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Study Findings

Chromium-6 in U.S. Tap Water: Study Findings

December 20, 2010

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

Carcinogenic Erin Brockovich Chemical Found in Tap Water Across the U.S.

Tests commissioned by the Environmental Working Group (EWG) detected carcinogenic hexavalent chromium in 31 of 35 tap water samples — 89 percent — collected in cities across the country. EWG targeted a mix of large cities and some smaller ones where testing by local water utilities had previously detected potentially significant amounts of “total chromium.” This less specific measurement includes trivalent chromium, an essential mineral that regulates glucose metabolism, as well the cancer-causing hexavalent form, also called chromium-6.

Chromium widely contaminates U.S. tap water


Red dots indicate EWG’s test sites and measured hexavalent chromium concentrations in parts per billion (ppb). Size of dot reflects the level found. Brown-shaded areas represent population-adjusted average concentrations of total chromium by county, calculated from EWG’s national tap water database (see Study Methodology).

Sources: EWG-commissioned testing for hexavalent chromium in tap water from 35 cities; EWG analysis of water utility testing data obtained from state water agencies (EWG 2009).

Hexavalent chromium (or chromium-6) gets into water supplies after being 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.

In California, the only state that requires water utilities to test for hexavalent chromium, the state’s Environmental Protection Agency (California EPA) has proposed a “public health goal,” or maximum safe concentration, of 0.06 parts per billion (ppb) in tap water to protect against excess cancer risk. However, the state’s current testing protocols are significantly less sensitive than those of the independent laboratory hired by EWG and may identify only the most extreme cases of contamination. Chromium-6 levels in tap water in all four California cities tested by EWG exceeded the proposed public health goal. (Once the goal is established, state regulators plan to embark on a rule-making process to set a legally enforceable upper limit.)

Chromium-6 is a common pollutant in California tap water


EWG measured concentrations of hexavalent chromium in four California cities — Los Angeles, Riverside, Sacramento and San Jose. Size of red dots reflects the level found. Colored areas reflect population-adjusted average concentrations of hexavalent chromium by county, as calculated from EWG’s tap water database (see Study Methodology). The state’s current testing protocols cannot detect chromium-6 in amounts lower than 1 ppb, more than 16 times higher than the proposed safe level.

Sources: EWG-commissioned testing for hexavalent chromium in tap water from four California cities; EWG analysis of water utility testing data obtained from state water agencies (EWG 2009).

Nationally, samples from 25 cities tested by EWG had levels of hexavalent chromium higher than the safe limit proposed in California.

Chromium-6 levels in 25 cities’ tap water exceed safe limit proposed by California officials*


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

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

For total chromium, the US Environmental Protection Agency has set a legal limit of 100 ppb in tap water to protect against “allergic dermatitis” (skin irritation or reactions). California’s legal limit for total chromium is half that — 50 ppb.

EWG’s analysis of California’s tap water testing data indicates that chromium-6 constitutes more than half of the total chromium found in most water supplies, a finding further supported by initial data from EWG’s nationwide survey. A proprietary 2004 study by the Water Research Foundation for its paying members, including water utilities, found that hexavalent chromium contamination of tap water was more common for systems using groundwater wells than for those drawing surface water (AWWARF 2004). The EPA’s 100 ppb legal limit for total chromium is more than 1,600 times higher than the California’s proposed public health goal for hexavalent chromium. This could mean that communities with higher concentrations of total chromium face a cancer risk well above the levels typically considered safe.

Chromium widely contaminates U.S. tap water



Red dots indicate EWG’s test sites and measured hexavalent chromium concentrations in parts per billion (ppb). Size of dot reflects the level found. Brown-shaded areas represent population-adjusted average concentrations of total chromium by county, calculated from EWG’s national tap water database (see Study Methodology).

Sources: EWG-commissioned testing for hexavalent chromium in tap water from 35 cities; EWG analysis of water utility testing data obtained from state water agencies (EWG 2009).

Chromium widely contaminates U.S. tap water



Red dots indicate EWG’s test sites and measured hexavalent chromium concentrations in parts per billion (ppb). Size of dot reflects the level found. Brown-shaded areas represent population-adjusted average concentrations of total chromium by county, calculated from EWG’s national tap water database (see Study Methodology).

Sources: EWG-commissioned testing for hexavalent chromium in tap water from 35 cities; EWG analysis of water utility testing data obtained from state water agencies (EWG 2009).

Chromium-6 is a common pollutant in California tap water



EWG measured concentrations of hexavalent chromium in four California cities — Los Angeles, Riverside, Sacramento and San Jose. Size of red dots reflects the level found. Pink-shaded areas reflect population-adjusted average concentrations of hexavalent chromium by county, as calculated from EWG’s tap water database (see Study Methodology). The state’s current testing protocols cannot detect chromium-6 in amounts lower than 1 ppb, more than 16 times higher than the proposed safe level.

Sources: EWG-commissioned testing for hexavalent chromium in tap water from four California cities; EWG analysis of water utility testing data obtained from state water agencies (EWG 2009).

Chromium-6 levels in 25 cities’ tap water exceed safe limit proposed by California officials*


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

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