If you’ve seen the movie Erin Brockovich, you’re likely familiar with hexavalent chromium. Also known as chromium-6, hexavalent chromium is a chemical that comes from chromium, a naturally occurring metal used for things like steel manufacturing and leather tanning.

 The U.S. Environmental Protection Agency (EPA) has classified chromium-6 as a likely carcinogen. Many experts believe the chemical can do serious damage if it is ingested.

 "We're most concerned about chromium-6 and cancer," said Dr. Rebecca Sutton, a senior scientist at Environmental Working Group (EWG). "We've known for a long time that when you inhale this chemical, it can cause cancer. But recent evidence also indicates that it's a problem when you drink it."

Dr. Sutton recently led a study of chromium-6 in U.S. public water supplies. EWG tested 35 cities across America and found the chemical in 31 of them. EWG conducted the study because, more than a decade after Erin Brockovich, the EPA only requires utilities to test for total chromium, not chromium-6. Earlier this month, the EPA delayed adopting a drinking water standard for chromium-6 until it completes an additional study.

“That is sobering news for some, especially since chromium-6 has been in the news for so long,” says attorney Martin Sweet of legal information websiteTHELAW.TV. The lawsuit on which Erin Brockovich was based was settled in 1996, with Pacific Gas and Electric paying out $333 million to residents of Hinkley, California, many of whom claimed groundwater contaminated with chromium-6 gave them cancer. The film, which was released in 2000, was a box office hit and received several Academy Award nominations.

“Chromium-6 is potentially a very dangerous chemical to have in our drinking water,” explains Reno, Nevada personal injury attorney Matthew Sharp of Law Offices of Matthew L. Sharp. "The EPA would be wise to set a standard for our water as soon as possible.”

Public water utilities might not test for chromium-6, but they do test for a lot of things, including total chromium. Each public water utility is required to issue a report that contains the results of their testing on an annual basis. According to EWG, which collects test results from all over America, more than 300 pollutants have been found in U.S. tap water since 2004. EWG claims more than half of the chemicals detected are not subject to health or safety regulations and can legally be present in any amount.

EWG has an online database that lets you check your utility's annual drinking water quality report. Click here to visit that database.