GARY, Ind. (CBS/WBBM) — A report out Monday says the cancer-causing chemical made famous in the movie “Erin Brockovich” is finding its way into drinking water in Northwest Indiana — likely at many times the level scientists consider safe.

As WBBM Newsradio 780’s Pat Cassidy reports, the Environmental Working Group says hexavalent chromium, or chromium-6, has been found in tap water in Northwest Indiana at levels 16 to 41 times what California officials have deemed safe.

LISTEN: Newsradio 780’s Pat Cassidy reports

But the Northwest Indiana Post-Tribune says some experts warn about the difference between chromium-6 and other isotopes of the metal. While dangerous chromium-6 comes is believed to come from discharge from Indiana steel mills, benign chromium-3 comes from natural sources and is an essential nutrient.

Total chromium is well within the guidelines set forth by the U.S. Environmental Protection Agency, but critics say those standards do not differentiate between good chromium-3 and bad chromium-6.

No measurable chromium was found in drinking water in Porter County, Ind.

The dangers of chromium-6 in drinking water have already gained notoriety in the city of Chicago. The amount in Lake Michigan water was nine times higher than a safety limit adopted by the State of California this month.

first, city Department of Water Management Commissioner Tom Powers said the water does meet existing standards, and is safe.

But as his staff reviews the findings, Powers has admitted there is currently no test required for the metal. Last week, the city announced that tests would begin for chromium-6.

The chromium-6 in the Chicago water supply is also believed to have originated at Indiana steel mills. Chromium-6 is carcinogenic.