Chromium-6 in U.S. Tap Water
December 20, 2010

Chromium-6 in U.S. Tap Water: Executive Summary

View and Download our report here: Chromium-6 in U.S. Tap Water

Chromium-6 – the Erin Brockovich Chemical – Is Widespread in U.S. Tap Water

Tests find cancer-causing chemical in 89 percent of cities sampled

Chromium-6 in tap water of 35 cities averaged 3 times California's proposed safety goal

Bar chart showing levels of chromium-6 in tap water of 35 cities averaged 3 times California's proposed safety goal

*Geometric average based on level of chromium-6 measured in 35 U.S. cities and a statistical estimate for the four cities where no chromium-6 was detected. The lowest level detectable by these tests is 0.02 ppb. For the purpose of calculating the nationwide average, the concentration of chromium-6 in these four cities was assumed to be 0.01 ppb, or half of the lowest detectable level.

**"Proposed safe limit" is California EPA's proposed public health goal (OEHHA 2009).

Source: EWG-commissioned testing for hexavalent chromium in tap water from 35 cities.

Executive Summary

Tap water from 31 of 35 U.S. cities tested contains hexavalent chromium (or chromium-6), the carcinogenic “Erin Brockovich chemical,” according to laboratory tests commissioned by Environmental Working Group (EWG). The highest levels were detected in Norman, Okla.; Honolulu, Hawaii; and Riverside, Calif.

Despite mounting evidence of the contaminant’s toxic effects, including a U.S. Environmental Protection Agency (EPA) draft toxicological review that classifies it as “likely to be carcinogenic to humans” when consumed in drinking water, the agency has not set a legal limit for chromium-6 in tap water and does not require water utilities to test for it. Hexavalent chromium is commonly discharged from steel and pulp mills as well as metal-plating and leather-tanning facilities. It can also pollute water through erosion of soil and rock.

The National Toxicology Program has found that hexavalent chromium in drinking water shows clear evidence of carcinogenic activity in laboratory animals, increasing the risk of otherwise rare gastrointestinal tumors (NTP 2007, 2008). In response to this study and others, California officials last year proposed setting a public health goal for chromium-6 in drinking water of 0.06 parts per billion (ppb). This is the first step toward establishing a statewide enforceable limit (OEHHA 2009).

Levels of the carcinogen in 25 cities tested by EWG were higher than California’s proposed public health goal. Tap water from Norman, Okla. (population 90,000) contained more than 200 times California’s proposed safe limit.

Millions of Americans drink chromium-contaminated water

EWG’s investigation is the broadest publicly available survey of hexavalent chromium to date. The 31 cities with chromium-polluted tap water draw from utilities that collectively serve more than 26 million people. In California, the only state that requires testing for hexavalent chromium, water utilities have detected the compound in tap water supplied to more than 31 million people, according to an EWG analysis of data from the state water agency (EWG 2009).

Top five chromium-contaminated cities tested by EWG

City City Population Hexavalent Chromium Contamination Level in Tap Water
Norman, Oklahoma 89,952 12.9 ppb
Honolulu, Hawaii 661,004 2.00 ppb
Riverside, California 280,832 1.69 ppb
Madison, Wisconsin 200,814 1.58 ppb
San Jose, California 979,000 1.34 ppb

EWG's tests provide a one-time snapshot of chromium-6 levels in 35 cities. But chromium pollution is a continuous, ongoing problem, as shown by the annual water quality reports that utilities must produce under federal law. Over the years, nearly all of the 35 cities tested by EWG regularly report finding chromium (in the form of total chromium) in their water despite using far less sensitive testing methods than those used by EWG.

The total number of Americans drinking tap water contaminated with this compound is likely far higher than is indicated by EWG's tests. At least 74 million people in nearly 7,000 communities drink tap water polluted with “total chromium,” which includes hexavalent and other forms of the metal, according to EWG’s 2009 analysis of water utility tests from 48,000 communities in 42 states (EWG 2009).

The EPA has set a legal limit in tap water for total chromium of 100 ppb to protect against “allergic dermatitis” (skin irritation or reactions). Measures of total chromium include the essential mineral trivalent chromium, which regulates glucose metabolism, as well as the cancer-causing hexavalent form. Preliminary EWG-commissioned water tests found that in most cases, the majority of the total chromium in water was in the hexavalent form, yet the EPA’s legal limit for total chromium is 1,700 times higher than California's proposed public health goal for hexavalent chromium. This disparity could indicate significant cancer risk for communities drinking chromium-tainted tap water.

The EPA’s new analysis of hexavalent chromium toxicity, released in draft form in September 2010 (EPA 2010a), cites significant cancer concerns linked to exposure to the contaminant in drinking water. It highlights health effects documented in animal studies, including anemia and damage to the gastrointestinal tract, lymph nodes and liver.

Industry deception delayed protections

The plight of the cancer-stricken residents of Hinkley, Calif., who in 1996 won a $333 million settlement from Pacific Gas and Electric Co. for contaminating their tap water with hexavalent chromium, was the basis of the 2000 movie “Erin Brockovich,” starring Julia Roberts.

Subsequently, a 2005 Wall Street Journal investigation and a separate EWG report based on court documents and depositions from a similar lawsuit in Kettleman City, Calif. revealed that PG&E had hired consultants to publish a fraudulent analysis of cancer mortality in Chinese villagers exposed to hexavalent chromium, in an attempt to disprove the link between the chemical and cancer. The study was published in the respected Journal of Occupational and Environmental Medicine, and scientists and regulators — including the EPA — cited the fraudulent article in research and safety assessments. The journal retracted the paper in 2006 in response to EWG’s request for corrective action.

California officials then conducted a rigorous re-assessment of the study data, finding a statistically significant increase in stomach cancer among the exposed. Their analysis is consistent with laboratory evidence from the National Toxicology Program and others showing that hexavalent chromium in tap water causes gastrointestinal tumors in multiple species.

Industry has sought for more than six years to delay state-mandated regulation of hexavalent chromium in tap water in California. Aerospace giant Honeywell International Inc. and others have stalled the adoption of the advisory public health goal by pressing for additional external scientific peer review. California’s Department of Public Health can neither set nor enforce a mandatory tap water standard for hexavalent chromium until the goal is finalized.


At least 74 million Americans in 42 states drink chromium-polluted tap water, much of it likely in the form of cancer-causing hexavalent chromium. Given the scope of exposure and the magnitude of the potential risk, the EPA should move expeditiously to establish a legal limit for the chemical in tap water and require water utilities to test for it.

The state of California must establish a strong standard for hexavalent chromium in tap water immediately. A truly health-protective hexavalent chromium regulation will reduce the cancer risk for Californians and serve as a model for the nation. With an enforceable standard already six years past the statutory deadline and the health of millions of Californians at stake, the state cannot move too quickly.