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An environmental group says millions of Americans are drinking tap water that contains too much cancer-causing chromium 6.

The Environmental Working Group's (EWG) study of drinking water in 35 cities found 31 — including Salt Lake City — where samples turned up hexavalent chromium, the contaminant made famous in the 2000 movie "Erin Brockovich."

Pointing to this "one-time snapshot," the group is calling on the U.S. Environmental Protection Agency to begin regulating chromium 6 and to start requiring water systems to test for it.

"The current regulation on chromium is completely outdated," said Rebecca Sutton, an environmental chemist with the Washington, D.C.-based watchdog group. "And EPA knows this."

The EWG study said that its test of Salt lake City water found chromium 6 at 0.3 parts per billion. That put Utah's largest city in 11th place among the 35 cities tested, though significantly lower than Norman, Okla., which had levels tested at 12.90 parts per billion.

Another way of looking at the level in the Salt Lake City test is to compare it to a standard that California regulators have proposed: .06 ppb. According to the EWG analysis, the Salt Lake City sample was five times higher.

Florence Reynolds, water quality and treatment administrator for the Salt Lake City Department of Public Utilities, had not seen the EWG's report and questioned details such as how many samples were taken, where they were drawn and how the testing compared with the EPA's tests.

She noted that the EPA does not require tests for chromium 6 but rather total chromium, which includes chromium 6, and Salt Lake City's water has not shown detectable levels of it ­— results which contradict EWG's findings.

"I've looked at the data, and I don't see any chrome," she said, noting that the EPA has yet to set standards for testing for chromium 6 and levels considered a cancer hazard in water.

Meanwhile, the EPA said it is updating its health assessment for chromium "and the agency does not believe it is appropriate to revise the standard on chromium while that effort is in process."

In an e-mail, an agency spokesperson wrote, "When the assessment is complete, EPA will evaluate the results and consider the appropriate next steps."

Until that's done, the EPA is sticking with its standard of 100 ppb of total chromium as an indicator of hexavalent chromium.

Said Reynolds: "If there's an issue [once the EPA finalizes any new regulations], we will take care of it. But at this point, we don't see an issue."

Chromium 6 can come from steel mills, pulp mills, metal-plating shops and leather-tanning facilities. It also can enter the water naturally as soil and rocks erode.

Reynolds pointed out that all of Salt Lake City's water supplies come from the mountains above industrial areas typically linked to the contaminant.

Another complication is that all chromium is not alike. Chromium 6 is linked to stomach cancers, anemia, gastrointestinal-tract damage and harm to the liver and lymph nodes. But its cousin, chromium 3, is essential to sugar and lipid metabolism.

Under the right conditions, chromium 3 can transform into chromium 6, and vice versa.

The EWG said in its report that treating both types of chromium the same, as EPA does, makes no sense.

"A safety standard that lumps levels of a toxic carcinogen with a nutrient necessary for health," the group said, "is like grouping arsenic and vitamin C." —

Cities with chromium 6*

Norman, Okla. • 12.9

Honolulu • 2

Riverside, Calif. • 1.69

Madison, Wis. • 1.58

San Jose, Calif. • 1.34

Salt Lake City • 0.3

Others • Indianapolis; Plano, Texas; Reno, Nev.; and San Antonio had levels too low to detect.

To see the entire report • Go to the group's website. > http://www.ewg.org

*in parts per billion

Source: Environmental Working Group