Water monitoring data collected in 2010–15 show that more than 7 million people in the US across 27 states had utility-supplied tap water that had detectable 1,4-dioxane, according to the Environmental Working Group. The problem of 1,4-dioxane pollution isn’t unique to the US. However, the US situation reveals a number of regulatory barriers. There is no federal limit on 1,4-dioxane in drinking water. And getting it out of water is challenging.