NORMAN â€” The level of chromium-6 in Norman's drinking water exceeds California's proposed limit for the chemical more than 200 times over, according to a national environmental study released today.
The Washington, D.C.-based Environmental Working Group says hexavalent chromium, or chromium-6, in drinking water has been shown in lab tests to increase the risk of cancer. The Environmental Protection Agency has yet to draw the same conclusion, although its website states that chronic exposure to inhaled chromium-6 can lead to cancer.
Some may recall chromium-6 as the chemical discussed in the biographical movie â€œErin Brockovich.â€
The Environmental Working Group commissioned a study to test water from 35 cities for chromium-6. Norman's result of 12.9 parts per billion far exceeded runner-up Honolulu, which had two parts per billion, and the study's average city of 0.18 parts per billion.
California is proposing a limit of 0.06 for its cities' water supplies.
â€œThey were not surprised that Norman had a high amount, but maybe a little surprised by how high,â€ said Rebecca Sutton, an environmental chemist who worked on the study, citing Norman's high amount of arsenic in some wells a few years ago.
Chromium-6 differs from chromium-3, or trivalent chromium, which the EPA says is an essential nutrient
The EPA mandates a maximum level of total chromium at 100 parts per billion, or 0.1 milligrams per liter, but the federal agency has set no limit specifically for chromium-6. California could become the first state to set an additional standard for chromium-6.
Sutton said Norman's high chromium-6 content most likely occurs naturally from erosion of heavy metals into central Oklahoma's Garber-Wellington aquifer, which serves central Oklahoma.