An analysis of 35 U.S. cities’ tap water has found that 31 one of these water sources (including Ann Arbor) contain exceedingly high levels of hexavalent chromium, a known carcinogen.The study is the first of its kind ever to be released to the public and comes, fortuitously, as the EPA is deciding whether to set safe drinking standards for hexavalent chromium in our tap water.

If the chemical name – also known as chromium 6 (Cr (VI))- sounds familiar, it’s probably because it was first made (in) famous in the movie Erin Brockovich. Just this past November, Hinkley, California, the town featured in the film (which is about 120 miles northeast of Los Angeles), made news again due to the continued spreading of an underground “plume” of chromium, which is contaminating the water supply.

The analysis was sponsored by the Environmental Working Group (EWG) and the results were officially released Monday but the news was quickly reported by the Washington Post and Yahoo News on Sunday, Dec. 19.

Quoting from the EWG’s report: “The highest levels were in Norman, Okla.; Honolulu, Hawaii; and Riverside, Calif. In all, water samples from 25 cities contained the toxic metal at concentrations above the safe maximum recently proposed by California regulators.”

Levels of Cr (VI) above 0.06 ppb (parts per billion) are considered carcinogenic. The study claims that 74 million in 42 states regularly drink tap water with high concentrations of chromium “much of it likely in the cancer-causing hexavalent form.”

Chromium, a hard metal element, gives many precious gems (like rubies) their color and is a main component of many synthetic pigments. Chromium is valued because of its high corrosion resistance and hardness. Stainless steel is made highly resistant to discoloration/corrosion and by adding chromium. Treating steel, along with chrome plating (electroplating with chromium), are currently the highest-volume uses of the metal.

World chromium production

Although trivalent chromium (Cr(III)) is required in trace amounts for carbohydrate and fat metabolism, in larger amounts (and/or different forms) chromium can be toxic and/or carcinogenic. Cr(VI), which has six valence electrons (making its boding action extra strong), is the most common form of toxic chromium. Abandoned chromium production sites often require extensive environmental cleanup.