Chromium-6, a carcinogen, contaminates the tap water of two-thirds of Americans at levels above what scientists say is safe, according an analysis of federal water testing data by the Environmental Working Group.
Under an Environmental Protection Agency program, from 2013 to 2015, local water utilities took more than 60,000 water samples and found chromium-6 in more than 75 percent of them. The EWG's analysis of the EPA data estimates that water supplies serving 218 million Americans have potentially unsafe levels of the chemical.
The EWG's interactive map shows the chromium-6 test results by county for the 50 states. Of major metro areas, Phoenix has the highest level of the contaminant, followed by St. Louis County, Houston, Los Angeles, and Suffolk County, New York. But every U.S. water system serving more than 1 million people has chromium-6 concentrations that could be harmful, the EWG analysis found.