A new report released by the Environmental Working Group reveals that over 218 million people across the United States are being exposed to potentially unsafe concentrations of hexavalent chromium in their drinking water, a chemical compound known to be toxic and carcinogenic in even extremely low concentrations. Nation-wide testing by local water utilities was ordered by the EPA between 2013 and 2016, resulting in over three-quarters of the 62,386 samples taken testing positive for the hexavalent chromium contaminant. An interactive map illustrating EWG’s findings can be found here.

Hexavalent chromium, also known as chromium-6, was the subject of a legal battle over high concentrations of the contaminant found in the tap water in Hinkley, California, and brought to widespread public attention in the 2000 film Erin Brockovich. In contrast to the essential nutrient trivalent chromium (chromium-3), chromium-6 is a genotoxic carcinogen, causing damage to the DNA of affected cells — damage that can lead to these cells becoming cancerous.

The Environmental Protection Agency currently places the total limit for both chromium-3 and chromium-6 at 100 parts per billion, a policy adopted in 2001. While many of the regions testing positive for Cr-6 have levels that are only a mere fraction of the EPA’s guidelines, EWG considers these safety levels to be far too high. Researchers with the California Department of Public Health have set a non-legally binding community goal to reduce the amount of Cr-6 to less than 0.02 parts per billion, far lower than California’s current enforceable limit of 10 parts per billion, itself already set at one-tenth of the EPA’s guideline. EWG estimates that if current Cr-6 levels are allowed to remain where they are, this may result in an additional 12,000 US citizens contracting cancer by the end of the century.

Unfortunately, new legislation has met with resistance from lawmakers, presumably due to the cost of ensuring that Cr-6, a common industrial byproduct, is reduced in drinking water. In 2010, former New Jersey Department of Environmental Protection planner Bill Wolfe claimed that Department of Environmental Protection Commissioner Bob Martin blocked the submission of their recommendation for new regulations regarding Cr-6, and subsequently blocked the institute from meeting for four years.

Similar do-not-drink recommendations were given to private well owners in North Carolina that were living near Cr-6 contaminated sites run by Duke Energy. These recommendations were rescinded by the head of the Department of Environmental Quality, Donald R. van der Vaart, a former employee of a company that was bought by Duke Energy, himself appointed by then Governor Pat McCrory — also a former long-term employee of Duke Energy.

Perhaps even more disturbingly, in fighting the lawsuit brought against them regarding the Cr-6 contamination in Hinkley, CA, Pacific Gas and Electric Company was found to have manipulated a Chinese study linking hexavalant chromium and stomach cancer, re-writing the original author’s work to hide the link to the chemical’s health risks, and republished the paper without disclosing PG&E’s involvement.

For the average consumer, there are ways to reduce your own exposure to hexavalent chromium in your drinking water. While not all activated-carbon water filters are certified to remove Cr-6, there are some that are designed to remove the contaminant — if you are purchasing a filtration system for this purpose, make sure it is specifically certified to filter out hexavalent chromium. Fortunately, most reverse-osmosis filtration systems will separate out Cr-6, but it is still wise to check the system’s certification before assuming that it is suited for this purpose.

The Environmental Working Group provides a water filter buying guide on their website that lists a variety of water filter types and manufacturers. Simply set the "Certified to reduce" field to "Chromium (hexavalent)" to search for the relevant products.