The cyclic ether 1,4-dioxane is a synthetic industrial chemical that is used as a solvent in products such as paints and lacquers and in processes such as organic chemical manufacturing. It was used in the past primarily with 1,1,1 trichloroethane (TCA), as a stabilizer and corrosion inhibitor, and has proven to be a contaminant of concern (a contaminant that poses a human health or environmental risk) at sites contaminated with TCA. It is a probable carcinogen and has been found in groundwater at sites throughout the United States. The physical and chemical properties and behavior of 1,4 dioxane create challenges for its characterization and treatment. It is highly mobile and has not been shown to readily biodegrade in the environment.