"No one has really established what is a carcinogenic level for drinking water," said Alfred Aleguas, managing director at the Northern Ohio Poison Control Center in Cleveland. "We need to establish what is a limit we have to be concerned about."
Aleguas also said that the levels of exposure in Hinkley were much higher -- 580 ppb -- than the 31 ppb the Environmental Working Group found in Norman, Okla., the city with the highest concentration of chromium-6 in the group's report.
Most unintentional chromium exposure comes from industrial processes, such as leather tanning and metal plating. It's also a naturally occurring substance.
Chromium-3 is a nontoxic form of chromium that is vital to the body's glucose metabolism. But while there's still debate over how much chromium-6 is too much, the EPA said in a statement that it's currently assessing the impact of chromium-6 on public health. The final scientific review will be available sometime next year, and the EPA will determine if a new level needs to be set.