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On December 20, the Environmental Working Group (EWG) released a report on a “study” they did regarding chromium (VI) in drinking water. Since then there have been a lot of newspaper and other media reports coming out talking about the same thing, so here’s some background info on the whole issue. Chromium (VI), which you’ll also see as chrome(VI), chrome-6, chromium-6, Cr (VI), hexavalent chromium, and many other variations on that theme, is a form of the metallic element chromium, which you used to be able to find on the bumper of every car. Other uses for this metal have included plating of other metallic parts; manufacturing stainless steel; producing dyes; as a wood preservative; and as an additive for anti-corrosion purposes. The (VI) or 6 part is a chemical designation that refers to what’s called the oxidation state of the element, which relates to the number of electrons the atom has. In this case, it is the highest oxidation state of chromium, the others being (II) and (III), with (III) being by far the most common. Although too much chromium in any state would not be good to eat, it is the highest oxidation form, chromium (VI) which is most reactive, and therefore of greatest concern from a health perspective. Small quantities of chromium (III) are actually required by all of us for proper sugar metabolism, but because chromium (VI) is so much more reactive, it can be disruptive to cellular metabolism and is a proven cancer causing agent when inhaled; it’s effect when ingested at low levels is still open to debate. Although there is no EPA or state regulation requiring monitoring or treating for Cr (VI), a Public Health Goal (PHG) of 0.02 ug/L has been proposed in California. Once a PHG has been formalized, then the process for determining an MCL will begin, and will take into consideration the economic and technical aspects of treating for this compound.
