Erin Brockovich Carcinogen Runs Rampant in US Tap Water Industrial pollutant hexavalent chromium found in 31 of 35 cities surveyed By Mark Russell, Newser Staff Posted Dec 19, 2010 7:01 AM CST 14 comments Comments The Environmental Working Group found hexavalent chromium, a probable carcinogen, in tap water in 31 US cities. (Shutterstock) (Newser) – Those who thought Erin Brockovich was just a decent movie might want to check their drinking water: An environmental group has found the probable carcinogen featured in the film in the tap water of 31 of 35 US cities it analyzed—the first such study of hexavalent chromium to be made public. Topping the list of offenders were Norman, Okla., Honolulu, Riverside, Calif., and Madison, Wis. "Our municipal water supplies are in danger all over the US," says Brockovich. "This is a chemical that should be regulated." The EPA is considering setting limits for hexavalent chromium, reports the Washington Post, after the National Institutes of Health labeled it a "probable carcinogen" in 2008. California took steps last year to become the first state to regulate hexavalent chromium in drinking water, but chemical industry advocates say the proposed standard of 0.06 parts per billion is too strict, noting that the substance can occur naturally at higher levels. The full report by the Environmental Working Group will be available tomorrow here.