Millions of Americans are drinking water contaminated with the carcinogenic chemical that came to national attention in the 2000 feature film Erin Brockovich. Laboratory tests commissioned by Environmental Working Group (EWG) found hexavalent chromium, or chromium-6, in the drinking water of 31 of 35 selected U.S. cities. Among those with the highest levels were Norman, Okla.; Honolulu; and Riverside, Calif.

Despite mounting evidence of the contaminant’s toxic effects, the U.S. Environmental Protection Agency (EPA) 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 natural deposits.

The authoritative National Toxicology Program (NTP) of the U.S. Department of Health and Human Services has said that chromium-6 in drinking water shows “clear evidence of carcinogenic activity” in laboratory animals, increasing the risk of gastrointestinal tumors. Just last October, a draft review by the EPA similarly found that ingesting the chemical in tap water is “likely to be carcinogenic to humans.” Other health risks associated with exposure include liver and kidney damage, anemia and ulcers.

In response to the NTP study and others, California last year became the first state to propose setting a public health goal for chromium-6 in drinking water of 0.06 parts per billion (ppb) – setting the stage for establishing a statewide enforceable limit.

The hazards of chromium-6 contamination first came to light in 1993, when Brockovich helped build a now-famous class action lawsuit against Pacific Gas and Electric Co. (PG&E) for polluting the water supply of Hinkley, Calif. The suit eventually led to a $333 million settlement.

“Every single day, pregnant mothers in Norman, Oklahoma, school children in Madison, Wisconsin, and many other Americans are drinking water laced with this cancer-causing chemical,” said EWG senior scientist Rebecca Sutton, Ph.D. “If the EPA required local water utilities to test for hexavalent chromium, the public would at least know if it was present in their local water. Without mandatory tests and a safe legal limit that all utilities must meet, many of us will continue to swallow some quantity of this carcinogen every day.”