Final Risk Evaluation for 1,4-Dioxane

In November 2024, EPA released the final revised risk determination for 1,4-dioxane as a whole chemical substance under the Toxic Substances Control Act (TSCA). The revised risk determination for 1,4-dioxane includes chemical-specific changes in accordance with the path forward for the first 10 risk evaluations under TSCA laid out by EPA in June 2021.

The revised risk determination does not assume that workers exposed to 1,4-dioxane are always provided or appropriately wearing personal protective equipment (PPE). The consideration of this information will be part of the risk management process.

EPA describes in the revised risk determination the conditions of use that significantly contribute to the determination that 1,4-dioxane presents an unreasonable risk of injury to human health.

Read the Federal Register notice.
Read the final revised risk determination for 1,4-dioxane.

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Risk evaluation findings
Next steps and public participation
Final risk evaluation and supporting documents

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Risk Evaluation Findings

In November 2024, EPA released the final revised risk determination for 1,4-dioxane.

In November 2024, EPA released the final supplement to the risk evaluation for 1,4-dioxane. The supplement considers air and water exposure pathways not evaluated in the December 2020 risk evaluation and exposure to 1,4-dioxane generated as a byproduct. EPA’s revised risk determination incorporates information from the 2020 risk evaluation and 2024 supplement.

In the December 2020 risk evaluation, EPA reviewed the exposures and hazards of 1,4-dioxane uses and made the risk findings on this chemical. The 2020 risk evaluation included input from the public and peer reviewers as required by TSCA and associated regulations. In the risk evaluation, EPA considered the hazards and exposure, magnitude of risk, exposed population, severity of the hazard, uncertainties, and other factors.

EPA determined that 1,4-dioxane presents unreasonable risk to human health.

EPA assessed the impact of 1,4-dioxane on workers (including occupational non-users), consumers, bystanders, the general public, and fenceline communities. EPA identified health risks, risks of liver toxicity, adverse effects in the olfactory epithelium, and cancer from inhalation or dermal exposures to 1,4-dioxane, as well as from ingestion of drinking water. Risk from several conditions of use (including manufacturing, import, processing, industrial and commercial uses, and disposal) of 1,4-dioxane, including as a byproduct, significantly contribute to the whole chemical determination of unreasonable risk of injury to health. Overall, based on the revised risk determination, EPA’s findings include that worker exposure to 1,4-dioxane from all but four occupational conditions of use significantly contribute to the unreasonable risk from 1,4-dioxane.

In the 2020 risk evaluation, EPA evaluated risks to consumers from eight conditions of use involving the use of products such as detergents and cleaning products that contain 1,4-dioxane as a contaminant and found that the use did not present an unreasonable risk to consumers or bystanders. In the 2024 revised unreasonable risk determination, EPA does not identify risks to consumers from the use of these products as contributing to the unreasonable risk determination from 1,4-dioxane. However, EPA notes that the manufacture of those consumer products, and, in some cases, the commercial use of similar products, the generation of 1,4-dioxane as an ethoxylation process byproduct—i.e., the upstream processing of many of these the consumer products—does significantly contribute to the unreasonable risk determination, due to worker risks of cancer and non-cancer effects from inhalation and dermal exposures during those processes and risk to fenceline communities from exposures to drinking water sourced from surface water contaminated with 1,4-dioxane discharged from industrial facilities. In addition, the presence of 1,4-dioxane as a contaminant in commercial and consumer products like dish soaps and laundry detergents also significantly contributes to the unreasonable risk determination when these products are washed down the drain and contaminate surface water that is used as a source for drinking water.

EPA has therefore determined that the risks to the general population and fenceline communities from drinking water sourced from surface water contaminated with 1,4-dioxane that is discharged from industrial facilities (including where it is produced as a byproduct) or consumer and commercial products that are washed down the drain significantly contribute to the unreasonable risk presented by 1,4-dioxane.

The revised risk determination for 1,4-dioxane does not reflect an assumption that workers always and appropriately wear personal protective equipment (PPE), even though some facilities might be using PPE as one means to reduce worker exposure, or that there is widespread non-compliance with applicable federal standards. EPA understands there could be occupational safety protections in place at some workplace locations; however, not assuming use of PPE in its baseline exposure scenarios reflects EPA’s recognition that certain subpopulations of workers exist that may be highly exposed because they are not covered by OSHA standards, because their employers are out of compliance with OSHA standards, because OSHA’s chemical-specific Permissible Exposure Limits (largely adopted in the 1970s) are described by OSHA as being “outdated and inadequate for ensuring protection of worker health,” or because the OSHA PEL alone may be inadequate for ensuring protection of worker health, as is the case for 1,4-dioxane. The consideration of information on use of PPE, engineering controls, and other ways industry protects its workers, as potential ways to address unreasonable risk will be part of the risk management rule development process.

Next Steps and Public Participation

EPA will now move forward on risk management to address the unreasonable risk presented by 1,4-dioxane. EPA will begin developing a proposed rule under TSCA section 6 to protect people from the unreasonable risks EPA identified.

Stay up to date on additional opportunities for public participation. Just like the risk evaluation process, there will be opportunities for public comment as EPA works to propose and finalize risk management actions for 1,4-dioxane. You can stay informed by signing up for our email alerts or checking the public dockets EPA-HQ-OPPT-2016-0723 and EPA-HQ-OPPT-2022-0905 for 1,4-dioxane at www.regulations.gov.

Final Risk Evaluation and Supporting Documents

Below are the 2024 revised risk determination, the 2024 supplement to the risk evaluation, the 2020 risk evaluation for 1,4-dioxane, non-technical summary, response to comments, and other supporting documents.

The discussion of the issues in the revised risk determination supersedes any conflicting statements in the 2020 1,4-dioxane risk evaluation and the response to comments documents.

Final Risk Evaluation for 1,4-Dioxane

Risk Evaluation Findings

Next Steps and Public Participation

Final Risk Evaluation and Supporting Documents

Assessing and Managing Chemicals under TSCA