Recent litigation and a U.S. Environmental Protection Agency Risk Evaluation strongly suggest that 1,4-dioxane (dioxane) may become a headline chemical. In June 2017, the agency issued its Scope of the Risk Evaluation for dioxane. Several states and foreign countries also have issued laws and regulations concerning it. Currently, there is no EPA drinking water standard for dioxane, although it has been a compound of emerging concern to regulators for the past several years.

Lawsuits concerning dioxane pollution have been filed by cities and public water supply agencies. In November 2017, Suffolk County Water Authority sued five dioxane manufacturers and distributors for drinking water contamination in that part of the state of New York. In another case, the city of Ann Arbor, Michigan, as well as the county and the township all are attempting to intervene in a lawsuit between the state of Michigan and a dioxane manufacturer. The putative intervenors assert that the shallow groundwater plume will impact local home and business owners. The case has been appealed to the Michigan Supreme Court.

Historically, the vast bulk of dioxane production was used to stabilize 1,1,1-trichlorethane (TCA). Since TCA was phased out by the Montreal Protocol in 1996, dioxane most frequently is used as a processing aid, a functional fluid in closed systems, and a chemical reagent in adhesives and sealants.

According to the EPA, dioxane’s characteristics can lead to extensive environmental contamination when applied or discharged onto the ground surface. EPA information about dioxane states that it is both mobile and persistent (virtually non-degradable) and readily moves through the soil into groundwater where it can migrate long distances.

Although the agency has not yet established a drinking water standard, it has classified dioxane as “likely to be carcinogenic to humans.”

Over the next several years, dioxane manufacturers, distributors, and users should anticipate more regulatory and court actions concerning this compound.