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