Hexavalent chromium, the chemical made famous by the 2000 movie Erin Brockovich, is in the news again because a U.S. environmental organization detected the probable carcinogen in 31 of the 35 cities where it tested the drinking water. Environmental Working Group found concentrations of chromium in public drinking water supplies that ranged from 1/2 to 200 times what would be allowable by the state of California if a proposed chromium safety limit goes into effect.
Update 12/20 – The full report is available on the Environmental Working Group website. EWG has also posted tips for consumers and a frequently asked questions list that is summarized below.
Chromium is found in several chemical forms in mineral deposits in rock around the world. It is used in many industrial an manufacturing processes such as chrome plating and as an additive to steel to make it stainless. Hexavalent chromium, which is also known as chromium 6, is used in dying fabric, tanning leather, manufacturing magnetic tape, and preventing corrosion in a variety of industrial applications.
Pacific Gas & Electric, the company investigated and sued by Erin Brockovich on behalf of families in Hinkley, CA, in the early 1990s, was using the chemical to prevent rust in its equipment and discharging it into holding ponds on PG&E property, where it ultimately seeped into the drinking water.
One form of chromium, in small amounts, is actually considered a nutrient that is good for us: chromium 3 or trivalent chromium. Trace amounts of that form of chromium is essential for human metabolism and you may find it in your multivitamin. However, chromium 6 was officially classified as a probable carcinogen by the National Institutes of Health in 2009.
That classification prompted the Environmental Protection Agency and the state of California to reconsider drinking water safety standards for the chemical. The federal standard for levels of all types of chromium in drinking water is 100 parts per billion (ppb), approximately the same concentration as chromium occurs in the earth’s crust. California is considering a safety standard for chromium 6 at only 0.06 ppb. A full 25 of the 35 cities tested had drinking water concentrations higher than that proposed standard.
The 10 highest concentrations found by EWG of hexavalent chromium in drinking water:
(Added 12/20) According to previous work by EWG, at least 74 million people in nearly 7,000 communities drink tap water polluted with “total chromium,” which includes hexavalent and other forms of the metal. The U.S. EPA does not require utilities to test for chromium-6, consequently, EWG’s report is the most comprehensive data public ally available.
“Every single day, pregnant mothers in Norman, Oklahoma, school children in Madison, Wisconsin, and many other Americans are drinking water laced with this cancer-causing chemical,” said EWG senior scientist Rebecca Sutton, Ph.D., in a press release. “If the EPA required local water utilities to test for hexavalent chromium, the public would at least know if it was present in their local water. Without mandatory tests and a safe legal limit that all utilities must meet, many of us will continue to swallow some quantity of this carcinogen every day.”
In the same release, Brockovich was quoted saying, “It is sometimes difficult to understand why I still have to warn the public about the presence of hexavalent chromium in drinking water 23 years after my colleagues and I first sounded the alarm. This report underscores, in fairly stark terms, the health risks that millions of Americans still face because of water contamination.”
Avoiding Chromium-6 in Your Drinking Water
Drinking fountain image by flickr user Darwin Bell
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