NORMAN â€” University of Oklahoma associate professor Robert Nairn, an expert on water quality, became popular among friends and colleagues when a report came out Monday that questioned the safety of Norman's water.
â€œI got a lot of e-mails from people wondering what's going on,â€ said Nairn, who directs OU's Center for Restoration of Ecosystems and Watersheds.
The concern is about hexavalent chromium, often called chromium 6. Norman had a chromium 6 reading of 12.9 parts per billion, which was highest among one-time samplings from 35 cities tested for a project commissioned by the Environmental Working Group.
Chromium 6 was proved decades ago to cause cancer or respiratory ailments when inhaled, and animal tests conducted in recent years by the National Toxicology Program show evidence that it also can be carcinogenic when ingested orally.
While Norman easily topped the new report's list of cities, the level was thousands times less than that given to lab animals that developed cancer.
It pales when compared to Hinkley, Calif., the city on which the movie â€œErin Brockovichâ€ was based, which had up to 580 parts per billion in its drinking water in the 1990s.
In spring 2009, Nairn was involved in the cleaning of shallow groundwater for Tinker Air Force Base, where he said the chemical's content ranged from 5,800 to 7,900 parts per billion.
â€œI think (the report) opened some eyes and said we should keep our eyes open for chrome 6,â€ Nairn said. â€œBut I don't have a feel for chrome 6. What I can say is 6,000 (parts per billion) is something to worry about; 500 is something to worry about. But 12.9, I don't know. We don't know.â€
Below the limit
What is known is that total chromium in Norman's ground wells consistently has tested below the federal and state limit of 100 parts per billion. Total chromium combines chromium 6 and the nutrient chromium 3.
According to a Norman Utilities Department statement, the most recent tests for total chromium had results ranging from 11 to 86 parts per billion in its ground water wells, while samples from the water treatment plant had levels that were not detectable.
Rebecca Sutton, an environmental chemist who worked on the Environmental Working Group study, said chromium 6 often is discharged by steel and pulp mills, and by metal plating and leather tanning facilities.
But Sutton, Nairn and Norman Utilities Director Ken Komiske all said chromium in the Norman area most likely occurs naturally because of heavy metal content in the area's groundwater.
Nairn said Norman's level of chromium 6 struck him as â€œpretty low, and we've got naturally occurring concentrations in our groundwater.â€
Reason for concern
Scientists are not sure how much chromium 6 ingested orally constitutes a cancer risk.
California legislators and health officials wanted to find out, so they asked the National Toxicology Program, headquartered at the National Institute of Environmental Health Sciences to conduct tests on the toxicity of chromium 6 in drinking water.
A compound that contained extremely high levels chromium 6, ranging from five to 180 milligrams per liter, was given to mice and rats over a two-year period. The rats had malignant tumors in their mouths while the mice had benign and malignant tumors in their small intestines that increased according to the dose they received.
Meanwhile, the EPA is assessing the risk of chromium 6 and will determine what new standards may be required.
Some states already have lowered the total chromium limit of 50 parts per billion for their water systems; and a proposal in California calls for limiting chromium 6 to 0.06 parts per billion.
Most cities in Monday's report had levels that exceed the proposed California limit, but that may not be an automatic cause for concern.
â€œThe report I saw compared everything to a number that's not approved by the EPA and is not fully vetted,â€ said David Sabatini, an OU civil engineering professor and director of Water Technologies for Emerging Regions (WaTER).
â€œThey're failing to point out that (Norman) is much lower than the EPA standard,â€ Sabatini said, â€œand just comparing the 12 to 0.06 creates a panic.â€
Sabatini and Nairn both brought up the EPA's science-based decision to lower the acceptable levels of arsenic, which forced Norman to close wells to meet compliance. They said the same could happen someday with chromium 6.
â€œThere's good data that it is carcinogenic, but what the â€˜quote unquote' safe level is still being explored; that's the big debate,â€ Nairn said.