Nearly 200 million Americans across all 50 states have been exposed through their tap water to higher-than-recommended levels of chromium-6, a cancer-causing chemical, according to a new report. Chromium-6 was made famous in the 2000 biographical film "Erin Brockovich," starring Julia Roberts as the titular activist. But what is it, and why is it a concern?
An odorless and tasteless metallic element, chromium occurs naturally in the environment and can be found in things like rocks, plants and soil. According to the Environmental Protection Agency (EPA), the two most common forms of chromium found in water are trivalent chromium (chromium-3) and hexavalent chromium (chromium-6).
A national report released Tuesday (Sept. 20) found unsafe levels of chromium-6 or hexavalent chromium — known to cause cancer in animals and humans — in tap water across the country. The Environmental Working Group (EWG), an independent advocacy group, analyzed data collected by the EPA for a nationwide test of chromium-6 contamination in drinking water. EWG's report found that if left untreated, chromium-6 in tap water will cause more than 12,000 new cases of cancer. [In Photos: World's Most Polluted Places]
Chromium-3 is an essential human dietary nutrient and can be found in many vegetables, fruits, meats, grains and yeast. It is known to enhance insulin, as well as help metabolize carbohydrates, fats and proteins, according to the National Institutes of Health.
Chromium-6, however, is a toxic form of the mineral. While this form does occur naturally in the environment, from the erosion of chromium deposits, chromium-6 can also be produced by industrial processes. The EPA has reported instances of chromium-6 being released into the environment from industrial pollution — leakage, poor storage or inadequate industrial waste disposal practices.
Studies of chromium-6 have established that breathing the particles can cause lung cancer. The U.S. Occupational Safety and Health Administration sets strict limits for levels of airborne chromium-6 in the workplace. The chemical has also been connected to liver damage, reproductive problems and developmental harm, according to the EWG, and presents greater risks to infants and children, people who take antacids, and people with poorly functioning livers.
A 2008 study by the National Toxicology Program, part of the National Institutes of Health, found that chromium-6 in drinking water caused cancer in laboratory rats and mice. [Top 10 Cancer-Fighting Foods]
That study and other research led scientists at the California Office of Environmental Health Hazard Assessment to conclude that chromium-6 can cause cancer in people. The office recommended a public health goal of 0.02 parts per billion in tap water to reduce risk (one part per billion is about equivalent to a single drop of water in an Olympic-size swimming pool). In 2014, California did adopt a legal limit to chromium-6— though, at 10 parts per billion, it was much higher than the public health goal. It is the only enforceable drinking water standard for chromium-6 at the state or federal level.
Currently, the EPA limits the total chromium— not exclusively chromium-6 — that can be present in drinking water. Chromium-6 and chromium-3 are covered under the same standard because "these forms of chromium can convert back and forth in water and in the human body, depending on environmental conditions," the agency said.
The EPA's drinking water limit for total chromium is 100 parts per billion, or 5,000 times California's public health goal and 10 times the state's legal limit.
According to the new EWG report, in almost 90 percent of water systems sampled,chromium-6 was found at an average level exceeding California's nonbinding recommended public health goal.
"Cleaning up water supplies contaminated with chromium-6 will not be cheap," the EWG report concluded. "But the answer to high costs is not allowing exposures at unsafe levels while pretending water is safe. And the fact that some unknown level of chromium-6 contamination comes from natural sources does not negate Americans' need to be protected from a known carcinogen."
Original article on Live Science.