Major cities include Tallahassee, Miami, Las Vegas, Phoenix, Los Angeles, Washington, DC, and Pittsburgh
A recent study of the drinking water in 35 US cities found alarming levels of hexavalent chromium, a probable cancer-causing carcinogen.
Hexavalent chromium was the chemical at the center of events depicted in the film "Erin Brockovich."
The first nationwide analysis measuring the presence of chromium, carried out by the nonprofit Environmental Working Group, was made public on Monday.
Norman, Oklahoma had by far the highest measure at 12.9 parts per billion. Honolulu, Hawaii, Riverside, California and Madison, Wisconsin were other cities with high levels.
Of the 35 cities where measurements were taken, 31 showed traces showed traces of hexavalent chromium. Of those, 25 exceeded California's proposed 0.06 parts per billion limit.
The federal Environmental Protection Agency is considering whether to set a limit for hexavalent chromium in tap water. The agency is reviewing the chemical after the National Institutes of Health, deemed it a "probable carcinogen" in 2008.
Hexavalent chromium has long been known to cause lung cancer when inhaled, and scientists recently found evidence that it causes cancer in laboratory animals when ingested. It has been linked in animals to liver and kidney damage as well as leukemia, stomach cancer and other cancers.
A widely used industrial chemical until the early 1990s, hexavalent chromium is still used in some industries, such as in chrome plating and the manufacturing of plastics and dyes. The chemical can also leach into groundwater from natural ores.
In 1993, Erin Brockovich was successful in bringing the high levels of hexavalent chromium in Hinckley, California into the national spotlight. PG&E paid 600 townspeople more than $300 million to settle a lawsuit brought by Brockovich.
The company was accused of leaking hexavalent chromium into the town's groundwater for more than 30 years.
"Our municipal water supplies are in danger all over the US," Brockovich told The Washington Post. "This is a chemical that should be regulated."
Read the full report from the Environmental Working Group.
The list of cities tested in this study follows:
Norman, Okla. - 12.9 ppb
Honolulu, Hi. - 2.00 ppb
Riverside, Calif. - 1.69 ppb
Madison, Wis. - 1.58 ppb
San Jose, Calif. - 1.34 ppb
Tallahassee, Fla. - 1.25 ppb
Omaha, Neb. - 1.07 ppb
Albuquerque, N.M. - 1.04 ppb
Pittsburgh, Pa. - 0.88 ppb
Bend, Ore. - 0.78 ppb
Salt Lake City, Utah - 0.30 ppb
Ann Arbor, Mich. - 0.21 ppb
Atlanta, Ga. - 0.20 ppb
Los Angeles, Calif. - 0.20 ppb
Bethesda, Md. - 0.19 ppb
Phoenix, Ariz. - 0.19 ppb
Washington, D.C - 0.19 ppb
Chicago, Ill. - 0.18 ppb
Milwaukee, Wis. - 0.18 ppb
Villanova, Pa. - 0.18 ppb
Sacramento, Calif. - 0.16 ppb
Louisville, Ky. - 0.14 ppb
Syracuse, N.Y. - 0.12 ppb
New Haven, Conn. - 0.08 ppb
Buffalo, N.Y. - 0.07 ppb
Las Vegas, Nev. - 0.06 ppb
New York, N.Y. - 0.06 ppb
Scottsdale, Ariz. - 0.05 ppb
Miami, Fla. - 0.04 ppb
Boston, Mass. - 0.03 ppb
Cincinnati, Ohio - 0.03 ppb
Indianapolis, Ind. - not detected
Plano, Texas - not detected
Reno, Nev. - not detected
San Antonio, Texas - not detected
-- with AFP