Hexavalent Chromium, Cancer-Causing Toxin, Common in Tap Water: What to Do

(CBS) Americans worried about the safety of their drinking water may have new cause for alarm.

A new study shows that tens of millions of us are drinking water contaminated with hexavalent chromium, a cancer-causing toxin that garnered national attention with the 2000 feature film "Erin Brockovich."

Recent tests found hexavalent chromium, a.k.a. chromium-6, in the drinking water of 31 of 35 cities tested, according to a statement issued by the Environmental Working Group, the Washingon, D.C.-based advocacy group that conducted the tests. Among the cities with the highest levels were Norman, Okla., Honolulu, and Riverside, Calif.

The study, the first of its kind to be made public, comes at a time when the EPA is considering whether to implement a national standard for hexavalent chromium in drinking water, the Washington Post reported. The compound was deemed a "probable carcinogen" by the National Institutes of Health in 2008. It's been linked to stomach cancer and leukemia, as well as other health conditions, Jane Houlihan, senior vice president of research for the group, told CBS News.

Where is the hexavalent chromium coming from? It's discharged by steel and pulp mills, as well as from metal-plating and leather-tanning facilities, according to the group's statement. It can also appear in tap water as a result of erosion of natural deposits.

Brockovich helped residents of Hinkley, California sue Pacific Gas & Electric, alleging that the company leaked hexavalent chromium into the town's drinking water for more than 30 years, according to the Post. The company paid $333 million in damages and pledged to clean up the contamination.

What does Brockovich say now about hexavalent chromium?

"This chemical has been so widely used by so many industries across the U.S. that this doesn't surprise me," she told the Post. "Our municipal water supplies are in danger all over the U.S. This is a chemical that should be regulated."

In the meantime, what can consumers do to limit the threat posed by hexavalent chromium?

"With levels this high, it's critically important that people begin to think about filtering their water," Houlihan said. Unfortunately, inexpensive carbon filters like the ones in filtration pitchers and tap faucet filtration units aren't good at removing hexavalent chromium, she said, adding that reverse-osmosis filtration systems costing hundreds of dollars were a much safer bet.

Bottled water is another option, but all the plastic bottles aren't very good for the environment, she said.

Given its vital role in protecting human health, Houlihan said there's one thing consumers should definitely not do about water stop drinking it.