In 25 of 35 U.S. cities where tap water supplies were tested for hexavalent chromium -- deemed likely to cause cancer in humans in a U.S. EPA draft review this year -- levels of the chemical exceeded the minimum set by the state of California to protect public health, according to a report released today by an environmental group.
The Environmental Working Group's (EWG) new findings mark a public flare-up in the behind-the-scenes battle over estimating the carcinogenicity of oral exposure to hexavalent chromium, also referred to as chromium-6. The draft EPA assessment released in September could pave the way for a national drinking-water standard for the chemical, best known for polluting groundwater in Hinkley, Calif., where activist Erin Brockovich won a multimillion-dollar settlement for locals and became a household name.
The outcry over cancer cases in Hinkley helped push California to set a tap-water public health goal of 0.06 parts per billion (ppb) of chromium-6, an early move on the way to a binding state standard (Greenwire, Aug. 21, 2009). Of the 35 cities where EWG tested drinking supplies, 31 contained some level of chromium-6, and 25 -- including Washington, Los Angeles and Norman, Okla., where samples showed 12.9 ppb -- contained levels higher than the California goal.
EWG senior scientist Rebecca Sutton, an environmental chemist who crafted today's report, said her group's data provide new ammunition for measuring and restricting chromium-6 in drinking water nationwide. The federal government made "a very poor choice" by mandating its current drinking-water tests for total chromium, a metric that blends hazardous chromium-6 with the essential nutrient trivalent chromium.
Sutton added that while "industry is doing its very best to slow the process down even further," she hopes to see California advancing its chromium-6 limits to serve as a potential model for broader action. "Sometimes the state of California can lead the way, can show, 'Hey, this is possible,'" she said.
Brockovich, now an author and full-time consumer advocate, predicted in an interview that further chromium-6 water contamination issues would emerge "not only at a national but a global level."
"There is no reason why we can't address this without sounding some kind of panic alarm, which [critics] are going to accuse us of doing," Brockovich said.
A heavy metal commonly used in industrial dyes and coatings that also occurs naturally in small amounts, chromium-6 is known to be carcinogenic via inhalation. The cancer-causing effects of oral exposure through water, however, remain the subject of intense debate between environmentalists and industry.
The recent EPA draft review of chromium-6 incorporated the results of a 2008 National Toxicology Program (NTP) study that found a higher occurrence of gastrointestinal tumors in exposed rodents. The American Chemistry Council and the American Water Works Association, which represents water utilities that could bear the costs of broader chromium-6 testing, have both questioned the application of the NTP study to human exposures at lower levels.
ACC and AWWA have called on EPA to postpone further action on its chromium-6 risk assessment until new studies, including one funded by industry, are released next year.
A senior official at the Southern California Water Committee (SCWC), an alliance of industry and local governments active on water quality issues in the state, also asked EPA to delay the chromium-6 assessment until more studies are released.
Using the 2008 NTP data to assess the cancer-causing effects of lower exposures to chromium-6 "may not reflect the true risk and will have significant consequences for the public's confidence in the quality and safety of their drinking water," SCWC Executive Director Richard Atwater wrote to EPA in October. "Furthermore, it would prematurely trigger regulatory levels that water supply agencies simply don't have the equipment to monitor and detect."
Click here to read EWG's full report on hexavalent chromium in drinking water.