The cancer-causing metal made infamous by the movie "Erin Brockovich" is turning up in tap water from Chicago and more than two dozen other cities, according to a new study that urges federal regulators to adopt tougher standards. Even though scientists at the US Environmental Protection Agency and National Toxicology Program have linked the ingestion of hexavalent chromium to cancer, the EPA doesn't require Chicago or other cities to test for the toxic metal. Nor does the EPA limit the dangerous form of chromium in drinking water. The amount in Lake Michigan water pumped to 7 million people in Chicago and its suburbs was 0.18 parts per billion, three times higher than a safety limit California officials proposed last year. Other cities include Norman, OK; Honolulu; Riverside, CA; and Madison, WI.