard in California is 0.6 parts per billion. Health Goals are set at levels that should pose no risk to the community and at worst should produce no more than 1 case in 1 million people of any related problems. The proposed standard right now in California is 0.1 parts per million. Steel tanks, pipes and other parts of the water system contain a portion of Chrome in their alloys in many cases. If there is Chromium in the water to begin with (and most Michigan water has some) the use of Ozone to purify the water will increase the amount of Chrome-6 in the water. The amount of increase is being debated. The choice of ozone over chlorine to purify water was made because some byproducts of chlorine are not nice and chlorine is a hazardous material. If you want to minimize your exposure to Chromium (and therefore possible Chromium-6) stop eating high fiber foods, green beans, broccoli, beer, and wine. But, first check your vitamin bottle and see that in many vitamins there is come Chromium, since your body requires it and it is in most of our food supply. That is not to say we need Chromium-6. All the scientific studies I can find and read all point to the same conclusion in Hinkley, California - no one can prove that any of the problems there were caused by Chromium-6 and no one can prove that the total cancer rate was any different from other locations in the area. But, PG&E had deep pockets and the lawyers were good. Emotion, not science won in court. Think about the level of Chromium-6 in Ann Arbor's water this way - there are about 6.8 billion people on the planet. If we were to use then as an analog for water you drink, one (1) of them would be Chromium-6, the other 6,799,999,999 would not be.


Wed, Dec 22, 2010 : 10:40 a.m.

Your best bet to filter poisons being added to our drinking water is the four or five stage reverse osmosis water filter. Cost is around $150-$300. By the way, fluoride is one of the most toxic poisons known to man. It is an industrial waste that causes cancer and many more illnesses per our own government. Look it up!


Wed, Dec 22, 2010 : 10:40 a.m.

I believe that granular activated carbon is not that effective in removing Chromium but utilizing a Reverse Osmosis filter can be very effective in removing Chromium from drinking water. It would be interesting to see a follow up to this piece to see what is possible for "at the tap" mitigation of Chromium.


Wed, Dec 22, 2010 : 10:35 a.m.

I want to hear a critique on the methods EWG used. They sampled water from one house in Ann Arbor!? At this point I am much more inclined to trust the City's results because the City doesn't need press coverage to remain relevant.


Wed, Dec 22, 2010 : 10:29 a.m.

@AlphaAlpha If you read the headline it says that the "impact...[is] unclear". I don't think the purpose was to elaborate on the side effects, but rather report the information that has been discovered.


Wed, Dec 22, 2010 : 10:20 a.m.

What is happening, in part, that as our ability to measure improves, we are finding things we never knew previously. These new findings will continue to arise - we can currently measure at sub-ppb levels - what happens when we start detecting chemicals at sub-ppt (trillion) levels? Just because something bad is detected doesn't mean it's harmful. We need to take all such reports in stride and let science dictate a meaningful response.


Wed, Dec 22, 2010 : 10:14 a.m.

Excellent follow-up to the EWG report and its ramifications posted over at the Ann Arbor Chronicle:

Kai Petainen

Wed, Dec 22, 2010 : 10:05 a.m.

I have a question. Note -- I'm not accusing anyone of anything, but I think it's important to ask these questions. If something is in the water, then it's important to look at areas that reside along the river. According to this document there are 88 outfalls that flow from UofM into the river system. So a portion of the outfalls in Ann Arbor go through UofM grounds. "The facility storm water system discharges through a series of nearly 88 permitted outfalls to the City of Ann Arbor storm water system, the Huron River, and tributaries to the Huron River (Allens Creek, Traver Creek, Fleming Creek, Mallets Creek, and Millers Creek)." And as I learned this summer, if something spills into those outfalls, then UofM has the jurisdiction to investigate and the city of Ann Arbor and the state don't get involved. (Hence why the City Police, the DNR and EPA never showed up to the July petrochemcial / 88% confident phosphoric acid spill) Although the article states some of the uses of Chromium-6 as... "an industrial pollutant discharged from metal-plating and leather-tanning facilities, as well as steel and pulp mills." According to this site, it talks about how cooling towers can use Chromium 6 Going back to the the OSEH document, it states: "Drainage ways that may discharge offsite are monitored in accordance with the MDNRE-approved Once-Through Cooling Water National Pollutant Discharge Elimination System (NPDES) permit and the facilitys Municipal Storm Water NPDES Permit." I think, if I'm reading that correctly, the UofM has cooling towers, and they have a permit to discharge stuff into the river. So here is my question: Do we use chromium in the cooling towers?


Wed, Dec 22, 2010 : 9:32 a.m.

@a2scio No, I don't think so. Chromium-6 is a dissolved ion. Filters would not remove dissolved ions. Think of salt water. A filter wouldn't desalinate water. It's the same.


Wed, Dec 22, 2010 : 9:28 a.m.

C6 - thank you for injecting actual facts and details and naming your sources. I get really tired of "We all know..."


Wed, Dec 22, 2010 : 9:11 a.m.

@DDOT1962 My thoughts exactly! I was just sitting here thinking how to put it into words. Some people are not to be believed.


Wed, Dec 22, 2010 : 8:49 a.m.

Do home water filters remove this?


Wed, Dec 22, 2010 : 8:44 a.m.

OMG, does anyone really care? Are we going to scrutinize the minutiae of our lives to uncover all potential pitfalls? Perhaps we should all revert to the State of Nature where it's understood that death is a part of the complete cycle, instead of trying to cheat the Reaper of his due... Just sayin'.

Linda Peck

Wed, Dec 22, 2010 : 8:13 a.m.

I agree with Dunne. Let's hear about some solutions, if there are any. All this defensive writing makes me impatient.


Wed, Dec 22, 2010 : 8:08 a.m.

@GRANDPABOB: The average hexavalent chromium levels in Hinkley were reportedly recorded at 1.19ppb, with a peak of 3.09ppb. @5c0++ H4d13y: Online I found the following information concerning the cancer rates reported in Hinkley: The study referenced by The Washington Post in their article is not provided with or in the article and could not be found nor be substantiated, based on the California Cancer Registry, which was claimed to be the source. However based on the article, 196 cases were reported over a 12 year period in a population averaging 1,915. That equates to roughly 853 cases per 100,000 population, per year. Based on the statistics at California Cancer Registry, San Bernadino County averaged 359 cases per 100,000 per year over the same time period, meaning the rate in Hinkley was 276% of the "expected value" in that area. This seems to contradict the claim of fraud put forth in The Washington Post and repeated by you.


Wed, Dec 22, 2010 : 7:53 a.m.

This article would be helpful if they could say what steps could be taken to remove the chromium 6 from the water.


Wed, Dec 22, 2010 : 7:50 a.m.

We must order the immediate closure of all steel and pulp mills as well as all the metal-plating and leather-tanning facilities in the city of Ann Arbor! And lower all the speed limits.

5c0++ H4d13y

Wed, Dec 22, 2010 : 6:54 a.m.

@GRANDPABOB The Hinkley case was a fraud propagated by lawyers. We now know that that town had a LOWER rate of cancer than the surrounding area.


Wed, Dec 22, 2010 : 6:37 a.m.

I was very happy to see Prof. Hu consulted in this. He is very knowledgeable, and should be the first person talked to. Hu's on first.


Wed, Dec 22, 2010 : 6:32 a.m.

I wonder how many ppm were in the water in the Hinkley case?


Wed, Dec 22, 2010 : 6:32 a.m.

"BPA has since captured global attention as an environmental contaminant with endocrine-disrupting properties. Scientists have recently linked the chemical that makes plastic hard and clear to everything from fertility problems to early puberty in American girls." Ms. Keeping - It might prove fascinating if you could elaborate on more of the side effects of BPA. Many of your readers might recognize some symptoms as familiar... In the meantime, one test? From one faucet? How reliable is that?