Final Risk Evaluation for 1,4-Dioxane

In July 2023, EPA released the 2023 Draft Revised Risk Determination for 1,4-Dioxane as a whole chemical substance under the Toxic Substances Control Act (TSCA). The proposed risk determination for 1,4-dioxane as a whole chemical substance 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 draft 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.

In July 2023, EPA released the 2023 Draft Supplement to the Risk Evaluation for 1,4-Dioxane, which is available for public comment and peer review through September 8, 2023. The draft 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 describes in the draft revised risk determination the conditions of use that contribute to the determination that 1,4-dioxane presents an unreasonable risk of injury to human health.

Read the Federal Register notice.

Risk Evaluation Findings

In July 2023, EPA released the 2023 Draft Revised Risk Determination for 1,4-Dioxane, which is available for public comment through September 8, 2023.

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 includes 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.

In July 2023, EPA released for public comment and peer reviewthe 2023 Draft Supplement to the Risk Evaluation for 1,4-Dioxane. The public comment period closes on September 8, 2023. The draft 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 draft revised risk determination incorporates information from the 2020 risk evaluation and 2023 draft supplement.

EPA proposes to determine that 1,4-dioxane, as a whole chemical substance, presents unreasonable risk to human health.

EPA assessed the impact of 1,4-dioxane on workers, 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, contribute to the whole chemical determination of unreasonable risk of injury to health. Overall, based on the revised risk determination, EPA’s preliminary findings include that worker exposure to 1,4-dioxane from all but four occupational conditions of use contribute to the unreasonable risk from 1,4-dioxane.

In the 2020 risk evaluation, EPA evaluated risks to consumers from eight conditions of use and found that the use did not present an unreasonable risk to consumers or bystanders. In the 2023 draft revised unreasonable risk determination, EPA does not propose to identify the consumer conditions of use 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, generation of 1,4-dioxane as an ethoxylation process byproduct—i.e., the upstream processing of many of these the consumer products—does 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.

EPA proposes to include 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) as contributing to the unreasonable risk determination.

The 2023 Draft 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 review public comments on the 2023 Draft Revised Risk Determination for 1,4-Dioxane and the 2023 Draft Supplement to the Risk Evaluation for 1,4-Dioxane before finalization. Following that, EPA will propose and take public comments on risk management actions to address the unreasonable risk identified in the risk evaluation, as updated by the final revised risk determination

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 bysigning up for our email alertsor checking the public docketsEPA-HQ-OPPT-2016-0723 andEPA-HQ-OPPT-2022-0905 for 1,4-dioxane at www.regulations.gov.

Final Risk Evaluation and Supporting Documents

Below are the draft revised risk determination, the 2023 draft 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 draft revised risk determination would supersede any conflicting statements in the 2020 1,4-dioxane risk evaluation and the response to comments documents.

2023 Draft Revised Risk Determination for 1,4-Dioxane (pdf) (544.5 KB)
2023 Draft Supplement to the 2020 Risk Evaluation for 1,4-Dioxane (pdf) (8.7 MB)
Final Risk Evaluation for 1,4-Dioxane (pdf) (11 MB)
1,4-Dioxane Final Risk Evaluation Non-technical Summary (pdf) (67.5 KB)
Summary of External Peer Review and Public Comments and Disposition for 1,4-Dioxane: Response to Support Risk Evaluation of 1,4-Dioxane (pdf) (1.4 MB)
Risk Evaluation for 1,4-Dioxane Systematic Review Supplemental File: Updates to the Data Quality Criteria for Epidemiological Studies (pdf) (990.3 KB)
Final Risk Evaluation for 1,4-Dioxane Systematic Review Supplemental File: Data Quality Evaluation of Environmental Releases and Occupational Exposure Data (pdf) (1.8 MB)
Final Risk Evaluation for 1,4-Dioxane Systematic Review Supplemental File: Data Quality Evaluation of Environmental Hazard Studies (pdf) (1.1 MB)
Final Risk Evaluation for 1,4-Dioxane Systematic Review Supplemental File: Data Quality Evaluation of Environmental Fate and Transport Studies (pdf) (372.2 KB)
Risk Evaluation for 1,4-Dioxane Systematic Review Supplemental File: Data Quality Evaluation of Human Health Hazard Studies, Animal and In Vitro Studies (pdf) (1.9 MB)
Final Risk Evaluation for 1,4-Dioxane Systematic Review Supplemental File: Data Quality Evaluation of Epidemiological Studies (pdf) (491 KB)
Final Risk Evaluation for 1,4-Dioxane Systematic Review Supplemental File: Data Quality Evaluation of Consumer Exposure Studies (pdf) (1.7 MB)
Final Risk Evaluation for 1,4-Dioxane Supplemental Information File on Aquatic Exposure Screen Facility Information (pdf) (1.8 MB)
Final Risk Evaluation for 1,4-Dioxane Supplemental Information File on Ambient Water Exposure Modeling Outputs from E-FAST (pdf) (1.6 MB)
Final Risk Evaluation for 1,4-Dioxane Systematic Review Supplemental File: Data Quality Evaluation of Physical-Chemical Properties Studies (pdf) (455 KB)

Final Risk Evaluation for 1,4-Dioxane | US EPA (2024)

Risk Evaluation Findings

Next Steps and Public Participation

Final Risk Evaluation and Supporting Documents

References