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Environmental Protection Agency Administrator Lisa Jackson announced Dec. 22 that the agency will offer “significant technical assistance” to cities with the highest levels of hexavalent chromium contamination in drinking water.
The cities were listed in a report by the activist group Environmental Working Group Dec. 20 (244 DEN A-5, 12/22/10).
The announcement came a day after Jackson briefed 10 senators on the issue of hexavalent chromium “as it relates to the recent Environmental Working Group report,” as Jackson phrased it in a statement issued by EPA.
Jackson also said EPA “will issue guidance to all water systems in the country to help them develop monitoring and sampling programs specifically for chromium-6,” another term for hexavalent chromium. The guidance will be one of “a series of actions that the EPA will take over the coming days to address chromium-6 in our drinking water,” she said.
EPA also “will work with local and state officials to get a better picture of exactly how widespread this problem is,” Jackson said.
The Environmental Working Group responded with a statement commending Jackson and the Obama administration “for taking these important steps.”
The Environmental Working Group sampled tap water in 35 cities--one sample per city--and took the samples to a laboratory for analysis. Traces of hexavalent chromium, a suspected carcinogen, were found in 31 of the samples. The traces were far below the maximum contaminant level set by EPA for total chromium, but the advocacy group emphasized that the levels in 25 of the samples exceeded the level of a goal proposed by California regulators in 2009 (161 DEN A-4, 8/24/09).
Jackson met Dec. 21 with Sens. Daniel Akaka (D-Hawaii), Jeff Bingaman (D-N.M.), Bob Casey (D-Pa.), Richard Durbin (D-Ill.), Jeff Merkley (D-Oregon), Ben Nelson (D-Neb.), Bill Nelson (D-Fla.), Dianne Feinstein (D-Calif.), Debbie Stabenow (D-Mich.), and Mark Kirk (R-Ill.).
At the meeting, Jackson described EPA's current effort to update its health risk assessment for hexavalent chromium. That assessment, issued in draft form Sept. 30, is to be completed in 2011.
“Jackson told the senators that based on the draft risk assessment, EPA will likely revise drinking water regulations to account for this new science,” EPA's said in a statement issued Dec. 22. “These revisions would only take place after an independent science panel has verified the underlying science.”
All public water systems test for total chromium, which includes hexavalent chromium. EPA's regulation of chromium, with a maximum contaminant level of 100 parts per billion, assumes that a detection of chromium could be 100 percent hexavalent chromium, avoiding the need for a separate test for the hexavalent form of the metal.
But the standard was set in 1991 when there was no evidence to suggest oral ingestion of hexavalent chromium might cause cancer.
In recent years, studies with rats and mice have suggested that the metal may be carcinogenic and studies of workers exposed to the metal “provide some evidence of the mutagenic activity of hexavalent chromium in occupationally exposed humans, but results have not been consistent across studies and endpoints,” EPA said in its draft assessment in September.
The studies indicate that hexavalent chromium may be carcinogenic to humans via the oral route of exposure, the draft assessment said. The draft went through a public comment period in October and November.
Hexavalent chromium enters water from metal-plating facilities, steel mills, pulp mills, and some other industrial activities. It also occurs naturally, but the traces in drinking water systems usually are presumed to have an industrial source.
Regulators in California have proposed setting a goal of 0.06 parts per billion for hexavalent chromium. California's testing protocols cannot detect hexavalent chromium in amounts lower than 1 ppb, the Environmental Working Group said. It remains to be seen what the state will set as a regulated limit.
EPA sets a target of zero as the goal in drinking water systems for any contaminant considered a known and probable carcinogen. The agency also sets a maximum contaminant level, the regulated cap, that depends on available detection technologies, control technologies, and cost-benefit analyses.
By Alan Kovski
More information on EPA's risk assessment for hexavalent chromium is available at http://cfpub.epa.gov/ncea/iris_drafts/recordisplay.cfm?deid=221433.
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