2024-26342. 1,4-Dioxane; Supplement to the Risk Evaluation and Revised Unreasonable Risk Determination Under the Toxic Substances Control Act (TSCA); Notice of Availability

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Environmental Protection Agency

1. [EPA-HQ-OPPT-2016-0723; FRL-7918-03-OCSPP]

AGENCY:

Environmental Protection Agency (EPA).

ACTION:

Notice.

SUMMARY:

The Environmental Protection Agency (EPA or the Agency) is announcing the availability of the final supplement to the risk evaluation and revised unreasonable risk determination under the Toxic Substances Control Act (TSCA) for 1,4-dioxane. The purpose of risk evaluations under TSCA is to determine whether a chemical substance presents an unreasonable risk of injury to human health or the environment, without consideration of costs or non-risk factors, including unreasonable risk to potentially exposed or susceptible subpopulations identified as relevant to the risk evaluation by EPA, under the conditions of use. The Agency used the best available science to prepare this final supplement to the risk evaluation and has determined that 1,4-dioxane poses unreasonable risk to human health. Under TSCA, EPA must initiate risk management actions to address the unreasonable risk.

ADDRESSES:

The docket for this action, identified by docket identification (ID) number EPA-HQ-OPPT-2016-0723, is available online at https://www.regulations.gov. Additional information about dockets generally, along with instructions for visiting the docket in-person, is available at https://www.epa.gov/​dockets.

FOR FURTHER INFORMATION CONTACT:

For technical information: Cindy Wheeler, Existing Chemicals Risk Management Division (7404M), Office of Pollution Prevention and Toxics, Environmental Protection Agency, 1200 Pennsylvania Ave. NW, Washington, DC 20460-0001; telephone number: [phone]; email address: [e-mail].

For general information: The TSCA-Hotline, ABVI-Goodwill, 422 South Clinton Ave., Rochester, NY 14620; telephone number: [phone]; email address: [e-mail].

SUPPLEMENTARY INFORMATION:

I. Executive Summary

A. Does this action apply to me?

This action is directed to the public in general and may be of particular interest to those involved in the manufacture, processing, distribution, use, and disposal of 1,4-dioxane, related industry trade organizations, non-governmental organizations with an interest in human and environmental health, State and local governments, Tribal Nations, and/or those interested in the assessment of risks involving chemical substances and mixtures regulated under TSCA. As such, the Agency has not attempted to describe all the specific entities that this action might apply to. If you need help determining applicability, consult the technical contact listed under FOR FURTHER INFORMATION CONTACT .

B. What is the Agency's authority for taking this action?

The Agency is conducting this risk evaluation under TSCA section 6, 15 U.S.C. 2605, which requires that EPA conduct risk evaluations on chemical substances and identifies the minimum components EPA must include in all chemical substance risk evaluations. Each risk evaluation must be conducted consistent with the best available science, be based on the weight of ( print page 89994) scientific evidence and consider reasonably available information. 15 U.S.C. 2625(h), (i), and (k). See also the implementing procedural regulations at 40 CFR part 702.

C. What action is the Agency taking?

EPA is announcing the availability of the final supplement to the 1,4-dioxane risk evaluation and final revised unreasonable risk determination under TSCA. The purpose of risk evaluations under TSCA is to determine whether a chemical substance presents an unreasonable risk of injury to health or the environment, without consideration of costs or non-risk factors, including unreasonable risk to potentially exposed or susceptible subpopulations identified as relevant to the risk evaluation by EPA, under the conditions of use. EPA has used the best available science to prepare this final risk evaluation and has determined that 1,4-dioxane poses unreasonable risk to human health. Upon a determination of unreasonable risk, EPA must initiate risk management action as required pursuant to 15 U.S.C 2605(a) to address the unreasonable risk.

II. Background

In 2016, EPA announced its designation of 1,4-dioxane for risk evaluation under TSCA (81 FR 91927, December 19, 2016 (FRL-9956-47)). 1,4-Dioxane was one of the first 10 chemical substances undergoing the TSCA risk evaluation process after passage of the Frank R. Lautenberg Chemical Safety for the 21st Century Act, which amended TSCA. 1,4-Dioxane is primarily used as a solvent in a variety of commercial and industrial applications such as the manufacture of other chemicals ( e.g., adhesives, sealants) or as a processing aid or laboratory chemical. Although there are no direct consumer uses of 1,4-dioxane, it is present as a contaminant in commercial and consumer products and is produced as a byproduct through several manufacturing processes including ethoxylation, sulfonation, sulfation, and esterification.

In the “Draft Risk Evaluation for 1,4-Dioxane” released in June 2019 (hereafter “2019 draft risk evaluation”) (84 FR 31315, July 1, 2019 (FRL-9995-40)), EPA reviewed the exposures and hazards of 1,4-dioxane for industrial and commercial uses and assessed risk from occupational exposures and surface water exposures to environmental organisms. That assessment, which included the physical and chemical properties, lifecycle information, environmental fate and transport information, and hazard identification and dose-response analysis, was peer reviewed by the Science Advisory Committee on Chemicals (SACC). In November 2020, EPA released the “Draft Supplemental Analysis to the Draft Risk Evaluation for 1,4-Dioxane” (hereafter “2020 draft supplement”) that assessed conditions of use (COUs) of 1,4-dioxane as a contaminant in consumer products and general population exposure from incidental contact with surface water. The Agency determined that the 2020 draft supplement did not warrant additional peer review as there was no novel analysis. The 2019 draft risk evaluation and 2020 draft supplement were both incorporated into the “Final Risk Evaluation for 1,4-Dioxane” that was released in December 2020 (hereinafter “2020 final risk evaluaton”).

In early 2021, and in response to presidential executive orders and policy changes, EPA reviewed the risk evaluations for the first 10 chemical substances to ensure that the risk evaluations met the requirements of TSCA, including the requirement to use the best available science in decision-making. As a result of that review, the Agency announced plans to revise specific aspects of the first 10 risk evaluations to ensure that they appropriately identify unreasonable risks and thereby help to ensure the protection of human health and the environment. EPA determined an additional supplement to the 2020 final risk evaluation was needed to consider critical exposure pathways not previously assessed. Specifically, that additional supplement (hereinafter “2023 draft supplement”) includes evaluation of additional conditions of use in which 1,4-dioxane is a byproduct in industrial processes and a contaminant in certain commercial products, and evaluates risks from general population exposures to 1,4-dioxane released to ambient surface water and groundwater, ambient air, and land. To evaluate these additional exposure pathways, the Agency used new methods and novel applications of existing methods. These new methods were subject to public comment and peer review as part of the 2023 draft supplement (88 FR 48249, July 26, 2023 (FRL-7918-02-OCSPP)).

Along with the 2023 draft supplement, EPA also published and took public comment on draft revisions to the unreasonable risk determination for 1,4-dioxane that considers the 2020 risk evaluation and the 2023 draft supplement. The 2023 draft revision to the unreasonable risk determination reflects policy changes announced in June 2021, and EPA preliminarily determined that 1,4-dioxane presents an unreasonable risk of injury to health when evaluated under its conditions of use.

The final revised unreasonable risk determination that is being released with this announcement considers the 2020 risk evaluation and the final supplement that is also being released with this announcement. This final revised unreasonable risk determination supersedes the condition of use-specific no unreasonable risk determinations in the 2020 risk evaluation (and withdraws the associated order) and makes a final determination of unreasonable risk for 1,4-dioxane as discussed in Unit III.

III. Unreasonable Risk Determination

EPA has determined that 1,4-dioxane presents an unreasonable risk of injury to human health under the conditions of use. The Agency has determined that the unreasonable risk to human health presented by 1,4-dioxane is based on 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 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) and down-the-drain disposals of commercial and consumer products that are contaminated with 1,4-dioxane generated as a byproduct.

Consistent with the statutory requirements of TSCA section 6(a), EPA will propose risk management regulatory actions to the extent necessary so that 1,4-dioxane no longer presents an unreasonable risk to health. The Agency expects to focus its risk management action on the conditions of use that significantly contribute to the unreasonable risk. However, it should be noted that under TSCA section 6(a), EPA is not limited to regulating the specific activities found to contribute significantly to unreasonable risk and may select from among a suite of risk management requirements in TSCA section 6(a) related to manufacture (including import), processing, distribution in commerce, commercial use, and disposal as part of its regulatory options to address the unreasonable risk. As a general example, EPA may regulate upstream activities ( e.g., processing, distribution in commerce) to address downstream activities ( e.g., consumer uses) contributing significantly to unreasonable risk, even if the upstream ( print page 89995) activities do not contribute significantly to the unreasonable risk.

In addition, as part of its evaluation, EPA has determined that 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) and down-the-drain disposals of commercial and consumer products that are contaminated with 1,4-dioxane significantly contribute to the unreasonable risk from 1,4-dioxane. TSCA section 9(b) requires EPA to coordinate TSCA actions with actions taken under other Agency authorities. In coordinating regulatory action under TSCA with other offices at EPA, the Agency considered the authorities of the Safe Drinking Water Act (SDWA) and has determined that certain regulatory actions under the SDWA may also be appropriate. Therefore, as described in more detail in a memorandum included in this docket, and consistent with TSCA section 9(b)(1), OCSPP has memorialized this agreement for coordinated action on risks from 1,4-dioxane contamination in drinking water through actions under both TSCA section 6(a) and, for Office of Water consideration of remaining risks and appropriate action, under SDWA.

For more information about the TSCA risk evaluation process for existing chemicals, go to https://www.epa.gov/​assessing-and-managing-chemicals-under-tsca.

Authority:15 U.S.C. 2601 et seq.

Dated: November 7, 2024.

Michal Freedhoff,

Assistant Administrator, Office of Chemical Safety and Pollution Prevention.