Hexavalent chromium, a likely carcinogen found in tap water

A chemical called chromium-6 or hexavalent chromium has been found in the tap water in 31 out of the 35 American cities tested, reports the Environmental Working Group.

Norman, Okla., Honolulu and Riverside, Calif., had the highest levels of the substance, dubbed the “Erin Brockovich chemical.” New York, while far down on the list of cities, still had more chromium-6 in the tap water than what California is proposing as a “public health goal” for safe levels: 0.06 parts per billion.