But other scientists say that's an extremely small amount. One
part per billion is equivalent to about a drop in 250 gallon
drums of water, or three seconds in a century. Even if a city
such as Norman has the highest concentration of chromium-6 of
all the cities tested, that doesn't mean it places the residents
at a higher risk for developing cancer than in other cities.
Toxicology experts say inhaling chromium-6 can cause cancer, but
there isn't much data on the dangers of drinking it. "The
evidence is fairly good that it's carcinogenic in people in
occupational settings who inhale it and get a good dose," said
Dr. Shan Yin, assistant medical director of the Cincinnati Drug
and Poison Information Center. "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