CHICAGO — Cancer-causing chromium is turning up in tap water in more than two dozen cities, according to a study that urges federal regulators to adopt tougher standards.
Even though scientists at the U.S. Environmental Protection Agency and National Toxicology Program have linked the ingestion of hexavalent chromium to cancer, the EPA doesn't require cities to test for the toxic metal. Nor does the EPA limit the dangerous form of chromium in drinking water.
To take a snapshot of what is flowing through taps across the nation, the Environmental Working Group hired an independent laboratory that found the metal in treated
drinking water from 31 cities. None was in Kansas.
The amount in Chicago water from Lake Michigan that is pumped to 7 million people in Chicago and its suburbs was 0.18 parts per billion, three times higher than a limit California officials proposed last year.
A handful of other cities were significantly above the proposed California limit, including Norman, Okla.; Honolulu; Riverside, Calif.; and Madison, Wis., according to a report to be released today. Levels in Milwaukee water were the same as in Chicago.
In other major cities, hexavalent chromium levels ranged from 0.20 parts per billion in Los Angeles and Atlanta to 0.18 in New York and 0.03 in Boston.
The new findings could pose another challenge for utilities that are detecting dozens of unregulated substances in treated drinking water, including pharmaceutical drugs and industrial chemicals that can pass unfiltered through conventional treatment methods. Chromium can be found naturally in the environment but also is released by industry into waterways.
While the potential health threats of many pollutants are still being studied, researchers say there is a clear risk of stomach cancer from drinking water contaminated with hexavalent chromium, also known as chromium-6.
"For years scientists assumed this wasn't a problem because acids in our stomachs can convert chromium-6 into chromium-3, an essential nutrient," said Rebecca Sutton, a senior scientist with the Environmental Working Group, a Washington-based research and advocacy organization. "Newer science is showing our stomachs can't take care of everything, which means the dangerous form of chromium is getting into our bodies and can cause damage."
Studies outlining the dangers of chromium-contaminated water add to longstanding concerns about inhaling metallic vapors, in particular by workers at chrome plating factories.
Officials at the Chicago Department of Water Management did not respond to repeated inquiries last week, but other water officials said tap water is still safe. Bottled water, which often comes from municipal supplies, wasn't tested.
Lon Couillard, water quality manager in Milwaukee, said more study is needed to determine the sources of chromium. He suggested that in some cases it could be coming from chrome-plated plumbing fixtures, not passing through municipal treatment plants.
"They're trying to scare people," Couillard said of the environmental group that found hexavalent chromium in his city's tap water.
The source of chromium in Chicago drinking water is unclear, though federal records show that some of the nation's biggest industrial sources are four steel mills in northwest Indiana, just southeast of Chicago, that discharge wastewater into the city's source of drinking water.
Environmental officials in New Jersey have backed the proposed California limit. And in September, the U.S. EPA published a draft review that found hexavalent chromium in drinking water is "likely to be carcinogenic in humans." The EPA's report could be the first step toward a national standard.