Chromium-6 Contaminates Water of 218M Americans, Report Says

Ken Terry

September 23, 2016

The drinking water of more than two thirds of Americans is contaminated by a carcinogenic chemical named chromium-6, according to a report released Tuesday by the Environmental Working Group (EWG), a nonprofit environmental organization. Chromium-6 was the focal point of the 2000 film Erin Brockovich, which concerned the real-life poisoning of tap water in a California town.

From its analysis of the results of more than 60,000 tap water tests conducted nationwide, EWG estimates that chromium-6 is in the drinking water of at least 218 million people. The tests were performed by the Environment Protection Agency (EPA) following a 2010 EWG investigation that found the chemical in the tap water of 31 cities. That report sparked a Senate hearing and demands for action.

The EPA has still not set a maximum limit for chromium-6 in drinking water, although the agency does have a limit for all types of chromium. The only state that currently has an enforceable legal limit for chromium-6 in drinking water is California. That cap is 10 parts per billion (ppb), which EWG considers too high. On the basis of scientific studies, California set its public health goal at 0.02 ppb but established the legal limit 500 times higher.

EWG's new report found that only one public water system had total chromium levels that exceeded EPA standards; but 2% of the water systems had chromium-6 levels exceeding California's standard of 10 ppb. According to EWG, more than 7 million Americans are served tap water from supplies in which chromium-6 was detected at levels higher than California's limit.

"Because the EPA tests covered only a fraction of the small systems and private wells that supply water to more than a third of Americans, it is highly likely that chromium-6 contamination is even more widespread," the report says.

The tests found chromium-6 in almost 90% of the water systems sampled. The highest average statewide levels were found in Oklahoma, Arizona, and California. Among major cities, Phoenix had the highest level; St. Louis and Houston also had comparatively high levels, EWG said.

Cancer Risk

California's public health goal represents the concentration of chromium-6 that would pose less than a one-in-a-million risk for cancer for people who drink water with that amount in it for 70 years, the report notes. By contrast, it notes that the state's legal limit represents a lifetime cancer risk of 500 per million.

Extrapolating from the difference between California's public health goal and the amounts of chromium-6 that turned up in the EPA tests, EWG estimates that, if left untreated, chromium-6 in tap water will cause more than 12,000 excess cases of cancer by the end of this century.

In 2008, the report notes, a 2-year study conducted by the National Toxicology Program found that drinking water containing chromium-6 caused cancer in laboratory rats and mice. On the basis of this and other animal studies, in 2010, scientists at the California Office of Environmental Health Affairs concluded that the ingestion of tiny amounts of chromium-6 can cause cancer in people. It was these scientists who recommended the public health goal of 0.02 ppb. But in 2014, after aggressive lobbying by industry and water utilities, EWG said, state regulators adopted the higher legal limit.

Scientists in New Jersey and North Carolina also calculated safe limits for chromium-6 in drinking water similar to California's public health goal, but regulators in both states blocked moves to cap exposure to the chemical, EWG said.

According to the report, the chemical can also cause liver damage, reproductive problems, and developmental harm, putting infants and children, people who take antacids, and people with poorly functioning livers at greatest risk.

Nothing New Here?

The EPA's test results in major cities closely matched those of EWG, the report says, except that chromium-6 levels detected by the EPA were higher in Phoenix and Albuquerque. Years before those tests were conducted, the study says, the EPA had completed a draft risk assessment but did not release it. The chemical industry argued successfully that the EPA should wait for the conclusions of industry-funded studies before taking that step, EWG notes.

At this point, the EPA predicts that the risk assessment will be released for public comment sometime in 2017, according to the report. Even if it is released, however, the federal agency may choose to do nothing. Of the 81 contaminants that EPA has investigated pursuant to the 1996 amendments to the Safe Drinking Water Act, it has moved forward on setting a regulation for just one.

Queried about the EWG's report, Bryan Goodman, a spokesman for the Washington, DC–based American Chemistry Council (ACC), a lobbying group, told Medscape Medical News that the report "does not provide any new information about hexavalent chromium [ie, chromium-6] in the water supply."

Goodman continued, "EPA's data show that when hexavalent chromium is found in the ground water, it's present at low levels that are well below the national drinking water standard set by EPA. EPA and the US Geological Survey attribute these low levels to geologic formations, such as rocks."

Because of the limited scientific data available, ACC supports a new large-scale study of chromium-6 in water supplies, Goodman said, before EPA makes any regulatory decisions.

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