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###### Environmental Protection Agency

          - [EPA-HQ-OPPT-2024-0425; FRL-12241-02-OCSPP]

# AGENCY:

Environmental Protection Agency (EPA).

# ACTION:

Notice.

# SUMMARY:

The Environmental Protection Agency (EPA or Agency) is announcing the availability of and soliciting public comment on the draft risk evaluation for 1,3-butadiene. The draft risk evaluation was prepared under the Toxic Substances Control Act (TSCA) and will be submitted to the Science Advisory Committee on Chemicals (SACC) for peer review. EPA is also announcing that there will be two virtual public meetings of the SACC: On February 4, 2025, a preparatory meeting for the SACC to consider the scope and clarity of the draft charge questions for the peer review; and on February 25 through 28, 2025, the peer review meeting for the SACC to consider the draft documents and public comments.

# DATES:

*Preparatory Public Meeting:*

*Meeting date:*                         February 4, 2025, 1:00 p.m. to approximately 4:00 p.m. (ET).                    

*Registration:*                         To request time to present oral comments during the preparatory meeting, you must register by noon (12:00 p.m. ET) on January 31, 2025. For those not making oral comments, registration will remain open through the end of this meeting on February 4, 2025.                    

*Comments:*                         Submit written comments on the scope and clarity of the charge questions, by noon (12:00 p.m. ET) on January 28, 2025. (Submit a written version of your oral comments by noon (12:00 p.m. ET) on January 31, 2025.)                    

*SACC Peer Review Public Meeting:*

*Meeting dates:*                         February 25 through 28, 2025, 10:00 a.m. to approximately 5:00 p.m. (ET).                    

*Registration:*                         To request time to present oral comments during the peer review meeting, you must register by noon, February 18, 2025. For those not making oral comments, registration will remain open through the end of this meeting on February 28, 2025.                    

*Comments:*                         Submit written comments on the draft documents, and written version of your oral comments, on or before February 3, 2025.                    

*Special Accommodations:*                         To allow sufficient time for EPA to process your request for special accommodations before the meeting, please submit the request at least ten business days in advance of the relevant meeting.                    

# ADDRESSES:

*Comments:*                         Submit written comments, identified by docket identification (ID) number EPA-HQ-OPPT-2024-0425, through                         *https://www.regulations.gov.*                         Follow the online instructions for submitting comments. Do not submit electronically any information you consider to be Confidential Business Information (CBI) or other information whose disclosure is restricted by statute. Additional information on commenting or visiting the docket, along with more information about dockets generally, is available at                         *https://www.epa.gov/​.*

*Meeting Registration:*                         Online registration will be available beginning in January 2025. Please refer to the SACC website at                         *https://www.epa.gov/​tsca-peer-review.*                         After registering, you will receive the webcast and streaming service meeting links and audio teleconference information.                    

*Special accommodation requests:*                         To request an accommodation for a disability, please contact the Designated Federal Official (DFO) listed under                         **FOR FURTHER INFORMATION CONTACT**                        .                    

# FOR FURTHER INFORMATION CONTACT:

*Designated Federal Official (DFO):*                         Alie Muneer, Mission Support Division (7602M), Office of Program Support, Office of Chemical Safety and Pollution Prevention, Environmental Protection Agency; telephone number: (202) 564-                              ( print page 95780)                            6369 or call the main office number: (202) 564-8450; email address:                         *muneer.alie@epa.gov.*

*Technical information:*                         Brooke Porter, Existing Chemicals Risk Management Division, Office of Pollution Prevention and Toxics, Office of Chemical Safety and Pollution Prevention, Environmental Protection Agency; telephone number: (202) 564-6388; email address:                         *porter.brooke@epa.gov.*

# SUPPLEMENTARY INFORMATION:

## I. Executive Summary

### A. What action is the Agency taking?

EPA is announcing the availability of and soliciting public comment on the draft risk evaluation for 1,3-butadiene. The draft risk evaluation was prepared under the Toxic Substances Control Act (TSCA) and will be submitted to the Science Advisory Committee on Chemicals (SACC) for peer review. EPA is also announcing that there will be two virtual public meetings of the SACC: On February 4, 2025, a preparatory meeting for the SACC to consider the scope and clarity of the draft charge questions for the peer review; and on February 25 through 28, 2025, the peer review meeting for the SACC to consider the draft risk evaluation and public comments.

This document provides instructions for accessing the materials, submitting written comments, and registering to provide oral comments and attend the public meetings.

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

                    EPA established the SACC in 2016 in accordance with TSCA, 15 U.S.C. 2625(o), to provide independent advice and expert consultation with respect to the scientific and technical aspects of issues relating to the implementation of TSCA. The SACC operates in accordance with the Federal Advisory Committee Act (FACA), 5 U.S.C. 10, and supports activities under TSCA, 15 U.S.C. 2601*et seq.,*                     the Pollution Prevention Act (PPA), 42 U.S.C. 13101*et seq.,*                     and other applicable statutes.                

### C. 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, and disposal of the subject chemical substances, and/or those interested in the assessment of risks involving chemical substances and mixtures regulated under TSCA (including members of at-risk communities, non-governmental organizations (NGOs), federal, state, and local officials). Since other entities may also be interested, the Agency has not attempted to describe all the specific entities that may be interested.

### D. What should I consider as I submit my comments to EPA?

                    1.                     *Submitting CBI.*                     Do not submit CBI or other sensitive information to EPA through                     *https://www.regulations.gov*                     or email. To include information in your comment that you consider to be CBI or otherwise protected, please contact the DFO listed under                     **FOR FURTHER INFORMATION CONTACT**                     to obtain special instructions before submitting that information.                

                    2.                     *Tips for preparing comments.*                     When preparing and submitting your comments, see                     *https://www.epa.gov/​dockets/​commenting-epa-dockets.*                     See also the instructions in Unit III.C.                

### E. How can I stay informed about SACC activities?

                    You may subscribe to the following listserv for alerts regarding this and other SACC-related activities:                     *https://public.govdelivery.com/​accounts/​USAEPAOPPT/​subscriber/​new?​topic_​id=​USAEPAOPPT_​101.*

## II. Background

### A. What is the purpose of the SACC?

                    The SACC provides independent advice and recommendations to the EPA on the scientific and technical aspects of risk assessments, methodologies, and pollution prevention measures and approaches for chemicals regulated under TSCA. The SACC is composed of experts in toxicology; environmental risk assessment; exposure assessment; and related sciences (                    *e.g.,*                     synthetic biology, pharmacology, biotechnology, nanotechnology, biochemistry, biostatistics, physiologically based pharmacokinetic (PBPK) modeling, computational toxicology, epidemiology, environmental fate, and environmental engineering and sustainability). When needed, the SACC committee will be assisted by                     *ad hoc*                     reviewers with specific expertise in the topics under consideration.                

### B. Why is EPA conducting these risk evaluations?

TSCA requires EPA to conduct risk evaluations on prioritized chemical substances and allows chemical manufacturers to request an EPA-conducted risk evaluation of a chemical substance (or category of chemical substances) using the procedures established in 40 CFR 702.37. TSCA also identifies the minimum components EPA must include in all chemical substance risk evaluations. The purpose of conducting risk evaluations is to determine whether a chemical substance presents an unreasonable risk to human health or the environment under the Conditions of Use (COUs). These evaluations include assessing unreasonable risks to relevant potentially exposed or susceptible subpopulations. As part of this process EPA: (1) Integrates hazard and exposure assessments using the best available science that is reasonably available to ensure decisions are based on the weight of the scientific evidence, and (2) Conducts peer review for risk evaluation approaches that have not been previously peer-reviewed.  

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

### C. Why is EPA evaluating this chemical substance?

In 2020, EPA issued final scope documents for the 20 chemical substances designated in December 2019 as High-Priority Substances for the TSCA risk evaluation process, which included 1,3-butadiene. The final scope documents outline the hazards, exposures, conditions of use, and the potentially exposed or susceptible subpopulations the Agency expected to consider in its risk evaluation for the substances (85 FR 55283, September 4, 2020 (FRL-10013-90)).

1,3-Butadiene (CASRN 106-99-0) is a volatile, colorless gas with a total U.S. production volume between 1 and 5 billion pounds. It is produced in petrochemical processing and extracted and further processed as a building block for several polymers and elastomers that do not readily depolymerize. Air is expected to be the major pathway of exposure for 1,3-butadiene in the environment. Although 1,3-butadiene is moderately soluble in water, monitoring data indicate that it is not detected in water. Environmental release data show that more than 98 percent of 1,3-butadiene facility releases are to air. Once in air, 1,3-butadiene will not deposit to land or adsorb to organic matter due to its chemical properties. Long-range transport in air is not expected, in part, because 1,3-butadiene has a short half-life (<8 hours) and will degrade into formaldehyde and acrolein.

                    Reduced fetal body weight and hematological effects are indicated as the most sensitive and robust non-cancer human health hazards. EPA has classified 1,3-butadiene as a human carcinogen and epidemiology studies have demonstrated an association between 1,3-butadiene exposure and                           ( print page 95781)                        increased incidence of leukemia in workers.                

### D. What is the topic of the planned SACC peer review?

EPA is submitting the draft risk evaluation of 1,3-butadiene and associated supporting documents to the SACC for peer review, along with the public comments received. The draft risk evaluation includes analyses of physical chemical properties, the fate and transport in the environment, releases to the environment, exposure to workers and the general population, including potentially exposed susceptible subpopulations, environmental risk characterization, and human health hazard and risk characterization for workers and the general population.

EPA is focusing its peer review charge on specific scientific areas and analyses. Many of the methods and analyses used in these evaluations are not novel and have been reviewed in the development of previous TSCA assessments. EPA is requesting feedback on approaches, results and calculations associated with the exposure, human health hazard, and environmental hazard analyses. EPA is releasing the draft risk evaluation for public comment and independent, expert peer review. Once EPA receives comment and input from public comment and peer review, revisions will be made, and the Agency will finalize the 1,3-butadiene risk evaluation.

EPA is requesting a focused panel discussion and feedback on novel approaches, unique exposure analyses and other calculations, and selection of key hazard endpoints for 1,3-butadiene:
    - No exposure to aquatic and terrestrial species is expected due to the physical and chemical properties of 1,3-butadiene, which is primarily released to air and does not partition, deposit, or persist in or on water or soil. Monitoring data indicate that 1,3-butadiene is not detected in water. Exposure of terrestrial organisms via ambient air will be brief due to the reactive nature of 1,3-butadiene. EPA is seeking comment on the preliminary determination that quantitative risk assessment for ecological taxa is not needed for 1,3-butadiene.
    - Reduced fetal body weight (the basis of the acute Reference Concentration (RfC) in the 2002 IRIS Assessment) is observed in both mice and rats following gestational exposure but is not expected to result from a single dose of 1,3-butadiene. Further, EPA did not identfy effects of teratogenicity or any other relevant endpoint following single exposures at doses relevant to human exposure scenarios. Therefore, EPA did not derive an acute point of departure (POD) or quantify risks from acute exposures. EPA is seeking comment on the preliminary determination that there is no appropriate POD to support acute risk estimates.
    - Ovarian atrophy is an adverse effect observed only in mice and can be attributed to a specific 1,3-butadiene metabolite (diepoxybutane) that is less prevalent in rats and humans. EPA has evaluated the relevance of ovarian atrophy for assessing human risk and determined that the ovarian atrophy endpoint is not appropriate for extrapolating to human risk due to differences in species-specific metabolites. EPA is proposing to use decreased fetal body weight as the basis for the intermediate and chronic points of departure for 1,3-butadiene. EPA is seeking comment on these preliminary conclusions to establish intermediate and chronic points of departure based on reduced fetal body weight.
    - OPPT revised the inhalation unit risk (IUR) for 1,3-butadiene presented in the IRIS 2002 assessment to incorporate updated epidemiological cohort data. EPA is seeking comment on the mathematical approach and new epidemiological cohort data used in the revised IUR. OPPT also derived bladder cancer risk estimates using the same epidemiological cohort and is seeking comment on the appropriate IUR for evaluating cancer risk.
    - EPA has conducted a mutagenic mode of action analysis and evaluating whether the use of an age-dependent adjustment factor (ADAF) for leukemia is appropriate. EPA has preliminarily concluded that a mutagenic mode of action is applicable to 1,3-butadiene and use of an age-dependent adjustment factor (ADAF) for leukemia is appropriate. EPA is seeking comment on this analysis and preliminary conclusion.
    - The majority of occupational exposure sampling data points, collected from OSHA, NIOSH, and ACC's report, were not quantifiable values but were identified as being below the limit of detection (LOD). For datasets including exposure data that were reported as below the LOD, EPA estimated exposure concentrations, following EPA's Guidelines for Statistical Analysis of Occupational Exposure Data.                      Based on these guidelines, EPA used the LOD value as the high-end estimate and half the LOD as central tendency. EPA is seeking comment on this approach and the relevance of this dataset for risk characterization.                
    - General population exposure to 1,3-butadiene was modeled using the Human Exposure Model (HEM) to estimate ambient air concentrations based on releases reported to the Toxic Release Inventory (TRI) for years 2016 to 2021. Exposure concentrations were modeled at discrete distances from releasing facilities and surrounding census blocks. EPA is seeking comment on this analysis and preliminary conclusions.

## III. Public Meeting of the SACC

### A. What is the purpose of the virtual public meeting(s)?

EPA is planning two virtual public meetings: (1) A preparatory public meeting for the SACC to consider and ask questions regarding the scope and clarity of the draft charge questions; and (2) a public peer review meeting for the SACC to consider and peer review the draft risk evaluation. These public meetings are part of the SACC's peer review of the Agency's methods and novel analyses for the draft risk evaluation of 1,3-butadiene. The agenda for these meetings will be posted in the docket and will also be available through the SACC website.

Recommendations from this SACC review and public comments will be considered in the development of the TSCA risk evaluation and may inform other EPA efforts related to the assessment and regulation of the chemical substance. The Agency will be seeking SACC review of its data analyses and methodologies relevant to human health hazard and exposure analyses that have not been previously peer-reviewed.

### B. How can I participate in the virtual public meeting(s)?

To participate in these virtual public meetings, you must register online to receive the webcast and streaming service meeting links and audio teleconference information for each meeting. Online registration will be available beginning approximately one month prior to the meeting and will remain open through the end of the meeting. To make oral comments during one of these meetings, follow the instructions in this document.

### C. How can I access the documents?

                    The draft risk evaluation for 1,3-butadiene and related documents, including background documents, related supporting materials, and draft charge questions, are available in the docket. As additional background materials become available, EPA will include those additional background                           ( print page 95782)                        materials (                    *e.g.,*                     SACC members and consultants participating in this meeting and the meeting agenda) in the docket and through links on the SACC website at                     *https://www.epa.gov/​tsca-peer-review.*

### D. How can I provide comments?

To ensure proper receipt of comments, it is imperative that you identify docket ID No. EPA-HQ-OPPT-2024-0425 in the subject line on the first page of your comments and follow the instructions in this document.

                    1.                     *Written comments.*                     Submit written comments by the deadlines set in the                     **DATES**                     section of this document and as described in the                     **ADDRESSES**                     section of this document.                

                    2.                     *Oral comments.*                     To request time to present oral comments during one of the virtual public meetings, you must register online by the deadlines set in the                     **DATES**                     section of this document. Oral comments during the virtual public meetings are limited to 5 minutes. In addition, each speaker should submit a written copy of their oral comments and any supporting materials (                    *e.g.,*                     presentation slides) to the DFO prior to the meetings for distribution to the SACC.                

### E. What happens after the SACC meeting(s)?

After the SACC public meeting, the SACC will prepare the meeting minutes and final report document summarizing its recommendations to the EPA, which will also be available in the docket and through the SACC website. EPA will consider the SACC recommendations and public comments to complete the risk evaluation and unreasonable risk determination under TSCA for this chemical substance. Under TSCA, EPA must then initiate risk management actions to address the unreasonable risk it identified.

*Authority:*15 U.S.C. 2625(o); 5 U.S.C. 10.                

Dated: November 26, 2024.

Michal Freedhoff,

Assistant Administrator, Office of Chemical Safety and Pollution Prevention.

[FR Doc. 2024-28286 Filed 12-2-24; 8:45 am]

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