As part of EPA’s mission to protect human health and the environment, the agency has completed a final risk evaluation for 1,4-dioxane under the Toxic Substances Control Act (TSCA). In the final risk evaluation, EPA reviewed 24 conditions of use, primarily as a solvent, a processing aid, functional fluid, laboratory chemical, adhesive, sealant, spray polyurethane foam, printing, and dry film lubricant.

The 1,4-dioxane risk evaluation contains the agency’s final determinations on which conditions of use present unreasonable risks to human health or the environment based on a robust review of the scientific data. To prepare the final risk evaluation, EPA reviewed extensive scientific literature, conducted modeling and other risk assessment activities, and collected toxicity, exposure, and hazard information from many sources.

Releasing a final risk evaluation is the last step in the scientific evaluation process required by TSCA and will guide the agency’s efforts to issue regulations to address unreasonable risks associated with this chemical. EPA has one year to propose appropriate risk management actions.

On this page:

• Risk evaluation findings
• Using products safely and alternatives
• Next steps and public participation
• Final risk evaluation and supporting documents

On other pages:

• Read about the steps in EPA’s risk evaluation process for 1,4-dioxane.
• Learn more about EPA’s risk evaluation process.

Risk Evaluation Findings

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

EPA found no unreasonable risks to the environment from any conditions of use. The agency assessed the impact of 1,4-dioxane on aquatic vertebrates and invertebrates, and aquatic plants, in surface waters. After reviewing these data, EPA found no unreasonable risk to the environment.

EPA found no unreasonable risks to consumers or bystanders from any conditions of use. EPA did not identify any direct consumer uses of this chemical. However, 1,4-dioxane may be found as a by-product in consumer products such as soaps and detergents when 1,4-dioxane is created from the breakdown of other chemicals that are used to make certain consumer products. After reviewing eight consumer uses of surface cleaners, laundry/dishwashing detergents, and paint/floor lacquer where 1,4-dioxane is present as a byproduct, the agency found no unreasonable risks.

EPA found no unreasonable risks to the general population. EPA assessed exposure to the general population from 1,4-dioxane in surface water and found no unreasonable risks.

EPA found unreasonable risks to workers and occupational non-users from 13 conditions of use of 1,4-dioxane. EPA found unreasonable risks to workers from 13 commercial uses of 1,4-dioxane. Additionally, EPA found unreasonable risks from most commercial uses of this chemical to workers nearby but not in direct contact with 1,4-dioxane (known as occupational non-users). Common commercial uses include in the manufacture of other chemicals, as a processing aid, in laboratory chemicals, and in adhesives and sealants. Unreasonable risks to workers and occupational non-users can come from both short- and long-term inhalation and dermal (through the skin) exposure.

Using Products Safely and Alternatives

EPA is working through the process required by TSCA to address the unreasonable risks found from 1,4-dioxane. The information below provides ways to reduce exposure.

For any chemical product, EPA strongly recommends that users carefully follow all instructions on the product’s label. For example, labels on products containing 1,4-dioxane may state that the product should be used only with adequate ventilation. The labels may also instruct users to move to fresh air if they feel unwell and contact their physician.

Workers using 1,4-dioxane products should continue to follow label instructions and applicable workplace regulations and should properly use appropriate personal protective equipment.

Next Steps and Public Participation

The next step in the process required by TSCA is risk management. EPA will propose and take public comments on actions to address the unreasonable risks identified in the risk evaluation. According to TSCA, the agency must finalize those actions within two years of completing the final risk evaluation. EPA’s proposed regulations could include requirements on how the chemical is used, or limiting or prohibiting the manufacture, processing, distribution in commerce, use, or disposal of this chemical substance, or other measures under TSCA as applicable.

EPA is committed to being open and transparent as the agency follows the process required by the law for evaluating unreasonable risks from chemicals. EPA will continue to keep the public updated as the agency moves through the risk management process. Following the comprehensive risk evaluation process required by TSCA, EPA has reached final conclusions about whether a chemical substance poses any unreasonable risks to health or the environment under the conditions of use. This allows EPA to develop and implement the appropriate risk management actions to ensure the safety of chemicals on the market.

There will be additional opportunities for public participation. Similar to the risk evaluation process, there will be opportunities for public input 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 docket for 1,4-dioxane at www.regulations.gov. 

Final Risk Evaluation and Supporting Documents

The final risk evaluation for 1,4-dioxane, non-technical summary, response to comments, and other supporting documents are below.

• Final Risk Evaluation for 1,4-Dioxane (PDF)(616 pp, 12 MB)
• 1,4-Dioxane Final Risk Evaluation Non-technical Summary (PDF)(2 pp, 69 K)
• Summary of External Peer Review and Public Comments and Disposition for 1,4-Dioxane: Response to Support Risk Evaluation of 1,4-Dioxane (PDF)(212 pp, 2 MB)
• Risk Evaluation for 1,4-Dioxane Systematic Review Supplemental File: Updates to the Data Quality Criteria for Epidemiological Studies (PDF)(16 pp, 1 MB)
• Final Risk Evaluation for 1,4-Dioxane Systematic Review Supplemental File: Data Quality Evaluation of Environmental Releases and Occupational Exposure Data (PDF)(168 pp, 2 MB)
• Final Risk Evaluation for 1,4-Dioxane Systematic Review Supplemental File: Data Quality Evaluation of Environmental Hazard Studies (PDF)(27 pp, 1 MB)
• Final Risk Evaluation for 1,4-Dioxane Systematic Review Supplemental File: Data Quality Evaluation of Environmental Fate and Transport Studies (PDF)(12 pp, 381 K)
• Risk Evaluation for 1,4-Dioxane Systematic Review Supplemental File: Data Quality Evaluation of Human Health Hazard Studies, Animal and In Vitro Studies (PDF)(189 pp, 2 MB)
• Final Risk Evaluation for 1,4-Dioxane Systematic Review Supplemental File: Data Quality Evaluation of Epidemiological Studies (PDF)(15 pp, 503 K)
• Final Risk Evaluation for 1,4-Dioxane Systematic Review Supplemental File: Data Quality Evaluation of Consumer Exposure Studies (PDF)(49 pp, 2 MB)
• Final Risk Evaluation for 1,4-Dioxane Supplemental Information File on Aquatic Exposure Screen Facility Information (PDF)(11 pp, 2 MB)
• Final Risk Evaluation for 1,4-Dioxane Supplemental Information File on Ambient Water Exposure Modeling Outputs from E-FAST (PDF)(76 pp, 2 MB)
• Final Risk Evaluation for 1,4-Dioxane Systematic Review Supplemental File: Data Quality Evaluation of Physical-Chemical Properties Studies (PDF)(17 pp, 466 K)