The findings were released Monday by the Environmental Working Group, which used laboratory tests. It found the highest concentrations of hexavalent chromium, also known as chromium 6, in the drinking water in Norman, Okla.; Honolulu; and Riverside, Calif. Levels ranged from 12.9 parts per billion in Norman to 0.03 ppb in Cincinnati and Boston.
For the 35 cities surveyed the average was .18 ppb. That's three times the “public health goal,” or ideal standard, under consideration by California's Office of Environmental Health Hazard Assessment. [Editor's note: The original version of this paragraph overstated the average concentration and the degree to which it overshot the public health goal.]
Scientific and legal debate has raged over the risk posed by hexavalent chromium in drinking water since the 1990s, when the then-obscure legal file clerk Erin Brockovich unearthed evidence that the substance had leaked from a Pacific Gas & Electric natural-gas plant into the groundwater in Hinkley, Calif.
Residents sued, and in 1996 PG&E paid a $333 million settlement to about 600 people who blamed exposure to the chromium 6 for high rates of cancer and other diseases.
The Environmental Working Group picked its subject cities from those listing high levels of total chromium in their water. While the Environmental Protection Agency does not require testing for hexavalent chromium, it does require testing and has set a limit of 100 parts per billion for all variants of the metal, including the healthful chromium 3.
Rebecca Sutton, who oversaw the Environmental Working Group survey, acknowledges that there have been periodic alarms and lawsuits across the country over chromium 6 contamination.
“What this report indicates is that this problem may be more widespread, just at lower levels of concentration,” she says. “These are chronic exposures we're concerned with. A little bit every day can involve increased risk.”
Many researchers say hexavalent chromium is an inhalation carcinogen, but some have claimed that the risks are negligible when the substance is ingested. Still, in 2009, National Toxicology Program scientists reported that their research “clearly demonstrates” that the compound is a carcinogen in drinking water.
Sam Delson, a spokesman for California's Office of Environmental Health Hazard Assessment, says his agency considers that finding conclusive. The agency is preparing a public health goal of .06 ppb that would be one factor in determining safe exposure levels.
In Norman, Okla, utilities director Ken Komiske says his agency has always monitored its water supplies closely to make sure it meets the federal standard for all chromium. Mr. Komiske says Norman does not test for chromium 6.
“This report is kind of new to us,” he says, adding that his offices fielded about two dozen calls from concerned Norman residents on Monday. “We've been in touch with the state and federal authorities, asking 'What are we supposed to do next?' ”
Ms. Sutton, of the Environmental Working Group, says her organization hopes the survey will prompt more widespread checks for hexavalent chromium contamination, and new federal regulation.