Still Don't Drink the Water?

During our water series last year, Student Voices bloggers wrote about World Water Day, wastewater, and the cultural significance of water, in addition to contaminated tap water. I posted on the last topic and wanted to revisit the issue after I read a report by a non-profit organization named the Environmental Working Group (EWG) that summarized recent findings of the National Toxicology Program.

This federal laboratory detected a carcinogen named hexavalent chromium, or chromium VI, in tap water from 31 out of the 35 US cities they tested, amounting to roughly 89% of their samples. Of the cities with contaminated water, 25 of them contained levels above the maximum limit then enforced by California regulators — 0.06 parts per billion — with the highest levels of the toxic metal being in Norman, Oklahoma; Honolulu, Hawaii; and Riverside, California. Made famous by the movie Erin Brockovich, chromium VI is considered a toxic metal by the Environmental Protection Agency (EPA) because of its demonstrated link to cancer.¹

The real-life Erin Brockovich was instrumental in prosecuting the utilities provider Pacific Gas and Electric Company (PG&E) for polluting the groundwater of Hinkley, California, with chromium VI. Between 1952 and 1966, PG&E used the chemical to prevent rust corrosion in the cooling towers of their natural gas compressor plant. Tower wastewater dissolved the toxin and allowed it to seep into unlined ponds on the facility and later, the local water supply, affecting a residential area roughly two miles long and one mile wide. People living there noticed the high cancer rate in their community and worked with Brockovich to build a case against PG&E. In 1996, they won the largest settlement ever awarded in a direct action lawsuit in US history, $333 million. After payments to the Hinkley claimants were completed in 2008, PG&E continued their land purchase initiative of all areas affected by the plume of polluted groundwater.²

Despite this indictment, a controversy still remains concerning cancer rates in Hinkley. In 2010, a report by the California Cancer Registry found proportionally lower cancer rates in Hinkley from 1988 to 2008 than its epidemiological profile predicted.³ Other sources claim that chromium VI is toxic only when directly inhaled and thus couldn't be responsible for the symptoms many Hinkley residents still present. Defenders of this position argue that gastric acids in the stomach neutralize chomium VI into trivalent chromium (or chromium III) a nutrient found in many foods such as whole grains and coffee. Empirical data seems to run counter to these positions, however, including private tap water tests that show high levels of chromium VI in Hinkley households with high incidences of cancer, not to mention a two-year animal study by the National Toxicology Program that found that chromium VI is "clearly" carcinogenic when ingested.⁴

Loosely subscribing to the latter evidence, the governmental response to the discovery of widespread chromium VI in US tap water has been quick but timid. After the EWG report, the US EPA offered to collaborate with water utilities on chromium VI monitoring and sampling.⁵ In addition, California's Office of Environmental Health Hazard Assessment recently announced a more stringent state public health goal of .02 parts per billion (ppb) for tap water chromium VI. Some scientists are claiming that the urgency of this action is alarmist, with one referring to the difference in California's revised limit (-.04 ppb) as a "dimensionless quantity" in an interview. To offer an idea of the relative amounts, he compares the ratio of "thirty seconds in a year" for parts per million to one of "three seconds in a century" for parts per billion.

Considering what is known about this chemical, I think the presence of chromium VI should be assessed for water sources worldwide, with increased testing requirements and enforcement of limits. I guess a carcinogenic exposure of zero seconds in a century is the kind of global public health goal I have in mind.

Image Credit: http://wikimedia.org

1. Costa, M. & Klein, C. B. Toxicity and Carcinogenicity of Chromium Compounds in Humans. Critical Reviews in Toxicology. 36(2), 155-163 (2006).

2. Fimrite, P. "PG&E Prepared to Buy Land in Tainted Mojave Desert." San Francisco Gate. November 20, 2010.

3. Sahagun, L. "Fewer Cancers Found in Hinkley than Expected." Los Angeles Times. December 13, 2010.

4. Cone, M. & Environmental Health News. "Chromium in Drinking Water Causes Cancer." Scientific American. February 20, 2009.

5. Layton, L. "EPA Urges Testing for Chemical in Tap Water." Washington Post. December 22, 2010.