EPA Issues a Final Revised Risk Determination for 1,4-Dioxane

The U.S. Environmental Protection Agency (EPA) on Nov. 14, 2024, issued a Notice of Availability of the Final Supplement to the Risk Evaluation and Revised Unreasonable Risk Determination for 1,4-Dioxane (Final Revised Risk Determination) under the Toxic Substances Control Act (TSCA). 1,4-Dioxane is an organic compound that is primarily used as a solvent in a variety of manufacturing and industrial operations and produced as a byproduct of several manufacturing processes. There are no direct consumer uses of 1,4-Dioxane.

The EPA's Final Revised Risk Determination for 1,4-Dioxane comes after the agency's multi-year evaluation of the potential effects of the chemical on human health and the environment. Through the Final Revised Risk Determination, the EPA concluded that 1,4-Dioxane poses an unreasonable risk to human health and environment. As a result, the EPA will initiate the next stage of the TSCA chemical review process – risk management – where it will evaluate and develop regulatory mechanisms for reducing the risks posed by the chemical.

The remainder of this Holland & Knight alert provides an outline of TSCA's Section 6 chemical review process, an overview of the EPA's risk evaluation of 1,4-Dioxane, the conclusions of the Final Revised Risk Determination and considerations for regulated entities whose business and operations may be impacted by the regulation of 1,4-Dioxane.

Overview of TSCA's Chemical Review Process

The 2016 amendments to TSCA (known as the Frank R. Lautenberg Chemical Safety for the 21st Century Act) designed a three-stage chemical review process under Section 6 of TSCA, requiring the EPA to conduct detailed evaluations the safety of existing chemicals to determine whether they present an unreasonable risk to health and the environment under their conditions of use. The process includes 1) prioritization, 2) risk evaluation and 3) risk management.¹

This first step of this process requires the EPA to designate chemicals as either "high-priority" or "low-priority" substances. Chemicals that are designated as high-priority move to the second stage of the process – risk evaluation. During this stage, the EPA must conduct an evaluation to "determine whether a chemical substance presents an unreasonable risk … including an unreasonable risk to a potentially exposed or susceptible subpopulation … under the conditions of use."² Conditions of use are generally the various ways that the chemical is used, including in manufacturing operations, in certain products, processing, distribution and disposal. Then, based on the "best available science" and "weight of the scientific evidence," the EPA must issue a risk determination of whether the uses of the chemical identified by the administrator pose unreasonable risk.³ If the EPA finds "unreasonable risk" is posed by the chemical, then the agency moves to the final stage – risk management – under which it will promulgate regulations to address the identified risks within two years of the final risk determination.⁴

Background on EPA's Evaluation of 1,4-Dioxane

1,4-Dioxane is currently used as a solvent in the manufacture of other chemicals, a processing aid, functional fluid, laboratory chemical and dry film lubricant, as well as in adhesives and sealants, spray polyurethane foam and printing inks. There are no direct consumer uses of 1,4-Dioxane, but it may be present as a contaminant in certain consumer soaps and detergents. The compound is produced as a byproduct through several manufacturing processes, including ethoxylation, sulfonation, sulfation and esterification.⁵

1,4-Dioxane was prioritized for review by the EPA in December 2016 as one of the first 10 chemicals evaluated under the TSCA amendments, thereby triggering the commencement of a risk evaluation. The EPA issued its draft risk evaluation for 1,4-Dioxane in 2019 (Draft Risk Evaluation),⁶ in which it reviewed the hazards and exposures that the use of 1,4-Dioxane in industrial and commercial uses poses. The EPA issued the final risk evaluation for 1,4-Dioxane in December 2020 (2020 Final Risk Evaluation).⁷ The 2020 Final Risk Evaluation concluded that 1,4-Dioxane did not pose an unreasonable risk of injury to human health or the environment under several conditions of use such as distribution in commerce, functional fluids, cleaning and furniture care products, and laundry and dishwashing products. However, it identified several manufacturing, processing, industrial, commercial and disposal uses that present an unreasonable risk to health.

In 2021, after the EPA reviewed the risk evaluations for the first 10 prioritized chemicals (including 1,4-Dioxane), it concluded that a supplement to the 2020 Final Risk Evaluation for potential 1,4-Dioxane exposures was needed to consider exposure pathways that it had not previously evaluated. Following this supplemental evaluation, the EPA issued a Draft Revised Final Risk Evaluation and Risk Determination in 2023 (2023 Draft) that preliminarily concluded that 1,4-Dioxane presents an unreasonable risk to human health and the environment.⁸ The 2023 Draft included an opportunity to submit public comments. Certain commenters expressed disagreement with various aspects of the EPA's draft conclusions that were nevertheless included in the Final Revised Risk Determination. The EPA issued a response to public comments document in conjunction with the Final Revised Risk Determination.⁹

The Final Revised Risk Determination

Now, through its Final Revised Risk Evaluation and Risk Determination, the EPA finalized its preliminary conclusions outlined in the 2023 Draft. Specifically, the EPA determined that 1,4-Dioxane presents an unreasonable risk to human health based on 1) "cancer and non-cancer risks (from liver toxicity and effects in the olfactory epithelium) to workers and occupational non-users (ONUs) from inhalation and dermal exposures" and 2) "cancer risks to the general population, including fenceline communities, from exposures to 1,4-Dioxane in drinking water sourced from surface water contaminated with industrial discharges of 1,4-Dioxane (including when it is generated as a byproduct)."¹⁰

The EPA identified several conditions of use of 1,4-Dioxane that contributed to the determination of unreasonable risk, including but not limited to manufacturing, processing, functional fluids, paints and coatings, cleaning and furniture care products, laundry and dishwashing products, laboratory chemicals, and adhesives and sealants.¹¹ The EPA concluded that the following conditions of use did not contribute to the unreasonable risk determination: distribution in commerce, commercial use of automobile antifreeze and textile dyes, and consumer use of automobile antifreeze and spray polyurethane foam .¹²

As a result of this Final Revised Risk Determination, the EPA must now enter the final stage of the chemical review process (risk management) and develop measures to address the unreasonable risks. For the risks associated with drinking water, the EPA has indicated its intent to coordinate its actions with the offices responsible for implementation and regulation under the Safe Drinking Water Act (SDWA).

Considerations and Next Steps

There is no statutory opportunity for the public to submit comments on the Final Revised Risk Determination. However, the public will have the opportunity to submit comments on the 1,4-Dioxane risk management rule. If the EPA follows the timeline outlined in TSCA, a proposed risk management rule will be published by Nov. 14, 2025. Note that this time frame assumes there will be no further delay as a result of the upcoming change in administrations.

Holland & Knight's Emerging Contaminants and PFAS Team can assist businesses and regulated entities in evaluating the potential legal and operational implications of the forthcoming 1,4-Dioxane risk management rule, as well as assist with drafting and submission of comments on the proposed rule once it is published.

Notes

¹ Frank R. Lautenberg Chemical Safety for the 21st Century Act, Pub. L. No. 114-182, 130 Stat. 448 (2016) (codified at 15 U.S.C. § 2601 et seq.).

² 15 U.S.C. § 2605(b)(4)(A).

³ Id. § 2605(b)(4)(A).

⁴ Id. § (a).

⁵ See 1,4-Dioxane; Supplement to the Risk Evaluation and Revised Unreasonable Risk Determination Under the Toxic Substances Control Act (TSCA); Notice of Availability, 89 Fed. Reg. 89,993, 89,994 (Nov. 14, 2024); Risk Evaluation for 1,4-Dioxane, U.S. Environmental Protection Agency (EPA).

⁶ Draft Toxic Substances Control Act (TSCA) Risk Evaluations and TSCA Science Advisory Committee on Chemicals (SACC) Meetings; Cyclic Aliphatic Bromide Cluster (HBCD) and 1,4-Dioxane; Notice of Availability and Public Meetings, 84 Fed. Reg. 31,315 (July 1, 2019).

⁷ Final Risk Evaluation for 1,4-Dioxane, EPA.

⁸ Unreasonable Risk Determination, EPA.

⁹ Response to Public Comments: Toxic Substances Control Act (TSCA) Risk Determination for 1,4-Dioxane, EPA.

¹⁰ Unreasonable Risk Determination for 1,4-Dioxane, EPA.

¹¹ Id.

¹² Id.

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