Tests of St. Louis area drinking water have revealed unacceptably high levels of chromium-6, a likely carcinogenic chemical, according to a nationwide report by a nonprofit environmental advocacy group.

The report, released this week by the Washington-based Environmental Working Group, found that Missouri American Water Co., which serves about 365,000 customers across St. Louis County, St. Charles County and northern Jefferson County, had the second-highest average level of chromium-6, based on 40 samples taken from 2013 to 2015. Only the city of Phoenix water system had a higher average among major U.S. metropolitan areas.

Test samples taken from other water systems in the St. Louis area also tested high for chromium-6, the report said.

The findings, the Environmental Working Group said, are a cause for concern and speak to the need for new regulatory standards for drinking water.

“It’s just one of the constant reminders of how broken our regulatory system is with respect to providing safe drinking water to Americans,” said David Andrews, a senior scientist with the Environmental Working Group.

Despite the group’s findings, Dr. Faisal Khan, director of the St. Louis County Department of Public Health, said there was no need for alarm. Khan noted that chromium-6 levels remained at just a fraction of the limits that would require action to ensure safety.

“At this time there is no sort of information that would prompt any kind of health concern,” Khan said. “The drinking water is perfectly fine.”

Chromium-6 gained national prominence as the pollutant featured in “Erin Brockovich,” a motion picture based on the true story of a California town with a fouled water supply. But 16 years after the movie’s release, the report from the Environmental Working Group states that chromium-6 can be found in the water distributed to more than 200 million Americans. The metallic element is a byproduct of industrial processes but also occurs naturally in the environment.

In a statement, Missouri American Water, the area’s largest water utility, said that its water meets or surpasses quality standards, “including those set for chromium.”

The statement pointed out that the U.S. Environmental Protection Agency “does not have specific drinking water regulations for chromium-6, only total chromium, which includes consideration of the health effects due to chromium-6.”

Khan said that his department is gathering more information about Missouri American’s testing protocol, but said the utility has been “very diligent” about standards that are in place.

Brian Russell, a spokesperson for the utility, said business would continue as usual.

“We don’t have any plans to change how we test or remove chromium from the water,” Russell said. “We’re not even close to that threshold.”

But those behind the Environmental Working Group report say that current safety thresholds for chromium levels in drinking water are far too loose and don’t reflect health concerns raised by studies from the last two decades.

The federal standard for total chromium was set in 1991 and was based on concerns regarding skin irritation, according to Andrews. Those guidelines don’t take into account a 2007 study that he says found “a significant increase in stomach and intestinal tumors” in rodents that drank water with elevated levels of chromium-6 over a period of two years.

“(The federal standard) overlooks or disregards 25 years of science that has been telling us about the more serious effects of chromium-6,” said Bill Walker, another Environmental Working Group representative.

Their report based its findings on the public health goal recommended by the California Office of Environmental Health Hazard Assessment, which determined that a chromium-6 concentration of 0.02 parts per billion would result in one excess cancer per lifetime for every million people. But California remains the only state to have implemented a chromium-6 threshold beyond the federal guidelines for total chromium, and even its threshold — 10 parts per billion — is 500 times higher than the maximally protective limit.

Missouri American officials declined to speculate on potential sources of the chromium-6 in the utility’s water. Even if it is naturally occurring chromium, with most of their service area’s water coming from the Missouri River, it’s possible that the source could be somewhere upstream.

“The Missouri River is collecting water from the western U.S., so it can have fairly different geochemistry than what we have here locally,” said Liz Hasenmueller, a professor of hydrochemistry at St. Louis University.

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