In December, the Washington-based Environmental Working Group (EWG) released a study that found traces of the possible carcinogen hexavalent chromium, also called chromium-6, in tap water in 31 of 35 U.S. cities tested, leading the Environmental Protection Agency (EPA) to release new recommendations in January for enhanced monitoring for the substance. However, the Washington-based American Water Works Association (AWWA) says the recommendations are not enough to help communities determine when a public health threat exists, and one expert says the levels of chromium-6 found in the study do not pose a danger.

The EPA's standard for total chromium in drinking water — which includes a combination of chromium-3, an essential nutrient, and chromium-6 — is 100 parts per billion (ppb). The EPA requires water utilities to test for only total chromium and has no standard for chromium-6. Norman, Okla.'s tap water topped the EWG's list with 12.9 ppb of chromium-6.

The EPA released a draft health risk assessment of chromium-6 in September for public comment, and once the assessment is finalized later this year, the agency will determine if a chromium-6 standard is warranted. EPA suggests that water utilities test water samples for chromium-6 quarterly or semi-annually using a specified laboratory method.

Until the health assessment is final, utility operators that find small traces of chromium-6 in the drinking water may raise public concerns without having the scientific data needed to put test results into context, says AWWA Deputy Executive Director for Government Affairs Tom Curtis. “It may well be that water utilities could find chromium-6 at extremely low levels that are meaningless in terms of public health,” Curtis says.

The levels of chromium-6 found in the EWG report are not high enough for public alarm, says Aaron Barchowsky, a professor of environmental and occupational health at the University of Pittsburgh. “A study by the National Toxicology Program established that high levels of chromium-6 in drinking water could cause cancer, but there hasn't been a clear risk assessment for low levels of chromium-6,” Barchowsky says.

The EPA's proposed guidelines and information about known chromium-6 risks are available at and at

Cause for concern

Chromium-6 gained national attention in the 2000 film “Erin Brockovich,” which portrayed how the utility company Pacific Gas & Electric was exposed for leaking the toxin into groundwater in Hinkley, Calif., and paid a landmark $333 million settlement in 1996. Hinkley's pollution woes, however, have continued. Just last month, the Desert Dispatch reported that the real-life Erin Brockovich, who owns a research and consulting firm, was in Hinkley leading a team of investigators to test private wells for chromium-6 contamination.

Gail Short is a Birmingham, Ala.-based freelance writer.

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