Dioxane has affected groundwater supplies in several areas. Dioxane at the level of 1 μg/L (~1 ppb) has been detected in many locations in the US. In the U.S. state of New Hampshire, it had been found at 67 sites in 2010, ranging in concentration from 2 ppb to over 11,000 ppb. Thirty of these sites are solid waste landfills, most of which have been closed for years. In 2019, the Southern Environmental Law Center successfully sued Greensboro, North Carolina's Wastewater treatment after 1,4-Dioxane was found at 20 times above EPA safe levels in the Haw River.