After a lengthy public comment review period, the U.S. Environmental Protection Agency (EPA) has released a Draft Supplemental Analysis to the Draft Risk Evaluation for 1,4-Dioxane. EPA’s underlying Draft Risk Evaluation for 1,4-Dioxane was released in June 2019. These documents have been prepared as required by the 2016 Frank R. Lautenberg Chemical Safety Act for the 21st Century Act amendments to federal Toxic Substances Control Act (TSCA). Those amendments direct EPA to conduct risk evaluations of certain chemicals to determine whether the substance presents an unreasonable risk of injury to health or the environment, under the conditions of use, without consideration of costs or other nonrisk factors, while using the best available science and ensuring that decisions are based on the weight of scientific evidence. EPA identified 1,4-dioxane in December 2016 as one of the first 10 chemicals to undergo risk evaluations under the TSCA amendments.