The EWG analyzed 60,000 samples of drinking water across the country and found chromium-6 in more than 75 percent of them. The nonprofit estimates that 218 million Americans are consuming water that contains the chemical.
Studies have found chromium-6, a fairly common industrial by-product, causes stomach and intestinal tumors when consumed by mice and rats. However, there are still questions about how much of it humans have to drink before it becomes carcinogenic in the body.
"The IARC has classified hexavalent chromium as a human carcinogen through the inhalation route of exposure. However, there are limited human studies on the health effects of hexavalent chromium when ingested," Dr. Rhea Mehta, a molecular toxicologist, explained to mindbodygreen. "What we know is that the initial amount one is exposed to orally is different from the amount entering cells, as it mostly gets detoxified in the gut."
The law currently caps the amount of chromium allowed in drinking water at 10 parts per billion, or 10 drops of water in an Olympic-size swimming pool. While there's still some gray area surrounding how much of the chemical is actually safe to consume, the EWG thinks that the pervasiveness of the chemical warrants stricter federal regulation.
With the support of scientists in California, New Jersey, and New York, the group is suggesting the legal limit be lowered to 0.02 parts per billion—a level that has been shown to pose negligible cancer risk over a lifetime of consumption.
"The EPA and state regulators must set drinking water standards to protect the public, including those more susceptible to the toxic effects of chromium-6," the EWG report reads.
The report shows that the water tested in 1,370 U.S. counties contained chromium-6 levels higher than this 0.02-parts-per-billion marker. Water systems in Phoenix, Missouri, and Houston, had the highest levels, with major urban centers like LA and Philadelphia not far behind.